JPH02219331A - Wavelength multiplex optical transmission system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a wavelength division multiplexing optical transmission system used for wavelength division multiplexing optical communications.

BACKGROUND OF THE INVENTION In recent years, wavelength division multiplexing optical transmission systems are capable of high-speed, large-capacity communication and are easy to expand using existing optical fiber communication systems, so research and development in this field has been progressing. Furthermore, in order to carry out large-capacity communications, it is necessary to increase the density of wavelength multiplexing by multiplexing a large number of wavelengths at narrow wavelength intervals.

An example of the above-mentioned wavelength division multiplexing optical transmission system will be described below with reference to the drawings.

FIG. 4 shows the configuration of a conventional wavelength division multiplexing optical transmission system. 41 (1), 41 (2L...
...41(n) is a modulation signal source, 42(1), 42(
2), ...42 (n) is a light source, 43 is an optical multiplexer, 44 is an optical demultiplexer, 45 (1), 45 (2),
..., 45(n) is an optical-to-electrical converter, 46 is an optical fiber, 47 is an optical transmitter, and 48 is an optical receiver.

FIG. 5 is a conceptual diagram of wavelength multiplexing in FIG. 4.

The horizontal axis represents the wavelength, the vertical axis represents the intensity in the case of spectral intensity distribution, and the passage rate in the case of wavelength selection characteristics. 51 (
1'1. 51 (2), ..., 51 (n) are the wavelength selection characteristics of the optical demultiplexer, 52 (1), 52 (2
), . . . , 52(n) is the spectral intensity distribution of multiplexed light.

The operation of the wavelength division multiplexing optical transmission system configured as described above will be described below with reference to FIGS. 4 and 5.

In the optical transmitter 47, n light sources 42(1) 42(2)
,..., mutually different wavelengths λ from 42(n)
1. The lights of λ2, ..., λn are modulated signal sources 41 (1), 41 (2), ..., respectively.
41(n). Modulated wavelength λ1
．． The lights of λ2...λn are wavelength-multiplexed into one optical fiber 46 by an optical multiplexer 43 and transmitted. The transmitted light is subjected to wavelength selection characteristics 51 (1), 51 (2), . . . by the optical demultiplexer 44 in the optical receiver 48
51(n), the wavelength λ1. λ2. ......, λn
and each light is sent to an optical-to-electrical converter 45.
(1), 45 (2), ...45(n) converts it into an electrical signal. (For example, "optical communication device engineering"
475-476 Vane (Engineering Book) Problems to be Solved by the Invention However, in the above configuration, only one wavelength is assigned to one wavelength selection region of the optical demultiplexer, and the wavelength of the light source of the optical transmitter is ~ If the wavelength width is narrow, even if you try to double the number of multiplexes within the same wavelength region, that is, halve the wavelength spacing, there will be a limit to the wavelength selection characteristics of the optical demultiplexer, making it difficult to increase the number of multiplexes. There was a problem.

In view of the above-mentioned problems, the present invention utilizes optical demultiplexers in which the center wavelengths of the respective wavelength selection regions are different, thereby doubling the number of multiplexed wavelengths in the same wavelength region. It provides an optical transmission system.

Means for Solving the Problems In order to solve the above problems, the wavelength division multiplexing optical transmission system of the present invention includes an optical transmitter including a plurality of light sources with different wavelengths and an optical coupler for wavelength multiplexing, and an optical branching unit. It consists of an optical receiving section equipped with two optical demultiplexers and a plurality of optical-to-electrical converters, and one of the optical demultiplexers has wavelength selection characteristics that do not overlap with each other, and the center wavelength of each wavelength selection range is The wavelengths of the light sources to be multiplexed correspond to each other, and the center wavelengths of the non-overlapping wavelength selection regions of the other optical demultiplexer correspond to the non-overlapping wavelength regions of two adjacent wavelength selection regions of the one optical demultiplexer. The wavelength of the light source to be multiplexed corresponds to this wavelength.

It is desirable to use a diffraction grating as a wavelength separation element in the optical demultiplexer.

Effect of the Invention With the above-described configuration, the present invention can double the number of wavelength-multiplexed lights, that is, the number of multiplexed lights, in the same wavelength region compared to the conventional method.

Embodiment Hereinafter, a wavelength division multiplexing optical transmission system according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a configuration diagram of a wavelength division multiplexing optical transmission system according to an embodiment of the present invention. In Figure 1, 10(1)
, 10 (21,..., 10 (2n) is 2
n modulating signal sources, I IQ), 11(2)s...
..., l 1 (2n) is 2n light sources, 12 is an optical coupler, 13 is an optical splitter, 14a and 14b are optical demultiplexers, 1
5 (1), 15 (2)..., 15 (
2n) is 2n optical-electrical converters, 16 is an optical fiber,
17 is an optical transmitter, and 18 is an optical receiver.

FIG. 2 is a conceptual diagram of the optical demultiplexer 14a in FIG. 1. In FIG. 2, the horizontal axis represents the wavelength, the vertical axis represents the intensity for the spectral intensity distribution, and the pass rate for the wavelength selection characteristic. 21(1).

21 (3), --, 21 (2n -1) is the selection characteristic of the wavelength range of the n optical demultiplexers 14a, 22 (1), 2
2 (2)..., 22 (2n) is optical demultiplexer 1
This is the spectral intensity distribution of 2n-wave multiplexed light input to 4a.

FIG. 3 is a conceptual diagram of the optical demultiplexer 14b in FIG. 1. In Figure 3, 31 (2L 31 (4),...
...31 (2n) is the wavelength selection characteristic of n optical demultiplexers 14b, 32 (1), 32 (2), ...
, 32 (2n) is 2n input to the optical demultiplexer 14b
This is the spectral intensity distribution of n-wave type light.

The operation of the wavelength division multiplexing optical communication system configured as described above will be explained below with reference to FIGS. 1, 2, and 3.

In the optical transmitter 17, modulated signal sources 10(1) 10(2)
, ..., 10 (2n) directly modulated light source 11 (]), 11 (2), ......, 11
(2n) with mutually different wavelengths λ1. λ2.・・・・・・
..., the light of λ2n each has a spectral intensity distribution of 22
(1), 22 (2).

..., 22 (2n), and this light is converted into a 2nn waveform by the optical coupler 12 and transmitted through one optical fiber I6. The transmitted light is split into two by the optical splitter 13 in the optical receiver 18 .

The split lights are input to optical demultiplexers 14a and 14b, respectively. The wavelength of the wavelength-multiplexed light is determined by the optical demultiplexer 14.
Wavelength selection characteristics of a 21 (1), 21 (3)...
..., with the center wavelength of 21 (2n-1), the optical demultiplexer 1
Wavelength selection characteristics of 4b 31 (2), 31 (4),
...31 (2n) wavelength ranges that do not overlap with each other, and the wavelength selection characteristics 31 (2) of the optical demultiplexer 14b,
At the center wavelength of 31 (4)..., 31 (2n), the wavelength selection characteristic 21 (]) of the optical demultiplexer 14a,
21 (3), . . . 21 (2n-1), which correspond to wavelength ranges that do not overlap with each other.

Therefore, in the optical demultiplexer 14a, among the wavelength-multiplexed lights,
Wavelength λ1. The lights with wavelengths λ3..., λ2□1 are separated, and the optical demultiplexer 14b separates the lights with wavelengths λ2. λ4.・・・・・・、
Light of λ2° is separated.

The separated light is transmitted to optical-to-electrical converters 15(1), 15(
2)..., 15 (2n) converts it into an electrical signal and takes it out.

As described above, according to this embodiment, the number of wavelengths to be multiplexed can be doubled by using a conventionally used optical demultiplexer with wavelength selection characteristics whose center wavelengths are shifted.

In addition, in this example, if a diffraction grating with steep wavelength selectivity is used in the zeta-optical demultiplexer, it is possible to widen the non-overlapping wavelength range of wavelength selectivity, resulting in a system with low crosstalk. In addition, it is easy in principle to vary the center wavelength of the wavelength selection characteristic.
This has the advantage that the system of the present invention is easy to construct.

Effects of the Invention As described above, the present invention includes an optical transmitter including a plurality of light sources with different wavelengths and an optical coupler for wavelength multiplexing, an optical branching device, two optical demultiplexers, and a plurality of optical and electrical devices. It consists of an optical receiver equipped with a converter, and one optical demultiplexer has wavelength selection characteristics that do not overlap with each other, and the wavelength of the light source to be multiplexed corresponds to the center wavelength of each wavelength selection region, and the other optical demultiplexer The center wavelength of each non-overlapping wavelength selection region of the optical demultiplexer is located in a non-overlapping wavelength region of two adjacent wavelength selection regions of the one optical demultiplexer, and the wavelength of the light source to be multiplexed is made to correspond to this wavelength. By doing so, the number of wavelengths to be multiplexed can be doubled while the wavelength range for wavelength multiplex transmission is the same.

[Brief explanation of the drawing]

Figure 1 is a configuration diagram of a wavelength division multiplexing optical transmission system in an embodiment of the present invention, Figure 2 is a conceptual diagram of an optical demultiplexer in the embodiment of Figure 1, and Figure 3 is an optical demultiplexer in the embodiment of Figure 1. Conceptual diagram of the vessel, No. 4
The figure is a block diagram of a conventional wavelength multiplexed optical transmission system, and FIG. 5 is a conceptual diagram of the conventional wavelength multiplexed optical transmission. 10(1) to 10(2n)--modulation signal source, 1
1 (11-11(2n)... light source, 12...
... Optical coupler, 13... Optical splitter, 14a,
14b... Optical demultiplexer, 15(1) to 15(2n
)... Optical-electrical converter, 16... Optical fiber, 17... Optical transmitter, 18...
Optical receiving section, 21(1) to 21 (2n-1)...
・Wavelength selection characteristics of optical demultiplexer 14a, 22(1) to 22
(2n) - Spectrum of wavelength multiplexed light, 31
(2) to 31 (2n)...Wavelength selection characteristics of optical demultiplexer 14b, 32(1) to 32 (2n)...
Spectrum of wavelength multiplexed light.

Claims (4)

[Claims] (1) An optical transmitter including a plurality of light sources with different wavelengths and an optical coupler for wavelength multiplexing, an optical branching unit, two optical demultiplexers, and a plurality of optical-to-electrical converters. The one optical demultiplexer has wavelength selection characteristics that do not overlap with each other, and the wavelength of the light source to be multiplexed corresponds to the center wavelength of each wavelength selection region, and the one optical demultiplexer has wavelength selection characteristics that do not overlap with each other. The center wavelength of each of the non-overlapping wavelength selection regions is in a non-overlapping wavelength region of two adjacent wavelength selection regions of the one optical demultiplexer, and the wavelength of the light source to be multiplexed is made to correspond to this wavelength. Features of wavelength multiplexed optical transmission system. (2) The wavelength division multiplexing optical transmission system according to claim (1), characterized in that an optical coupler is used for the optical coupler and the optical splitter. (3) The wavelength multiplexing optical transmission system according to claim (1), wherein a diffraction grating is used as a wavelength dispersion element in the optical demultiplexer. (4) The wavelength multiplexed optical transmission system according to claim (1), characterized in that a semiconductor laser is used as a light source.