JPH0481135A - Optical transmission line - Google Patents

Abstract

PURPOSE:To ensure the communication among nodes by using an optical amplifier provided to an optical tap so as to amplify optical signals from each optical tap thereby making output levels of the signals equal to each other. CONSTITUTION:When an electric signal is sent from a computer 42 of a transmission node 4 to an E/0 converter 40 through an electric signal transmission line 41, the electric signal is electrooptic-converted and the result is inputted to an optical tap 2 through an optical fiber 45, an optical demultiplexer multiplexer 46 and an optical drop cable 3. An optical signal entering a trunk line optical fiber 1 is branched into two at a 1st optical demultiplexer multiplexer 20 of an adjacent optical tap 2. The optical signal entering an optical amplifier 5 is amplified therein, in which a transmission loss or the like by the 1st optical demultiplexer multiplexer 20 in the optical tap 2 and the trunk line optical fiber 1 is compensated, and the level is kept the same as the level having been inputted from the optical tap and the signal is outputted to the trunk line optical fiber 1.

Description

[Detailed Description of the Invention] (Industrial Application Field) The optical transmission line of the present invention is an optical L A N (Local Ar
ea Network), optical C5MA/CD (Carrier 5ense M
ultiple Access / Co11isio
nDetection).

(Prior Art) In a conventional bus-type optical transmission line, as shown in FIG. 5, at least two or more optical taps B are attached to one trunk optical fiber A, and each optical tap B has a node D. Connected. In this optical transmission line, an electrical signal reversed from the computer E of one of the nodes D is converted from electrical to optical by an E10 converter G, and this optical signal is transmitted to the trunk optical fiber A via the optical tap B. The signal is branched by another optical tap B and transmitted to the node D connected to each optical tap B.

Then, in the node D that received the optical signal in Fig. 5,
The optical signal is subjected to optical-to-electrical conversion by the O/E converter F, and its average reception level is compared with a pre-stored level of the optical signal under normal conditions without collision. At this time, if optical signals are simultaneously transmitted from two or more nodes D and these optical signals collide and mix on the optical transmission path, the average reception level of the mixed optical signals will be the same as the normal optical signal level. Since it is relatively large, the data of that optical signal is not captured.

At this time, the node D that transmitted the optical signal sends a part of the optical signal to the O/E converter F as a transmission monitor signal. At this time, if no optical signal is transmitted from another node D, the O/E converter F receives only the transmitted monitor electrical signal, so there is no signal collision.
It is determined that the transmission was successful.

However, when an optical signal is being transmitted from another node D at the same time, the 0/E converter G in the transmitting node D
In addition to the above-mentioned transmitted monitor signal, the optical signal transmitted from another node D is also increased in strength, causing collision between the two signals, and the average reception level of the 0/E converter F becomes higher than in a normal state without collision. In this case, there is a collision of optical signals, it is determined that the transmission has failed, and retransmission is attempted.

(Problem to be Solved by the Invention) However, in the conventional optical transmission line, the optical signal of the main optical fiber A is attenuated each time it passes through the optical tap B, and is also attenuated due to the transmission loss of the @ line optical fiber A itself. Therefore, the level of the optical signal transmitted from the node D at the far end becomes low when it is received by the node D at the other end, making it difficult to perform reliable communication. Another problem is that when the level of the optical signal decreases, it becomes difficult to determine whether the transmission was successful or not.

(Objective of the Invention) The object of the present invention is to compensate for attenuation in optical taps and optical fibers, ensure communication between nodes connected to the trunk optical fiber, and check whether transmission is successful or not. It is an object of the present invention to provide an optical transmission line that can reliably detect the

(Means for Solving the Problems) As shown in FIGS. 1 and 2, the optical transmission line of the present invention has at least two or more optical taps 2 attached to a main optical fiber 1, and each optical tap 2 A node 4 is connected to the node 4, and an optical signal from one of the nodes 4 is transmitted to the trunk optical fiber 1 via the optical tap 2, and the optical signal is transmitted to the other optical tap 2.
In the optical transmission line, the optical signals are branched and transmitted to other nodes 4, and when two or more nodes 4 transmit optical signals at the same time, the optical signals collide. It has a built-in optical amplifier 5 that amplifies the optical signal so that the output level of all the optical taps 2 becomes the same when there is no collision with the Ig.

(Function) In the optical transmission line of the present invention, an optical amplifier 5 is provided in each optical tap 2 as shown in FIG. The output levels from all optical taps 2 are amplified to be the same.

Therefore, the average reception level of the optical signal that is mixed when the optical signals transmitted simultaneously from two nodes 4 collide is approximately twice that of the optical signal level under normal conditions when there is no collision. The average reception level of the received optical signals is proportional to the number of colliding optical signals, such that the level of the minxed optical signal caused by collision of simultaneously transmitted optical signals is approximately twice as high. Therefore, it is not only possible to reliably determine whether or not received optical signals collide, but also to reliably determine whether or not the transmission was successful at the node that transmitted the optical signal.

(Embodiment) FIGS. 1 to 3 show an embodiment of the optical transmission line 1″f of the present invention.

In FIG. 1, 1 is a trunk optical fiber, and 3 is an optical drop cable, both of which use single mode quartz optical fibers.

Reference numeral 2 shown in FIGS. 1 and 2 is an optical tap attached to the trunk optical fiber 1. As shown in FIG. As clearly shown in FIG. 2, this optical tap 2 includes a first optical branch/combiner 20 attached to the trunk optical fiber 1, and an optical fiber 21 connected to the first optical branch/combiner 20. An apparatus consisting of a second optical branch/combiner 22 attached and an optical amplifier 5 attached to the main optical fiber l between the two first optical branch/multiplexers 20. A single-mode quartz optical fiber 11 splitter is used for the optical branch/combiner 20 and 22, a single-mode quartz optical fiber is used for the optical fiber 21, and an erbium-doped A
A bidirectional optical fiber amplifier with GC (Auto Galn Control) is used.

4 in FIGS. 1 and 3 is a node, which, like conventional nodes, includes an optical transmitting/receiving section 40 and an electrical signal running path 4.
1 is connected to a computer 42. As shown in FIG.
The E10 converter 43 and the O/E converter 44 are connected by a monitor signal transmission path 47.

For example, the E10 converter 43 has a transmission rate of 20
Mbps, output light level 20dBm, output speed 1.53
A laser diode having a semiconductor laser diode of mm is used.

For example, the 0/E converter 44 has a transmission rate of 20
A device having a PIN photodiode made of InGaAs with a light receiving level of -35 dBm and a reception level of -35 dBm is used.

A single mode quartz optical fiber is used as the optical fiber 45, and a single mode quartz optical fiber 11 splitter is used as the optical branch/combiner 46.

Reference numeral 6 in FIG. 1 is a reflected light attenuator attached to both ends of the trunk optical fiber 1. This is for terminating the optical signal that has reached both ends of the trunk optical fiber 1 so as not to reflect it. be. As this reflected light attenuator 6, for example, an FC connector which has been subjected to diagonal polishing is used.

Signal transmission is performed in the optical transmission line shown in FIG. 1 as follows.

When an electrical signal is transmitted from the computer 42 (FIG. 3) of the sending node 4 to the E10 converter 43 through the electrical signal running path 41, the electrical signal is electrical-to-optical converted by the E10 converter 43, and the optical signal is transmitted to the optical fiber 45, The optical branch/combiner 46 is manually supplied to the optical tap 2 through the optical drop cable 3. This optical signal is split into one by a second optical branch/combiner 22 in the optical tap 2 of FIG. 2, enters the first optical branch/combiner 20, and then merges into the trunk optical fiber l.

The optical signal entering the trunk optical fiber 1 is branched into two by the first optical branch/combiner 20 of the adjacent optical tap 2. One of these optical signals enters the optical amplifier 5, and the other optical signal enters the second optical branch/combiner 22.

The optical signal entering the optical amplifier 5 is amplified by the amplifier 5, and then sent to the first optical branch/combiner 20 in the optical tap 2 through the trunk optical fiber 1.
The transmission loss etc. due to this are compensated for, and the signal is output to the trunk optical fiber 1 at the same level as the level at which it was input from the previous optical tap 2.

The optical signal that has entered the second optical branch/combiner 22 is input to the node 4 through the optical drop cable 3. The optical signal inputted to this node 4 is transmitted to the optical branch/combiner 4 shown in Fig. 3.
6 to the O/E converter 44 for optical-to-electrical conversion, and is input to the computer 42 through the signal running path 41, where it is compared with the level of the optical signal during normal times without collision. If the level of the optical-electrical converted electrical signal is detected to be twice the normal level, twice, etc., the electrical signal will be detected as the optical-electrical signal mixed by the collision. It is determined that the electrical signal has been converted, and the data of the electrical signal is not taken into the receiving node 4.

On the other hand, in the transmitting node 4, E1 in FIG.
The transmission monitor signal is sent from the 0 converter 43 to the O/E converter 44, and when only the transmission monitor signal is received by the 0/E converter 44, it is determined that there was no collision of optical signals and the transmission was successful. It is judged that. Also, O
If the average reception level of the /E converter 44 is detected to be twice the level of the transmitted monitor signal, twice, etc., it is determined that the optical signals collided and the transmission failed, and the transmission is retransmitted. is attempted.

What is shown in FIG. 4 is another example of the node 4 used in the optical transmission line of the present invention.

This node 4 includes an optical splitter/combiner 46, an O/E converter 44, a computer 42, an E10 converter 43, an optical splitter 48 that branches monitor light from the optical signal transmitted therefrom, and an optical attenuator that attenuates the monitor light. 50, and a light combiner 49 for combining the monitor lights.

Incidentally, the optical attenuator 50 used has an attenuation amount of 18 dB.

In this node 4, the optical attenuator 50 optically attenuates the output level of the monitor light so that it becomes almost the same as the output level of the received optical signal from the other node 4 input to the 0/E converter 44. As a result, the level difference between the optical signal merged into the optical combiner 49 and the transmitted monitor light becomes small, so when the level fluctuation detected by the 0/E converter 44 is large, the optical signal is reduced in the trunk optical fiber l. Since it can be assumed that a collision has occurred, it is easy to identify a collision.

(Effects of the Invention) In the optical transmission line of the present invention, the optical amplifier 5 provided in the optical tap 2 amplifies the optical signals from each optical tap 2 so that the output levels thereof are all the same. Communication between nodes 4 is ensured.

Furthermore, since it is possible to accurately determine not only whether there is a signal collision but also whether the transmission was successful at the node 4 that transmitted the optical signal, retransmission can be performed until the transmission is successful.

[Brief explanation of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of the optical transmission line of the present invention, FIG. 2 is a configuration diagram of an optical tap of the same transmission line, and FIGS.
The figure is a configuration diagram showing different examples of nodes on the same transmission line, and FIG. 5 is an explanatory diagram showing a conventional optical transmission line. 1 is the trunk optical fiber, 2 is the optical tap 4 is the node, and 5 is the optical amplifier box diagram.

Claims (1)

[Claims] At least two or more optical taps 2 are attached to one trunk optical fiber 1, a node 4 is connected to each optical tap 2, and an optical signal from one of the nodes 4 is transmitted to the optical tap 2.
The optical signal is transmitted to the main optical fiber 1 via another optical tap 2 and transmitted to another node 4. If two or more nodes 4 transmit optical signals at the same time, the optical signals will collide. In the optical transmission line, the optical tap 2 has a built-in optical amplifier 5 that amplifies the optical signal so that the output level of all the optical taps 2 becomes the same without collision of the optical signals. An optical transmission line characterized by: