JP2009284262A - Optical transmission system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce components in a system to the required minimum number, and to efficiently perform package APC control of a plurality of channels when parallel optical transmission of the plurality of channels is attained in one direction optical transmission. <P>SOLUTION: In the optical transmission system 100, in which a plurality of optical transmission paths 104a-104n formed by optical transmitters 101a-101n, and optical receivers 102a-102n are provided in parallel, a serial interface 103a and a serial interface 103b connected by a serial bus 105 are included, and the output intensity of the optical signals of the optical transmitters 101a-101n is adjusted from the outside, based on the intensity information acquired by the serial interface 103a, by communication processing for acquiring the intensity information of an optical signal between the serial interface 103a and the serial interface 103b. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention provides a multi-channel batch APC (optimization of an optical signal output level so as to maintain high transmission quality of optical signals transmitted to a plurality of parallel channels and to minimize power consumption. The present invention relates to an optical transmission system that efficiently performs control.

  2. Description of the Related Art Conventionally, an optical transmission system includes a transmission device that transmits an optical signal modulated according to information to be transmitted, an optical fiber cable for transmitting the optical signal, and a reception device that receives the optical signal. The performance of the optical transmission system is affected by a loss in a transmission path such as an optical fiber cable and a connector, and variation in light emission characteristics among individual light emitting elements. For this reason, an optical transmission system having a function for eliminating the degradation of an optical signal is desired.

  Therefore, the output level of the optical signal transmitted from the transmitting apparatus is detected by the receiving apparatus, and the increase / decrease information is transmitted from the receiving apparatus to the transmitting apparatus, thereby controlling the output level of the optical signal transmitted from the transmitting apparatus. The technique (APC control) which performs this automatically is described in patent document 1 and patent document 2, for example.

  In the optical communication system described in Patent Document 1, between optical communication apparatuses that can transmit and receive each other, one optical communication apparatus transmits an optical signal in which optical output increase / decrease data is superimposed on a main signal composed of transmission data to the other optical communication apparatus. The other optical communication device controls the output level of its own optical signal according to the optical output increase / decrease data detected from the received optical signal, and derives the main signal composed of the transmission data from the previous optical signal. An optical signal on which the optical output increase / decrease data is superimposed is transmitted to one optical communication apparatus. One optical communication apparatus controls the output level of its own optical signal according to the optical output increase / decrease data detected from the received optical signal. As a result, the output levels of the mutual optical signals are optimized.

  In the optical communication system described in Patent Document 1, an optical transmission path for transmitting an optical signal from one optical communication device to the other optical communication device, and an optical signal from the other optical communication device to the one optical communication device. In contrast, in the optical communication system described in Patent Document 2, bidirectional optical communication is performed using one optical transmission path. The system is realized.

  Next, the optical communication system described in Patent Document 2 will be described with reference to FIG.

  FIG. 13 is a block diagram showing a configuration of an optical communication system including conventional optical transmission apparatuses 900a and 900b having a transmission / reception function.

  As shown in FIG. 13, the optical transmission devices 900a and 900b include light emitting units 901a and 901b, light output control circuits 902a and 902b, light emission control circuits 903a and 903b, reception level detection circuits 904a and 904b, light receiving units 905a and 905b, In addition, directional couplers 906a and 906b are provided, respectively. Further, the optical transmission device 900a and the optical transmission device 900b are connected by an optical fiber cable 921.

  In the optical transmission device 900a, when transmission data from the outside (such as a CPU) is input to the light output control circuit 902a, the light output control circuit 902a transmits an optical signal to be transmitted based on an instruction from the light emission control circuit 903a. While adjusting the output level, the laser diode included in the light emitting unit 901a is caused to emit light to generate an optical signal. The optical signal generated by the light emitting unit 901a is transmitted to the outside by the optical fiber cable 921 through the directional coupler 906a.

  In the optical transmission device 900b, an optical signal transmitted from the optical transmission device 900a via the optical fiber cable 921 is received by the light receiving unit 905b including a photodiode via the directional coupler 906b. The light receiving unit 905b converts the optical signal into an electric signal, and outputs the converted electric signal to the outside (CPU or the like) as reception data.

  The light receiving unit 905b also outputs an electrical signal to the reception level detection circuit 904b. The reception level detection circuit 904b detects the light reception intensity of the optical signal based on the electrical signal, and outputs the detected value to the light emission control circuit 903b. The light emission control circuit 903b compares the detected value of the received light intensity of the optical signal with a reference value stored in advance, and determines whether the received light intensity of the optical signal is normal.

  If it is determined that the received light intensity is not normal, the receiving-side optical transmission apparatus 900b transmits information requesting the setting change of the output level of the optical signal to the transmitting-side optical transmission apparatus 900a. That is, when the light emission control circuit 903b notifies the light output control circuit 902b that the received light intensity is not normal, the light output control circuit 902b receives an optical signal composed of information requesting a change in the output level of the optical signal, A laser diode included in the light emitting unit 901b is caused to emit light and generated. The optical signal generated by the light emitting unit 901b is transmitted to the optical transmission device 900a by the optical fiber cable 921 via the directional coupler 906b.

  In the optical transmission device 900a, an optical signal transmitted from the optical transmission device 900b via the optical fiber cable 921 is received by the light receiving unit 905a including a photodiode via the directional coupler 906a. The light receiving unit 905a converts the optical signal into an electrical signal, and outputs the converted electrical signal to the reception level detection circuit 904a. Then, the reception level detection circuit 904a outputs the electrical signal to the light emission control circuit 903a.

  The light emission control circuit 903a adjusts the output level of the optical signal to be transmitted by giving an instruction to the light output control circuit 902a when an electric signal composed of information requesting a change in setting of the output level of the optical signal is input. To do. Specifically, by controlling the light output control circuit 902a so that the light output control circuit 902a changes the bias current supplied to the laser diode of the light emitting unit 901a and the current value of the pulse current superimposed on the bias current. The light emission control circuit 903a adjusts the output level of the optical signal to be transmitted.

  On the other hand, when the optical signal is transmitted from the optical transmission device 900b to the optical transmission device 900a, the output level of the optical signal is similar to the procedure for transmitting the optical signal from the optical transmission device 900a to the optical transmission device 900b. Adjustments are made. In other words, the optical transmission device 900a on the receiving side detects the light reception intensity when receiving the optical signal, and if the detected light reception intensity is not normal, the optical transmission apparatus 900a includes information for requesting the setting change of the output level of the optical signal. The optical signal is transmitted to the optical transmission device 900b on the transmission side. Then, in the optical transmission device 900b on the transmission side, when receiving the optical signal composed of the request information for changing the output level of the optical signal, the light emission control circuit 903b gives an instruction to the optical output control circuit 902b to transmit the optical signal The output level is adjusted.

  As described above, the information requesting the setting change of the output level of the optical signal is sent to the optical transmission device on the transmission side via the optical fiber cable 921, that is, the same transmission path as the data to be transmitted and received. In order to distinguish between an optical signal composed of information requesting a change in setting of the output level of an optical signal and an optical signal composed of data to be transmitted / received, an optical signal flowing between optical transmission apparatuses via an optical fiber cable 921 is: It is a packet format with tag information added.

As a prior art related to the invention of this application, there is a technique described in Japanese Patent Application No. 2007-300540. This technique will be described later as a comparative example of the present invention.
JP-A-5-56002 (published March 5, 1993) JP 2004-104362 A (published on April 2, 2004)

  However, in the optical communication system described in Patent Document 1, an optical transmission path for transmitting an optical signal is provided in each of the opposite optical communication apparatuses, and the optical output increase / decrease data is superimposed on the main signal composed of transmission data. The transmission data is transmitted to the optical communication device, and the control information of the output level of the optical signal is transmitted. In the optical communication system described in Patent Document 2, an optical signal composed of data to be transmitted and received and an optical signal composed of information for requesting setting change of the output level of the optical signal are transmitted and received using the same optical transmission line. ing. Therefore, in the above two optical communication systems, in order to notify the information of the output level of the optical signal, it is essential that bidirectional optical transmission can be performed.

  For this reason, when there is no need to implement bidirectional optical transmission and optical transmission is performed in an environment that requires only unidirectional optical transmission, there is no means for transmitting setting change information for the output level of the optical signal, There is a problem that the setting of the output level of the signal cannot be changed. If the design change information of the output level of the optical signal is designed to be able to be transmitted to each other, it is necessary to always construct bidirectional optical transmission, which increases the cost.

  Further, in the optical communication system described in Patent Document 2, in order to transmit and receive an optical signal composed of data to be transmitted and received and an optical signal composed of setting change information of the output level of the optical signal using the same optical transmission path, There is a problem that the data to be transmitted / received must be in a packet format, and a problem that a separate conversion device is required when the data to be transmitted / received is not in a packet format.

  By the way, the required speed band of data transmission in equipment in recent years is increasing, and it is desired to adopt an optical transmission system using an optical fiber cable in various places. Approaches to achieve high-speed data transmission include a method of transmitting data using a single ultra-high-band optical fiber cable, or a parallel transmission using a conventional transceiver and multiple conventional low-band-width optical fiber cables. There is a way to transmit. Particularly in the transition period of the system, an optical transmission system is often used in which a conventional transmission / reception device and an optical fiber cable are used as they are, and the same kind of data is individually divided into a plurality of channels and transmitted in parallel.

  When parallel optical transmission of a plurality of channels is realized, it is necessary to introduce an APC function to the optical transmission device of each channel, which causes a problem that the system scale increases in proportion to the number of channels. In addition, APC control is complicated, and the time required for APC control of the entire optical transmission system is also affected.

  The present invention has been made in view of the above-described conventional problems, and an object thereof is not to require bidirectional optical transmission, but based on information on an output level of an optical signal obtained by an optical receiver. In a configuration capable of controlling the output level of an optical signal transmitted by a transmission apparatus, when realizing parallel optical transmission of a plurality of channels, the number of components in the system is reduced to the minimum necessary number, and a plurality of channels collectively APC An object of the present invention is to provide an optical transmission system capable of efficiently performing control.

  In order to solve the above problems, an optical transmission system according to the present invention is an optical transmission system in which a plurality of transmission / reception channels formed by one optical transmission device and one optical reception device are provided in parallel. A first serial interface provided on the installation side of the optical transmission device and a second serial interface connected to the plurality of optical reception devices, and each of the optical transmission devices has a drive current. A transmission means for transmitting an optical signal based on the above, a transmission storage means for storing the value of the drive current, a drive current created based on the communication data and the value of the drive current stored in the storage means for transmission. Each of the optical receivers receives the optical signal transmitted from the transmitter, and the receiver receives the optical signal transmitted from the transmitter. A detection unit that determines whether the signal has reached a predetermined intensity and outputs the determination result as a flag; and a reception storage unit that stores the flag, and includes the first serial interface and the second The serial interface is connected by a first serial bus, and the first serial interface receives a request signal for obtaining flag information stored in the reception storage means of the plurality of optical receivers. When the second serial interface receives the request signal, the second serial interface acquires flag information stored in the reception storage means of the plurality of optical receivers, and receives the request signal. A signal indicating flag information is transmitted to the first serial interface, and the first serial interface receives the signal from the outside. Based on the flag information, it is possible to refer to and update the value of the drive current stored in the transmission storage means of the plurality of optical transmission devices, and from the outside, the first serial interface and the second serial The flag stored in the receiving storage means of the plurality of optical receivers can be referred to and updated via the interface.

  According to the above configuration, the optical signal is transmitted and received between the optical transmission device and the optical reception device, and the first serial bus is a transmission path different from the optical transmission path of the optical signal, With the serial interface and the second serial interface, the flag information stored in the reception storage means of all the optical receivers is sent to the first serial interface.

  As a result, it is possible to obtain information on whether or not the optical signals of all the optical transmission devices have reached a predetermined intensity simply by accessing only the first serial interface. Based on this information, the value of the drive current stored in the transmission storage means of the plurality of optical transmitters is referred to and updated from outside, or via the first serial interface and the second serial interface. Thus, it is possible to control the output intensity of the optical signal transmitted from the transmission means by referring to and updating the flags stored in the reception storage means of the plurality of optical reception apparatuses.

  In addition, when a parallel optical transmission system with one-way multiple (N) channels that does not establish bidirectional optical transmission is constructed, 2 × N serial interfaces need to be provided, and 2 × N different types are provided. Although the bus ID must be prepared, in the optical transmission system of the present invention, even if the number of channels increases, only one serial interface needs to be provided on the transmission side and only one on the reception side. The number of bus IDs may be two.

  Therefore, in a system in which a multi-channel parallel optical transmission is constructed, it is possible to reduce the number of components in the system to the minimum necessary number and to efficiently perform multi-channel batch APC control.

  When incorporating the optical transmission system of the present invention into any application system, leaving the APC control program to the host processor of the application system not only increases the load on the host processor but also the entire application system. It can be complicated to control. For this reason, it is desirable that APC control is completed in the optical transmission system, and only the exchange of the APC control start signal and end signal is performed between the host processor and the optical transmission system.

  Therefore, the optical transmission system of the present invention is an optical transmission system in which a plurality of transmission / reception channels formed by one optical transmission device and one optical reception device are provided in parallel. A first serial interface provided on the installation side, a second serial interface connected to the plurality of optical receivers, and the plurality of optical transmitters and the first serial interface. Each of the optical transmission devices includes a transmission means for transmitting an optical signal based on a drive current, a transmission storage means for storing the value of the drive current, communication data, and the transmission memory. Drive means for supplying the transmission means with a drive current created based on the value of the drive current stored in the means, and each of the optical receivers A receiving unit that receives an optical signal transmitted from the transmitting unit; a detecting unit that determines whether the optical signal received by the receiving unit has reached a predetermined intensity; and outputs the determination result as a flag; and Receiving storage means for storing a flag, wherein the first serial interface and the second serial interface are connected by a first serial bus, and the first serial interface includes the plurality of optical interfaces. When the request signal for obtaining the flag information stored in the receiving storage means of the receiving device is transmitted to the second serial interface, and the second serial interface receives the request signal, The flag information stored in the receiving storage means of the optical receiver is obtained, and a signal indicating the flag information is sent to the first serial And the APC control circuit refers to the value of the drive current stored in the transmission storage means of the plurality of optical transmission devices based on the flag information received by the first serial interface and In addition to updating, the flag stored in the reception storage means of the plurality of optical receivers is referred to and updated via the first serial interface and the second serial interface.

  According to the above configuration, the above-described effects of the optical transmission system of the present invention can be obtained in the same manner, and the multiple channel batch APC control can be completed in the system by the processing of the APC control circuit.

  The APC control circuit triggers input of a control start request signal supplied from the outside to cause the first serial interface to start transmitting a request signal, and also stores transmission means for the plurality of optical transmission devices. When the update of the value of the drive current stored in is completed, it is preferable to output a control end notification signal to the outside.

  Alternatively, the APC control circuit triggers the input of a reset signal or a power-on signal to cause the first serial interface to start transmitting a request signal and is stored in the transmission storage means of the plurality of optical transmission devices. When the update of the drive current value is completed, it is preferable to output a control end notification signal to the outside.

  Thus, in the optical transmission system of the present invention, a control start request signal is issued from the outside (for example, a host) to the APC control circuit, or only a reset signal or a power-on signal is input to the optical transmission system. By the processing of the APC control circuit, it is possible to execute APC processing for all N channels. Further, when the execution is completed, a control end notification signal is issued from the APC control circuit to the outside. Therefore, it is possible to recognize the end of APC control only by observing one control end notification signal.

  In the optical transmission system of the present invention, the APC control circuit starts a process of updating the value of the drive current stored in the transmission storage means of a certain optical transmission device among the plurality of optical transmission devices. In this case, the drive current value stored in the transmission storage means of the optical transmitter is updated to the initial value, and the drive current value updated to the initial value is received by the first serial interface. When updating based on the flag information, it is preferable to update to a value obtained by adding a predetermined value.

  Further, the APC control circuit may include a storage unit that stores the initial value and a predetermined value used for the addition.

  This makes it possible to set a suitable value as the value of the drive current in advance. Therefore, in the present optical transmission system, it is possible to efficiently optimize the output level of the optical signal.

  Alternatively, the optical transmission system of the present invention includes a third serial interface connected to the plurality of optical transmission devices, a fourth serial interface connected to the plurality of optical reception devices, and the second serial interface. An arbitration circuit that performs arbitration when the serial interface and the fourth serial interface communicate with the plurality of optical receivers; and the third serial interface and the fourth serial interface are the second It is preferable that they are connected by a serial bus.

  According to the above configuration, from the third serial interface and the fourth serial interface connected to the second serial bus (for example, a public serial bus connected to an external host), a plurality of optical transmission devices and Each of the plurality of optical receivers can be accessed. Further, by providing the arbitration circuit, complicated control such as multi-master control due to the provision of the first serial bus and the second serial bus can be eliminated.

  Therefore, it is possible to refer to and update the value of the drive current stored in the transmission storage means of the plurality of optical transmission devices from the outside via the second serial bus and the third serial interface. Yes, it is desirable that the flags stored in the reception storage means of the plurality of optical receivers can be referred to and updated from the outside via the second serial bus and the fourth serial interface. .

  Further, the third serial interface is connected to the APC control circuit, and is stored in the storage means of the APC control circuit from the outside via the second serial bus and the third serial interface. It is desirable that the initial value and the predetermined value used for the addition can be referred to and updated.

  In the optical transmission system of the present invention, each of the optical transmission devices may further include parallel-serial conversion means for converting communication data given as parallel data into serial data and outputting the serial data to the driving means. . Each of the optical transmission devices preferably further includes 8B10B encoding means for performing 8B10B conversion on communication data given as parallel data and outputting the converted data to the parallel-serial conversion means.

  According to the above configuration, input / output of communication data to be transmitted between the optical transmitter and the external application system is performed in a parallel data state, thereby enabling data input / output using a low-speed synchronous clock. Thus, the present optical transmission system can be easily incorporated into an application system.

  Further, by further including 8B10B encoding means, it is possible to prevent transmission bit errors in high-speed serial transmission without placing an encoding processing load specific to serial data transmission on the application system.

  In the optical transmission system of the present invention, each of the optical receivers includes a demodulator that demodulates an optical signal output from the receiver into communication data of serial data, and serial data output from the demodulator. And serial / parallel conversion means for converting the communication data given in (5) into parallel data by detecting word communication by detecting that the communication data includes a predetermined parallel synchronization code. Good.

  Each of the optical receivers preferably further includes 8B10B decoding means for inversely converting communication data given as parallel data output from the serial / parallel conversion means.

  According to the above configuration, it is possible to perform data input / output using a low-speed synchronous clock by performing input / output of received communication data between the optical receiver and the external application system in a parallel data state. This optical transmission system can be easily incorporated into an application system.

  Further, by further providing 8B10B decoding means, it is possible to prevent transmission bit errors in high-speed serial transmission without applying a decoding processing load specific to serial data transmission to the application system.

  Each of the optical receivers further includes code storage means for storing the predetermined parallel synchronization code, and the plurality of optical receivers are externally connected via the second serial bus and the fourth serial interface. It is desirable that the parallel synchronization code stored in the code storage means can be referred to and updated.

  As described above, the optical transmission system of the present invention includes the first serial interface provided on the installation side of the plurality of optical transmission devices and the second serial interface connected to the plurality of optical reception devices. Each of the optical transmission devices is stored in a transmission means for transmitting an optical signal based on a drive current, a transmission storage means for storing the value of the drive current, a communication data, and a transmission storage means. Driving means for supplying the transmission current generated based on the value of the driving current to the transmission means, and each of the optical reception devices, receiving means for receiving the optical signal transmitted from the transmission means, A detector that determines whether the optical signal received by the receiver has reached a predetermined intensity and outputs the determination result as a flag; and a storage unit for reception that stores the flag. The serial interface is connected to the second serial interface via a first serial bus, and the first serial interface is flag information stored in the receiving storage means of the plurality of optical receivers. When the second serial interface receives the request signal, the flag stored in the receiving storage means of the plurality of optical receivers is transmitted to the second serial interface. And transmitting a signal indicating the flag information to the first serial interface, and the plurality of optical transmission devices based on the flag information received by the first serial interface from the outside. It is possible to refer to and update the value of the drive current stored in the transmission storage means, and from the outside, the above Via a serial interface and the second serial interface of a reference and updating are possible configuration flags stored in the reception memory means of said plurality of optical receiving devices.

  Therefore, it is possible to obtain information as to whether the optical signals of all the optical transmission devices have reached a predetermined intensity by accessing only the first serial interface. Based on this information, the value of the drive current stored in the transmission storage means of the plurality of optical transmitters is referred to and updated from outside, or via the first serial interface and the second serial interface. Thus, referring to and updating the flags stored in the reception storage means of the plurality of optical reception devices, the output intensity of the optical signal transmitted from the transmission means can be controlled.

  In the optical transmission system according to the present invention, even if the number of channels increases, only one serial interface needs to be provided on the transmission side and one on the reception side, and the number of bus IDs to be prepared is two. Good. Therefore, in a system in which a parallel optical transmission of a plurality of channels is constructed, it is possible to reduce the number of components in the system to the minimum necessary number and to perform a plurality of channels batch APC control efficiently.

  The optical transmission system of the present invention includes a first serial interface provided on the installation side of a plurality of optical transmitters, a second serial interface connected to the plurality of optical receivers, and the plurality of the plurality of optical transmitters. An optical transmission device and an APC control circuit connected to the first serial interface, each of the optical transmission devices transmitting a light signal based on a drive current, and a value of the drive current A transmission storage means for storing; and a drive means for supplying the transmission means with a drive current created based on communication data and a value of the drive current stored in the transmission storage means. Each of which determines a receiving means for receiving the optical signal transmitted from the transmitting means and whether or not the optical signal received by the receiving means has reached a predetermined intensity. The first serial interface is connected to the second serial interface by a first serial bus, and the first serial interface and the second serial interface are connected to the first serial interface. The serial interface transmits a request signal for obtaining flag information stored in the reception storage means of the plurality of optical receivers to the second serial interface, and the second serial interface When the request signal is received, the flag information stored in the reception storage means of the plurality of optical receivers is acquired, and a signal indicating the flag information is transmitted to the first serial interface. The APC control circuit, based on the flag information received by the first serial interface, has the plurality of optical transmission devices. The drive current value stored in the transmission storage means is referred to and updated, and stored in the reception storage means of the plurality of optical receivers via the first serial interface and the second serial interface. It is the structure which refers to and updates the flag currently set.

  Therefore, the operational effect of the above-described optical transmission system of the present invention can be obtained in the same manner, and the effect that the multi-channel batch APC control can be completed in the system by the processing of the APC control circuit.

[Embodiment 1]
An embodiment of the present invention will be described below with reference to the drawings.

(Configuration of optical transmission system)
FIG. 1 is a block diagram illustrating a configuration example of the optical transmission system 100 according to the present embodiment.

  As shown in FIG. 1, the optical transmission system 100 of the present embodiment includes N optical transmission devices 101a, 101b,..., 101n and N optical reception devices 102a, 102b,. And a serial interface (serial I / F) 103a (first serial interface) and a serial interface 103b (second serial interface). N indicates the number of transmission / reception channels that the optical transmission system 100 has, and is an integer of 2 or more.

  The optical transmission system 100 according to the present embodiment is constructed so as to have N transmission / reception channels for one-way transmission. In other words, the optical transmission device 101a is connected to the optical reception device 102a by the optical transmission path 104a, thereby forming a first transmission / reception channel. The optical transmission device 101b is connected to the optical reception device 102b through the optical transmission path 104b, thereby forming a second transmission / reception channel. Similarly, the optical transmitters 101c,..., 101n and the optical receivers 102c,..., 102n are connected by the optical transmission lines 104c,. ˜N transmission / reception channels are formed.

  The optical transmitters 101a, 101b,..., 101n and the optical receivers 102a, 102b,..., 102n are respectively connected to an external host (information processing device, etc.) not shown in the figure. Transfer data.

  The optical transmitters 101a, 101b,..., 101n all have the same configuration. The optical transmission device 101a will be described as an example. The optical transmission device 101a converts transmission data transferred from the outside via the electric wiring 106a into an optical signal, and transmits the optical signal via the optical transmission path 104a. Send to. The optical transmitter 101a determines the output level of the optical signal based on the drive current level given from the outside via the electric wiring 108a.

  The optical receivers 102a, 102b,..., 102n all have the same configuration. The optical receiver 102a will be described as an example. The optical receiver 102a receives an optical signal sent from the optical transmitter 101a via the optical transmission path 104a, converts the optical signal into received data, The data is transferred to the outside via the wiring 107a.

  The optical transmission lines 104a, 104b,..., 104n all have the same configuration, and are constructed by, for example, a wire that can transmit an optical signal such as an optical fiber cable. The optical transmission lines 104a, 104b,..., 104n are provided in parallel, the optical transmitters 101a, 101b,..., 101n are collectively installed on one end side, and the optical receivers on the other end side. 102a, 102b,..., 102n are installed together.

  The serial interfaces 103a and 103b are hardware interfaces capable of transmitting and receiving digital data by serial transmission. The serial interface 103a is provided on the installation side of the optical transmission devices 101a, 101b,. The serial interface 103b is provided on the installation side of the optical transmitters 101a, 101b,..., 101n, and is connected to the optical receivers 102a, 102b,. That is, the serial interface 103a and the serial interface 103b are respectively provided on both end sides across the N-channel optical transmission path.

  The serial interface 103a and the serial interface 103b are connected to each other by a serial bus 105 (first serial bus). As the serial bus 105, for example, a general-purpose serial bus typified by I2C or SPI is used, and the standard is not strictly defined.

  Different bus IDs are assigned to the serial interface 103a and the serial interface 103b, respectively. The serial interface 103 a has a bus master function of the serial bus 105, and the serial interface 103 b has a bus slave function of the serial bus 105.

(Configuration of optical transmitter)
Next, a detailed configuration of the optical transmission devices 101a, 101b,..., 101n configured in the optical transmission system 100 of the present embodiment will be described. Since all of the optical transmission apparatuses 101a, 101b,..., 101n have the same configuration, the optical transmission apparatus 120 will be described for convenience of explanation.

  FIG. 2 is a block diagram illustrating a schematic configuration of the optical transmission device 120.

  As shown in FIG. 2, the optical transmission device 120 includes a light emitting element 121 (transmission means), a light emitting element driver 122 (driving means), a driver control circuit 123, and a drive current level storage register 124 (transmission storage means). ing.

  The light emitting element 121 is formed of a laser diode, and emits light based on a driving current (drive current) supplied from the light emitting element driver 122 to generate an optical signal. When the light emitting element 121 emits light, an optical signal is transmitted to the optical receiver (for example, the optical receiver 102a) via the optical transmission path (for example, the optical transmission path 104a).

  The light emitting element driver 122 is a driver that drives the light emitting element 121 by supplying a driving current to the light emitting element 121. When the light emitting element driver 122 receives transmission data transferred from the outside via an electric wiring (for example, the electric wiring 106 a), the light emitting element driver 122 generates a driving current based on the transmission data and a control signal output from the driver control circuit 123. And output to the light emitting element 121.

  The driver control circuit 123 is a circuit that controls the drive current of the light emitting element driver 122 by giving a control signal to the light emitting element driver 122. The driver control circuit 123 generates a bias current and a modulation current as control signals based on the value of the drive current level storage register 124, and outputs them to the light emitting element driver 122.

  The drive current level storage register 124 (hereinafter abbreviated as a register 124) is a register that holds a bias current level and a modulation current level that determine an output level (output intensity) of an optical signal transmitted from the optical transmitter 120. is there. That is, the register 124 stores the value of the drive current. The register 124 can set a value in advance or refer to / update the value via an electric wiring (for example, the electric wiring 108a).

(Configuration of optical receiver)
Next, the detailed configuration of the optical receivers 102a, 102b,..., 102n configured in the optical transmission system 100 of the present embodiment will be described. The optical receivers 102a, 102b,..., 102n all have the same configuration, and will be described as the optical receiver 140 for convenience of explanation.

  FIG. 3 is a block diagram illustrating a schematic configuration of the optical receiver 140.

  As shown in FIG. 3, the optical receiver 140 includes a light receiving element 141 (receiving means), a light receiving TI amplifier (light receiving TI-AMP) 142, a limit amplifier (Limit AMP) 143, a CDR circuit 144 (demodulating means), and a light receiving state. A detection circuit 145 (detection means) and a flag storage register 146 (reception storage means) are provided.

  The light receiving element 141 is formed of a photodiode, and receives an optical signal transmitted from an optical transmission device (for example, the optical transmission device 101a) via an optical transmission path (for example, the optical transmission path 104a) and converts it into an electrical signal. And output to the light receiving TI amplifier 142.

  The light receiving TI amplifier 142 is an amplifier that converts an electric signal output from the light receiving element 141 into a current-voltage. The light receiving TI amplifier 142 outputs the converted electric signal to the limit amplifier 143.

  The limit amplifier 143 is an amplifier that amplifies the electrical signal output from the light receiving TI amplifier 142 so that the CDR circuit 144 can easily identify the received data as received data. The limit amplifier 143 outputs the amplified electrical signal to the CDR circuit 144 and also outputs it to the light receiving state detection circuit 145.

  The CDR circuit 144 decomposes the electrical signal output from the limit amplifier 143 bit by bit by a clock whose phase relationship with the electrical signal is dynamically adjusted, and decodes it as meaningful received serial data. The CDR circuit 144 outputs the received serial data to the outside via an electric wiring (for example, the electric wiring 107a).

  The light reception state detection circuit 145 determines whether the electrical signal output from the limit amplifier 143 has reached a predetermined intensity. The light reception state detection circuit 145 outputs a flag “1” to the flag storage register 146 when the predetermined intensity is reached, and a flag “0” when the predetermined signal intensity is not reached.

  The flag storage register 146 (hereinafter abbreviated as a register 146) is a register that holds the value of the flag output from the light receiving state detection circuit 145. The register 146 can refer to the value or clear 0 through an electrical wiring (for example, the electrical wiring 109a).

(Operation of optical transmission system)
Next, optical transmission in the optical transmission system 100 of the present embodiment will be described with reference to FIGS.

  In the optical transmission device 101a, when transmission data is sent from the outside, the light emitting element driver 122 inputs this transmission data. The light emitting element driver 122 generates a drive current for driving the light emitting element 121 based on the transmission data and a control signal supplied from the driver control circuit 123, that is, a bias current and a modulation current, and outputs the drive current to the light emitting element 121. The light emitting element 121 transmits an optical signal created by emitting light based on the supplied drive current to the optical receiving device 102a via the optical transmission path 104a.

  In the optical receiver 102a, when an optical signal is transmitted via the optical transmission path 104a, the light receiving element 141 receives the optical signal. The light receiving element 141 converts the optical signal into an electrical signal and outputs the electrical signal to the light receiving TI amplifier 142. This electrical signal is output to the outside as received data through the processing of the light receiving TI amplifier 142, the limit amplifier 143, and the CDR circuit 144 in order. Thus, one-way optical transmission is performed in the first transmission / reception channel.

  Similarly, in other transmission / reception channels, on the condition that transmission data is sent from the outside, the transmission condition is between the optical transmission apparatuses 101b,..., 101n and the optical reception apparatuses 102b,. One-way optical transmission is performed.

  Next, output level optimization control in the optical transmission system 100 will be described.

  The optimization control is performed while optical transmission is performed between the optical transmission apparatuses 101a, 101b,..., 101n and the optical reception apparatuses 102a, 102b,. During optical transmission, the optical transmitters 101a, 101b,..., 101n determine the output level of the optical signal according to the value of the register 124, and the optical receivers 102a, 102b,. A flag “1” indicating that the optical signal has reached a predetermined intensity or a flag “0” indicating that the optical signal has not reached a predetermined intensity is stored in the register 146.

  As shown in FIG. 1, the optimization control of the output level of the optical signal is started when a serial interface control signal is sent from the outside to the serial interface 103a via the electric wiring 110.

  In the optimization control, serial data communication is performed via the serial bus 105 between the serial interface 103a and the serial interface 103b. In most cases of the present embodiment, the serial interface 103a functions as a bus master that controls the protocol for serial data communication, and the serial interface 103b functions as a bus slave for serial data communication.

  First, the serial interface 103a creates a request signal that inquires the serial interface 103b whether the intensity of the optical signal received by the optical receivers 102a, 102b,..., 102n reaches a predetermined intensity. Send to.

  Alternatively, the serial interface 103a may create a request signal for clearing the contents of the register 146 of the optical receivers 102a, 102b,..., 102n before transmitting the inquiry, and transmit the request signal to the serial interface 103b. Upon receiving this request signal, the serial interface 103b clears the contents of the register 146 of the optical receivers 102a, 102b,. Then, the serial interface 103b outputs a signal indicating a 0 clear result to the serial interface 103a.

  When the serial interface 103b receives the inquiry request signal, the serial interface 103b acquires information indicating whether the intensity of the optical signal received by the optical receivers 102a, 102b,..., 102n has reached a predetermined intensity. That is, the serial interface 103b acquires the flag stored in the register 146 of the optical receivers 102a, 102b,..., 102n via the electrical wirings 109a, 109b,. Then, the serial interface 103b transmits a signal indicating flag information to the serial interface 103a.

  When the serial interface 103a receives a signal indicating flag information transmitted from the serial interface 103b via the serial bus 105, the serial interface 103a outputs the signal to the outside via the electrical wiring 110.

  As a result, the external host can recognize whether or not the output levels of the optical signals of all the channels have reached a predetermined intensity by checking the signal indicating the flag information.

  If the predetermined intensity is reached, the host ends the output level control of the optical signal, or transmits a serial interface control signal to the serial interface 103a, for example, according to a preset interval, and outputs the optical signal. Monitor the level.

  On the other hand, if the predetermined strength is not reached, the host refers to the values of the registers 124 of all the optical transmission devices 101a, 101b,..., 101n via the electrical wirings 108a, 108b,. And update. Then, the serial interface control signal is transmitted again to the serial interface 103a, and a signal indicating flag information is acquired by serial data communication to check whether the output level of the optical signal has reached a predetermined signal strength. By repeating this process until the output levels of the optical signals of all channels reach a predetermined intensity, the output level of the optical signal can be optimized.

  As described above, the external host refers to and updates the value of the register 124 via the electric wirings 108a, 108b,..., 108n, and via the electric wirings 109a, 109b,. The value of the register 146 can be referred to and cleared to zero. Therefore, the optimization control in the N-channel optical transmission can be efficiently performed by programming the combination of the reference and update of the drive current level and the reference and clearing of the flags in an appropriate order.

  As described above, in the optical transmission system 100 according to the present embodiment, optical signals are transmitted and received between the optical transmitters 101a, 101b,..., 101n and the optical receivers 102a, 102b,. , 104n, which is a transmission path different from the optical transmission paths 104a, 104b,..., 104n of the optical signal called the serial bus 105, and the optical receivers 102a, 102b,. , 102n, information indicating whether the intensity of the optical signal received at the predetermined level has been reached is sent to the serial interface 103a.

  As a result, it is possible to obtain information on whether or not the optical signals of all the channels have reached a predetermined intensity only by accessing only the serial interface 103a. Then, based on this information, the output level of the optical signal transmitted from the light emitting element 121 can be controlled by updating the value of the register 124 of the optical transmitters 101a, 101b,. It becomes possible.

  Therefore, in the optical transmission system 100, it is possible to optimize the output level of the optical signal to be transmitted by acquiring information on the intensity of the optical signal in a batch for N channels regardless of the one-way optical transmission. Yes.

  Further, when a one-way N-channel parallel optical transmission system in which bidirectional optical transmission is not established is constructed, it is necessary to provide 2 × N serial interfaces as in an optical transmission system 800 of a comparative example described later. Furthermore, 2 × N different bus IDs must be prepared.

  On the other hand, in the optical transmission system 100, no matter how many channels the number of channels increases, only one serial interface needs to be provided on the transmission side and only one on the reception side, and the number of bus IDs to be prepared is two. One is enough. Therefore, the number of components in the system can be reduced to the minimum necessary number, and the multi-channel batch APC control can be efficiently performed.

(Other examples of optical transmitter)
In the optical transmission system 100 described above, the configuration of the optical transmission devices 101a, 101b,..., 101n is not limited to the configuration of the optical transmission device 120 shown in FIG. The configuration may be 160.

  FIG. 4 is a block diagram illustrating a schematic configuration of the optical transmission device 160.

  As shown in FIG. 4, the optical transmission device 160 includes a light emitting element 161, a light emitting element driver 162, a driver control circuit 163, a drive current level storage register 164, a parallel serial conversion circuit (P / S conversion circuit) 165 (parallel serial conversion). And an 8B10B encoding circuit (8B10BEnc circuit) 166 (8B10B encoding means).

  The light emitting element 161, the light emitting element driver 162, the driver control circuit 163, and the drive current level storage register 164 are the same as the light emitting element 121, the light emitting element driver 122, the driver control circuit 123, and the register 124 illustrated in FIG. The description thereof will be omitted.

  The parallel-serial conversion circuit 165 converts the 10-bit width parallel data output from the 8B10B encoding circuit 166 into serial data. The parallel / serial conversion circuit 165 outputs the converted serial data to the light emitting element driver 162.

  The 8B10B encoding circuit 166 converts 8-bit parallel data (8-bit parallel data) transferred from the outside via an electrical wiring (for example, the electrical wiring 106a) into 10-bit parallel data (10-bit parallel data). Convert to The 8B10B encoding circuit 166 outputs the converted 10-bit parallel data to the parallel-serial conversion circuit 165.

  Here, the detailed operation of the 8B10B encoding circuit 166 will be described.

  In the optical transmission device 120, the light emitting element driver 122 inputs the transmission data sent from the outside as it is. However, in the optical transmission device 160, the light emitting element driver 162 includes the 8B10B encoding circuit 166, so that the light emitting element driver 162 is encoded. The sent transmission data is input.

  A 1-bit comma code (K code) identification flag is sent to the 8B10B encoding circuit 166 from the outside through an electrical wiring (for example, the electrical wiring 106a) together with 8-bit parallel data.

  When the comma code identification flag is “0”, it indicates that 8-bit parallel data is normal transmission data. As a result, the 8B10B encoding circuit 166 performs normal encoding on the 8-bit parallel data and converts it to 10-bit parallel data.

  When the comma code identification flag is “1”, it indicates that the 8-bit parallel data is a special comma code different from normal transmission data. Thereby, the 8B10B encoding circuit 166 performs special encoding different from normal encoding on the 8-bit parallel data, and converts the data into 10-bit parallel data.

  Note that 10-bit parallel data subjected to normal encoding and 10-bit parallel data subjected to special encoding are set so as not to have the same value. Special comma codes are used for various types of transmission protocols, such as a start code indicating the beginning of valid data to be transmitted and an end code indicating the end of valid data to be transmitted to an external host. It is used as an identification code.

  There are two conversion tables for encoding from 8 bits to 10 bits in the 8B10B encoding circuit 166: a conversion table in the table (+) and a conversion table in the back (−). The 8B10B encoding circuit 166 dynamically switches between the front conversion table and the reverse conversion table every time 8-bit parallel data is input in order to play two roles.

  The first role is to perform 10-bit encoding so that the composition ratio between bit “0” and bit “1” of the serial data output from the parallel-serial conversion circuit 165 is about 50 percent. is there. For example, in the 8B10B encoding circuit 166, when the number of bits “1” is larger than the number of bits “0” in the configuration of certain 10-bit parallel data encoded, the next input 8 For bit parallel data, the front and back conversion tables are switched so that the number of bits “0” is larger.

  The second role is to reduce the number of consecutive bits “0” and consecutive bits “1” in the serial data output from the parallel-serial conversion circuit 165 to 4 or less (in the case of a comma code, 5 or less). It is to be. In each 10-bit parallel data encoded by the 8B10B encoding circuit 166, five or more bits “0” or “1” do not continue (six or more in the case of a comma code). The front and back conversion tables are switched so that five or more bits (0 or six) in the case of comma codes do not continue across two consecutive 10-bit parallel data. For example, in the 8B10B encoding circuit 166, when the end of certain 10-bit parallel data that is encoded is composed of “0” that is continuous, the next input 8-bit parallel data is encoded. The conversion tables on the front and back sides are switched so that consecutive “0” s are not included at the beginning of the 10-bit parallel data to be converted.

  The above two roles of the 8B10B encoding circuit 166 are functions necessary for eliminating transmission bit errors in high-speed serial transmission. Therefore, it is desirable to use the optical transmission device 160 also in the optical transmission system 100, and it is possible to prevent transmission bit errors in high-speed serial transmission.

  Further, by using the optical transmission device 160, transmission / output of transmission data between the optical transmission device and an external host can be performed in a parallel data state, and data input / output may be performed using a low-speed synchronous clock. Therefore, the optical transmission system 100 can be easily incorporated into an application system. In addition, the processing load of encoding peculiar to serial data transmission is not applied to the application system.

  The optical transmission device 160 includes both the parallel-serial conversion circuit 165 and the 8B10B encoding circuit 166. However, the configuration is not limited to this, and the configuration may include only the parallel-serial conversion circuit 165.

(Other examples of optical receiver)
In the optical transmission system 100 described above, the configuration of the optical receivers 102a, 102b,..., 102n is not limited to the configuration of the optical receiver 140 shown in FIG. In particular, when the configuration of the optical transmission devices 101a, 101b,..., 101n has the configuration of the optical transmission device 160 shown in FIG. 4, the configuration of the optical reception device 180 as shown in FIG. desirable. As a result, the transmission bit error prevention function in high-speed serial transmission can be further enhanced.

  FIG. 5 is a block diagram illustrating a schematic configuration of the optical receiver 180.

  As shown in FIG. 5, the optical receiver 180 includes a light receiving element 181, a light receiving TI amplifier 182, a limit amplifier 183, a CDR circuit 184, a light receiving state detection circuit 185, a flag storage register 186, a serial / parallel conversion circuit (S / P conversion). Circuit) 187 (serial parallel conversion means), a parallel synchronization code storage register 188 (code storage means), and an 8B10B decoding circuit (8B10Bdec circuit) 189 (8B10B decoding means).

  Note that the light receiving element 181, the light receiving TI amplifier 182, the limit amplifier 183, the CDR circuit 184, the light receiving state detection circuit 185, and the flag storage register 186 are shown in FIG. 3 as the light receiving element 141, the light receiving TI amplifier 142, and the limit amplifier 143. Since it has the same function as the CDR circuit 144, the light reception state detection circuit 145, and the flag storage register 146, description thereof is omitted.

  The serial / parallel conversion circuit 187 converts the received serial data output from the CDR circuit 184 into parallel data in units of 10 bits based on the value of the parallel synchronization code having a 10-bit width held in the parallel synchronization code storage register 188. To divide. The serial / parallel conversion circuit 187 outputs the 10-bit parallel data to the 8B10B decoding circuit 189.

  In the serial-parallel conversion circuit 187, the received serial data output from the CDR circuit 184 includes a 10-bit sequence corresponding to the 10-bit width parallel synchronization code held in the parallel synchronization code storage register 188. Always monitor whether or not. When the serial-to-parallel conversion circuit 187 detects that the received serial data includes 10 bits corresponding to the parallel synchronization code, the serial-to-parallel conversion circuit 187 sets the received serial data as the head of the detected 10 bits. Divide into parallel data every 10 bits.

  The parallel synchronization code storage register 188 is a register that holds a 10-bit width parallel synchronization code. The parallel synchronization code storage register 188 outputs the parallel synchronization code held in the serial / parallel conversion circuit 187.

  The 8B10B decoding circuit 189 converts the 10-bit parallel data output from the serial / parallel conversion circuit 187 into 8-bit parallel data. The 8B10B decoding circuit 189 outputs the converted 8-bit parallel data to the outside via the electric wiring (for example, the electric wiring 107a).

  Here, the detailed operation of the 8B10B decoding circuit 189 will be described.

  The optical receiving apparatus 140 outputs the received serial data decoded by the CDR circuit 144 to the outside, but the optical receiving apparatus 180 includes the 8B10B decoding circuit 189 so that the 8B10B decoding circuit 189 decodes it. The received parallel data is output to the outside.

  From the 8B10B decoding circuit 189, a 1-bit comma code (K code) identification flag is output to the outside through the electrical wiring (for example, the electrical wiring 107a) together with the 8-bit parallel data.

  When the comma code identification flag is “0”, it indicates that 8-bit parallel data is normal transmission data. Further, when the comma code identification flag is “1”, it indicates that the 8-bit parallel data is a special comma code different from normal transmission data.

  The conversion process from the 10-bit parallel data to the 8-bit parallel data in the 8B10B decoding circuit 189 corresponds to the inverse conversion of the conversion process from the 8-bit parallel data to the 10-bit parallel data in the 8B10B encoding circuit 166. The 8-bit parallel data and 1-bit comma code identification flag output from the 8B10B decoding circuit 189 completely match the 8-bit parallel data and 1-bit width comma code identification flag input to the 8B10B encoding circuit 166. .

  In the optical transmission system 100, by using the optical receiver 180, input / output of received data between the optical receiver and an external host can be performed in a parallel data state, and data input / output is performed using a low-speed synchronous clock. Therefore, the optical transmission system 100 can be easily incorporated into the application system. In addition, the application processing system is not subjected to a decoding processing load specific to serial data transmission.

  Note that the optical receiving device 180 includes both the serial-parallel conversion circuit 187 and the 8B10B decoding circuit 189, but the configuration is not limited thereto, and only the serial-parallel conversion circuit 187 may be provided.

[Comparative example]
A comparative example of the present invention will be described with reference to FIG.

  FIG. 12 is a block diagram showing a configuration of an optical transmission system 800 of this comparative example.

  As shown in FIG. 12, the optical transmission system 800 includes N optical transmitters 801a, 801b,..., 801n, N optical receivers 802a, 802b,. , 803n, N reception side serial interfaces 804a, 804b,..., 804n, and N transmission side APC control circuits 805a, 805b,. And N receiving side APC control circuits 806a, 806b,..., 806n. N indicates the number of transmission / reception channels that the optical transmission system 800 has, and is an integer of 2 or more.

  The optical transmitters 801a to 801n and the optical receivers 802a to 802n are connected by optical transmission lines 810a to 810n in a one-to-one relationship. Thereby, N transmission / reception channels for one-way transmission are formed in parallel.

  The transmission-side serial interfaces 803a to 803n and the reception-side serial interfaces 804a to 804n are connected to a common serial bus 811.

  The transmission side APC control circuits 805a to 805n are connected to the optical transmission devices 801a to 801n, respectively, and also connected to the transmission side serial interfaces 803a to 803n. The transmission side APC control circuits 805a to 805n are connected to an external host 807a.

  The reception side APC control circuits 806a to 806n are connected to the reception side serial interfaces 804a to 804n, respectively. The receiving side APC control circuits 806a to 806n are connected to an external host 807b.

  Since the transmission-side serial interfaces 803a to 803n and the reception-side serial interfaces 804a to 804n are connected to the common serial bus 811, each serial interface can be uniquely identified on the serial bus 811. A different bus ID is assigned to each serial interface. In addition, the same value as the bus ID assigned to each serial interface connected to each APC control circuit is also input to the transmission side APC control circuits 805a to 805n and the reception side APC control circuits 806a to 806n. .

  As a result, in the optical transmission system 800, since there are N serial interfaces on the transmission side and N on the reception side, 2 × N different bus IDs are used in total.

  Next, the operation of the optical transmission system 800 will be described.

  First, APC start request signals are simultaneously input from the host 807a to the transmission side APC control circuits 805a to 805n and from the host 807b to the reception side APC control circuits 806a to 806n.

  Each APC control circuit shifts to an APC processing state when an APC start request signal is input. However, since 2 × N serial interfaces are connected to the common serial bus 811, APC of each transmission channel is not performed at the same time, and APC is performed in order for each channel.

  The execution order of APC for each channel is defined by the value of the bus ID. It is assumed that APC is executed first for the transmission channel having the smallest bus ID, and this is the channel for the optical transmission path 810a.

  The transmission-side APC control circuit 805a optimizes the optical output level of the optical transmission device 801a while observing the reception state of the optical reception device 802a using the transmission-side serial interface 803a as a bus master and the reception-side serial interface 804a as a bus slave. When the optimization is completed, the transmission side APC control circuit 805a outputs an APC end notification signal to the host 807a and the reception side APC control circuit 806a outputs to the host 807b.

  Furthermore, it is assumed that the next smallest bus ID is the channel of the optical transmission line 810b. At this time, the transmission side APC control circuit 805a sends an APC end notification signal to the transmission side serial interface 803b and the reception side serial interface 804b via the transmission side serial interface 803a and the reception side serial bus 811. Thereby, the APC processing of the optical transmission line 810b is similarly started.

  Subsequently, N-channel APC proceeds according to the bus ID, and the hosts 807a and 807b receive all N APC completion notification signals, thereby recognizing that the APC of the entire optical transmission system 800 has been completed.

  As described above, in the optical transmission system 800, each transmission channel is unidirectional, and feedback of the optical reception state using the bidirectional optical transmission channel cannot be performed. Therefore, APC using the general-purpose serial bus 811 is performed. It has been broken.

  However, if the multi-channel optical transmission system is configured as shown in FIG. 12, 2 × N bus IDs for uniquely identifying the serial interface on the serial bus 811 are required. It is not very suitable for incorporation into some application system.

  This is because the application system uses many devices in addition to the optical transmission system, and these devices are already connected on the general-purpose serial bus because the host processor controls them. This is because there are many. Therefore, with a limited number of terminals of the optical transmission system, it is easy to secure 2 × N bus IDs without overlapping with the bus IDs used by other connected devices. I can't say that.

  Also, 2 × N APC control circuits are provided. When all the APC control circuits input / output the APC start request signal and the APC end notification signal to the host processor, the host processor ends N APCs. Since a process for aggregating the notification signals is required, a slightly complicated image may be given when introducing and providing the optical transmission system to the application side.

  Furthermore, the communication of the APC end notification signal between the transmission channels via the serial bus also complicates the control of the APC control circuit and affects the time required for APC of the entire optical transmission system. Become.

  On the other hand, the above-described optical transmission system 100 is configured to realize unidirectional parallel optical transmission of a plurality of channels, but requires two bus IDs. Further, as described in the second embodiment, only one APC control circuit needs to be provided, and the control of the APC control circuit is simplified, which is suitable for incorporation into an application system.

[Embodiment 2]
The following will describe another embodiment of the present invention with reference to the drawings. Configurations other than those described in the present embodiment are the same as those in the first embodiment. For convenience of explanation, members having the same functions as those shown in the drawings of the first embodiment are given the same reference numerals, and explanation thereof is omitted.

  When considering incorporating the optical transmission system of the present invention into any application system, leaving the APC control program to the host processor of the application system not only increases the load on the host processor, but also controls the entire application system. Can be complicated.

  For this reason, it is desirable that the APC control is completed within the optical transmission system, and only a start signal and an end signal of the APC control are exchanged between the host processor and the optical transmission system. Specifically, the host processor simply outputs an APC control start request signal to the optical transmission system, and the optical transmission system performs all APC controls. When all the APC controls are completed, the optical transmission system performs APC control. It is desirable to output an end notification signal to the host processor.

  FIG. 6 is a block diagram illustrating a configuration example of the optical transmission system 200 according to the present embodiment.

  As shown in FIG. 6, the optical transmission system 200 according to the present embodiment includes an APC control circuit 201 in addition to the configuration of the optical transmission system 100 according to the first embodiment.

  The APC control circuit 201 is a control unit that performs APC control on the output level of the optical signal output from the optical transmitters 101a, 101b,. The APC control circuit 201 is provided on the installation side of the optical transmitters 101a, 101b,. The APC control circuit 201 is connected to the optical transmitters 101a, 101b,..., 101n via the electric wirings 203a, 203b,..., 203n, and is connected to the serial interface 103a via the electric wiring 204. It is connected to an external host 202 via wirings 205 and 206.

  The APC control circuit 201 refers to and updates the value of the drive current stored in the register 124 of the optical transmitters 101a, 101b,..., 101n via the electrical wirings 203a, 203b,. It can be carried out.

  In addition, the APC control circuit 201 uses the bus master function of the serial interface 103a to cause the serial interface 103b to function as a bus slave, so that the optical receivers 102a, 102b,. The flag stored in the register 146 can be referred to and cleared to zero.

  Further, the APC control circuit 201 receives an APC start request signal from the host 202 via the electric wiring 205 and outputs an APC end notification signal to the host 202 via the electric wiring 206. When an APC start request signal is input, the APC control circuit 201 starts and executes all N-channel APC processes, and outputs an APC end notification signal after all N-channel APC processes are completed.

  Next, output level optimization control in the optical transmission system 200 of the present embodiment will be described.

  Here, it is assumed that the optical transmission system 200 is incorporated in some application system. A host 202 that controls the entire application system including the optical transmission system 200 exists outside the optical transmission system 200, and the host 202 is connected to the APC control circuit 201.

  In the optical transmission system 100 described in the first embodiment, the output level (drive current level) is adjusted from the outside. However, the optical transmission system 200 of the present embodiment includes the APC control circuit 201. Thus, APC control is completed within the optical transmission system. The output level optimization control will be described below with the operation of the APC control circuit 201 as the main axis.

  For convenience of explanation, the optical transmission devices 101a, 101b,..., 101n are represented as optical transmission devices 1 to N, and the optical reception devices 102a, 102b,. The optical transmission lines 104a, 104b,..., 104n are denoted as optical transmission lines 1 to N.

  FIG. 7 is a flowchart showing a processing flow of the APC control circuit 201.

  The APC control circuit 201 is initially waiting for input of an APC start request signal. The APC control circuit 201 starts APC control when receiving an APC start request signal sent from the host 202 outside the optical transmission system 200 via the electric wiring 205 (step S10a). Alternatively, the APC control circuit 201 may start APC control by inputting a reset signal (or a power-on signal) (step S10b).

  Subsequently, the APC control circuit 201 resets the value of the counter K to 0 (step S11). When the APC control circuit 201 receives an APC control start command, the APC control circuit 201 first follows the APC of the first transmission / reception channel, then the APC of the second transmission / reception channel, and finally the APC of the Nth transmission / reception channel. Thus, APC control of the entire optical transmission system 200 is performed. This sequential application is prescribed in advance. The APC control circuit 201 includes a counter K for managing the number of transmission / reception channels currently executing APC. For example, if the value of the counter K is M, the APC control circuit 201 This means that APC is being executed.

  In addition, in any channel APC processing, the serial interface 103a and the serial interface 103b are commonly used as a bus master and a bus slave, respectively.

  Subsequently, the optical transmitters 1 to N transmit dummy optical signals to the optical receivers 1 to N (step S12). During execution of APC of the entire optical transmission system 200, dummy optical signals are continuously input to all of the first to Nth transmission / reception channels. The dummy signal input here may have any content, and need not be meaningful data, but is preferably repetitive data such as “010101...”. Further, the transmission source of the dummy signal is not limited to the optical transmission devices 1 to N, and may be outside the optical transmission system 200.

  For example, in the case of the configuration shown in FIG. 2 in which the optical transmission devices 1 to N do not include the parallel-serial conversion circuit 165 and the 8B10B encoding circuit 166, a function of repeatedly transmitting the above-described data to the light-emitting element driver 122. Therefore, the transmission source of the dummy signal is “external”. On the other hand, when the optical transmitters 1 to N have the configuration shown in FIG. 4, an additional function for automatically issuing dummy data can be added to the parallel-serial conversion circuit 165. Of course, dummy data is input from the outside. It is also possible. As a result, the transmission source of the dummy data can be selected from either “external” or “optical transmission device”.

  In addition, since it is considered that the input of the dummy optical signal is often controlled by an external host, the start timing of the input of the dummy optical signal does not have to be after the start of APC of the entire optical transmission system 200. The host 202 may be before issuing the APC start request signal.

  Subsequently, when starting APC for a new transmission / reception channel, the APC control circuit 201 adds 1 to the value of the counter K (step S13). That is, APC of the first transmission / reception channel is performed immediately after the start of APC of the entire optical transmission system 200.

  The APC processing flow limited to the Kth transmission / reception channel will be described below.

  When the APC process of the Kth transmission / reception channel is started, the APC control circuit 201 sets the value of the register 124 to a predetermined initial level via the electric wiring 203k (step S14). The APC control circuit 201 preferably includes an internal memory for storing the initial level.

  Subsequently, the APC control circuit 201 clears the flag of the optical receiving device K to 0 (step S15). Specifically, the APC control circuit 201 outputs a request signal for clearing the register 146 of the optical receiving device K to the serial interface 103a through the electric wiring 204. Upon receiving this request signal, the serial interface 103 a sends a request signal for clearing the register 146 to the serial interface 103 b via the serial bus 105. The serial interface 103b clears the register 146 to 0 via the electric wiring 109k. Thereafter, the serial interface 103 b sends a 0 clear result to the serial interface 103 a via the serial bus 105. The serial interface 103a outputs a 0 clear result to the APC control circuit 201.

  Subsequently, the APC control circuit 201 refers to the flag of the optical receiver K (step S16). Specifically, the APC control circuit 201 outputs a request signal that refers to the contents of the register 146 of the optical receiver K to the serial interface 103a via the electrical wiring 204. When receiving the request signal, the serial interface 103 a sends a request signal referring to the contents of the register 146 to the serial interface 103 b via the serial bus 105. The serial interface 103b refers to the contents of the register 146 via the electric wiring 109k. Thereafter, the serial interface 103b sends the reference result to the serial interface 103a via the serial bus 105. The serial interface 103a outputs the reference result to the APC control circuit 201.

  Here, the communication speed of the serial bus 105 (assuming a maximum of several tens of megahertz) is sufficiently slower than the communication speed of the optical transmission lines 1 to N (assuming 1 gigahertz or more). When attention is paid to this, the light reception state detection circuit 145 outputs the electrical signal output from the limit amplifier 143 between the timing when the register 146 is cleared to 0 (step S15) and the timing when the register 146 is referred to (step S16). There is sufficient time to determine whether or not has reached a predetermined strength. Therefore, the APC control circuit 201 receives the 0 clear result of the register 146 from the serial interface 103a without worrying about whether or not the light reception state detection circuit 145 has completed the determination. The process from step S15 to step S16 can be advanced.

  Subsequently, the APC control circuit 201 determines whether the received light intensity of the optical signal has reached a predetermined intensity by looking at the reference result of the register 146 sent from the serial interface 103a (step S17).

  At this time, if the flag reference result is “0”, that is, if the received light intensity does not reach the predetermined intensity (No in step S17), the APC control circuit 201 considers that the drive current level is not yet close to the optimum value. . Thereby, in order to continue the APC process of the Kth transmission / reception channel, the APC control circuit 201 adds and updates the value of the register 124 by a predetermined difference level via the electrical wiring 203k (step S18). It should be noted that the difference level is also preferably stored in the internal memory of the APC control circuit 201. When the update of the register 124 is completed, the process returns to the process of clearing the register 146 to 0 (step S15), and the APC control circuit 201 performs the processes of steps S15 to S17 again.

  On the other hand, when the reference result of the flag is “1”, that is, when the received light intensity reaches the predetermined intensity (Yes in step S17), the APC control circuit 201 considers the drive current level to be the optimum value. Thereby, the value of the register 124 is held at the current value, and the APC process of the Kth transmission / reception channel is ended.

  Thus, while it is determined that the received light intensity has not reached the predetermined intensity (No in step S17), the processes in steps S15 to S18 are repeated. When it is determined that the received light intensity has reached a predetermined intensity (Yes in step S17), or when the drive current level has reached the maximum controllable level in step S18, the processes in steps S15 to S18 are completed. To do.

  After completing the APC process for the Kth transmission / reception channel, the APC control circuit 201 determines whether the value of the counter K is equal to N (step S19). Here, when the value of the counter K is equal to N (Yes in step S19), the APC processing for all the first to Nth transmission / reception channels is completed, so the APC processing of the entire optical transmission system 200 is completed. Considered complete.

  If the value of the counter K is less than N (No in step S19), the APC process of the entire optical transmission system 200 continues. In this case, the process returns to step S13, 1 is added to the value of the counter K, and the APC process of the (K + 1) th transmission / reception channel is started. Until the APC process of the Nth transmission / reception channel is completed, the processes of steps S15 to S18 are performed again.

  As described above, while it is determined that the value of the counter K is less than N (No in step S19), in other words, until the APC processing for all the first to Nth transmission / reception channels is completed, step S13 is performed. The process of S19 is repeated.

  After completing the APC processing for all of the first to Nth transmission / reception channels, the APC control circuit 201 outputs an APC end notification signal to the host 202 via the electrical wiring 206 (step S20). Thereby, the APC processing of the entire optical transmission system 200 is completed.

  As described above, in the optical transmission system 200, when N-channel APC is executed, signals related to the start and end of APC processing are exchanged between the optical transmission system 200 (APC control circuit 201) and the external host 202. Therefore, the burden on the external host 202 can be reduced.

  In other words, in the optical transmission system 200, the APC control is performed simply by issuing an APC start request signal from the host 202 to the APC control circuit 201 or by inputting a reset signal or a power-on signal to the optical transmission system 200. Control of the circuit 201 makes it possible to execute APC processing for all N channels. Further, since the APC end notification signal is issued from the APC control circuit 201 to the host 202 when the execution is completed, the host 202 can know the end of APC only by observing one APC end notification signal. Therefore, the control for performing the APC processing of the optical transmission system 200 from the host 202 can be greatly simplified.

  Also, for control to shift from APC processing of a certain channel to APC processing to the next channel, it is necessary to send an APC end notification signal via a general-purpose serial bus as in the optical transmission system 800 of the comparative example shown in FIG. Therefore, only the state control process in the APC control circuit 201 can be performed. Since the time required for the state control process in the APC control circuit 201 is much shorter than the time required for the communication of the serial bus 105, it contributes to the reduction of the processing time related to the entire APC process.

[Embodiment 3]
The following will describe another embodiment of the present invention with reference to the drawings. Configurations other than those described in the present embodiment are the same as those in the first and second embodiments. For convenience of explanation, members having the same functions as those shown in the drawings of the first and second embodiments are given the same reference numerals, and explanation thereof is omitted.

  In consideration of incorporating the optical transmission system of the present invention into any application system, it is desirable to complete APC control in the optical transmission system. In the second embodiment, the configuration for realizing this has been described.

  In many application systems to which the host 202 belongs, a general-purpose serial bus such as the serial bus 105 is often provided. Therefore, it is further desirable that the host 202 can arbitrarily refer to and update all the registers including the register 124, the register 146, and the parallel synchronization code storage register 188 included in the optical transmission system 200.

  For example, FIG. 8 shows a configuration when it is assumed that the serial bus 105 of the optical transmission system 200 shown in FIG. 6 is shared with the public serial bus (serial bus 251) managed by the host 202 of the application system. .

  As shown in FIG. 8, in the optical transmission system 250, the serial interface 103a and the serial interface 103b are respectively connected to the serial bus 251 to which the host 202 is conventionally connected.

  However, in the optical transmission system 250, the host 202 can be a bus master in the serial bus 251 and the serial interface 103a can also be a bus master in the serial bus 251. The fact that two or more bus masters are connected to one common serial bus is called a multi-master and makes the control of the serial bus very difficult.

  The difficult process in the multi-master is the arbitration process of the serial bus when the host 202 tries to start communication as the bus master of the serial bus 251 and the serial interface 103a also starts communication as the bus master of the serial bus 251. is there. In the conventional application system, the host 202 is the only bus master, but by incorporating the optical transmission system 250 into the application system, a multi-master state is obtained, and the control of the host 202 is greatly complicated.

  In this embodiment, an optical transmission system that solves the problem of the multi-master will be described.

  FIG. 9 is a block diagram illustrating a configuration example of the optical transmission system 300 according to the present embodiment.

  As shown in FIG. 9, in addition to the configuration of the optical transmission system 200 of the second embodiment, the optical transmission system 300 of the present embodiment has a serial interface 301a (third serial interface) and a serial interface 301b ( A fourth serial interface) and an arbiter circuit 302 (arbitration circuit). In the optical transmission system 300, for the sake of simplicity, the register 124, the register 146, the parallel synchronization code storage register 188, the predetermined initial code and the predetermined difference code described in the second embodiment are used. It is assumed that a plurality of storage registers are collectively provided as a register group 303a on the transmission side and a register group 303b on the reception side.

  The serial interfaces 301a and 301b are hardware interfaces capable of transmitting and receiving digital data by serial transmission. The serial interface 301a is provided on the installation side of the optical transmission devices 101a, 101b,..., 101n, and is connected to the optical transmission devices 101a, 101b,. The serial interface 301b is provided on the installation side of the optical receivers 102a, 102b,..., 102n, and is connected to the optical receivers 102a, 102b,.

  The serial interface 301a and the serial interface 301b are commonly connected to a public serial bus (serial bus 304 (second serial bus)) to which the external host 202 is connected. Both the serial interface 301a and the serial interface 301b have a bus slave function of the serial bus 304, and the internal circuit thereof may have the same configuration as the serial interface 103b.

  The register group 303a can be directly referenced and updated from the APC control circuit 201. On the serial bus 304, the host 202 becomes a bus master and the serial interface 301a becomes a bus slave, so that the register group 303a can be referred to and updated.

  The register group 303b can be referred to and updated on the serial bus 105 by making the serial interface 103a a bus master and the serial interface 103b a bus slave. Alternatively, on the serial bus 304, the host 202 becomes a bus master and the serial interface 301b becomes a bus slave, so that the register group 303b can be referred to and updated.

  As described above, the serial interfaces 301 a and 301 b are only bus slaves of the serial bus 304, and are not bus masters of the serial bus 304.

  The arbiter circuit 302 arbitrates communication with the register group 303b for the serial interface 103b and the serial interface 301b. For example, when the serial interface 103b and the serial interface 301b attempt to perform reference or update to the register group 303b at the same time, the arbiter circuit 302 first permits reference or update by one of the serial interfaces, and performs reference or update processing. Is completed, the reference and update order control to the register group 303b is performed such that the reference or update by the other serial interface is permitted.

  The arbiter circuit 302 is connected between the serial interface 103b and the serial interface 301b and the optical receivers 102a, 102b,. The serial interface 103 b and the serial interface 301 b can access the register group 303 b for reference and update via the arbiter circuit 302.

  Next, output level optimization control in the optical transmission system 300 of the present embodiment will be described. The optical transmission system 300 is based on the output level optimization control of the optical transmission system 200 described in the second embodiment, and a configuration / process for solving the multi-master problem is added. Hereinafter, a configuration / process for solving the problem of multi-master will be described.

  FIG. 10 is a block diagram showing an example of a signal connection relationship between the arbiter circuit 302 and the serial interface 103b / 301b when an I2C bus is adopted as the serial bus 105/304.

  FIG. 11 is a timing chart showing signal timings when both serial interfaces 103b / 301b perform Read processing on the register group 303b. Read_en, sel, and address are internal signals of the arbiter circuit 302.

  As shown in FIG. 10, a register read request signal Read_Req_0 / 1 and a register local address Address_0 / 1 are connected from the serial interface 103b / 301b to the arbiter circuit 302. Conversely, a register read permission signal Read_Ack_0 / 1 and read data Read_Data_0 / 1 are connected from the arbiter circuit 302 to the serial interface 103b / 301b.

  Since serial bus 105/304 is an I2C bus, SCL0 / 1 and SDA0 / 1 are connected from serial bus 105/304 to serial interface 103b / 301b. The clock signal CLK input to the arbiter circuit 302 is a clock having a frequency that is about four times or more the frequency of SCL0 / 1.

  When the serial interface 103b / 301b becomes an I2C slave and communication is started, the serial interface 103b / 301b determines that the data read request from the register group 303b and the local address of the data to be read are determined. High of the register read request signal Read_Req_0 / 1 is output to the arbiter circuit 302 for a period corresponding to a half cycle of / 1.

  In the arbiter circuit 302, the rising edge of the clock signal CLK is defined as a “detection” phase, and the falling edge of the clock signal CLK is defined as a “processing” phase. In the arbiter circuit 302, the high period of the register read request signal Read_Req_0 and the low period of the register read enable signal Read_Ack_0 are defined as the valid period of the register read request 0, and the high period of the register read request signal Read_Req_1 and the register read enable signal The Low period of Read_Ack_1 is defined as the valid period of the register read request 1.

  In the “detection” phase, during the valid period of the register read request 0/1, the arbiter circuit 302 selects one of the local addresses Address_0 / 1 to generate the internal address signal address.

  In the “processing” phase, the arbiter circuit 302 reads data corresponding to the selected internal address signal address from the register group 303b. Then, the arbiter circuit 302 outputs the register read permission signal Read_Ack_0 / 1 at High simultaneously with outputting to the read data Read_Data_0 / 1.

  Priorities are determined in advance for the register read request 0/1. In the “detection” phase, when the register read requests 0 and 1 are simultaneously valid, for example, it is determined that the register read request 0 is given priority, and in the immediately subsequent “processing” phase, the read data Read_Data_0 and the register read are read. High of the permission signal Read_Ack_0 is output. In the next “detection” phase, the register read request 0 is an invalid period. Therefore, the internal address signal address is generated from the local address Address_1, and in the next “processing” phase, the read data Read_Data_1 and the register read enable signal Read_Ack_1 are High. Is output.

  Since the arbiter circuit 302 executes processing corresponding to two register read requests 0/1 over two cycles of the clock signal CLK, the clock signal CLK is 2 during the High period of the register read request signal Read_Req_0 / 1. It is a condition for the arbitration process to include more than a period.

  As described above, in the optical transmission system 300, the APC of the entire optical transmission system 300 can be automatically completed only by exchanging the APC start request signal and the APC end notification signal between the host 202 and the APC control circuit 201. In addition, the application system host 202 requires complex control such as serial bus multi-master control for register values of various parameters that can be set in the optical transmission system 300 using the serial bus 304. It is possible to freely access (reference and update) without having to do so.

  Therefore, not only the method of executing the APC processing of the optical transmission system 300 using the input of the APC start request as a trigger, but also the host 202 refers to the flag stored in the register 146 of the optical receivers 102a to 102n. A programmable method of updating the drive current level stored in the register 124 of the optical transmitters 101a to 101n can also be selected.

  Therefore, according to the configuration of the optical transmission system 300, the ease of incorporation into the application system can be remarkably improved.

  Further, in the optical transmission system 300, no matter how many transmission channels the number of transmission channels is increased, it is only necessary to connect at most two serial interfaces on the serial bus 304 to which the host 202 of the application system is connected as a bus master. Two bus IDs should be prepared.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  INDUSTRIAL APPLICABILITY The present invention can be suitably used in the field related to an optical transmission system for optimizing the output level of an optical signal transmitted to a plurality of parallel channels, as well as the field related to an optical transmission method and optical transmission for constructing an optical transmission system. The present invention can be widely used in the field relating to devices, and further in the field relating to the manufacture of optical transmission devices.

It is a block diagram which shows one Embodiment of the optical transmission system in this invention. It is a block diagram which shows one of the structures of the optical transmitter in the said optical transmission system. It is a block diagram which shows one of the structures of the optical receiver in the said optical transmission system. It is a block diagram which shows the other structure of the optical transmitter in the said optical transmission system. It is a block diagram which shows the other structure of the optical receiver in the said optical transmission system. It is a block diagram which shows other embodiment of the optical transmission system in this invention. It is a flowchart which shows the process of the APC control circuit in the said optical transmission system. FIG. 7 is a block diagram showing a configuration when the optical transmission system shown in FIG. 6 is modified to use a public serial bus managed by a host as a serial bus between serial interfaces. It is a block diagram which shows other embodiment of the optical transmission system in this invention. It is a block diagram which shows the signal connection relationship of each serial interface and an arbiter circuit in the said optical transmission system. It is a timing chart which shows the timing of the signal processing of the said arbiter circuit. It is a block diagram which shows the structure of the optical transmission system in the comparative example of this invention. It is a block diagram which shows the structure of the conventional optical transmission system.

Explanation of symbols

100, 200, 300 Optical transmission systems 101a, 101b,..., 101n Optical transmitters 102a, 102b,..., 102n Optical receivers 103a Serial interface (first serial interface)
103b Serial interface (second serial interface)
104a, 104b,..., 104n Optical transmission line 105 Serial bus (first serial bus)
120,160 Optical transmission device 121,161 Light emitting element (transmission means)
122, 162 Light emitting element driver (driving means)
123, 163 Driver control circuit 124, 164 Drive current level storage register (transmission storage means)
140,180 Optical receiver 141,181 Light receiving element (receiving means)
142,182 light receiving TI amplifier 143,183 limit amplifier 144,184 CDR circuit (demodulation means)
145, 185 Light reception state detection circuit (detection means)
146, 186 Flag storage register (reception storage means)
165 Parallel serial conversion circuit (parallel serial conversion means)
166 8B10B encoding circuit (8B10B encoding means)
187 Serial-parallel conversion circuit (serial-parallel conversion means)
188 Parallel synchronization code storage register (code storage means)
189 8B10B decoding circuit (8B10B decoding means)
201 APC control circuit 202 Host 301a Serial interface (third serial interface)
301b Serial interface (fourth serial interface)
302 Arbiter circuit (arbitration circuit)
303a, 303b Register group 304 Serial bus (second serial bus)

Claims (14)

In an optical transmission system in which a plurality of transmission / reception channels formed by one optical transmission device and one optical reception device are provided in parallel,
A first serial interface provided on the installation side of the plurality of optical transmission devices;
A second serial interface connected to the plurality of optical receivers,
Each of the optical transmitters is
Transmitting means for transmitting an optical signal based on the drive current;
Transmission means for storing the value of the drive current;
Drive means for supplying the transmission means with the drive current created based on the communication data and the value of the drive current stored in the transmission storage means,
Each of the optical receivers is
Receiving means for receiving the optical signal transmitted from the transmitting means;
Detecting means for determining whether the optical signal received by the receiving means has reached a predetermined intensity, and outputting the determination result as a flag;
Receiving storage means for storing the flag,
The first serial interface and the second serial interface are connected by a first serial bus,
The first serial interface transmits a request signal for obtaining flag information stored in the reception storage means of the plurality of optical receivers to the second serial interface;
When the second serial interface receives the request signal, the second serial interface acquires flag information stored in the reception storage means of the plurality of optical receiving apparatuses, and transmits a signal indicating the flag information to the first serial interface. To the serial interface of
Based on the flag information received by the first serial interface from the outside, it is possible to refer to and update the value of the drive current stored in the transmission storage means of the plurality of optical transmission devices, and from the outside An optical transmission system capable of referencing and updating the flags stored in the reception storage means of the plurality of optical receivers via the first serial interface and the second serial interface. . In an optical transmission system in which a plurality of transmission / reception channels formed by one optical transmission device and one optical reception device are provided in parallel,
A first serial interface provided on the installation side of the plurality of optical transmission devices;
A second serial interface connected to the plurality of optical receivers;
A plurality of optical transmitters and an APC control circuit connected to the first serial interface,
Each of the optical transmitters is
Transmitting means for transmitting an optical signal based on the drive current;
Transmission means for storing the value of the drive current;
Drive means for supplying the transmission means with the drive current created based on the communication data and the value of the drive current stored in the transmission storage means,
Each of the optical receivers is
Receiving means for receiving the optical signal transmitted from the transmitting means;
Detecting means for determining whether the optical signal received by the receiving means has reached a predetermined intensity, and outputting the determination result as a flag;
Receiving storage means for storing the flag,
The first serial interface and the second serial interface are connected by a first serial bus,
The first serial interface transmits a request signal for obtaining flag information stored in the reception storage means of the plurality of optical receivers to the second serial interface;
When the second serial interface receives the request signal, the second serial interface acquires flag information stored in the reception storage means of the plurality of optical receiving apparatuses, and transmits a signal indicating the flag information to the first serial interface. To the serial interface of
The APC control circuit refers to and updates the value of the drive current stored in the transmission storage means of the plurality of optical transmission devices based on the flag information received by the first serial interface. An optical transmission system characterized by referring to and updating a flag stored in the reception storage means of the plurality of optical receivers via the first serial interface and the second serial interface.   The APC control circuit uses the input of a control start request signal supplied from the outside as a trigger to cause the first serial interface to start transmitting a request signal and stores it in the transmission storage means of the plurality of optical transmission devices 3. The optical transmission system according to claim 2, wherein when the update of the drive current value is completed, a control end notification signal is output to the outside.   The APC control circuit triggers input of a reset signal or a power-on signal to start transmission of a request signal to the first serial interface, and is stored in the transmission storage means of the plurality of optical transmission devices. The optical transmission system according to claim 2, wherein when the update of the value of the drive current is completed, a control end notification signal is output to the outside. The APC control circuit is
Among the plurality of optical transmission devices, when starting the process of updating the value of the drive current stored in the transmission storage unit of a certain optical transmission device, it is stored in the transmission storage unit of the optical transmission device. Update the drive current value to the initial value,
The drive current value updated to the initial value is updated to a value obtained by adding a predetermined value when the drive current value is updated based on the flag information received by the first serial interface. 2. The optical transmission system according to 2.   6. The optical transmission system according to claim 5, wherein the APC control circuit has storage means for storing the initial value and a predetermined value used for the addition. A third serial interface connected to the plurality of optical transmission devices;
A fourth serial interface connected to the plurality of optical receivers;
An arbitration circuit that performs arbitration when the second serial interface and the fourth serial interface communicate with the plurality of optical receivers;
The optical transmission system according to claim 1, wherein the third serial interface and the fourth serial interface are connected by a second serial bus. The drive current value stored in the transmission storage means of the plurality of optical transmission devices can be referred to and updated from the outside via the second serial bus and the third serial interface.
The flag stored in the receiving storage means of the plurality of optical receivers can be referred to and updated from the outside via the second serial bus and the fourth serial interface. The optical transmission system according to claim 7. A third serial interface connected to the plurality of optical transmission devices;
A fourth serial interface connected to the plurality of optical receivers and connected by the third serial interface and a second serial bus;
The third serial interface is connected to the APC control circuit,
It is possible to refer to and update the initial value and the predetermined value used for the addition stored in the storage means of the APC control circuit from the outside via the second serial bus and the third serial interface. The optical transmission system according to claim 6, wherein the optical transmission system is provided. Each of the optical transmitters is
10. The optical transmission according to claim 1, further comprising parallel-serial conversion means for converting communication data given as parallel data into serial data and outputting the serial data to the driving means. system. Each of the optical transmitters is
11. The optical transmission system according to claim 10, further comprising 8B10B encoding means for performing 8B10B conversion on communication data given as parallel data and outputting the communication data to the parallel-serial conversion means. Each of the optical receivers is
Demodulating means for demodulating the optical signal output from the receiving means into serial data communication data;
Serial parallel that converts communication data given as serial data output from the demodulating means into parallel data by detecting word communication by detecting that the communication data includes a predetermined parallel synchronization code. The optical transmission system according to claim 1, further comprising conversion means. Each of the optical receivers is
13. The optical transmission system according to claim 12, further comprising 8B10B decoding means for inversely converting communication data given as parallel data output from the serial / parallel conversion means. Each of the optical receivers is
Code storage means for storing the predetermined parallel synchronization code;
The parallel synchronization code stored in the code storage means of the plurality of optical receivers can be referred to and updated from the outside via the second serial bus and the fourth serial interface. The optical transmission system according to claim 12.

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