JP2000010136A - Wavelength converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable wavelength conversion near to signal light by operating even to the high speed signal with a wavelength converter utilizing the gain suppression phenomenon of a semiconductor optical amplifier and outputting only the wavelength conversion light without using an optical filter. SOLUTION: A semiconductor optical amplifier region is inserted into two arm waveguides 13a, 13b of a symmetrical Mach-Zehnder interferometer. Intensity modulation signal light of a wavelength λs and stationary light of a wavelength λc are inputted from different ports. The stationary light of the wavelength λc is complementarily modulated by the intensity modulation signal light of the wavelength λs in the semiconductor optical amplifier region and is outputted as the wavelength conversion light to cross ports countering the input ports.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a wavelength converter for converting the wavelength of an optical signal into another wavelength.

[0002]

2. Description of the Related Art As a wavelength converter, a wavelength converter utilizing a gain suppression phenomenon of a semiconductor optical amplifier is known. this is,
This utilizes the effect that the signal gain decreases when high-power light is input to the semiconductor optical amplifier. As shown in FIG. 4A, the semiconductor optical amplifier 41 supplies the intensity-modulated signal light having the wavelength λs and the steady-state light having the wavelength λc. A configuration is used in which light is input simultaneously.

In the semiconductor optical amplifier 41, the gain becomes small when the intensity-modulated signal light having the wavelength λs is on and becomes large when the intensity-modulated signal light is off.
Is intensity-modulated. That is, the stationary light having the wavelength λc is complementarily modulated by the intensity-modulated signal light having the wavelength λs. This is substantially equivalent to the wavelength conversion of the signal light having the wavelength λs into the signal light having the wavelength λc.

[0004]

In the configuration shown in FIG. 4A,
The original signal light (wavelength λ) together with the wavelength-converted light (wavelength λc)
s) is also output at the same time. Therefore, if it is desired to obtain only the wavelength-converted light, it is necessary to provide an optical filter for blocking the original signal light, which complicates the device configuration.

In this case, it is necessary that the wavelength of the converted light and the wavelength of the original signal light are separated from each other by an optical filter. That is, in a configuration including an optical filter, it may be difficult to convert the wavelength to a wavelength near the signal light, which may be a factor of narrowing the application range to the system.

On the other hand, as shown in FIG. 4B, the intensity modulation signal light having the wavelength λs and the wavelength λc
Is input from the opposite direction and the wavelength demultiplexer 42 separates the wavelength-converted light (wavelength λc) from the intensity-modulated signal light (wavelength λs). It is possible to take out. However, in practice, the signal light component of the wavelength λs output together with the converted wavelength light cannot be completely reduced to zero due to the residual reflection of the end face of the semiconductor optical amplifier. Therefore, similarly to the case where an optical filter is used, it is necessary that the converted light wavelength and the original signal light wavelength are separated from each other so as to be separated by the optical demultiplexer.

In order to convert the wavelength of a high-speed signal without signal degradation, it is preferable that the intensity-modulated signal light (wavelength λs) and the stationary light (wavelength λc) be input to the semiconductor optical amplifier 41 from the same direction. However, the configuration shown in FIG. 4B is not preferable in that sense.

The present invention provides a wavelength converter utilizing a gain suppression phenomenon of a semiconductor optical amplifier, which operates even for a high-speed signal, and can output only wavelength-converted light without using an optical filter. It is an object of the present invention to provide a wavelength converter that enables wavelength conversion to near signal light.

[0009]

The wavelength converter according to the present invention comprises:
The configuration is such that a semiconductor optical amplification region is inserted into two arm waveguides of a symmetric Mach-Zehnder interferometer or an asymmetric Mach-Zehnder interferometer or a loop waveguide of a loop mirror.
When the intensity-modulated signal light having the wavelength λs and the stationary light having the wavelength λc are input from different ports, the steady light having the wavelength λc is complementarily modulated by the intensity-modulated signal light having the wavelength λs in the semiconductor optical amplification region, and the wavelength-converted light is converted. Becomes

In the symmetric Mach-Zehnder interferometer, the intensity-modulated signal light and the wavelength-converted light (stationary light) are output separately from the cross port with respect to the input port. In an asymmetric Mach-Zehnder interferometer, intensity-modulated signal light and wavelength-converted light (stationary light) are separately output to through ports for input ports. However, since the optical lengths of the two arm waveguides are set so as to differ from the intensity-modulated signal light of wavelength λs by half a wavelength, all of the intensity-modulated signal light is output to the through port. Light causes some crosstalk to the crossport. However, the wavelength-converted light output to the through port does not include crosstalk of the intensity-modulated signal light, so there is no problem.

In the loop mirror, the intensity-modulated signal light and the wavelength-converted light (stationary light) are separately output from the input ports. Separation of the stationary light and the wavelength-converted light input / output from the same port of the loop mirror can be performed using an optical circulator or an optical directional coupler.

[0012]

(First Embodiment) FIG. 1 shows a configuration example of a first embodiment of the present invention.

The wavelength converter of the present embodiment has a configuration based on a symmetric Mach-Zehnder interferometer. The symmetric Mach-Zehnder interferometer has a 3 dB coupler 11 having one of two ports as input ports A and B, a 3 dB coupler 12 having one of two ports as output ports C and D, and a 3 dB coupler 11,
12 of the same optical length that connects the other two ports of each other
It is composed of the arm waveguides 13a and 13b.
In this configuration, input port A and output port D, input port B and output port C are cross ports, input port A and output port C, input port B and output port D are through ports.

The wavelength converter has a configuration in which semiconductor optical amplification regions 14a and 14b having the same characteristics are inserted into each arm waveguide 13a and 13b of a symmetric Mach-Zehnder interferometer.
An intensity-modulated signal light of wavelength λs is input from input port A,
The stationary light having the wavelength λc is input from the input port B.

The intensity-modulated signal light having the wavelength λs is split into two by the 3 dB coupler 11, and is divided into the arm waveguides 13a and 13a, respectively.
The laser light is input to the semiconductor optical amplification regions 14a and 14b via 3b. As a result, the gain of each semiconductor optical amplification region becomes equal to the wavelength λ.
s is modulated according to the intensity modulated signal light. The intensity-modulated signal light that has passed through each semiconductor optical amplification region is
Are multiplexed. At this time, the intensity-modulated signal light 2
Since the two paths are completely symmetric, the multiplexed intensity-modulated signal light is output to the output port D which is a cross port with respect to the input port A.

On the other hand, the stationary light having the wavelength λc is split into two by the 3 dB coupler 11, and the arm waveguides 13a and
b is input to the semiconductor optical amplification regions 14a and 14b. In each semiconductor optical amplification region, the gain is modulated by the intensity-modulated signal light having the wavelength λs, so that the steady light having the wavelength λc is complemented by the intensity-modulated signal light having the wavelength λs according to the wavelength conversion principle similar to the conventional technology. It becomes modulated wavelength converted light. The wavelength converted light that has passed through each semiconductor optical amplification region is 3
The signals are multiplexed by the dB coupler 12. At this time, since the two paths through which the stationary light and the wavelength-converted light have passed are completely symmetric, the combined wavelength-converted light having the wavelength λc is output to the output port C which is a cross port with respect to the input port B. You.
That is, the signal is completely separated from the intensity-modulated signal light having the wavelength λs.

Each of the semiconductor optical amplification regions 14a and 14b
In this case, since the intensity-modulated signal light having the wavelength λs and the stationary light having the wavelength λc pass in the same direction, the apparatus can operate even with a high-speed signal. Further, by using a perfect symmetric Mach-Zehnder interferometer, the intensity-modulated signal light and the wavelength-converted light can be completely separated into different output ports, so that wavelength conversion near the input wavelength is also possible.

(Second Embodiment) FIG. 2 shows a second embodiment of the present invention.
1 shows a configuration example of the embodiment. The wavelength converter of the present embodiment has a configuration based on an asymmetric Mach-Zehnder interferometer. The asymmetric Mach-Zehnder interferometer has a 3 dB coupler 11 having one of two ports as input ports A and B, and a two
A 3 dB coupler 12 whose ports are output ports C and D;
It is composed of two asymmetrical arm waveguides 15a and 15b connecting the other two ports of the 3dB couplers 11 and 12, respectively. The optical lengths (= optical path length × refractive index) of the two arm waveguides are set so as to differ from the intensity modulated signal light of wavelength λs by a half wavelength. The optical length difference may be adjusted using a phase shifter or the like according to the wavelength of the input signal light. In this configuration, input port A and output port D, input port B and output port C are cross ports, input port A and output port C, input port B and output port D are through ports.

The wavelength converter has a configuration in which semiconductor optical amplification regions 14a and 14b having the same characteristics are inserted into the respective arm waveguides 15a and 15b of the asymmetric Mach-Zehnder interferometer. , And the stationary light having the wavelength λc is inputted from the input port B.

The intensity-modulated signal light having the wavelength λs is branched into two by the 3 dB coupler 11, and the arm waveguides 15a, 15
5b are input to the semiconductor optical amplification regions 14a and 14b. As a result, the gain of each semiconductor optical amplification region becomes equal to the wavelength λ.
s is modulated according to the intensity modulated signal light. The intensity-modulated signal light that has passed through each semiconductor optical amplification region is
Are multiplexed. At this time, the intensity-modulated signal light 2
Since the optical lengths of the two paths are different by λs / 2, the multiplexed intensity-modulated signal light is output from the input port A to the output port C which is a through port.

On the other hand, the stationary light having the wavelength λc is split into two by the 3 dB coupler 11, and the arm waveguides 15a and
b is input to the semiconductor optical amplification regions 14a and 14b. In each semiconductor optical amplification region, the gain is modulated by the intensity-modulated signal light of wavelength λs, so that the steady light of wavelength λc is complemented by the intensity-modulated signal light of wavelength λs according to the wavelength conversion principle similar to the prior art. It becomes modulated wavelength converted light. The wavelength converted light that has passed through each semiconductor optical amplification region is 3
The signals are multiplexed by the dB coupler 12. At this time, since the two paths through which the stationary light and the wavelength-converted light have passed are asymmetric,
The multiplexed wavelength-converted light having the wavelength λc is divided into an output port D which is a through port and an output port C which is a cross port with respect to the input port B at a predetermined ratio (mostly the output port D) and output. Is done. However, since the intensity-modulated signal light having the wavelength λs is not output to the output port D, only the wavelength-converted light having the wavelength λc can be output from the output port D.

Each of the semiconductor optical amplification regions 14a, 14b
In this case, since the intensity-modulated signal light having the wavelength λs and the stationary light having the wavelength λc pass in the same direction, the apparatus can operate even with a high-speed signal. Further, by using the asymmetric Mach-Zehnder interferometer, the wavelength-converted light can be separated and extracted from the intensity-modulated signal light, so that the wavelength can be converted to near the input wavelength.

(Third Embodiment) FIG. 3 shows a third embodiment of the present invention.
1 shows a configuration example of the embodiment. The wavelength converter of the present embodiment has a configuration based on a loop mirror. The loop mirror has two ports of the 3 dB coupler 21 as input / output ports A and B, and the other ports C and D as loop optical waveguides 2.
This is a configuration connected by 2.

The wavelength converter has a configuration in which a semiconductor optical amplification region 23 is inserted into a loop waveguide 22, an intensity modulated signal light having a wavelength λs is input from a port A, and a wavelength λc is input from a port B via an optical circulator 24. Is input. The optical circulator 24 has a function of separating the stationary light input to the port B from the wavelength-converted light output from the port B.

The intensity-modulated signal light having the wavelength λs is branched into two by the 3 dB coupler 21, respectively, follows the optical waveguide 22 in the opposite direction, and is input to the semiconductor optical amplification region 23. As a result, the gain of the semiconductor optical amplification region 23 is modulated according to the intensity modulation signal light having the wavelength λs. The intensity-modulated signal light that has passed through the semiconductor optical amplification regions 23 in the opposite directions is 3 dB.
The signals are multiplexed by the coupler 21. At this time, since the paths through which the intensity modulated signal lights have passed are the same, the multiplexed intensity modulated signal light is output from the input port A. This is the basic operation of the loop mirror.

On the other hand, the stationary light having the wavelength λc is branched into two by the 3 dB coupler 21, respectively, follows the optical waveguide 22 in the opposite direction, and is input to the semiconductor optical amplification region 23. In the semiconductor optical amplification region 23, the gain is modulated by the intensity-modulated signal light having the wavelength λs, so that the stationary light having the wavelength λc is complementarily complemented by the intensity-modulated signal light having the wavelength λs according to the wavelength conversion principle similar to that of the prior art. It becomes modulated wavelength converted light. The wavelength-converted lights that have passed through the semiconductor optical amplification regions 23 in opposite directions are multiplexed by the 3 dB coupler 21. At this time, since the paths through which the stationary light and the wavelength-converted light have passed are the same, the multiplexed wavelength-converted light is output from the input port B and separated from the stationary light via the optical circulator 24.

In the semiconductor optical amplification region 23, the wavelength λ
Since the intensity-modulated signal light of s and the stationary light of wavelength λc pass in the same direction for each direction, it can operate even for high-speed signals. Also, since the intensity-modulated signal light and the wavelength-converted light can be completely separated into different output ports by the characteristics of the loop mirror, wavelength conversion near the input wavelength is also possible. Instead of the optical circulator 24 for separating the stationary light having the wavelength λc and the wavelength-converted light, a normal optical directional coupler (optical coupler) may be used.

The components of each embodiment described above can be partially or wholly integrated on a semiconductor substrate. Further, among the components of each embodiment described above, some or all of the components other than the semiconductor optical amplification region can be formed of a glass waveguide.

[0029]

As described above, the wavelength converter of the present invention operates even for high-speed signals because the input signal light and the stationary light (wavelength-converted light) pass in the same direction in the semiconductor optical amplification region. It is possible. In addition, since the input signal light and the wavelength-converted light can be separated and output without using an optical filter, wavelength conversion near the input wavelength is also possible.

[Brief description of the drawings]

FIG. 1 is a view showing a configuration example of a first embodiment of the present invention.

FIG. 2 is a diagram showing a configuration example of a second embodiment of the present invention.

FIG. 3 is a diagram showing a configuration example according to a third embodiment of the present invention.

FIG. 4 is a diagram showing a configuration example of a conventional wavelength converter using a semiconductor optical amplifier.

[Explanation of symbols]

 11, 12, 21 3dB coupler 13a, 13b, 15a, 15b Arm waveguide 14a, 14b, 23 Semiconductor optical amplification region 22 Loop waveguide 24 Optical circulator 41 Semiconductor optical amplifier 42 Optical demultiplexer

Claims (6)

[Claims] 1. A first 3 dB coupler having one of two ports as input ports A and B, a second 3 dB coupler having one of two ports as output ports C and D, and first and second 3 dB. A symmetric Mach-Zehnder interferometer composed of two arm waveguides having the same optical length for connecting the other two ports of the coupler, and a semiconductor having the same characteristics inserted into each arm waveguide of the symmetric Mach-Zehnder interferometer An optical amplification region, an intensity-modulated signal light having a wavelength λs is input from the input port A, and a stationary light having a wavelength λc is input from the input port B;
The output port C, which serves as a cross port with respect to the input port B, outputs wavelength-converted light having a wavelength λc in which stationary light having a wavelength λc is complementarily modulated by intensity-modulated signal light having a wavelength λs. A wavelength converter characterized by the above-mentioned. 2. The wavelength converter according to claim 1, wherein, instead of the symmetric Mach-Zehnder interferometer, optics of two arm waveguides connecting the other two ports of each of the first and second 3 dB couplers. Using an asymmetric Mach-Zehnder interferometer having a length different by λs / 2, inputting an intensity-modulated signal light having a wavelength λs from the input port A, and inputting a stationary light having a wavelength λc from the input port B;
The output port D, which is a through port with respect to the input port B, outputs wavelength-converted light having a wavelength λc in which stationary light having a wavelength λc is complementarily modulated by intensity-modulated signal light having a wavelength λs. A wavelength converter characterized by the above-mentioned. 3. A loop mirror comprising a 3 dB coupler having one of two ports as input / output ports A and B, and a loop waveguide connecting the other two ports C and D in a loop, and the loop mirror. And an optical circulator connected to the input / output port B. An intensity modulated signal light having a wavelength λs is input from the input / output port A, and the optical circulator is The stationary light having the wavelength λc is inputted from the input / output port B via the input / output port B, and the stationary light having the wavelength λc is complementarily modulated by the intensity modulated signal light having the wavelength λs from the optical circulator connected to the input / output port B. A wavelength converter having a configuration for outputting wavelength-converted light having a wavelength λc. 4. The wavelength converter according to claim 3, wherein an optical directional coupler is used instead of the optical circulator. 5. The wavelength converter according to claim 1, wherein a part or all of the components are integrated on a semiconductor substrate. 6. The wavelength converter according to claim 1, wherein a part or all of the components other than the semiconductor optical amplification region are formed of a glass waveguide. vessel.