JPS58197930A - Optical demultiplexer - Google Patents

Abstract

PURPOSE:To obtain a large quenching rate and remove the necessity of consideration of insertion loss by making a demultiplexer to have a construction so that it separates and amplifies only a fixed wavelength by means of a semiconductor laser. CONSTITUTION:For instance, three wavelengths lambda1, lambda2 and lambda3 are made incident to an incident terminal 1. They are branched respectively by a branch circuit 5 and made incident to semiconductor lasers 6-8. The central wavelengths of gains of the lasers 6-8 are lambda1, lambda2 and lambda3, and three waves of lambda1-lambda3 are seperated by the lasers 6-8. In this case, the inrush current of lasers 6-8 is kept at a value less than threshold current Ith such as 0.99Ith. As a result, a large quenching rate is obtained and there is no need to consider insertion loss because only a specific wavelength can be separated and amplified.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field) The present invention relates to an optical demultiplexer for wavelength multiplexed optical transmission.

(Background technology) Optical demultiplexers are essential for wavelength multiplexed optical transmission.

Optical demultiplexer methods include (1) interference film, (2) diffraction grating,
Structures that utilize (3) prism dispersion and (4) optical coupling have been proposed. Most of the optical separation methods reported so far are based on (1) or (2).
This is because the method 3) has poor resolution, and the method 4) is extremely difficult to manufacture. In both methods using (1) or (2), glass is processed and polished, an interference film or a diffraction grating is formed thereon, and the glass is connected to a fiber via a small lens or Rondo lens. All of these configurations are bulk type and have a large number of parts, making it extremely difficult to adjust the optical axis and causing problems such as the high cost of polishing each part.

Particularly in the case of a single mode system, the optical axis adjustment must be performed with an accuracy of around IIfrL, making it almost impossible to realize a bulk type optical demultiplexer.

(Problems to be solved by the invention) In order to eliminate these drawbacks, the present invention uses a semiconductor laser to extract and amplify light of a specific wavelength. Oh(・te,
an optical branching circuit having a number of branches corresponding to the output for branching the optical input; a semiconductor laser disposed at each output end of the optical branching circuit and each having a gain curve corresponding to the wavelength of the light to be branched; Optical demultiplexing includes a means for guiding the emitted light of a semiconductor laser to an emission end corresponding to the wavelength, and is configured such that only a predetermined wavelength is passed and amplified by setting the injection current of the semiconductor laser to an appropriate value below a threshold current. It's in the container.

(Structure and operation of the invention) FIG. 1 shows an embodiment of the invention, in which 1 is an input terminal, 2, 3.4 are output terminals, 5 is a branch circuit, 6, 7
．． 8 is a semiconductor laser. For example, the input terminal has 3
Light wavelength λ, = 0.8 μm.

λ, = 0.85 μm, λ3 = 0.9 μm are incident. Then, they are branched by a branch circuit 5 and incident on a semiconductor laser 6°7.8. At this time, 6 has λ8. λ2
．． Three waves of light of λ3 are incident. The same applies to 7 and 8.

The gain curve of the semiconductor laser 6.7.8 has wavelength characteristics (9, 10, 11) as shown in Figure 2, where 6 is the center wavelength of 0.8 p-s, 7 is 0.85 μm, and 8 is 0. ．．
It is 9 μm. The bandwidth is about 300^ each,
0.785μm to 0.815μm for 60 semiconductor laser
Almost all of the light passes through and is amplified.

Therefore, the light emitted from the semiconductor laser 6 is 0.8 of the three waves.
Only μm. The same applies to the semiconductor laser 7.8, and λ1. λ2. Three waves of λ are separated.

Here, as the semiconductor laser, for example, GaAlAs
/Q3As type is used, and the threshold current I
If the value is held at 0.99 times th, an amplification degree of about 20 dB can be obtained for light having a wavelength within the gain curve. For light of other wavelengths, the semiconductor laser medium becomes a loss medium, so the amplification degree is less than 150 dB. Therefore, an extinction ratio of 50 dB or more can be obtained. The wavelength dependence of the gain curve is determined by changing the composition of the semiconductor laser medium, and can be arbitrarily selected. In this example, an example of 3-wave division was shown, but
The demultiplexing number can be changed as required. Also, both single mode and multi-mode are possible. Furthermore, conversely, it is also possible to use it as a multiplexer by inputting light of each wavelength from each output terminal, amplifying it with a semiconductor laser, and extracting it from the input terminal.

(Effects of the Invention) As explained above, the optical demultiplexer according to the present invention uses a semiconductor laser to separate and amplify only a specific wavelength, so it has a large extinction ratio and does not require consideration of insertion loss. There is an advantage. It also has the advantage that it can be integrated and can be incorporated into future optical integrated circuits.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of an optical demultiplexer according to the present invention, and FIG. 2 shows a gain curve of a semiconductor laser used in the optical demultiplexer. 1... Input terminals 2 to 4... Output terminals 5... Branch circuits 6 to B... Semiconductor lasers 9 to 11... Semiconductor laser gain curve Patent applicant Rimoto Telegraph and Telephone Corporation Patent application agent Private patent attorney Megumi Yamamoto - Seiichi Figure

Claims (1)

[Claims] In an optical demultiplexer that demultiplexes multi-wavelength light, there is an optical branching circuit having the number of branches corresponding to the output of demultiplexing the optical input, and an optical demultiplexer arranged at each output end of the optical branching circuit to separate the light to be demultiplexed. It has a semiconductor laser having a gain curve corresponding to the wavelength and a means for guiding the emitted light of each semiconductor laser to an emission end corresponding to the wavelength, and the injection current of the semiconductor laser is set to a predetermined value below the threshold current. An optical demultiplexer characterized in that it passes through and amplifies only wavelengths.