JP6842869B2 - Station side termination device - Google Patents

Description

The present invention relates to a station-side termination device, and more particularly to a station-side termination device that performs optical communication with a plurality of subscriber-side devices.

The PON (Passive Optical Network) system, which is known as a subscriber optical fiber network for subscribers' homes such as general households, uses a single optical fiber connected to an OLT (Optical Line Thermal). This is an optical transmission system that branches by an optical splitter, connects to a plurality of ONUs (Optical Network Units), and shares one optical fiber among a plurality of users. In the PON system, one optical fiber is shared by a plurality of users, so that the service can be provided at a low fiber laying cost.

In the PON system, continuous optical signals are transmitted by a broadcast method in the case of downlink communication from OLT to ONU, and in the case of uplink communication from ONU to OLT, in order to avoid collision of optical signals, time is required. Intermittent optical signals (optical burst signals) are transmitted by the division method.

Further, as the transmission capacity increases, the 10G-EPON (10Gigabit-Ethernet Passive) specified by IEEE (Institute of Electrical and Electronics Engineers) 802.3av, which enables communication at a transmission speed of 10 Gbit / s, is possible. , And ITU-T (International Telecommunication Union Telecommunication Union Telecommunication Union Standardization sector) G.I. The XG-PON specified in 987 has appeared. For these 10G optical transmitters on the OLT side, a technique of keeping the temperature of the LD (Laser Diode) constant with respect to a change in the environmental temperature to prevent the optical transmission wavelength shift due to the temperature may be used.

Generally, the optical transmitter on the OLT side includes a thermoelectric element that generates and cools heat and cools by an electric current represented by a Peltier element, and a TEC (Thermo-Electric Cooler) controller for controlling the thermoelectric element. .. In the temperature control by the TEC controller, the temperature of the LD is read by a temperature sensor such as a thermistor, and information such as a current or a voltage corresponding to the read temperature is fed back to the TEC controller. The TEC controller controls the temperature of the LD so that the current or voltage indicated by the fed-back information becomes constant corresponding to the target temperature.

For example, as such a conventional technique, there is an optical transmitter described in Patent Document 1. This optical transmitter includes an LD, a drive circuit, a temperature sensor, a LUT (look-up table), a compensating circuit, and a control circuit. The compensating circuit acquires a compensating coefficient corresponding to the temperature of the LD detected by the temperature sensor from the LUT, and generates a compensating signal in which the monitor signal is compensated by the compensating coefficient. The control circuit controls the drive current of the drive circuit based on the error between the compensation signal and the predetermined reference voltage.

JP-A-2007-59537

In general, LD has a temperature dependence such that the drive current is small at a low temperature, the drive current is large at a high temperature, and the oscillation wavelength is shifted depending on the temperature. In order to eliminate the temperature dependence, temperature control is performed using a thermoelectric element such as a Peltier element and a TEC controller.

In the temperature control, a certain target temperature Tld is determined as in the prior art, and the control is performed so that the temperature of the LD becomes the target temperature Tld. Here, for example, when the target temperature Tld is set low, when the ambient temperature around the LD is high, a large amount of current is consumed for cooling by the thermoelectric element. On the contrary, when the target temperature Tld is set high, the thermoelectric element heats the LD when the ambient temperature around the LD is low, and the drive current of the LD increases when the ambient temperature around the LD is high. Therefore, a large amount of current is consumed.
Therefore, even if there is an LD having good characteristics at a high temperature (a sufficient light output can be obtained with a small current), in the conventional technology, the LD is controlled to a constant target temperature Tld, and wasteful power is generated. It will be consumed.

Therefore, an object of the present invention is to reduce the power consumption of the station-side termination device.

The station-side termination device according to one aspect of the present invention is a station-side termination device that performs optical communication with a plurality of subscriber-side devices, and is an optical transmitter that transmits an optical signal and the plurality of subscriber-side devices. Each includes an optical receiver that receives received power information indicating the received power of the optical signal transmitted by the optical transmitter, and the optical transmitter includes a light emitting element that emits light according to a drive current. A drive unit that controls the drive current, a thermoelectric element that heats or cools the light emitting element according to an input current, a temperature detection unit that detects the temperature of the thermoelectric element as a detection temperature, and the detection temperature are set. A temperature control unit that controls the input current and a control unit that sets the target temperature in the temperature control unit are provided so that the target temperature is reached. The control unit changes the target temperature and receives the light. By confirming the received power indicated by the power information, the target temperature range, which is the range of the target temperature at which all the received powers in the plurality of subscriber-side devices are equal to or higher than the predetermined first threshold value, is specified. The temperature within the target temperature range is set as the optimum target temperature in the temperature control unit.

According to one aspect of the present invention, the power consumption of the station-side termination device can be reduced by varying the target temperature of the thermoelectric element.

It is a block diagram which shows schematic structure of the optical communication system 100 which concerns on Embodiment 1. FIG. It is a block diagram which shows schematic structure of ONU in Embodiment 1. FIG. (A) and (B) are schematic views showing a hardware configuration example. It is a block diagram which shows schematic structure of OLT in Embodiment 1. FIG. It is a block diagram which shows schematic structure of the control part in Embodiment 1. FIG. (A) to (C) are schematic views for explaining the control of the optical transmission wavelength of OLT in Embodiment 1.

Embodiment 1.
FIG. 1 is a block diagram schematically showing the configuration of the optical communication system 100 according to the first embodiment.
The optical communication system 100 is a PON system including a plurality of ONU 110A, 110B, 110C, ..., And an OLT 130.
When it is not necessary to distinguish each of the plurality of ONU110A, 110B, 110C, ..., It is referred to as ONU110.
In the optical communication system 100, the OLT 130 performs optical communication with a plurality of ONU 110s.

In the optical communication system 100, one optical fiber 101 connected to the OLT 130 is branched into a plurality of optical fibers 103A, 103B, 103C, ... By an optical splitter 102.
When it is not necessary to distinguish each of the plurality of optical fibers 103A, 103B, 103C, ..., It is referred to as an optical fiber 103.

FIG. 2 is a block diagram schematically showing the configuration of the ONU 110.
The ONU 110 includes a WDM (Wavelength Division Multiplexing) filter 111, a bandpass filter 112, a light receiving element 113, a light emitting element 114, and a control unit 115.

The WDM filter 111 combines and separates light of different wavelengths.
The bandpass filter 112 selects and transmits light of a specific wavelength.
The light receiving element 113 is a light receiving unit composed of a PD (Photodiode) or the like.
The light emitting element 114 is a light emitting unit composed of an LD or the like.
The control unit 115 controls the processing in the ONU 110. For example, the control unit 115 has a DDM (Digital Diagnostics Measurement) function for measuring the received power (received power) of an optical signal defined in the SFF-8472 standard. Then, the control unit 115 generates light-receiving power information indicating the light-receiving power of the light-receiving element 113, and transmits the information to the OLT 130 via the light-emitting element 114.

The optical signal from the light emitting element 114 is transmitted to the OLT 130 via the optical fiber 103 after passing through the WDM filter 111.
On the other hand, the optical signal transmitted from the OLT 130 enters from the optical fiber 103, is reflected by the WDM filter 111, and is detected by the light receiving element 113 through the bandpass filter 112.

As shown in FIG. 3A, for example, a part or all of the control unit 115 described above includes a memory 10 and a CPU (Central Processing Unit) that executes a program stored in the memory 10. ) And the like. Such a program may be provided through a network, or may be recorded and provided on a recording medium.

Further, as shown in FIG. 3B, for example, a part or all of the control unit 115 includes a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, and an ASIC (Application Specific Integrated Circuitd). It can also be configured by a processing circuit 12 such as a Circuits) or an FPGA (Field Processor Gate Array).

FIG. 4 is a block diagram schematically showing the configuration of the OLT 130.
The OLT 130 includes an OLT optical receiver 140, an environmental temperature detection unit 141, a host-side control unit 142, and an OLT optical transmitter 150.

The OLT optical receiver 140 is an optical receiver that receives an optical signal from the optical fiber 101. For example, the OLT optical receiver 140 receives an optical signal of the received power information SI from each ONU 110, and gives the received received power information SI to the host side control unit 142.
The environmental temperature detection unit 141 detects the environmental temperature, which is the ambient temperature of the OLT 130. For example, the environmental temperature detection unit 141 can acquire the difference from the environmental temperature by learning in advance using the temperature detection function of an MCU (MicroControl Unit) or the like which is usually used as a control unit of a transceiver. it can. The environmental temperature detection unit 141 gives the host side control unit 142 the environmental temperature information STI indicating the detected environmental temperature.
The host-side control unit 142 controls the entire processing in the OLT 130. For example, the host-side control unit 142 gives the received power information SI and the environmental temperature information STI to the OLT optical transmitter 150.

The OLT optical transmitter 150 is an optical transmitter that transmits an optical signal to the optical fiber 101.
The OLT optical transmitter 150 includes an LD 151, an LD drive circuit 152, a thermoelectric element 153, a thermistor 154, a TEC controller 155, and a control unit 160.

The LD 151 is a light emitting element that emits light according to the drive current DI input from the LD drive circuit 152. The LD 151 gives a monitor current MI indicating its own light emitting power to at least one of the LD drive circuit 152 and the control unit 160.
The LD drive circuit 152 is a drive unit that controls the drive current DI input to the LD 151 based on the data given from the host side control unit 142 and the monitor current MI. The LD drive circuit 152 provides the control unit 160 with drive current information DII indicating the drive current DI set by the LD drive circuit 152.

The thermoelectric element 153 is a heating / cooling unit such as a Peltier element that heats or cools the LD 151 according to the input current II input from the TEC controller 155.
The thermistor 154 is a temperature detection unit that detects the temperature of the thermoelectric element 153 as a detection temperature. The thermistor 154 provides the TEC controller 155 and the control unit 160 with the detected temperature information TI indicating the detected temperature.
The TEC controller 155 inputs an input current II to the thermoelectric element 153 so that the detection temperature indicated by the detection temperature information TI given by the thermistor 154 becomes the target temperature Tld indicated by the target temperature information given by the control unit 160. It is a temperature control unit that controls. The TEC controller 155 provides the control unit 160 with input current information III indicating an input current II to be input to the thermoelectric element 153.

The control unit 160 controls the processing in the OLT optical transmitter 150. For example, the control unit 160 changes the target temperature Tld set in the TEC controller 155 and confirms the received power indicated by the received power information SI from each ONU 110, whereby the received power in all ONU 110s is predetermined. The target temperature range, which is the range of the target temperature Tld that is equal to or higher than the threshold value (first threshold value), is specified.

Further, the control unit 160 sets the temperature within the specified target temperature range as the optimum target temperature Tld in the TEC controller 155.
Here, the optimum target temperature Tld is a temperature at which the sum of the input current II input to the thermoelectric element 153 and the drive current DI input to the LD 151 is minimized, so that the power consumption of the OLT optical transmitter 150 is minimized. It becomes.

FIG. 5 is a block diagram schematically showing the configuration of the control unit 160.
The control unit 160 includes a transmission line information calculation unit 161, an APC control unit 162, and a Tld adjustment unit 163.

The transmission line information calculation unit 161 collects the received power information SI from each ONU 110 via the host side control unit 142, and based on the received power indicated by the received power information SI, the target temperature Tld is in the range of the target temperature Tld. Identify the temperature range.
The APC control unit 162 constantly controls the light emitting power of the LD 151 based on the monitor current MI from the LD 151. Further, the APC control unit 162 gives the drive current information DII from the LD drive circuit 152 to the Tld adjustment unit 163.

The Tld adjustment unit 163 sets the target temperature Tld in the TEC controller 155. When the transmission line information calculation unit 161 specifies the target temperature range, the Tld adjustment unit 163 specifies the optimum target temperature Tld within this target temperature range, and sets the optimum target temperature Tld to the TEC controller 155. Set. For example, the Tld adjustment unit 163 identifies the optimum target temperature Tld based on the environmental temperature information STI, the detected temperature information TI, the input current information III, and the drive current information DII.
Specifically, when the environmental temperature indicated by the environmental temperature information STI is included in the target temperature range, the Tld adjustment unit 163 sets the environmental temperature as the target temperature Tld in the TEC controller 155. When the ambient temperature is not included in the target temperature range, the Tld adjustment unit 163 uses the minimum value (when the ambient temperature is lower than the target temperature range) or the maximum value (when the ambient temperature is lower than the target temperature range) of the target temperature range. (If high) is set in the TEC controller 155 as the target temperature Tld. Then, in the process until the temperature of the thermoelectric element 153 (detection temperature detected by the thermistor 154) reaches the set target temperature, the detection temperature at the time when the sum of the input current II and the drive current DI becomes the minimum is optimized. Specify as the target temperature Tld.

Hereinafter, the processing in the control unit 160 will be specifically described.
First, the transmission line information calculation unit 161 changes the target temperature Tld set by the Tld adjustment unit 163 in the TEC controller 155, and confirms the received power indicated by the received power information SI sent from each ONU 110. , Specify the target temperature range.

For example, the transmission line information calculation unit 161 gradually raises the target temperature Tld from the initial value Tld−d of the predetermined target temperature Tld to the Tld adjustment unit 163, and receives light from all the connected ONU 110s. The maximum value Tld-max of the target temperature Tld at which the power becomes equal to or higher than a predetermined threshold is detected.
Specifically, the transmission line information calculation unit 161 causes the Tld adjustment unit 163 to raise the predetermined temperature (ΔT) from the initial value Tld−d of the predetermined target temperature Tld, and then raises the temperature (ΔT) from the thermistor 154. When the detection temperature indicated by the detection temperature information TI reaches the target temperature Tld, the light-receiving power information SI sent from each ONU 110 is confirmed, and the light-receiving power of all the connected ONU 110s is predetermined. It is judged whether or not it is equal to or higher than the threshold value. When the received power received by all ONU 110s is equal to or higher than a predetermined threshold value, the temperature set in the Tld adjusting unit 163 at that time is set as the maximum value Tld-max of the target temperature Tld. When the received power received by all ONU 110s is equal to or higher than a predetermined threshold value, the transmission line information calculation unit 161 causes the Tld adjustment unit 163 to further raise the temperature (ΔT) predetermined to each ONU 110. Check the received power information SI sent from. By repeating the above processing until any received power indicated by the received power information SI sent from the ONU 110 becomes smaller than a predetermined threshold value, the transmission line information calculation unit 161 can set the target temperature Tld. The maximum value Tld-max can be specified.

Further, for example, the transmission line information calculation unit 161 gradually lowers the target temperature Tld from the initial value Tld-d of the predetermined target temperature Tld to the Tld adjustment unit 163, and all the ONU 110s connected to the Tld adjustment unit 163. The minimum value Tld-min of the target temperature Tld at which the received power is equal to or higher than a predetermined threshold is detected.
Specifically, the transmission line information calculation unit 161 causes the Tld adjustment unit 163 to lower the predetermined temperature (ΔT) from the initial value Tld−d of the predetermined target temperature Tld, and then causes the thermistor 154 to lower the temperature (ΔT). When the detection temperature indicated by the detection temperature information TI reaches the target temperature Tld, the light-receiving power information SI sent from each ONU 110 is confirmed, and the light-receiving power of all the connected ONU 110s is predetermined. It is judged whether or not it is equal to or higher than the threshold value. When the received power received by all ONU 110s is equal to or higher than a predetermined threshold value, the temperature set in the Tld adjusting unit 163 at that time is set as the minimum value Tld-min of the target temperature Tld. Further, when the received power received by all the ONU 110s is equal to or higher than a predetermined threshold value, the transmission line information calculation unit 161 causes the Tld adjustment unit 163 to further lower the temperature (ΔT) by a predetermined temperature. Check the received power information SI sent from the ONU110. By repeating the above processing until any received power indicated by the received power information SI sent from the ONU 110 becomes smaller than a predetermined threshold value, the transmission line information calculation unit 161 can set the target temperature Tld. The minimum value Tld-min can be specified.

By the above processing, the transmission line information calculation unit 161 sets the range of the minimum value Tld-min or more and the maximum value Tld-max or less as the target temperature range. The transmission line information calculation unit 161 provides the Tld adjustment unit 163 with target temperature range information indicating the target temperature range specified as described above.

6 (A) to 6 (C) are schematic views for explaining the control of the optical transmission wavelength of the OLT 130 in the first embodiment. In the optical communication system 100, which is an actual PON system, a plurality of ONU 110s are connected to one OLT 130. The ONU 110 to be connected may be manufactured by a plurality of companies. In such a case, the characteristics of the bandpass filter 112 applied to each ONU 110 are different as shown in FIGS. 6 (A) to 6 (C).

Therefore, by using the DDM function of the ONU 110 and changing the target temperature Tld of the OLT optical transmitter 150 while monitoring the received power of each ONU 110, the wavelength characteristics of the optical signal on the OLT 130 side are changed, and each bandpass is changed. The received power of each ONU 110 also varies depending on the characteristics of the filter 112. In this way, the transmission line information calculation unit 161 fluctuates the target temperature Tld until one ONU 110 shows the received power that is the reception limit so that all the ONU 110s connected to the OLT 130 can receive the optical signal from the OLT 130. And specify the target temperature range.

The Tld adjustment unit 163 searches for the target temperature Tld having the lowest power consumption within the target temperature range specified by the transmission line information calculation unit 161.
In order to obtain the optimum target temperature Tld within the Tld allowable range determined above, basically, by setting the target temperature Tld to the ambient temperature of the OLT optical transmitter 150, the thermoelectric element 153 by the TEC controller 155 is used. The input current II of is minimized. When the ambient temperature of the OLT optical transmitter 150 is low and the target temperature Tld is lowered, the OLT optical transmission wavelength shifts to the short wavelength side and shifts to the left side in FIG. Further, as for the temperature characteristic of the LD 151, if the target temperature Tld is lowered, the drive current DI can be small, so that the effect of reducing the power consumption is high. On the contrary, when the environmental temperature of the OLT optical transmitter 150 is high, when the target temperature Tld is raised, the OLT optical transmission wavelength shifts to the long wavelength side, and in FIG. 6, it shifts to the right side. However, the temperature characteristic of the LD 151 requires a large drive current DI if the target temperature Tld rises. Therefore, it is necessary to search for the optimum point while monitoring the bias current with the DDM function of the OLT optical transmitter 150.

From the above consideration, the Tld adjustment unit 163 sets the environmental temperature as the target temperature Tld when the environmental temperature indicated by the environmental temperature information STI is within the target temperature range. When the ambient temperature is higher than the target temperature range, the Tld adjusting unit 163 sets the maximum value Tld-max of the target temperature range as the target temperature Tld. When the ambient temperature is lower than the target temperature range, the Tld adjusting unit 163 sets the minimum value Tld-min of the target temperature range as the target temperature Tld.

Then, the Tld adjusting unit 163 adjusts the input current II so that the TEC controller 155 reaches the set target temperature Tld, in other words, the process until the thermoelectric element 153 reaches the set target temperature Tld. In, the sum of the drive current DI indicated by the drive current information DII given from the APC control unit 162 and the input current II indicated by the input current information III is sequentially calculated, and is indicated by the detected temperature information TI at the time when the sum is the smallest. The detected temperature is set to the TEC controller 155 again as the optimum target temperature Tld (final target temperature Tld).

In the process of adjusting the input current II so that the TEC controller 155 reaches the set target temperature Tld, the Tld adjustment unit 163 exceeds the predetermined threshold (second threshold) for the drive current DI. In this case, the TEC controller 155 is made to stop heating or cooling the thermoelectric element 153, and the detection temperature indicated by the detection temperature information TI at the time when the total sum calculated so far is the smallest is optimized. The target temperature Tld (final target temperature Tld) may be set again in the TEC controller 155.

A part or all of the host side control unit 142, the control unit 160, and the TEC controller 155 described above are stored in the memory 10 and the memory 10 as shown in FIG. 3A, for example. It can be configured by a processor 11 such as a CPU that executes a program. Such a program may be provided through a network, or may be recorded and provided on a recording medium.

Further, a part or all of the host side control unit 142, the control unit 160, and the TEC controller 155 are, for example, a single circuit, a composite circuit, a programmed processor, and parallel as shown in FIG. 3 (B). It can also be configured by a processing circuit 12 such as a programmed processor, ASIC or FPGA.

According to the control method as described above, the low power consumption of the OLT optical transmitter 150 can be achieved by using the margin of the wavelength characteristic of the bandpass filter 112 that each company has to absorb the manufacturing variation. In other words, the bandpass filter 112 of the ONU 110 has a filter characteristic capable of transmitting a wider range of wavelengths in order to satisfy the optical transmission wavelength standard of the OLT 130. Therefore, the target temperature Tld can be changed to a portion where the bandpass filter 112 attenuates to some extent.

Embodiment 2.
In the first embodiment, it is assumed that the plurality of ONU 110s are manufactured by different companies, or the plurality of ONU 110s are different models, and the difference in the filter wavelength characteristics of the bandpass filter 112 is used to obtain the OLT light. The power consumption of the transmitter 150 is reduced.
In this regard, even if a plurality of ONU 110s are of the same model, if the loss budget between the OLT 130 and the ONU 110 is a small transmission line, the margin of the transmission line loss can also contribute to the reduction of power consumption due to the fluctuation of the target temperature Tld. it can.
In other words, when the number of ONU 110s to be connected is small and the number of branches in the transmission line is small, the branch loss due to the branch coupler is reduced. Further, when the transmission distance is short, the transmission loss of the optical fibers 103 and 101 is reduced. The wavelength can be changed by the margin of the transmission line loss, and the target temperature Tld can be changed.
That is, by using the same model as the plurality of ONU 110s in the second embodiment, the threshold value of the received power when determining the target temperature range can be lowered as compared with the first embodiment.

100 optical communication system, 101, 103 optical fiber, 102 optical splitter, 110 ONU, 111 WDM filter, 112 bandpass filter, 113 light receiving element, 114 light emitting element, 115 control unit, 130 OLT, 140 OLT optical receiver, 141 environment Temperature detection unit, 142 Host side control unit, 150 OLT optical transmitter, 151 LD, 152 LD drive circuit, 153 thermoelectric element, 154 thermistor, 155 TEC controller, 160 control unit, 161 transmission line information calculation unit, 162 APC control unit , 163 Tld adjuster, 10 memory, 11 processor, 12 processing circuit.

Claims (4)

A station-side termination device that performs optical communication with multiple subscriber-side devices.
An optical transmitter that transmits optical signals and
Each of the plurality of subscriber-side devices includes an optical receiver that receives received power information indicating the received power of the optical signal transmitted by the optical transmitter.
The optical transmitter
A light emitting element that emits light according to the drive current,
The drive unit that controls the drive current and
A thermoelectric element that heats or cools the light emitting element according to the input current,
A temperature detection unit that detects the temperature of the thermoelectric element as a detection temperature,
A temperature control unit that controls the input current so that the detected temperature becomes the set target temperature.
A control unit that sets the target temperature in the temperature control unit,
With
By changing the target temperature and confirming the received power indicated by the received power information, the control unit sets all the received powers in the plurality of subscriber-side devices to a predetermined first threshold value or higher. A station-side termination device characterized in that a target temperature range, which is a range of the target temperature, is specified, and a temperature within the target temperature range is set as an optimum target temperature in the temperature control unit. The first aspect of the present invention, wherein the control unit specifies, among the temperatures within the target temperature range, the temperature at which the sum of the input current and the drive current is the minimum as the optimum target temperature. Station side termination device. An environmental temperature detection unit that detects the ambient temperature of the station-side termination device as the environmental temperature is further provided.
When the environmental temperature is included in the target temperature range, the control unit sets the environmental temperature as the target temperature in the temperature control unit, and when the environmental temperature is not included in the target temperature range. Sets the minimum or maximum value of the target temperature range as the target temperature in the temperature control unit, and in the process until the thermoelectric element reaches the set target temperature, the input current and the drive current The station-side termination device according to claim 1 , wherein the detected temperature at the time when the sum of the above is minimized is specified as the optimum target temperature. An environmental temperature detection unit that detects the ambient temperature of the station-side termination device as the environmental temperature is further provided.
When the environmental temperature is included in the target temperature range, the control unit sets the environmental temperature as the target temperature in the temperature control unit, and when the environmental temperature is not included in the target temperature range. Is set in the temperature control unit with the minimum value or the maximum value of the target temperature range as the target temperature, and the drive current is predetermined in the process until the thermoelectric element reaches the set target temperature. When the temperature exceeds the second threshold value, the heating or cooling of the light emitting element is stopped, and the sum of the input current and the drive current becomes the sum of the input current and the drive current until the drive current reaches the second threshold value or more. The station-side termination device according to claim 1 , wherein the detected temperature at the time when the temperature becomes the minimum is specified as the optimum target temperature.

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