JPS62241387A - Semiconductor light frequency filter - Google Patents

Abstract

PURPOSE:To separate wavelength-multiplexed optical signal at every one wavelength by current control from the outside by selecting only an optical signal having a wavelength coinciding with the amplification wavelength of an amplifier A in beams projected to a semiconductor laser amplifier (group) by semiconductor laser amplifiers. CONSTITUTION:At least two distributed feedback type semiconductor amplifier groups having diffraction gratings having different Bragg frequency and optically connected in series are provided. g=alphao is selected to an amplifier 21, g=0.9gth to an amplifier 22 and g=alphao to amplifiers 23-25. Consequently, only lambda2 is amplified, and outputted. When wavelength intervals are selected in 10Angstrom , the semiconductor laser amplifiers have a gain wavelength of approximately 200Angstrom , and waves can be branched to approximately twenty waves. When incident bears are divided previously, beams can be branched according to wavelengths to each waveguide by the selective amplification of wavelengths, and have an amplification factor of approximately one hundred times, thus sufficiently supplementing optical loss by division of approximately twenty division.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a semiconductor optical frequency filter characterized by having a narrow band and amplification efficiency for separating wavelength-multiplexed signals into wavelengths. It is something.

(Prior art and problems to be solved by the invention) Conventionally,
As a narrowband filter for separating wavelength-multiplexed optical signals, a filter that utilizes the dispersion of a diffraction grating, as shown in FIG. 7, has been used.

In the figure, 1 is an input optical fiber, 2 is a lens, 3 is a glass block, 4 is a diffraction grating, 5 is a lens, and 6 is an output fiber. However, this structure has drawbacks such as difficulty in miniaturization, large insertion loss, and difficulty in externally controlling the selection of 'tL length.

(Children to Solve Problems) It is an object of the present invention to provide a frequency filter that solves these drawbacks and allows '11 length selection from the outside using an injected Ti flow.

The above purpose is 1! In order to achieve this, the present invention includes at least two distributed feedback semiconductor laser amplifier groups having diffraction gratings with different black frequencies and optically connected in series, one of which (amplifier A) is a laser amplifier. Biased just below the threshold for oscillation, the other amplifiers are biased to cancel out the fundamental absorption of the semiconductor and have zero out of phase, and the m semiconductor laser amplifiers are biased to , is characterized in that it selects only the optical signal whose wavelength matches the amplification wavelength of amplifier A'! This is a summary of the four-conductor conductor wave frequency filter.

The principle of the present invention is shown in FIG. 10 indicates a semiconductor laser amplifier including a diffraction grating. 11 and 12 are anti-reflection coatings, and 13 is a diffraction grating. Pin is optical input, P
Oold indicates output. Therefore, its black wavelength is λ1. For example, consider a case where a semiconductor laser amplifier has a diffraction grating including a 1'4 wavelength shift and the reflection at both end faces is zero.

In the configuration shown in Figure 1, when a current is passed to cancel the optical absorption of the semiconductor (0 = αn), and when a current that is 0.9 times the oscillation threshold of the semiconductor laser is passed (g =
FIG. 2 shows the total optical input/output characteristics of the 0.9 g th). This calculation uses the coupled wave theory (W, 5 treifer at.

at, 1[FE J, Quantu+n Elect
Ron, vol, QE-11, page 154 (1975)
l was used. The laser amplifier used in this total n has an InP, /InGaAsP, 'lnP double hetero structure, and calculations were performed assuming that the wavelength was 1.3 μm. From this calculation result, at q-α0, the black wavelength λ1
And 1 of the stop band width! For both wavelengths λ2, which are separated by '2, there is a loss O1.

At 0 years old and 0.9 gth, approximately 1 for black ItL length λ1
00 (8) can be obtained. Therefore, as shown in FIG.
．． 15 are connected in series, and λ1. Table 1 shows the output light when light of wavelength 2 of λ2 is input.

Table 1 By simply changing the flow of Ti implanted in this way, it is possible to select wavelengths that are adjacent to each other in a range of several λ to more than 10-odd wavelengths and have approximately 100 times as much St'N. In addition, by switching the injected Ti flow, n5
19-degree 8-speed switching is possible.

Next, embodiments of the present invention will be described with reference to the accompanying drawings.

Note that the embodiments are merely illustrative, and it goes without saying that various changes and improvements can be made without departing from the spirit of the present invention.

Using the principle described above, multi-wavelength filtering is possible as shown in FIG. In the figure, numerals 21 to 25 indicate semiconductor laser amplifiers having growth λ1 to λ2, respectively. Thus, for amplifier 21, Q-α0# for amplifier 22, g=0,9gtb.

For amplification fi23 and fi24.25, Q-α0 is selected.

As a result, only λ2 is selectively amplified and output.

For example, if the wavelength interval is selected to be 10, the semiconductor laser amplifier has a gain wavelength width of about 200^, and can separate about 20 waves.

As shown in FIG. 5, if the incident light is divided in advance, it can be branched into each SX path according to the wavelength by selective amplification of the wavelength. Since it has an amplification factor of about 100 fF5, it can sufficiently compensate for the optical loss caused by division at the 20-minute division rate.

The laser beam splitter has a Y-shaped branch as shown in Figure 6 (A) and a 3 dB direction splitter as shown in Figure 6 (B), and the one in Figure 6 is often used. It will be done. In addition, 4
In the case of branching, division as shown in (c) is used.

Next, it is already known that the oscillation wavelength of the distributed feedback laser Lj shown in FIG. 8 changes depending on the control current 1c. (Semiconductor and Materials Division, Institute of Electronics and Communication Engineers, 1985)
National Conference Lecture Collection 1-140) This M4 element operates as an optical amplifier if the excitation ffi current is set below the laser oscillation threshold.

FIG. 9 shows the wavelength dependence of the optical output at this time.

When Q=0.9Qth, the half lia width of the transmission characteristic accompanied by optical amplification is about 0.6s, and its center frequency (
The black frequency 'tLm) is shifted by about 1^/mA by changing the control current 1c. Therefore, by using the same method as described above, λ1. λ2
．． λ3. ... can selectively amplify only the wavelength that matches the center frequency (Fig. 10), and by changing 1c, λ7. λ2. It is possible to arbitrarily select from among λ, . . . .

Furthermore, as shown in FIG. 11, if the incoming rJ1 light is split in advance, wavelength selective amplification can be applied to each waveguide. 1
It is exactly the same as above that it can be branched according to the branch.

(Effects of the Invention) As explained above, according to the present invention, at least two distributed feedback semiconductor lasers having diffraction gratings with different black frequencies and optically connected directly One of the amplifiers (!amplifier A) is biased slightly below the lasing threshold, and the other amplifier is biased to cancel the fundamental absorption of the semiconductor and reduce the loss to zero. configuration, or the Blang frequency is tIIJI.
II. Wavelength multiplexing is achieved by selecting only an optical signal with a wavelength that matches the amplification wavelength of amplifier A from among the light incident on the semiconductor laser amplifier (group) using a semiconductor laser amplifier that changes depending on the current. The resulting optical signal is separated one wavelength at a time by external current control, and because it has optical amplification characteristics, it has the advantage of being useful as a basic element for optical switching and demultiplexing for wavelength multiplexed optical transmission.

[Brief explanation of drawings]

Figure 1 is a conceptual diagram of a laser amplifier including a diffraction grating, Figure 2 is the transmission characteristics of the amplifier, Figure 3 is a principle diagram of an optical frequency filter, Figure 4 is an example of an optical frequency filter, and Figure 5 is Other embodiments of the optical frequency filter, FIG. 6 shows a branching example, FIG. 7 shows a conventional filter, FIG. 8 shows another conceptual diagram of a laser amplifier including a diffraction grating, FIG. 9 shows the transmission characteristics of the amplifier, and FIG. FIG. 10 shows the principle of an optical frequency filter, and FIG. 11 shows an embodiment of the optical frequency filter. 1... Input optical fiber, 2... Lens, 3...
...Glass block, 4...Diffraction grating, 5...
・Lens, 6...Output optical fiber, 10--
Laser amplifier, 11.12... Anti-reflection coating, 13... Diffraction grating, 21---1nGaAsP
Active layer, 22...p-1nP min 111! , 23”
” p-rnaaAsp optical waveguide threshold, 24-...-n-
1nP, 25---p-1nP, 26... wavelength control electrode, 27... optical amplifier excitation electrode, 28...
...Electrode 711 Fig. 1 Fig. 2 Fig. 3 Fig. 4 Fig. 5 Fig. 1 λ2 person, 4 person 5 Fig. 10

Claims (4)

[Claims] (1) A semiconductor optical frequency filter, characterized in that it allows incident light of multiple wavelengths to enter at least one distributed feedback semiconductor laser amplifier, and selects only optical signals with wavelengths that match a predetermined amplification wavelength. (2) When the distributed feedback semiconductor laser amplifier has one layer, the current value supplied to the laser amplifier is controlled to change the black frequency, and from among the multi-wavelength light incident on the amplifier, 2. The semiconductor optical frequency filter according to claim 1, wherein only an optical signal having a wavelength matching the amplification wavelength of the amplifier is selected. (3) When there are multiple distributed feedback semiconductor laser amplifiers, at least two laser amplifiers with diffraction gratings set so as to make each black frequency different are optically connected in series, and one of the laser amplifiers is connected in series. (Amplifier A)
is biased slightly below the lasing threshold,
The other amplifiers are biased so that the basic absorption of the semiconductor is canceled and the loss becomes zero, and from among the light incident on the semiconductor laser amplifier group, only the optical signal with the wavelength matching the amplification wavelength of amplifier A is used. The semiconductor optical frequency filter according to claim 1, wherein the semiconductor optical frequency filter is selected from the following. (4) Each diffraction grating includes a 1/4 wavelength shift, and amplifiers having different widths by 1/2 wavelength of the stop band width are sequentially connected in series. Semiconductor optical frequency filter.