JPS62146024A - Optical communication system - Google Patents

Abstract

PURPOSE:To extent the transmission distance without increasing the intensity of the output of each light source. CONSTITUTION:An optical multiplexer 2 is attached to one end of an optical transmission line 1 consisting of optical fibers, and a light receiver 3 is attached to the other end, and output beams of light difference in wavelength from plural light sources 4a-4n are introduced to the optical multiplexer 2. The light receiver 3 has a sensitivity to any of output beams of light from light sources 4a-4n, and the same modulating signal 5 is supplied to all light sources. Consequently, an input power is equal to the sum of input powers Pa-Pn due to light sources; and though the modulated light is attenuated in a prescribed proportion while it is transmitted on the optical transmission line 1, the reception demodulating operation or the like is performed by the light receiver 3 to take out a required signal.

Description

[Detailed description of the invention] Industrial application field> The present invention relates to an optical communication system, and more specifically, an optical communication system that uses light as a carrier signal and modulates the light with a transmitted signal. Regarding the method.

<Prior Art and Problems to be Solved by the Invention> Conventionally, optical fibers have been commonly used as optical transmission lines in optical communications that use light as a carrier signal.

Since this optical fiber has a wide band, the transmission distance is hardly affected by the width or narrowness of the band, but is greatly affected by loss, and this loss limits the transmission distance of the optical fiber. For example, if the input power of an optical fiber is Q
d3m, the transmission loss of the optical fiber is 3 dB/Km, and the minimum receivable power on the receiver side is 130 dBm, then a transmission distance of only 10 Km can be obtained.

In order to transmit signals over long distances under the above conditions, it is necessary to increase the input power of the optical fiber, reduce the transmission loss of the optical fiber, or improve the minimum receivable power of the receiver. I will have to.

However, in the case of optical communications that use laser light for projection, increasing the output light intensity of the light source is extremely difficult and is practically impossible. In addition, reducing transmission losses in optical fibers and increasing the minimum receivable power of the receiver are extremely difficult, as is increasing the output light intensity of the light source, and are almost impossible in practice. .

Therefore, in order to transmit signals over long distances, relay stations must be installed at predetermined distance intervals, and the signals must be amplified at these relay stations.

<Object of the invention> This invention was made in view of the above problems,
It is an object of the present invention to provide an optical communication system that can increase transmission distance without increasing the output light intensity of a single light source.

Means for Solving the Problems> In order to achieve the above object, the optical system of the present invention is to output light from a plurality of light sources whose wavelengths are equal to each other,
Modulated by the same modulation signal and guided to one end of the optical transmission line,
At the other end of the optical transmission line, the transmitted light is received by a receiver capable of receiving all of the above output lights.

However, the optical transmission line is preferably an optical fiber.

In the optical communication system described above, the output lights of different wavelengths from multiple light sources are modulated by the same modulation signal and guided to one end of the optical transmission path. The input power of the optical transmission line can be increased without increasing the output light intensity, and the transmitted light is received by a receiver capable of receiving all of the above output lights at the other end of the optical transmission line. In response to an increase in the input power of the optical transmission line, the power received by the receiver can be increased.

When an optical fiber is used as the optical transmission line, transmission loss can be significantly suppressed and the ratio of received power to input power can be increased.

In addition, the following may be considered as another effect.

In order to improve reliability, submarine repeaters are equipped with two light-emitting elements, and if the first light-emitting element in use begins to deteriorate, the ff
12 light emitting elements are designed to switch to automatic fishing.

This switching uses an optical switch and a polarization combiner instead of a normal optical branching coupler so as not to degrade the coupling efficiency between the light emitting element and the optical fiber. However, these optical elements have complicated structures, and it is impossible to detect that the light emitting elements have been switched at the receiving end.

Therefore, if, for example, a semiconductor laser with an oscillation wavelength of 1.3 μm is used as the first light emitting element and a semiconductor laser with an optical wavelength of 1.2 μm is used as the second light emitting element, as in Honkitamon, - The optical multiplexer/demultiplexer used for transmission is used as a coupler for the light emitting element and the optical fiber, and it becomes possible to detect that the light emitting element has been switched at the receiving end.

<Example> Hereinafter, embodiments will be explained in detail with reference to the accompanying drawings.

The drawing is a schematic diagram showing an embodiment of the optical communication system by Kitamon, in which an optical multiplexer (2) is attached to one end of an optical transmission line (1) consisting of an optical fiber, and an optical receiver is attached to the other end. (3) is installed. Then, a plurality of light sources (4a
)(4b)...(4n), output lights having mutually different wavelengths are introduced into the optical multiplexer (2).

Further, the optical receiver (3) includes at least each of the light sources (
It is sensitive to any of the output lights from 4a), (4b), . . . (4n). Furthermore, all of the above light sources (4
a) The same modulation signal (5) is supplied to each of (4b)...(4n).

If the above optical transmission method is 8, multiple light sources (4a) (
4b) ...(4n), output lights with different wavelengths or modulated by the same modulation signal are sent to the optical multiplexer (
2) into the optical transmission line (1), the input power P is the sum of the input power - Pa, Pb, ... pn from each light source (4a) (41))...(4n). be equal. The modulated light is attenuated at a predetermined rate while being transmitted through the optical transmission line (1), and is finally received by the optical receiver (3) that is sensitive to all of the modulated light. , demodulation, etc., it is possible to extract the necessary signals.

Specifically, the output light from two optical transmitters with oscillation wavelengths of 1.2 μm and 1.3 μm is transmitted with an inter-port loss of 1 d.
[3 optical multiplexers combine the signals and couple them into one optical fiber, and each of the above optical transmitters is combined with Qd3
When adjusted to couple to an optical fiber with a coupling power of m, the optical fiber coupling power after multiplexing becomes 2 dBm, which is an improvement of 2 dB compared to the conventional method described above.

Also, the light source is 1011! l, the optical fiber input power from each light source is Qc13m, and the optical fiber transmission loss is 3.
dB/Km, and the minimum receivable power is set to 130 cjBm, the input power of the optical fiber is 10
This will increase the transmission distance to 13.3km. this is,
This results in an increase in transmission distance of 3.3 km compared to 10 km when there is only one light source.

As is clear from the above explanation, the transmission distance between the light source and the optical receiver can be increased without increasing the output light intensity of the light source alone, allowing signal transmission over long distances. It becomes possible to reduce the number of relay stations when performing the following.

<Effects of the Invention> As described above, this defense is based on the unique feature that the input power of the optical transmission line can be increased and the transmission distance can be increased without increasing the output light intensity of the light source alone. It has the effect of

Furthermore, low-loss switching of the light emitting elements becomes possible, and the reliability of the transmission path also improves.

[Brief explanation of drawings]

The drawing is a schematic diagram showing an embodiment of an optical communication system according to the present invention.

Claims (1)

[Claims] 1. Light from multiple light sources with different wavelengths The output light is modulated by the same modulation signal. and guide it to one end of the optical transmission line. At the other end, receive all the above output lights The transmitted light is received by a capable receiver. An optical communication method characterized by: 2. The above patent in which the optical transmission line is an optical fiber An optical communication system according to claim 1.