JPH09224001A - Optical network terminating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove various kinds of noise components, to prevent the power of optical signal from being attenuated and to attain long-distance repetition even at the time of fault by only selecting a main signal at a transmitter. SOLUTION: When optical signals from both an optical transmission line 31a for incoming access and an optical transmission line 28a for bypass are inputted to a transmitter 26a, only an optical signal 32d coming through the optical transmission line 31a for incoming access having more optical signal power is reproduced and repeated. This signal 32d is impressed to an optical transmission line 21b as an optical signal 32e, reproduced, repeated at a receiver 24b, impressed to a beam splitting part 27b later, branched to optical signals 32f and 32g here and impressed to an optical transmission line 28b for bypass and a node 32b. When any fault occurs at a node 23a, there is no input of optical signal from the optical transmission line 31a to the transmitter 26a, the transmitter 26a reproduces and repeats an optical signal 32b from the optical transmission line 28a for bypass, and it is transmitted to the optical transmission line 21b as an optical signal 32e. Thus, long-distance repetition is possible even at the time of fault.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for connecting optical communication networks to each other when optical communication is carried out mainly between optical networks connected to a loop type optical transmission line. Regarding

As a highly reliable loop configuration method in a loop type optical network system, an optical access type applied to a large-scale indoor optical transmission system has been proposed (Tokura "Large-scale indoor optical transmission system" (NTT Research Practical Use). Report, No.
Vol. 34, No. 5, pp. 861-875, 1985)).

A part of an example of this type of optical network system is conceptually shown in FIG. In the figure, 1a and 1b are optical transmission lines, 2a to 2c are optical accessors, 3a to 3c are nodes, 4a to 4c are optical branching units in the optical accessors, and 5a to 5c are optical transmission lines for bypass in the optical accessors. 6a to 6c are optical multiplexers in the optical accessor, 7a to 7c are optical transmission lines for downlink access, 8a to 8c are optical transmission lines for uplink access, 9a to 9c are O / E converters, and 10a to 10c.
Is an E / O converter, and 11 and 11a to 11g are optical signals.

First, considering the state in which communication from the node 3c to the node 3b is performed via the node 3a, the operation when the node 3a is operating normally will be described. The electric signal transmitted from the node 3c is converted from an electric signal into an optical signal by the E / O converter 10c, passes through the optical multiplexer 6c in the optical accessor 2c, and is transmitted to the optical transmission line 1a. The optical signal 11 propagating on the optical transmission line 1a is sent to the optical branching unit 4a in the optical accessor 2a.

In the optical branching section 4a, the optical signal 11 is an optical signal.
11a and an optical signal 11b are branched into two. One optical signal
11a is sent to the bypass optical transmission line 5a in the optical accessor 2a, and the other optical signal 11b is sent to the O / E converter 9a through the downstream access optical transmission line 7a, where the optical signal is converted into an electrical signal. It is converted and transmitted to the node 3a. The optical signal 11b is regenerated and relayed at the node 3a, converted from an electric signal to an optical signal by the E / O converter 10a, and transmitted as an optical signal 11c. In the optical multiplexer 6a, the optical signal transmitted from the E / O converter 10a
11c and the optical signal 11a that has passed through the bypass optical transmission line 5a are multiplexed, and this is transmitted to the optical branching unit 4b.

In the optical branching unit 4b, the optical signal 11c is branched into the optical signal 11d and the optical signal 11e, and the optical signal 11a is branched into the optical signal 11f and the optical signal 11g by the same operation as that of the optical branching unit 4a. The optical signal 11e and the optical signal 11g are sent to the O / E converter 9b, and the optical signal 11d and the optical signal 11f are sent to the bypass optical transmission line 5b. The optical signal 11e and the optical signal 11g are converted from an optical signal into an electric signal in the O / E converter 9b and transmitted to the node 3b. Of the optical signals sent from the O / E converter 9b, the node 3b receives only the electrical signal from the optical signal 11e whose power has reached the discrimination level, and the communication is established. This power identification level is fixedly preset.

Next, the case where the node 3a does not operate due to a failure or the like will be described. In this case, the optical signal flowing through the optical transmission line 1b is only the optical signal 11a coming through the bypass optical transmission line 5a. The optical branching unit 4b branches the optical signal 11a into an optical signal 11f and an optical signal 11g, sends one optical signal 11g to the O / E converter 9b through the optical transmission line 7b for downlink access, and outputs the other optical signal 11f. To the bypass optical transmission line 5b.

At this time, the optical signal 11 entering the O / E converter 9b
Since the power of g passes through the optical accessor 2a, it is attenuated by several dB or more from the optical signal 11. Therefore, if the optical transmission path 1b, which is the distance between the relay node and the receiving node, is long, the bypassed optical signal power causes the O / E converter 9b to accurately operate due to the decrease in power due to branching and the attenuation due to distance. There are cases where optical signals cannot be received.

[0009]

As described above, according to the conventional method, even if the node or the access optical transmission line responsible for relaying a certain communication does not operate due to a failure or the like, the communication is not interrupted by the optical signal passing through the bypass. However, in this case, each time the optical signal passes through the optical accessor, it is attenuated by several dB or more compared to the power before passing, so it is sent to the node that should receive the data. Considering the attenuation up to, the relayable transmission distance becomes shorter,
For example, it was difficult to apply it to a loop-type optical network on a nationwide scale.

Therefore, an object of the present invention is to provide a long-distance relay by sending an optical signal of sufficient power to the optical transmission line even if the node or the optical transmission line for access that does not operate due to a failure or the like does not operate. It is to provide an optical network system capable of performing.

[0011]

In order to achieve the above object, an optical network terminating device according to the present invention is a receiver for regenerating and repeating an optical signal received from an optical transmission line, and an optical signal regenerated and repeated by the receiver. Optical branching device for branching into two, an optical transmission line for bypass for transmitting one optical signal branched by the optical branching device to the optical multiplexer, and transmitting the other optical signal branched by the optical branching device to the optical network From an optical transmission line for downstream access, an optical transmission line for upstream access that transmits an optical signal transmitted from an optical network to the optical multiplexer, an optical signal transmitted to an optical transmission line for bypass and an optical transmission line for upstream access It is characterized by comprising an optical multiplexer for multiplexing an optical signal to be sent and a transmitter for regenerating and repeating the optical signal multiplexed by the optical multiplexer and transmitting the optical signal to an optical transmission line.

In such an optical network terminating device according to the present invention, since the receiver and the transmitter are located closer to the optical transmission line side than the optical accessor, the power of the optical signal attenuated by passing through the optical accessor is transmitted by the receiver. It is regenerated to the power of and transmitted. Further, in the transmitter, if the bypass light is ignored under normal conditions, the threshold for code identification is adjusted so as to identify only the main signal, and if it is adjusted so that the bypass light is regenerated during a failure, the power of the optical signal is attenuated. It is possible to prevent it and to carry out long-distance relay even in the case of a failure.

[0013]

Next, embodiments of the present invention will be described.
FIG. 2 is a schematic diagram illustrating the configuration of an optical network terminator 20 according to the present invention. In the figure, 21 and 22 are optical transmission lines, 23 is an optical network or node, 24 is a receiver, 25 is an optical accessor, 26 is a transmitter, 27 is an optical branching unit in the optical accessor, and 28 is a bypass in the optical accessor. Optical transmission line, 29 is an optical multiplexer in the optical accessor, 30 is a downlink access optical transmission line, and 31 is an upstream access optical transmission line.

FIG. 3 is a diagram for explaining an example in which the optical network termination device according to the present invention is applied to, for example, a loop type optical network system. In the figure 23a, 23b, 23c
May be an optical network or a single node with optical input and output. In the following description, the latter is taken as an example for simplicity.

First, the operation when the communication from the node 23c to the node 23b is performed through the node 23a and the node 23a is operating normally will be described. The optical signal 32 transmitted from the node 23c is the upstream access optical transmission line 31c.
And the optical accessor 25c through the optical combiner 29c and the transmitter.
The optical signal 32a is regenerated and relayed at 26c. The optical signal 32a flows through the optical transmission line 21a, is regenerated and relayed by the receiver 24a, and is then sent to the optical branching unit 27a in the optical accessor 25a.

In the optical branching unit 27a, the optical signal 32a is converted into the optical signal 32b.
And the optical signal 32c, and one optical signal 32b is routed to the bypass optical transmission line 28a in the optical accessor and the other optical signal 32c.
c is transmitted to the node 23a via the downlink access optical transmission line 30a. The optical signal 32d from the node 23a passes through the upstream access optical transmission line 31a and passes through the optical multiplexer in the optical accessor.
The optical signal 32b that has passed through the bypass optical transmission line 28a at 29a
And is sent to the transmitter 26a.

When the optical signal is input from both the upstream access optical transmission line 31a and the bypass optical transmission line 28a to the transmitter 26a during normal operation, the upstream access optical transmission line 31a having a higher optical signal power is supplied. Only the optical signal 32d that has passed through is regenerated and relayed, and is transmitted to the optical transmission line 21b as the optical signal 32e. The optical signal 32e is regenerated and relayed by the receiver 24b and sent to the optical branching unit 27b. In the optical branching unit 27b, the optical signal 32e is branched into the optical signal 32f and the optical signal 32g, and one optical signal 32f
Is transmitted to the bypass optical transmission line 28b, and the other optical signal 32g is transmitted to the node 23b.

Next, the operation when the node 23a is in failure will be described. There are cases where the optical signal level becomes 0 and cases where an abnormal signal is generated, but when an abnormal signal occurs, it is assumed that the network control mechanism operates to reach the former state. set to target.

In this case, the optical signal 32a is received at the receiver 24a.
The operation until is received is the same as the normal operation. Optical signal
32a is an optical signal 32b and an optical signal 32c in the optical branching unit 27a.
Branched to But if node 23a is down,
Only the optical signal 32b that has passed through the bypass optical transmission line 28a is input to the optical multiplexer 29a. In this case, since there is no optical signal input from the upstream access optical transmission line 31a to the transmitter 26a, the transmitter 26a can recognize that the node 23a is out of order, thereby regenerating the bypass light. The threshold can be adjusted so that Therefore, the transmitter
At 26a, the optical signal 32b from the bypass optical transmission line 28a is regenerated and relayed, and is transmitted to the optical transmission line 21b as an optical signal 32e.

The optical signal 32e coming through the optical transmission line 21b is
It is regenerated and relayed by the receiver 24b and sent to the optical branching unit 27b.
At the optical branching unit 27b, the received optical signal 32e is converted into the optical signal 32f.
And an optical signal 32g, one optical signal 32f is transmitted to the bypass optical transmission line 28b, and the other optical signal 32g is transmitted to the node 23b. The node 23b receives the optical signal 32g sent from the optical branching unit 27b and establishes communication bypassing the faulty node 23a.

In the above description, an example in which a node fails has been described, but the optical network termination device according to the present invention can, of course, be used even when the upstream access optical transmission line or the downstream access optical transmission line fails. It can operate similarly.

The optical network terminator according to the present invention comprises:
Functions of optical branching device, optical multiplexer and optical transmission line for bypass 1
It is preferably constructed in an optical accessor consisting of three optical components. Such a structure can be easily realized by the recent optical integration technology, and by adopting such a structure, downsizing and improvement in performance can be realized.

The optical network terminator according to the present invention comprises:
It is extremely suitable as a terminator when connecting an optical network with a loop type optical transmission line, but of course, as a terminator when connecting an optical network to another type, such as a linear type or a branch type optical transmission line. Can also be used. In such a case, when performing bidirectional transmission, a bidirectional optical transmission path may be provided.

[0024]

As described above, in the optical network terminator according to the present invention, various noise components can be removed by selecting only the main signal at the transmitter, and further, the receiver and the transmitter. By regenerating and relaying with, the optical signal of sufficient power can be output to the optical transmission line, and the distance between nodes at which communication is possible can be extended.

[Brief description of drawings]

FIG. 1 is a diagram showing a part of an example of a conventional optical network system.

FIG. 2 is a diagram showing an embodiment of an optical network termination device according to the present invention.

FIG. 3 is a diagram showing a part of an example of an optical network system using an optical network terminal device according to the present invention.

[Explanation of symbols]

 1, 21, 22 Optical transmission line 2, 25 Optical accessor 3 Node 4, 27 Optical branching unit 5, 28 Bypass optical transmission line 6, 29 Optical multiplexing unit 7, 30 Downstream access optical transmission line 8, 31 Upstream access Optical transmission line 9 O / E converter 10 E / O converter 11, 32 Optical signal 20 Optical network terminating device 23 Optical network or node 24 Receiver 26 Transmitter

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Jun Sasaki 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo Inside Nippon Telegraph and Telephone Corporation

Claims (2)

[Claims] 1. An optical network terminator installed at a connection point between a plurality of optical networks and an optical transmission line for connecting these optical networks, regenerates and relays an optical signal received from the optical transmission line. A receiver, an optical branching device for branching an optical signal regenerated and relayed by the receiver into two, an optical transmission path for bypass for transmitting one optical signal branched by the optical branching device to an optical multiplexer, the optical Downstream access optical transmission line for transmitting the other optical signal branched by the splitter to the optical network, upstream access optical transmission line for transmitting the optical signal transmitted from the optical network to the optical multiplexer, the bypass optical An optical multiplexer for multiplexing an optical signal transmitted to the transmission line and an optical signal sent from the upstream access optical transmission line, and to the optical transmission line by regenerating and repeating the optical signal multiplexed by the optical multiplexer. Send send An optical network terminating device comprising a receiver. 2. The optical network terminator according to claim 1, wherein the functions of the optical branching device, the optical multiplexer and the optical transmission line for bypass are configured in an optical accessor composed of one optical component.