JPS62620B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical communication device. In recent years, the use of communication lines has increased significantly for image transmission, computer data buses, facsimile networks, and the like.
Optical communication systems using fiber optics are expected to become future communication systems because they enable lighter line cables and wider transmission bands. In order to realize more advanced optical communication systems, optical devices with the functions of modulators, demodulators, exchangers, and dividers are required. Among these, optical modulators and optical IC elements using electro-optic crystals are being considered as devices that have the function of switching and exchanging light. However, these devices have considerable limitations on light incident angle, mode, polarization conditions, etc., and it is quite difficult to realize an optical exchanger in which multiple elements are connected in cascade. For this reason, conventional optical communication systems use optical fiber only for the transmission circuit, and other switching functions are performed electrically, making it impossible to take advantage of the multiplex communication and bidirectional communication features of optical communication.

An object of the present invention is to provide a multidirectional optical communication device that does not require optical switching.

According to the invention, there is provided a semiconductor laser that oscillates at a plurality of wavelengths, a demultiplexer that demultiplexes a plurality of oscillation lights from the semiconductor laser, and a plurality of light beams that propagate the light demultiplexed by the demultiplexer. An optical communication device comprising a propagation path, a light detection means placed at each terminal of the light propagation path, and an optical feedback means having a modulation function is obtained.

Hereinafter, this invention will be explained in detail with reference to the drawings. FIG. 1 shows an optical communication device according to the present invention. Light 2 of a plurality of wavelengths is emitted from a semiconductor laser 1 that oscillates in a plurality of longitudinal modes, and these lights are guided by a demultiplexer 3 to an optical propagation path 4 corresponding to the light of each wavelength. Light propagation path 4
_The light passing _{through a , . 6c} , the light is sent back to the light propagation path _4a ,..., _4c . The returning light passes through the demultiplexer 3 and enters the semiconductor laser 1.
Returning to , the output light of the semiconductor laser changes due to the self-coupling effect due to the returned light. The self-coupling effect of semiconductor lasers can be explained as an effect caused by the formation of an external cavity. Regarding the self-coupling effect of semiconductor lasers, see, for example, "No. 39
Proceedings of the Academic Conference of Japan Society for Applied Physics, 1978
This is described in the preliminary paper ``Self-coupling effect of diffraction gratings in CSP semiconductor lasers'' published on page 478. When a diffraction grating is used for a semiconductor laser that oscillates at multiple wavelengths in the longitudinal mode and only one of the wavelengths is returned to the semiconductor laser, the light at other oscillation wavelengths is suppressed and only one wavelength is produced. It is reported that only light oscillated. Figures 2 and 3 show the oscillation spectra of semiconductor lasers, with inputs a,...
It is assumed that light of N wavelengths with input b, input c, etc. are oscillating. If the light with the wavelength input a is returned to this semiconductor laser, the only light that the semiconductor laser oscillates will be the light with the wavelength input a, as shown by the solid line in FIG. Furthermore, when the light with the wavelength input c is returned, the oscillation light becomes only the light with the input c shown by the dotted line. The present invention applies this self-coupling effect of semiconductor lasers. 1st
In the figure, the semiconductor laser need only be an element that oscillates in a plurality of longitudinal modes and has a self-coupling effect, and does not need to have a striped structure. The demultiplexer can be made up of a half mirror and an interference filter, or it can use a diffraction grating to separate light of each wavelength.

FIG. 4 shows an example of a duplexer using a diffraction grating. Through the optical fiber 10, the wavelengths a, b,
Suppose that an incident light beam propagates. optical fiber 1
Light 14 emitted from 0 is made parallel by lens 15 and then enters diffraction grating 16 . A diffraction grating diffracts each wavelength of light in a different direction. The diffracted light of each wavelength is focused at different positions by a lens 15, and an optical fiber 1 is placed at the focusing point.
At wavelengths 1, 12, and 13, light having wavelengths a, b, and c is separated and extracted.

In this way, a demultiplexer can be created that independently guides the light at wavelengths a, b, and c to the optical fibers corresponding to each wavelength. In addition, in the opposite direction, the individual fibers 11,
The lights of wavelengths a, b, and c from 12 and 13 are guided to one optical fiber 10 again. When a semiconductor laser oscillates in multiple modes, the oscillation wavelengths are arranged at intervals of approximately 1 nm around a central wavelength of 820 nm. To separate and extract these wavelengths, for example, if you use a diffraction grating of 1180 lines/mm and a lens focal length of 250 mm, it is possible to separate the light with a separation power of 0.1 nm using the second-order diffracted light. It's easy to do.

Next, in FIG. 1, the light propagation path 4 is an optical fiber, preferably a fiber with low loss.

An example of the light detection means 5 _a , . . . , 5 _b , _. The optical feedback means 6 _a , 6 _b , ... 6 _c may be any element that modulates the incident light again and returns it, such as a device that shakes a reflecting mirror with a piezoelectric element, an optical modulation using an electro-optic element or an acousto-optic element. There are some that combine a vessel and a reflecting mirror. FIG. 5 shows an example of an optical feedback means using an acousto-optic element.

The laser beam 18 is deflected by the acousto-optic deflector 17 to become a laser beam 21, which is focused onto a reflecting mirror 22 by a lens 20. The laser beam reflected by the reflecting mirror 22 travels backwards and passes through the acousto-optic deflector 1.
The laser beam 18 is deflected again by the laser beam 18, and becomes light that returns in the opposite direction to the laser beam 18.

When the acousto-optic deflector 17 does not work, the laser beam 18 becomes light 19 that travels straight and never returns. In this way, an acousto-optic deflector
By turning it ON and OFF, the laser beam can be returned or prevented from returning.

FIG. 6 explains the operation of the optical communication device according to the present invention. The receiver outputs 7 _a , 7 _b , and 7 c received by three terminals A, B, and _C are shown.
Optical feedback means 6 _a , 6 _b , 6 _c of each terminal do not work
During the time up to T ₁ , the light of the wavelength corresponding to each terminal emitted from the semiconductor 1 passes through the demultiplexing circuit 3 and the optical propagation paths 4 _a , 4 _b , 4 _c to the photodetecting means 5 _a , 5 _b ,5 _c
The outputs 7 _a , 7 _b , and 7 _c are obtained.

Each output receives light with the same intensity, so
It has a value of V ₁ . Assume that the optical feedback means 6 _a of terminal A starts operating from T ₁ and modulates the light of wavelength a and returns it. At this time, by returning the light of wavelength a to the semiconductor laser 1, the light of other wavelengths emitted from the semiconductor laser 1 is suppressed, and only the light of wavelength a is emitted.

Therefore, the light does not reach the terminals B and C, and the outputs 7 _b and 7 _c of the light detection means 5 _b and 5 _c become 0. Terminal A
The output 7 _a of the photodetecting means 5 _a takes the value of V ₂ . That is, the negative polarity of the transmission signal _7a from terminal A is sent to other terminals B and C at the same time. This effect is the same when terminal C operates the optical feedback means 6 _c from time T ₂ to transmit, and signals of negative polarity are sent to terminals A and B. In this way, since an exchange having a switching element is not required, information can be mutually sent between multiple stations at high speed.

As described in detail below, according to the present invention, a multi-directional communication device can be obtained that can exchange information between multiple stations at high speed without requiring a switching element.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an optical communication device according to the present invention;
Figures 2 and 3 are diagrams showing the oscillation spectrum of a semiconductor laser, Figure 4 is a diagram showing an example of a duplexer, and Figure 5 is a diagram showing an example of a duplexer.
The figure shows an example of the optical feedback means, and FIG. 6 explains the operation of the optical communication device according to the present invention. In the figure, 1 is a semiconductor laser, 2, 18, 1
9, 21 are semiconductor laser beams, 3 is a branching circuit, 4,
4 _a , 4 _b , 4 _c , 10 , 11 , 12 , 13 are optical propagation paths; 5 _a , 5 _b , 5 _c are optical detection means; 6 _a , 6 _b , 6
_c Optical feedback means, 15 and 20 are lenses, 16 is a diffraction grating, 17 is an acousto-optic optical deflector, and 22 is a reflecting mirror.

Claims (1)

[Claims] 1. A semiconductor laser that oscillates at a plurality of wavelengths, a demultiplexer that demultiplexes the multiple oscillation lights from the semiconductor laser, and a plurality of optical propagation paths that respectively propagate the light demultiplexed by the demultiplexer; A multidirectional optical communication device characterized by comprising a light detection means disposed at each terminal of the optical propagation path and an optical feedback means having a modulation function.