JPS6337982B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical communication system, and particularly to an optical data link for communicating between a large number of discretely installed devices.

In recent years, optical communication systems have made remarkable progress, and their applications are expanding to various fields.One of the advanced application forms is the optical connection of multiple optical communication devices dispersed in the middle of an optical transmission line. Optical communication systems that perform time-division multiplex transmission of optical signals have been considered. This type of optical communication system, which is generally called an optical data link, is superior in terms of system flexibility and economy, and because it uses a non-conductive optical transmission path, it is free from electromagnetic induction. It has the advantage of being less susceptible to disturbances, and requiring only the optical communication device that is transmitting and receiving to be in operation, resulting in high circuit reliability.

However, in the case of optical data links, unlike electrical data links, losses in transmission paths, connection points, branch circuits, etc. are considerably large, so optical signals sent in a time-sharing manner are sent from which optical communication device. The power of the optical signal changes significantly depending on how it is sent.

On the other hand, the operating range of the identification circuit used in the optical receiving circuit is not very wide. Therefore, in order to receive signals with large power changes, ordinary optical communication systems other than optical data links usually use an amplifier gain control method (hereinafter referred to as AGC method) to compensate for the power changes. things are being done. However, in optical data links, there is a power change in the optical signal that occurs during time-division multiplexing, and this change occurs in a very short time of 1 bit or less.
Methods with slow response such as the AGC method cannot be applied. Therefore, conventionally configurable optical data links have the disadvantage that they are limited to very short distances with little difference in transmission loss, and are limited to connections with a small number of optical communication devices.

Note that it is possible to adjust the optical transmission power to an appropriate value in advance so that the optical reception power is almost constant. This method is not generally applicable to optical data links, where one of the features is the ability to freely add or remove optical communication devices, since the values change, requiring adjustment each time.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical data link that eliminates the above-mentioned drawbacks of the conventional link, allows relatively long-distance transmission, and connects a large number of optical communication devices.

According to the present invention, one or more optical communication devices are optically connected in the middle of an optical transmission line system starting from an optical transmission device and terminating at an optical receiving device, and using the optical transmission line system. In an optical data link that transmits optical signals in a time-division manner, means for the optical communication device to detect at least the peak power of the optical reception signal;
means for controlling the peak power of the optical transmission signal of the optical communication device, and an optical data link is obtained that controls the peak power of the optical transmission signal so as to be proportional to the peak power of the optical reception signal.

In this optical data link, each optical communication device detects the peak power of its optical reception signal and sends out an optical transmission signal with a peak power proportional to that value. The peak power of the optical signal is proportional to the peak power of the optical signal transmitted through the optical transmission line system. Therefore, by setting the proportionality constant to an appropriate value, power fluctuations in the multiplexed signal can be reduced, relatively long-distance transmission is possible, and a large number of optical communication devices can be connected.

Next, the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing the configuration of a first embodiment of the present invention, which is an optical data link in which two optical communication devices are connected in the middle.

The optical transmitter 1 and the optical receiver 6 are connected to both ends of the optical transmission line 2, respectively.
An optical signal is sent out at predetermined intervals. Further, each optical communication device 41, 42 is connected in the middle of the optical transmission line 2 via an optical branching circuit 31, 32 and an optical combining circuit 51, 52, respectively. Each optical communication device 41, 42 has an optical branch circuit 31, 3, respectively.
2, the optical signal branched from the optical transmission line 2 is received by the optical receiving circuits 411 and 412, and the transmitted signal is converted into an optical signal by the optical transmitting circuits 431 and 432, and then is transmitted through the optical combining circuits 51 and 52. , and is sent to the optical transmission line 2.

FIG. 3 shows the signal format of this embodiment. This format has a transmission rate of 32.77 Mb/s and consists of 16 frames. Each frame consists of 512 bits, a frame identification signal,
501 bits, excluding 11 bits such as frame synchronization signals, can be used as data signals. This example is F
This is a so-called fixed allocation method in which each frame from 0 to F15 is allocated to each node. Specifically, the optical transmitter 1 has F0, F1, F
2 and 3 frames, the optical communication device 41 receives frame F.
3 and the optical communication device 42 occupy frame F4, respectively. Frames F5 to F15 are empty frames, and in this embodiment, 11 additional nodes can be additionally connected. Moreover, if a demand assignment method is adopted in which free frames are searched for and used freely instead of fixed assignment, even more nodes can be connected. The optical receiver 6 receives optical signals from all nodes and functions to control the loop, and can control the circulation of signals within the loop, connect signals with the main computer outside the loop, etc. I can do it.

In the optical communication device 41, the optical signal from the optical transmitter 1 is sent to the optical receiver circuit 41 via the optical branch circuit 31.
Receive at 1. In this case, the received signal includes F0 to F
This means that only two frames contain the signal. When attempting to transmit a signal from the optical communication device 41, the optical transmission circuit 431 transmits the optical signal with timing aligned with the time range corresponding to frame F3. In this case, the optical signals of frames F0 to F2 from the optical branching circuit 31 and the optical signal of frame F3 from the optical transmitting circuit 431 are combined via the optical combining circuit 51 and sent to the optical transmission line 2. When combined in this way, in order to make the optical signal power of frame F3 almost equal to the optical signal power of frames F0 to F2, it is proportional to the peak power of the optical reception signal of frames F0 to F2 detected by the optical power detection circuit 421. The optical signal output from the optical transmitting circuit 431 is controlled so as to perform the following. Thereby, even when an optical signal is inserted from each node, the level of the optical signal does not fluctuate from frame to frame and can always be maintained at a constant level.

Similarly, the optical communication device 42 sends out an optical signal with timing and output aligned with the time range of frame F4. The method is the same as that for the optical communication device 41, so the explanation will be omitted.

With this configuration, the peak power of the optical signal sent out from the optical transmission circuits 431 and 432 of each optical communication device 41 and 42 is determined by the optical power detection circuits 421 and 422, respectively.
The proportional constant is controlled so that the peak power of the optical signal coupled from the optical transmission circuits 431 and 432 to the optical transmission line 2 is proportional to the peak power of the optical reception signal detected by the optical transmission line 2. 2 is determined to be equal to the peak power of the optical signal being transmitted.

Therefore, even if the peak power of the optical signal transmitted through the optical transmission line 2 changes for some reason, the peak power of the optical signal coupled from each optical communication device 41, 42 will always change accordingly. , no power fluctuations occur due to multiplexing. Differences in optical reception power between devices can be compensated for using a simple AGC circuit, making it possible to create an optical data link that is capable of relatively long-distance transmission and can connect a large number of optical communication devices. It will be done.

FIG. 2 is a block diagram showing the configuration of a second embodiment of the present invention, in which two optical communication devices 41 and 42 are connected to each other.
This is an optical data link connected to real optical transmission lines 21 and 22. In this embodiment, an optical branch circuit 3 is provided for each of the first optical transmission line 21 starting from the optical transmitting device 1 and the second optical transmission line 22 terminating at the optical receiving device 6.
Two optical communication devices 41 and 42 are connected to each other via optical synthesis circuits 51 and 52, and data transmission from the optical transmitter 1 to each optical communication device 41 and 42, , 42 to the optical receiver 6
It is used to transmit data to. An optical signal sent out at a predetermined time from the optical transmitter 1 is transmitted through a first optical transmission line 21, and a part of the signal is branched at optical branching circuits 31 and 32 connected to this optical transmission line 21. , are received by the optical receiving circuits 411, 412 of the optical communication devices 41, 42. On the other hand, the transmission signals from each optical communication device 41, 42 to the optical receiver 6 are converted into optical signals in optical transmission circuits 431, 432, and sent to the second optical transmission line 22 via optical combining circuits 51, 52. There is. At that time, the peak power of the optical transmission signal is determined by the optical power detection circuits 421 and 422.
By setting this proportionality constant to an appropriate value, the power fluctuation of the time-division multiplexed optical signal received by the optical receiver 6 can be controlled to be proportional to the peak power of the optical reception signal detected by the optical receiver 6. Since it can be made small, an optical data link that can perform relatively long-distance transmission and connect a large number of optical communication devices can be obtained.

It should be noted that the signal format is the same as in the first embodiment, so a description thereof will be omitted.

In addition, although each of the above-mentioned embodiments is an example in which two optical communication devices are connected, it is also possible to similarly realize an arrangement in which one or more optical communication devices are connected.

Furthermore, there are various ways to vary the optical transmission power in each of the above embodiments, but when a light emitting diode or semiconductor laser is used as the light emitting element, this can be achieved by simply changing the applied current. ,
By using a variable applied current circuit with the same configuration as the variable attenuation circuit for AGC in the optical receiving circuit and working in conjunction with the AGC circuit, it is possible to obtain optical transmission power proportional to optical reception power.

The time division multiplex transmission method shown in each example is generally TDMA (Time Division Multiple Access).
However, the embodiments of the present invention are not limited to this, and can be applied to any method that controls communication in a time-division manner. For example, the well-known token passing method, CSMA/CD (Carrier Sense Multiple
It can also be applied to other systems such as Access/Collision Detection).

As described in detail above, by controlling the power of the optical transmission signal so that it is proportional to the power of the optical reception signal using the configuration of the present invention, it is possible to suppress the power fluctuation of the multiplexed optical signal. An optical data link that is capable of long-distance transmission and that can connect a large number of optical communication devices can be obtained.

[Brief explanation of the drawing]

FIGS. 1 and 2 are block diagrams of embodiments of the present invention, and FIG. 3 is a diagram showing the format of an optical signal. 1... Optical transmitter, 2, 21, 22... Optical transmission line, 31, 32... Optical branch circuit, 41, 42...
Optical communication device, 51, 52...Photosynthesis circuit, 6...
Optical receiving device, 411, 412... Optical receiving circuit, 4
21,422...Optical power detection circuit, 431,43
2...Optical transmission circuit.

Claims (1)

[Scope of Claims] 1. One or more optical communication devices are optically connected in the middle of an optical transmission line system having an optical transmission device as a starting point and an optical receiving device as a terminal end, and the optical transmission line system is used. In an optical data link that performs time-division multiplex transmission of optical signals, the optical communication device includes at least a means for detecting the peak power of the optical reception signal, and a means for controlling the peak power of the optical transmission signal of the optical communication device. and means for controlling the peak power of the optical transmission signal so as to be proportional to the peak power of the optical reception signal. 2. If the optical transmission line system is a single optical transmission line, and in an optical communication device, the ratio of the peak power of the optical transmission signal and the optical reception signal is calculated as the peak power of the optical signal coupled from the optical communication device to the optical transmission line. Claim 1, characterized in that the power is made to be approximately equal to the peak power of the optical signal being transmitted through the optical transmission line.
Optical data link described in section.