JPH02149144A - Optical communication node device - Google Patents

Abstract

PURPOSE:To improve the transmission characteristic of a system by detecting the level of a reception optical signal from a preceding node, and controlling the output level of an optical signal from an optical transmission circuit based on the level. CONSTITUTION:An optical communication node device is provided with an optical branching device 1 which branches part of the reception optical signal from the preceding node, a level detection circuit 2 which detects the level of a demultiplexed optical signal, an optical transmission circuit 4 which outputs the optical signal from its own node, and an output level control circuit 3 which controls the output level of the optical signal from the optical transmission circuit 4 corresponding to a detected level. Furthermore, an optical multiplexer 5 which multiplexes the optical signal from the optical transmission circuit 4 on the optical signal from the preceding node is provided, and the output level control circuit 3 controls the level of a carrier from its own node so as to be equal to that of the carrier from the preceding node. Therefore, the signal of its own node can be inserted to a transmission signal without demodulating the reception optical signal to an electrical signal. In such a way, it is possible to improve the transmission characteristic without necessitating an optical reception circuit with high performance.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an optical communication node device in a system that collects transmission signals from nodes installed at a plurality of locations using a single optical fiber.

[Conventional technology]

Conventionally, as shown in FIG. 2, this type of optical communication node equipment receives an optical signal transmitted from a previous node through a single-core optical fiber 11, demodulates it into an electrical signal, and amplifies it. a circuit 6, a combining circuit 7 which combines a signal having a carrier wave of a frequency f7 different from that of other nodes and modulated by the transmission signal of the own node with the output signal of the optical receiving circuit 6, and a combining circuit 7 which combines the output signal of the optical receiving circuit 6 with the combined signal It includes an optical transmission circuit 8 that sends a transmission optical signal to the next node through a single-core optical fiber.

This device sequentially frequency-division multiplexes the signal of its own node onto the signal of the previous node, and as a result collects the signals of a plurality of nodes.

[Problem to be solved by the invention]

In the conventional device described above, since the signal of the own node is combined with the signal sent to other nodes in the form of an electrical signal, it is necessary to demodulate the received optical signal once into an electrical signal, especially when modulating it with a frequency division multiplexed signal. In the demodulation of the received optical signal, there is a problem in that the transmission characteristics inevitably change due to noise and distortion in the optical receiving circuit 6, and a high-performance optical receiving circuit is required.

Another problem is that the number of carrier waves multiplexed in the input signal to the optical transmission circuit 8 increases as it reaches subsequent nodes, making it difficult to modulate a good optical signal.

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical communication node device that improves deterioration of system transmission characteristics.

[Means to solve the problem]

The optical communication node device of the present invention includes an optical splitter that branches part of the received optical signal from the previous node, a level detection circuit that detects the level of the branched optical signal, and outputs the optical signal from the own node. an output level control circuit that controls the optical signal output level from the optical transmission circuit in accordance with the detected level; The output level control circuit controls the carrier wave level from the own node to be equal to the carrier wave level from the previous node.

[Effect]

With the above-described configuration, the own node signal can be inserted into the transmission signal without demodulating the received optical signal into an electrical signal.

〔Example〕

Next, the present invention will be explained with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of an optical communication node device according to the present invention. In FIG. 0, 1 is an optical branching device, which is connected to a preceding node by a single optical fiber 11. This branch path includes a level detection circuit 2, an output level control circuit 3.
Optical transmitter circuit 4. and a light combiner 5, and the branched signal is sent to the single-core optical fiber 11 again in the light combiner 5.
are combined into the transmitted signal.

That is, a part of the received optical signal from the previous node is branched by the optical branching device 1, and a detection signal corresponding to the level of the received optical signal is detected by the level detection circuit 2. Based on this detection signal, the output level control circuit 3 controls the optical transmission circuit 4.

The optical transmission circuit 4 modulates the signal of its own node with a carrier wave having a frequency f7 different from that of other nodes, and the output level of this optical signal is controlled by the output level control circuit 3.

Level control at this time is performed so that the carrier wave level of the transmitted optical signal combined in the optical combiner 5 becomes equal to the carrier wave level of the preceding node transmitted through the single-core optical fiber 11.

As a result, the transmitted optical signal becomes a signal that is modulated by a frequency division multiplexed signal in which the carrier wave of the own node is inserted together with the carrier waves of each node up to the own node, and the levels of each carrier wave are uniform.

Here, the level detection circuit 2 obtains a detection signal corresponding to the optical signal level as described above, but for example, at the foremost node, only the level reference pilot signal inserted in advance into the received optical signal is detected. A detection signal can be obtained by detection, and it can be easily realized. Further, the optical transmission circuit 4 transmits a carrier wave 1 having a frequency f.
Since it is sufficient to modulate the optical signal using only waves, it is easier to realize the optical transmission circuit than the conventional device, and it is possible to obtain good modulation characteristics.

Furthermore, by appropriately setting the branching ratio of the optical splitter 1 and the combining ratio of the optical combiner 5, it is possible to reduce the loss between the received optical signal and the transmitted optical signal as much as possible.

〔Effect of the invention〕

As explained above, the present invention is configured to detect the level of the received optical signal from the previous node, control the optical signal output level from the optical transmission circuit based on this level, and combine it into the transmitted optical signal. As a result, the own node's signal can be inserted into the transmitted signal without demodulating the received optical signal into an electrical signal, and there is no need for a high-performance optical receiving circuit. It has the effect of allowing you to acquire characteristics.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of an optical communication node device according to the present invention, and FIG. 2 is a block diagram of a conventional device. 1... Optical splitter, 2... Level detection circuit, 3...
Output level control circuit, 4... Optical transmitting circuit, 5... Optical combiner, 6... Optical receiving circuit, 7... Combining circuit, 8.
...Optical transmission circuit, 11...1-core optical fiber. (Jfl: Bun 1 Kf)

Claims (1)

[Claims] 1. In an optical communication system in which multiple nodes each having a carrier wave of a different frequency are connected by a single-core optical fiber and transmission signals from each node are collected using frequency division multiplexing, one of the received optical signals from the previous node is an optical branching device for branching the optical signal; a level detection circuit for detecting the level of the branched optical signal; an optical transmission circuit for outputting the optical signal from its own node; and the detection of the optical signal output level from the optical transmission circuit. an output level control circuit that controls the output level according to the output level;
an optical combiner that combines an optical signal from the optical transmission circuit with an optical signal from the preceding node, and the output level control circuit is configured such that a carrier wave level from the own node is equal to a carrier wave level from the preceding node. An optical communication node device characterized in that it is configured to perform control as follows.