JP3056779B2 - Optical transmission system - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical transmission system, and more particularly to an optical transmission system, in which an optical branching circuit is used to transmit an optical signal from one optical transmitting circuit to a plurality of optical receiving circuits. The present invention relates to an optical transmission system for performing point-to-multipoint transmission in which an optical signal is received by a single optical receiving circuit.

(Prior Art) Conventionally, in order to improve reliability, when transmission is performed using a main transmission (also called working) and backup optical transmission device, a main transmission optical transmission device and a backup optical transmission device are used. A method of switching an apparatus by an optical switch is often used. This example is shown in FIG.

In FIG. 7A, 101 is an optical transmission device for main transmission, 102 is a spare optical transmission device, 103 is an optical switch for switching, and 104 is an optical receiving device.

On the transmitting side, the optical switch 103 is normally connected to the optical transmission device 101 for main transmission, but when the optical transmission device 101 operates abnormally, this is detected and switched to the standby optical transmission device 102. Can be The optical receiving device 104 receives an optical signal from the optical transmitting device 101 or the optical transmitting device.

In FIG. 7B, 105 is an optical receiving device for main transmission, 106 is a spare optical receiving device, 103 is an optical switch for switching, and 107 is an optical transmitting device.

On the receiving side, the optical switch 103 is normally connected to the main transmission optical receiving device 105, but when the optical receiving device 105 becomes abnormally operated, this is detected and switched to the standby optical receiving device 106. Can be The optical transmitting device 107 transmits an optical signal to the optical receiving device 105 or the optical receiving device 106.

(Problem to be Solved by the Invention) Here, the optical switch 103 has a disadvantage that the reliability of the optical switch 103 is not good with the current technology, and the purpose of improving the reliability cannot be sufficiently exhibited. Further, since the insertion loss is large, the transmission distance has to be sacrificed.

An object of the present invention is to provide an optical transmission system that can improve reliability in a point-multipoint optical transmission system that has recently emerged due to the development of optical transmission technology.

(Means for Solving the Problems) In order to achieve this object, the optical transmission system of the present invention comprises:
In the point-multipoint optical transmission system, a spare input connected to a spare optical transmission line on the point side in addition to one input terminal or output terminal connected to the main optical transmission line on the point side to the optical branch circuit used. A terminal or an auxiliary output terminal is added, and the optical branching circuit is provided with a monitoring function for detecting an abnormal operation of the optical transmitting device or the optical receiving circuit connected to the main optical transmission line. Optical transmission side (working side)
If the monitoring function detects that the other device has become abnormal, the operation of the active device connected to the main transmission line is stopped and the standby device connected to the standby optical transmission line is operated. Is configured.

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(Embodiment) FIG. 1 is a block diagram showing a main part of a transmission system according to a first embodiment of the present invention. In FIG. 1, 201 is an optical transmission device for main transmission used in the point-multipoint transmission system, 202 is a spare optical transmission device used in the point-multipoint transmission system, 203 is an optical branching circuit, 204
Reference numerals −1 to 204-n and the like denote optical receivers used in the point-multipoint transmission system.

Here, the optical branching circuit 203 shows a configuration example of two inputs and n outputs. Here, n is an integer of 2 or more. Normally, the optical signal from the optical transmission device 201 for main transmission is
, And is received by the optical receiver 204-1 or 204-n.
When the optical transmission device 201 for main transmission has an abnormal operation,
The spare optical transmission device 202 operates, and the main transmission optical transmission device 2
01 is turned off.

The configuration of the two-input / n-output optical branching circuit 203 is not so complicated as compared with the one-input / n-output optical branching circuit.
Reliability does not degrade as much. Also, if you devise the configuration,
The insertion loss does not increase.

FIG. 2 shows an optical coupling circuit which is a component of the optical branching circuit 203. In FIG. 2, 301 and 302 are input terminals, and 303 and 304.
Denotes an output terminal, and 305 denotes a substrate constituting an optical coupling circuit.
The optical input from the input terminal 301 is split by the coupling circuit 305 and is split into output terminals 303 and 304, respectively. Similarly, the optical input from the input terminal 302 is branched by the coupling circuit 305, and the output terminal 3
Divided into 03 and 304 respectively.

FIG. 3 shows an example of the configuration of an optical branching circuit configured by combining the optical coupling circuit 305 of FIG. Reference numerals 407, 408, and 409 denote optical coupling circuits in FIG. 2, reference numerals 401 and 402 denote input terminals, and reference numerals 403 to 406 denote output terminals. In this figure, optical coupling circuits are cascaded in multiple stages.

In FIG. 3, an optical signal from an input terminal 401 is split into two by an optical coupling circuit 407, and further split into two by optical coupling circuits 408 and 409, respectively. As a result, the optical signal is split into quarters. Similarly, the optical signal from the input terminal 402
Branched into each. In such a method, generally, 2
An input / n output optical branching circuit can be easily configured, and
The insertion loss does not increase as compared with the one-input / n-output optical branch circuit.

Next, control for switching from the optical transmission device for main transmission to the backup optical transmission device will be described. FIG. 4 shows the first embodiment of the present invention.
An example will be described. In FIG. 4, reference numeral 601 denotes a circuit for monitoring the operation of the optical transmitter 201 or 202, and 602 denotes a circuit for monitoring the optical transmitter 201 or 202.
Is a control circuit for switching between.

If the optical transmission device 201 for main transmission operates abnormally (for example, a decrease in optical output), the monitoring circuit 601 detects this and switches to the backup optical transmission device 202 in conjunction with the control circuit 602.
At this time, the optical transmitter
It is only necessary to turn off the output of 201 and operate the optical transmitter 202. This control has the effect of improving reliability not only in the optical transmission device but also in the optical transmission path from the optical transmission device 201 or 202 to the optical branch circuit 203.

FIG. 5 shows a main part of the transmission system according to the second embodiment of the present invention. In FIG. 5, reference numeral 701 denotes an optical receiver for main transmission used in the point-multipoint transmission system, 702 denotes a spare optical receiver used in the point-multipoint transmission system, and 703-1 to 703-n denote points. An optical transmitter used in the multipoint transmission system, and 705 represents an n-input / 2-output optical branch circuit.

Here, the optical branch circuit 705 shows a configuration example of n inputs and 2 outputs. Here, n is an integer of 2 or more. The optical signal from the optical transmission device 703-1 is always input to the optical transmission devices 701 and 702 via the optical branching circuit 705, but the reception operation is usually performed by the optical transmission device 701 for main transmission. Output side is both receivers 7
When the main transmission optical receiving device 701 is abnormally operated when the main transmission optical receiving device 701 operates abnormally and the main transmission optical receiving device 701 is disconnected, Is done. Practically, the transmission to the output side is an optical receiver for main transmission
It is only necessary to switch from 701 to the spare optical receiver 702.

The n-input / two-output optical branch circuit 705 is basically the same as the two-input / n-output optical branch circuit 203. That is, if the input and output of the optical branching circuit 203 are reversed, it can be used as the optical branching circuit 705.

Next, control for switching from the main transmission optical receiving device to the standby optical receiving device will be described. FIG. 6 shows a second embodiment of the present invention. In FIG. 6, reference numeral 901 denotes an optical transmitter for monitoring the operation of the optical receiver; and 902, a circuit for monitoring the operation of the optical receiver and controlling the monitoring and switching so that the normal optical receiver operates.

The optical transmission device 901 sends out a predetermined optical signal in order to check whether the optical transmission device 701 for main transmission is operating normally. When the optical receiving device 701 operates abnormally, the monitoring control circuit 902 detects this abnormality and switches to the standby optical receiving device 702. At this time, if both the receiving devices 701 and 702 are commonly connected to the output side, the optical receiving device 701 need only be turned off and the optical receiving device 702 can be operated without switching with the optical switch. In addition, the connection to the output side is
May be switched to the optical receiving device 702. In this method, as compared with the embodiment of FIG.
In addition to the optical transmission path from the optical branching circuit 705 to the optical receiving device 701 or 702, there is an effect that the reliability can be improved including the optical transmission path.

As a method of detecting an abnormality of the optical receiving device 701, it is possible to transmit a specific pattern from the monitoring optical transmitting device 901 and confirm that the optical receiving device 701 is correctly receiving the pattern. Alternatively, by using another means, a specific optical signal is sent to the monitoring optical transmitting device 901 and returned again from the monitoring optical transmitting device 901 so that the optical receiving device 7
It is also possible by collating with 01.

Here, as for the optical branch circuits 203 and 705, the configuration of two inputs and n outputs or n inputs and two outputs is taken as an example.
It is also possible to further enhance the reliability by setting the above inputs or two or more outputs.

(Effects of the Invention) As described above, according to the present invention, it is easy to improve the reliability in point-to-multipoint transmission, and it is necessary to sacrifice the transmission distance for improving the reliability. There is no.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main part of a transmission system in a first embodiment of the present invention, and FIG. 2 is a schematic diagram showing an example of an optical coupling circuit which is a component of an optical branch circuit used in the present invention. ,
FIG. 3 is a block diagram showing an example of an optical branch circuit constituted by combining the optical coupling circuits of FIG. 2, and FIG.
FIG. 5 is a block diagram showing a main part of a transmission system according to a second embodiment of the present invention. FIG. 6 is a block diagram showing a second embodiment of the present invention. FIGS. 1A and 1B are block diagrams showing examples of a conventional optical transmission system. 101, 201 ... main transmission optical transmission device, 102, 202 ... standby optical transmission device, 103 ... optical switch, 104, 204-1, 204-n ...
Optical receiving device, 105,701 ... Optical receiving device for main transmission, 106,702
... Stand-by optical receiving device, 107, 703-1, 703-n optical transmitting device, 203,705 optical branching circuit, 301, 302, 401, 402 input terminal of optical coupling circuit, 303, 404, 403, 404, 405, 406 output terminal of optical coupling circuit, 305, 407, 408, 409 optical coupling Circuit, 6
01 monitoring circuit, 602 control circuit, 901 monitoring optical transmitter, 902 monitoring control circuit.

────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Tetsuya Miki 1-6, Uchisaiwaicho, Chiyoda-ku, Tokyo Nippon Telegraph and Telephone Corporation (56) References JP-A-2-97139 (JP, A) JP-A Heisei 4-63032 (JP, A) JP-A-3-230625 (JP, A) JP-A-61-105141 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04B 10/02 H04B 1/74 G08C 25/00

Claims (2)

(57) [Claims] According to a point-multipoint optical transmission system, an optical signal from an optical transmission device for main optical transmission on a point side via a main optical transmission line is branched into a plurality of optical signals by an optical branching circuit. The optical signal is configured to be received by each of the plurality of optical receivers on the multipoint side, and the optical branching circuit is connected to one input terminal connected to the main optical transmission line on the point side, and to a spare. An input terminal is provided, a spare optical transmission device on the point side is connected to the spare input terminal via a spare optical transmission line, and an operation of the main transmission optical transmission device is provided on an output side of the optical branch circuit. A monitoring function for monitoring, when the monitoring function detects an abnormality in the operation of the optical transmission device for the main transmission, stops the operation of the optical transmission device for the main transmission and sets the spare optical transmission device to Control function to operate Optical transmission scheme. 2. A point-multipoint optical transmission system, wherein optical signals from a plurality of optical transmitters on the multipoint side are joined by an optical branching circuit, and the combined optical signals are transmitted via a main optical transmission line. Along with being configured to be received by the optical receiving device for point-side main transmission, the optical branch circuit has a spare output terminal in addition to one output terminal connected to the point-side main optical transmission line. A point-side standby optical receiving device is connected to the standby output terminal via a standby optical transmission line, and the input side of the optical branch circuit is used to monitor the operation of the main transmission optical receiving device. A monitoring optical transmitter, and operates the spare optical transmitter when an abnormality in the operation of the main transmission optical receiver is detected using an optical signal from the monitoring optical transmitter. Optical transmission method with control function .