JPS60125029A - Two-way optical transmission system - Google Patents

Abstract

PURPOSE:To reduce the cost of an optical transmission line by making light signals in two ways different in wavelength, and using a light signal with an intermediate wavelength between the two wavelengths for two-way optical communication using an optical fiber cable in common. CONSTITUTION:Wavelengths lambda1-lambda3 are so set that lambda1<lambda2<lambda3; an optical wavelength demultiplexing and multiplexing filter 5 transmits and outputs a light signal with the wavelength lambda1 to the optical fiber cable and transmits and inputs a light signal within a band including the wavelengths lambda2 and lambda3 from the cable, and a filter 6 transmits and outputs a light signal with the wavelength lambda3 and transmits and inputs signals with the wavelengths lambda1 and lambda2. Then, a signal transmitter and receiver 3 receives both signals from a transmitting terminal station device 1 and the signal of another transmitter and receiver at the side of the terminal station device 1 passed through a two-way repeater as light signals having the wavelength lambda1, the signal which is not passed through the two-way repeater from another transmitter and receiver as a light signal having the wavelength lambda2, and the signal of another device at the side of the device 4 passed through the device 4 and two-way repeater as a signal having the wavelength lambda3, and the transmitter and receiver 3 also transmits those three kinds of signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a bidirectional optical transmission system. In particular, it relates to a bidirectional optical transmission system for the purpose of mutual communication between any two points or between any two or more points.

[Description of prior art]

For this purpose, a meeting telephone for maintenance and inspection of electric power cables, etc. needs to be placed at a relatively close distance so that the electric power cables can be easily inspected. In conventional telephones using copper cables, the transmission quality deteriorates significantly due to electromagnetic interference caused by the power cable, and since the copper cable is a conductor, it is necessary to keep it at least a certain distance away from the power cable. Maintenance inspection was not possible. Similar problems often occur with maintenance and monitoring telephones located in strong electric field areas such as transmitting stations at broadcasting stations.

It is optimal to use optical fiber cables as transmission lines for maintenance and inspection telephone lines that are exposed to strong electromagnetic fields. Fiber optic table is
As is well known, it has characteristics such as low loss, no interference from external electromagnetic fields, and is an insulator, making it ideal as a signal medium under conditions of exposure to strong electric fields.

However, when using optical fiber cables, optical fibers, optical signal transmitting/receiving equipment, optical branching/connection circuits for coupling the optical fibers and optical signal transmitting/receiving equipment, and bidirectional cables to compensate for transmission loss due to optical branching are required. It requires a repeater and has the disadvantage of high cost. In order to reduce costs, a method of bidirectional communication using a single optical fiber using optical wavelength division multiplexing transmission is also being considered. Need to send a signal.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an optical transmission system suitable for telephones for maintenance and inspection of power cables, etc., which can reduce the cost of optical transmission lines.

[Features of the invention]

The bidirectional optical transmission system of the present invention, in bidirectional optical communication using an optical fiber cable, makes bidirectional optical signals have different wavelengths, and transmits an optical signal with an intermediate wavelength between the two wavelengths to both directions. The feature is that it can be shared for mutual transmission.

That is, a first transmission terminal equipment installed at one end of the optical fiber transmission line, a second transmission terminal equipment installed at the other end of the optical fiber transmission line, and a a repeater inserted into the optical fiber transmission line, and a signal transmitting/receiving device inserted in the middle of the optical fiber transmission line, and a wavelength λ is transmitted in the direction from the first transmission terminal equipment to the second transmission terminal equipment.
In a frequency multiplexing bidirectional transmission system, an optical signal of wavelength λ3 is relay-transmitted from the second transmission terminal device to the first transmission terminal device, and an optical signal of wavelength λ3 is relay-transmitted from the second transmission terminal device to the first transmission terminal device,
The signal transmitting/receiving device includes a device for transmitting and receiving a signal of wavelength λ2 between wavelength λ1 and wavelength λ3 to the optical fiber transmission line, and a device having a wavelength λ1 transmitted to the optical fiber transmission line.
and a device for intercepting a signal of wavelength λ3, and the repeater combines information of the received signal of wavelength λ2 with a signal of wavelength λ1 or A3 transmitted in the direction of arrival of the signal, The present invention is characterized in that it is equipped with a device for transmitting it as an A3 signal.

[Explanation based on examples]

The figure is a block configuration diagram of an optical transmission line according to an embodiment of the present invention.

The optical transmission line between the transmission terminal equipment l and the transmission terminal equipment 4 includes:
One bidirectional optical repeater 2 and one optical signal transmitting/receiving device 3 each.
transmission terminal equipment 1, a plurality of bidirectional optical repeaters 2, a plurality of optical signal transmitting/receiving equipment 3, and a transmission terminal equipment 4.
are connected by fiber optic cables.

The transmission terminal device 1 includes an optical wavelength separation/coupling filter 5, and the optical wavelength separation/coupling filter 5 is connected to an optical fiber cable.

The bidirectional optical repeater 2 includes an optical wavelength separation/coupling filter 5 , an optical wavelength separation/coupling filter 6 , an optical signal converter 8 , and a p-optical signal converter 9 . The optical wavelength separation/coupling filter 6 is connected to an optical fiber cable of one example of transmission terminal equipment, and the optical wavelength separation/coupling filter 6 is connected to the optical signal converters 8 and 9.
connected to.

Optical signal converters 8 and 9 are each connected to optical wavelength separation/coupling filter 5. The optical wavelength separation/coupling filter 5 is
It is connected to the optical fiber cable on the transmission terminal equipment 4 side.

The optical signal transmitting/receiving device 3 includes an optical branching/connecting circuit 7.

In the signal transmission system of the present invention, an optical wavelength division multiplexing transmission system is adopted for bidirectional signals. In the description of this embodiment, it is assumed that the modulation method for converting an electrical signal for a meeting telephone into an optical signal is a direct optical intensity modulation method.

Next, the relationship between optical wavelengths of transmission signals, which is a feature of the present invention, will be described.

In order to perform bidirectional transmission, in this embodiment, the first wavelength λ1
, using optical signals having a second wavelength λ3 and a third wavelength λ2. The wavelength has the following relationship λ1〈λ2〈λ3 −−−−・−・−(11).

The optical wavelength separation/coupling filter 5 transmits and outputs an optical signal having a wavelength λ1 to the optical fiber cable, and transmits and inputs an optical signal having a band including wavelengths λ2 and λ3 from the optical fiber cable. On the other hand, the optical wavelength separation/coupling filter 6 transmits and outputs an optical signal of wavelength λ3 to the optical fiber cable, and transmits and inputs an optical signal of a band including wavelengths λ1 and wavelength λ2 from the optical fiber cable.

The optical signal converter 8 converts both the optical signal with the wavelength λ1 and the optical signal with the wavelength λ2 that have passed through the optical wavelength separation/coupling filter 6 into an optical signal with the wavelength λ1, and converts the optical wavelength separation/coupling filter 5 into an optical signal with the wavelength λ1. The converted optical signal of wavelength λ1 is sent to the optical fiber cable through the optical fiber cable.

On the other hand, the optical signal converter 9 converts both the optical signal with the wavelength λ2 and the optical signal with the wavelength λ3 that have passed through the optical wavelength separation/coupling filter 5 into an optical signal with the wavelength λ3, and separates the optical wavelength. The converted optical signal of wavelength λ3 is sent out to the optical fiber cable via the coupling filter 6.

The optical signal transmitting/receiving device 3 includes a device that transmits and receives a signal of wavelength λ2 between wavelength λ1 and wavelength λ3, and a device that intercepts signals of wavelength λ1 and wavelength λ3 transmitted on the optical fiber transmission line. There is. Thereby, the optical signal transmitting/receiving device 3 receives optical signals of wavelengths λ1, λ2, and λ3, and transmits an optical signal of wavelength λ2 from its own station via the optical branching/connection circuit 7.

In this way, the optical transmission line of this embodiment has a wavelength λ1 and a wavelength λ2 in the direction from the transmission terminal equipment 1 to the transmission terminal equipment 4.
The configuration is such that an optical signal of wavelength λ2 and wavelength λ3 are transmitted in the opposite direction. However, the optical signal of wavelength λ2 is transmitted between the optical signal transmitting/receiving device 3 that transmitted this signal and the nearest two-way optical repeater or transmission terminal device placed on both sides of this optical signal transmitting/receiving device 3. is configured to be transmitted only in

Communication between the optical signal transmitting/receiving device 3, the transmission terminal device 1.4, and any other optical signal transmitting/receiving device in the optical transmission line configured as described above will be explained.

First, the case of reception will be explained. Signal transmitting/receiving device 3
, the signal from the transmission end equipment W1 and the signal from the other signal transmitting/receiving device on the transmission end station device 1 side via the bidirectional repeater arrive as an optical signal of wavelength λ1, and the signal from the two-way optical repeater arrives. A signal from another optical signal transmitting/receiving device that does not go through the transmission terminal device 4 arrives as an optical signal with wavelength λ2, and the signal from the transmission terminal device 4 and other optical signals on the transmission terminal device 4 side via the bidirectional optical repeater arrive. A signal from the signal transmitting/receiving device arrives as an optical signal of wavelength λ3. The optical signal transmitting/receiving device 3 uses these three types of wavelengths λ1 and λ
2 and λ3 optical signals can all be received. Therefore, the optical signal transmitting/receiving device 3 is the transmission terminal device 1
, the transmission terminal device 4, and any optical signal transmitting/receiving device.

Next, the case of transmission will be explained. The optical signal transmitting/receiving device 3 transmits an optical signal having a wavelength λ2 in both directions of the optical fiber cable. The optical signal with wavelength λ2 is transmitted to bidirectional optical repeater 2.
As a result, the optical signal heading towards the transmission terminal equipment w1 is converted into an optical signal with a wavelength λ3, and the optical signal heading towards the transmission terminal equipment 4 is converted into an optical signal with a wavelength λ1. 4 and other optical signal transmitting/receiving devices. Also,
Since the transmission terminal device 1, the transmission terminal device 4, and the optical signal transmitting/receiving device are configured to be able to input an optical signal of wavelength λ2, the bidirectional optical repeater 2 is connected to the optical signal transmitting/receiving device 3. Even if it is not arranged, the optical signal transmitted by the optical signal transmitting/receiving device 3 can be received. Therefore, the optical signal transmitting/receiving device 3 can transmit an optical signal to the transmission terminal device 1, the transmission terminal device 4, and any optical signal transmitting/receiving device.

Further, the transmission terminal device 1 and the transmission terminal device 4 can communicate with each other using a signal with a wavelength λ1 and a signal with a wavelength λ3.

In this way, communication is possible between both end station devices and any station located between them.

In the case of communication between optical signal transmitting/receiving devices without a bidirectional repeater in between, an optical signal of wavelength λ2 is used for transmission and reception. However, by adopting an alternate call method,
Does not cause any problems.

In this embodiment, the relationship between the wavelengths of optical signals is defined as shown in Equation (1), but the following relationship may also be used.

λ1>λ2>λ3 ・−−−・−(21 This corresponds to the case where the top, bottom, left, and right of the figure are reversed.

〔Effect of the invention〕

As explained above, in the optical transmission line according to the present invention, the optical signal transmitted by the optical signal transmitting/receiving device provided in the middle is 1
Optical signals of different wavelengths are required, which has the effect of reducing manufacturing costs of optical signal transmitting and receiving devices.

Particularly, when a large number of optical signal transmitting/receiving devices are used, this brings about a significant cost reduction.

Furthermore, by setting the third wavelength to an intermediate wavelength between the first wavelength and the second wavelength, the present invention can be achieved simply by widening the band of the optical wavelength separation/coupling filter of the conventional bidirectional optical repeater. can be carried out.

It is technically easy to widen the band of the filter, and the cost increase due to this is extremely low.

[Brief explanation of the drawing]

The figure is a block configuration diagram of an optical transmission line according to an embodiment of the present invention. 1... Transmission terminal equipment, 2... Bidirectional optical repeater, 3...
... Optical signal transmitting and receiving device, 4... Optical transmission terminal device, 5.
... Optical wavelength separation/coupling filter, 6... Optical wavelength separation/coupling filter, 7... Optical branch/connection circuit, 8... Optical signal converter, 9... Optical signal converter.

Claims (1)

[Scope of Claims] A repeater inserted in the middle of a fiber transmission line, and a signal transmitting/receiving device inserted in the middle of the optical fiber transmission line, the direction from the first transmission terminal equipment to the second transmission terminal equipment. In a frequency multiplexing bidirectional transmission system, an optical signal with a wavelength λ1 is relayed and transmitted in the direction from the second transmission terminal device to the first transmission terminal device, and an optical signal with a wavelength λ3 is relayed and transmitted in the direction from the second transmission terminal device to the first transmission terminal device. , the signal transmitting and receiving device includes a device that transmits and receives a signal with a wavelength λ2 between the wavelength λ1 and the wavelength λ3 to the optical fiber transmission line, and a signal with the wavelength λ1 and the wavelength λ3 transmitted to the optical fiber transmission line. and a device for intercepting the signal, and the repeater combines the information of the received signal of wavelength λ2 with the signal of wavelength λ1 or λ3 transmitted in the direction of arrival of the signal, and generates a signal of wavelength λ1 or λ3. A bidirectional optical transmission system characterized by being equipped with a transmission device.