JPH02207586A - Integrated type semiconductor optical amplifier - Google Patents

Abstract

PURPOSE:To construct a subscriber optical system and the like with the low system cost by forming an integrated semiconductor amplifier in which a signal light incident upon one input optical waveguide is distributed to a plurality of output active waveguides through an optical coupling part. CONSTITUTION:An electrode 21 is formed on a cladding layer 23 and a substrate such that a current is directed only to an active waveguide 3 part, and an insulating film 22 is formed on the active waveguide 3 part. An optical signal incident through an input waveguide 2 is entered into the active waveguide 3 in an output waveguide through four optical coupling parts located in the direction of light propagation. Once the current is driven between the upper and lower electrodes 21, carriers are injected into the active waveguide 3 for light amplification.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an integrated semiconductor optical amplifier.

[Conventional technology]

Semiconductor optical amplifiers are linear amplifiers in optical communication systems,
It is used in a wide range of fields as a preamplifier, a loss compensation amplifier, etc., and is an indispensable and important device for lengthening transmission relay intervals. In particular, traveling wave optical amplifiers (hereinafter abbreviated as TWA), which have anti-reflection films formed on both end faces (light input/output surfaces) of the element, are actively being researched because they have a wide band and can provide a net gain of about 15 dB. Development is underway.

On the other hand, there is also an attempt to construct a subscriber optical system using TWA, which distributes optical signals of more than ten channels to subscriber terminals. An example of such a system is shown in FIG. In this example, the output signal light of the light source 10 consisting of a total of 16 semiconductor lasers is multiplexed using the star coupler 11, and then the 16
Branch to X 16=256. There are a total of 256 T
The attenuated optical signal is amplified using the WA 15, and further distributed to 256 x 256 = 65,536 subscriber terminals 13 at the final stage via an lX256 branch fiber 16B. Each subscriber side is configured to select one of the original 16 channels.

[Problem to be solved by the invention]

However, in such a system, a large number of TWAs (256) are required to distribute optical signals to a huge number of subscribers, which increases the system cost.
The system cost can be reduced by reducing the number of fibers, for example, placing a TWA in front of the branch fiber 16A, but the saturation output of the TWA is several dBm, and there is a problem with each subscriber terminal. The distributed optical signal output becomes extremely weak.

In view of the above, an object of the present invention is to provide an integrated semiconductor optical amplifier useful for system applications.

[Means to solve the problem]

The means provided by the present invention to solve the above-mentioned problem is that one input waveguide and a plurality of output waveguides are formed on a semiconductor substrate, and an active waveguide that causes an optical amplification effect by current injection is used. An integrated semiconductor optical amplifier, which is formed in at least a portion of the output waveguide and the input waveguide, and the output waveguide is optically coupled to the input waveguide and the output waveguide by an optical coupling part. It is.

[Effect]

In the present invention, the branch fiber 1 in the configuration shown in FIG.
Since the functions of 6A and TWA 15 are integrated, a highly functional integrated TWA can be constructed, an optical system can be realized with a simple configuration, and a highly reliable one can be obtained at a low price.

〔Example〕

The invention will be explained in more detail below with reference to the drawings of embodiments. FIG. 1(a) shows a schematic plan view of an integrated TWA which is an embodiment of the present invention. The device can be manufactured using the LPE method in the same manner as the growth of a normal buried structure. A waveguide layer with an emission wavelength of 1.2 μm on the InP substrate 1,
After growing an InGaAsP active layer with an emission wavelength of 1.59 μm, selective etching and mesa etching for buried growth are performed to form input waveguides 2 and 2 as shown in the figure.
An active waveguide 3 and an optical coupling section 4 are formed. The width of both the input waveguide and the active waveguide was 1.5 μm, and the thickness of the active layer was 0.1 μm. The periphery of the waveguide was formed in the same manner as a normal buried semiconductor laser, and the optical coupling section 4 used a directional coupler configuration.

Figure 1 (a) Cross-sectional views of the A-A', B-B', and C-C' portions are shown in Figure 1 (b), (c), and (d), respectively. Figure 1 (b) As shown in , the optical coupling section 4 has a directional coupler configuration in which two waveguides are arranged close to each other, and a current blocking layer 24A of a different conductivity type is provided in a portion other than the mesa stripe including the waveguide layer 2. -B is formed.

Further, the active waveguide 3 was partially formed in the BB' portion as shown in FIG. 1(c). An etch stop layer 25 is not formed between the active waveguide 3 and the waveguide layer 2. As shown in the figure, an electrode 21 was formed on the cladding layer 23 and the substrate so that a current could flow only through the active waveguide 3 portion, and an insulating film 22 was formed on the active waveguide 3 portion. The c-c' portion has the structure shown in FIG. 1(d), with the active waveguide 3. Waveguide 2 is formed vertically (active waveguide 3 is layered on waveguide 2 information)
has been done.

An optical signal input from one input waveguide 2 passes through four optical coupling sections in the direction in which the light travels, and enters an active waveguide 3, which is an output waveguide. By passing a current between the upper and lower electrodes 21, carriers are injected into the active waveguide 3, which can provide a light amplification effect. By making it possible to independently inject current into a plurality of different active waveguides 3, the same light can be generated on the output side of all active waveguides 3 by adjusting the current flowing through each electrode independently. It can be aligned with the output. Immediately before the active waveguide, the power was approximately 1724 times the amount of incident light, including waveguide loss. length 500
The amplification amount in the μm active waveguide was 28 dB. The overall length of the integrated device is 2.7 mm, which is relatively small. As shown in FIG. 1(a), the input end face and output end face of the element are
An antireflection film 5 was formed using Sin.

FIG. 2 shows an example of a subscriber optical system using the integrated semiconductor optical amplifier of the present invention. In this example, the branch fiber 16A and the optical amplifier 15 in the configuration shown in FIG. 3 are replaced with the integrated semiconductor optical amplifier 12, and the optical output from the light source 10 is 65
-37dB as an output to subscriber terminals with a number of 000 or more
Good optical transmission can be achieved with m. The number of integrated semiconductor optical amplifiers I2 required for this purpose is only 16, compared to 256 in the conventional example.

In addition, in the example, the wavelength is 1 μm using InP as the substrate.
Although the band element has been described, the material system used is not limited to this, and other materials such as GaAs may also be used. In addition, not only chemical etching but also methods such as dry etching may be used to fabricate the device, and the waveguide structure is not limited to a buried structure. Any structure that is currently used or that can be used, such as a rib type, may be used. Further, the optical coupling section 4 may also be of a Y-branch type or similar structure rather than a directional coupler type.

The semiconductor layers shown in the examples, such as the cladding layer, the waveguide layer, and the current blocking layer, can be realized by using the same structure, materials, etc. as those of commonly used semiconductor lasers, so a detailed explanation will be omitted.

〔Effect of the invention〕

A feature of the present invention is that an integrated TWA is formed in which a signal light incident on one input optical waveguide is distributed to a plurality of output active waveguides via an optical coupling section. Such integrated TWAs have made it possible to construct subscriber optical systems and the like with low system costs.

[Brief explanation of the drawing]

FIG. 1(a) is a plan view of an integrated TWA which is an embodiment of the present invention, and FIGS. 1(b), (c), and (d) are respectively
2 is a diagram showing an example of the configuration of an optical system using the integrated semiconductor optical amplifier of the present invention, FIG. 3 is a diagram showing an example of a conventional system configuration. 1... Substrate, 2... Input waveguide, 3... Active waveguide, 4... Optical coupling section, 5... Anti-reflection film, 10...
- Light source, 11... Star coupler, 12... Integrated optical amplifier, 13... Subscriber terminal, 15... Optical amplifier,
16A-B... Branch fiber, 21... Electrode, 22
...Insulating film, 23...Clad layer, 24A-B...
- Current block layer, 25... etch stop layer.

Claims (1)

[Claims] An input waveguide and a plurality of output waveguides are formed on a semiconductor substrate, an active waveguide that causes an optical amplification effect by current injection is formed in at least a part of the output waveguide and the input waveguide, and the output waveguide is formed on a semiconductor substrate. An integrated semiconductor optical amplifier characterized in that a waveguide is optically coupled to the input waveguide and the output waveguide by an optical coupling section.