JP2001007450A - Optical amplifier module - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an optical amplifier module without depending on polarization using SOAs(semiconductor optical amplifiers) on which alignment adjustment can be performed easily. SOLUTION: Two SOAs 1a and 1b are arranged, with the surfaces of their active layers orthogonally crossing each other and their optical axes being in parallel with each other. Input light is split into two linearly polarized light rays 4a and 4b by means of a polarization beam splitter 2a, and the light ray 4a is inputted to the SOA 1a as it is. The light ray 4b bent by 90 deg. is inputted to the SOA 1b. Therefore, the SOAs 1a and 1b amplify their input light at appropriate multiplication factors. Since another polarization beam splitter 2b multiplexes the output light ray of the SOA 1a inputted to the splitter 2b as it is and that of the SOA 1b inputted to the splitter 2b after the light ray is bent by 90 deg., polarization non-dependent optical amplification is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical amplifier module for performing optical amplification without polarization dependence using a semiconductor optical amplifier.

[0002]

2. Description of the Related Art Conventionally, a semiconductor optical amplifier (SO) has been used as a small optical amplifier.
A) is known. SOA has the advantage of being small in size, but has the disadvantage of poor polarization characteristics. That is, the SOA differs greatly in the amplification factor between the TE wave and the TM wave, and cannot be used in a stage where the polarization characteristic is important. On the other hand, fiber amplifier modules represented by erbium-doped fibers have the advantage of very good polarization characteristics, but they require space for winding and storing the fibers, which poses a problem in terms of miniaturization of the equipment. is there.

As a solution to these difficulties, a proposal has been made to construct a polarization-independent optical amplifier module using two SOAs (Japanese Patent Laid-Open No. Hei 5-299746).
No.). The method is to separate the input light into two linearly polarized lights using a wedge-shaped birefringent prism, amplify these linearly polarized lights by two SOAs rotated by 90 ° around the optical axis, and then re-wedge the light. In this method, the light is synthesized by a refraction prism.

[0004]

SUMMARY OF THE INVENTION The above-mentioned Japanese Patent Laid-Open Publication No.
In the method of 99746, a wedge-shaped birefringent prism is used as means for separating input light into two linearly polarized lights.
In this case, the two obtained linearly polarized lights are separated with a separation angle determined by the wavelength of the input light and the apex angle of the birefringent prism. For this reason, when two SOAs are arranged with their optical axes parallel, a lens is required to make the two separated linearly polarized lights parallel to each other. Two more S
Since a wedge-shaped birefringent prism is also used for synthesizing the output light of the OA, a lens that converges parallel output light from the two SOAs at a certain angle is required. Therefore, when assembling the optical amplifier module, it is necessary to consider the characteristics and arrangement of the lens according to the characteristics of the wedge-type birefringent prism and the wavelength of the input light. Otherwise, a desired polarization-independent optical amplifier module cannot be obtained. In the wedge-type birefringent prism, the separation angle between the two obtained linearly polarized lights is small, so that it is difficult to secure a space for disposing the two SOAs when trying to reduce the size of the module.

The present invention has been made in consideration of the above circumstances, and has as its object to provide a polarization-independent optical amplifier module using an SOA, which can easily perform alignment adjustment.

[0006]

According to a first optical amplifier module of the present invention, an input light is divided into a first linearly polarized light traveling straight on an optical path thereof, and a first linearly polarized light traveling by being deflected by 90 °. A first polarization beam splitter that separates the light into a second linearly polarized light whose polarization plane is orthogonal to the first polarization beam splitter; and the second linearly polarized light separated by the first polarization beam splitter is deflected by 90 ° to produce the light. A first mirror that translates with the first linearly polarized light, a first semiconductor optical amplifier that amplifies the first linearly polarized light that has traveled straight through the first polarization beam splitter, and the first semiconductor optical amplifier Means that the active layer surface is 90
A second semiconductor optical amplifier that is arranged in a rotated state and has an optical axis parallel to the first semiconductor optical amplifier, and amplifies the second linearly polarized light reflected by the first mirror;
A second mirror for deflecting the output light of the first semiconductor optical amplifier by 90 °, and a second polarized beam for combining the reflected light from the second mirror with the output light of the second semiconductor optical amplifier And a splitter.

In the second optical amplifier module according to the present invention, the input light has a plane of polarization of the first linearly polarized light traveling straight on the optical path and the first linearly polarized light traveling 90 °. A first polarization beam splitter for splitting into orthogonal second linearly polarized light, and the second linearly polarized light separated by the first polarization beam splitter is deflected by 90 ° to produce the first linearly polarized light. A first mirror that amplifies the first linearly polarized light that has traveled straight through the first polarization beam splitter;
A second semiconductor optical amplifier having an active layer surface and an optical axis parallel to the first semiconductor optical amplifier for amplifying the second linearly polarized light reflected by the mirror; A second mirror for deflecting the output light of the amplifier by 90 °, a second polarization beam splitter for multiplexing the reflected light from the second mirror with the output light of the second semiconductor optical amplifier, A first polarization plane rotator disposed at one of the input sections of the first and second semiconductor amplifiers for rotating the plane of polarization of the input light by 90 °; and one of the first and second semiconductor optical amplifiers And a second polarization plane rotating element disposed at the output section for making the polarization planes of the output lights of the first and second semiconductor optical amplifiers orthogonal to each other.

According to the present invention, two semiconductor optical amplifiers (SOAs) are juxtaposed to amplify two linearly polarized light beams obtained by separating input light at the same multiplication factor, and then re-synthesize, thereby obtaining polarization dependence. Optical amplification without noise. Moreover, in the present invention, a polarization beam splitter is used to split the input light into two linearly polarized lights, and the two linearly polarized lights thus separated have optical paths orthogonal to each other. If the linearly polarized light on the side deflected by 90 ° is again deflected by 90 ° by a mirror, two linearly polarized lights can be input in parallel to two SOAs. Regarding the combination of the output lights of the two SOAs, the output light traveling straight may be deflected by 90 ° and then combined. Therefore, unlike the related art in which the separation angle is not 90 °, a lens for changing an optical path is not required, and alignment adjustment of each optical component is easy. Also, two SOAs
And a small-sized module can be obtained.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. [Embodiment 1] FIG. 1 is a diagram showing a configuration of an optical amplifier module according to Embodiment 1 of the present invention. Two SOAs1
Reference numerals a and 1b denote SOAs under the same manufacturing conditions, in which the active layer surfaces are orthogonal to each other and the optical axes are arranged in parallel. The polarization beam splitter 2a has a 45
When the signal light to be input to the two SOAs 1a and 1b is circularly polarized light or elliptically polarized light, the light is separated into two linearly polarized lights 4a and 4b having polarization planes orthogonal to each other. One linearly polarized light 4a is TE polarized light,
The light goes straight on the optical path of the input light and enters one SOA 1a. S
It is assumed that the OA 1a is arranged so that the optical axis is parallel to the input light. The other separated linearly polarized light 4b
Is TM polarized light, which is deflected by 90 ° from the optical path of the input light.

[0010] The linearly polarized light 4b, which is TM polarized light, is converted into SOA.
A total reflection mirror 3a is provided, which is arranged to be inclined by 45 ° with respect to the optical path of the linearly polarized light 4b, so as to be inputted to 1b. As a result, the linearly polarized light 4b deflected by 90 ° by the polarization beam splitter 2a is again deflected by 90 °, and becomes parallel to the linearly polarized light 4a that has traveled straight through the polarization beam splitter 2a. This allows two SOs
A1a and 1b can amplify input linearly polarized light 4a and 4b under the same multiplication factor.

The output light of the SOA 1a is transmitted to a total reflection mirror 3a.
Is deflected by 90 ° by a total reflection mirror 3b arranged in parallel with the above. The light reflected by the total reflection mirror 3b and the SOA
1b is input to the polarizing beam splitter 2b. The output side polarization beam splitter 2b is arranged in parallel with the input side polarization beam splitter 2a. At this time, the optical path length from the two linearly polarized lights 4a and 4b separated by the input-side polarization beam splitter 2a to the output-side polarization beam splitter 2b is the same. Therefore, S
The two linearly polarized lights amplified by the OAs 1a and 1b are multiplexed in a state where the phases are aligned by the polarization beam splitter 2b.
It is extracted as amplified output light of the same circularly polarized light or elliptically polarized light as the input light without polarization dispersion or the like.

According to this embodiment, two SOAs 1a,
By arranging 1b such that an optimum multiplication factor is obtained for two linearly polarized lights separated from the input light, optical amplification independent of polarization can be achieved. Moreover, in this embodiment, by using the polarization beam splitter, the two separated linearly polarized lights draw a rectangular trajectory from the separation point to the multiplexing point, and the mirror and the polarization beam splitter move with respect to the optical path. Since the optical components are arranged at an angle of 45 °, alignment of the optical components is easy, and alignment adjustment such as fine angle adjustment and position adjustment is not required.

[Embodiment 2] FIG. 2 shows Embodiment 2 of the present invention.
FIG. 2 is a diagram showing a configuration of an optical amplifier module according to the first embodiment. The basic component arrangement is the same as that of the first embodiment, and the same reference numerals are given to portions corresponding to the first embodiment, and the detailed description is omitted. In this embodiment, the two SOAs 1a and 1b are:
This embodiment differs from the first embodiment in that the active layer surface and the optical axis are arranged parallel to each other. Further, in connection with this difference, in order to satisfy the condition that the two SOAs 1a and 1b have the same multiplication factor, one of the input lights, ie, the linearly polarized light
Rotate 0 °. Specifically, in the case of FIG. 2, the polarization plane is set to 90 ° at the input of the SOA 1a on the side of the linearly polarized light 4b which is a TM wave.
A polarization plane rotation element (Faraday element) 5a to be rotated is inserted. Then, in order to return the polarization plane rotated at the input section of the SOA 1a at the output section, a polarization plane rotation element 5b for rotating the polarization plane by 270 ° is provided at the output section of the SOA 1a.
Is inserted.

As a result, optical amplification without polarization dependence similar to that of the first embodiment can be performed with the active layer surfaces of the two SOAs 1a and 1b parallel. According to this embodiment, the same effect as that of the previous embodiment can be obtained, and two SOs
The advantage that A1a and 1b can be integrated into one chip is obtained. As in the first embodiment, two SOAs 1a, 1
It is difficult to make the active layers b perpendicular to each other on one chip in terms of a manufacturing process. Therefore, in the case of Example 1, SO
Separate components must be used for A1a and 1b. On the other hand, in this embodiment, two SOAs 1a,
1b makes the active layer plane parallel, so that it is suitable for one chip. Thereby, the size of the optical amplifier module can be reduced, and the characteristics of the two SOAs 1a and 1b are uniform, so that the polarization dependence and the polarization dispersion are further reduced. The same effect can be obtained by arranging the polarization plane rotation elements 5a and 5b in the input / output section of the SOA 1a.

Third Embodiment FIG. 3 shows a third embodiment of the present invention.
FIG. 2 is a diagram showing a configuration of an optical amplifier module according to the first embodiment. Parts corresponding to those of the first embodiment are denoted by the same reference numerals, and detailed description is omitted. In this embodiment, as in the second embodiment, the two SOAs 1a and 1b are arranged with their active layer surfaces and optical axes parallel to each other. In order to satisfy the condition that the two SOAs 1a and 1b have the same multiplication factor, a polarization plane rotation element (Faraday element) 5a for rotating the polarization plane by 90 ° is provided at the input part of the SOA 1a on the side of the linearly polarized light 4b which is a TM wave. And correspondingly the other SOA
A polarization plane rotation element 5b 'for rotating the polarization plane by 90 ° is also arranged at the output section 1a. As a result, the phases of the two linearly polarized lights entering the output side polarization beam splitter 2b can be aligned.

According to this embodiment, the same effect as that of the second embodiment can be obtained. Also, the polarization plane rotation element 5a is
a, and the polarization plane rotating element 5 b ′ is connected to the SOA 1
The same effect can be obtained by arranging on the output side of b.

[0017]

As described above, according to the present invention, alignment adjustment is easy by combining two SOAs, a polarizing beam splitter, and a mirror.
An optical amplifier module having no polarization dependence can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an optical amplifier module according to Embodiment 1 of the present invention.

FIG. 2 is a diagram showing a configuration of an optical amplifier module according to Embodiment 2 of the present invention.

FIG. 3 is a diagram showing a configuration of an optical amplifier module according to Embodiment 3 of the present invention.

[Explanation of symbols]

1a, 1b: SOA, 2a, 2b: polarizing beam splitter, 3a, 3b: total reflection mirror, 4a, 4b: linearly polarized light, 5a, 5b, 5b ': polarization plane rotating element.

Claims (4)

[Claims] 1. An input light is converted into a first linearly polarized light traveling straight on its optical path and a second linearly polarized light having a polarization plane orthogonal to the first linearly polarized light traveling 90 °. A first polarizing beam splitter to be separated, a first mirror that deflects the second linearly polarized light separated by the first polarizing beam splitter by 90 ° and translates the second linearly polarized light with the first linearly polarized light, A first semiconductor optical amplifier for amplifying the first linearly polarized light that has traveled straight through the first polarization beam splitter; and a first semiconductor optical amplifier having an active layer surface rotated by 90 ° and an optical axis. Are arranged in parallel with the first semiconductor optical amplifier, amplify the second linearly polarized light reflected by the first mirror, and an output light of the first semiconductor optical amplifier. A second mirror for deflecting by 90 °, An optical amplifier module characterized by having a second polarization beam splitter for multiplexing the output light from the reflected light a second semiconductor optical amplifier from the second mirror. 2. The input light is converted into a first linearly polarized light that travels straight on its optical path and a second linearly polarized light whose polarization plane is orthogonal to the first linearly polarized light that is deflected by 90 ° and travels. A first polarizing beam splitter to be separated, a first mirror that deflects the second linearly polarized light separated by the first polarizing beam splitter by 90 ° and translates the second linearly polarized light with the first linearly polarized light, A first semiconductor optical amplifier that amplifies the first linearly polarized light that has traveled straight through the first polarization beam splitter; and a first semiconductor optical amplifier that amplifies the second linearly polarized light reflected by the first mirror. A second semiconductor optical amplifier having an active layer surface and an optical axis parallel to the first semiconductor optical amplifier; a second mirror for deflecting the output light of the first semiconductor optical amplifier by 90 °; Light reflected from a mirror and the second semiconductor A second polarization beam splitter for multiplexing with the output light of the amplifier; and a second polarization beam splitter disposed at an input portion of one of the first and second semiconductor amplifiers for rotating the polarization plane of the input light by 90 °. A first polarization plane rotation element, and a second polarization plane rotation element disposed at one of the output units of the first and second semiconductor optical amplifiers to orthogonalize the polarization planes of the output lights of the first and second semiconductor optical amplifiers. An optical amplifier module comprising a polarization plane rotation element. 3. The second polarization plane rotation element rotates the polarization plane by 270 °, and is disposed at an output part of the semiconductor optical amplifier on the side where the first polarization plane rotation element is disposed. The optical amplifier module according to claim 2, wherein: 4. The second polarization plane rotation element rotates the polarization plane by 90 °, and is disposed at an output part of the semiconductor optical amplifier opposite to the side on which the first polarization plane rotation element is disposed. The optical amplifier module according to claim 2, wherein