JPH09304801A - Optical wavelength converter - Google Patents

Abstract

(57) [Summary] [Object] To realize wavelength conversion without wavelength dependence while taking advantage of the injection-locked wavelength conversion. A control circuit for inputting intensity-modulated signal light of wavelength λ _S and outputting control light of wavelength λ _i according to ON / OFF without depending on the input wavelength, and control of wavelength λ _i synchronized injection by light same, the first semiconductor laser oscillator oscillating wavelength changes the wavelength lambda _i or wavelength lambda _C according to the on-off of the control light, the wavelength of the first semiconductor laser oscillator lambda _C
And a wavelength selection means for extracting the output light as the wavelength-converted light for the signal light having the wavelength λ _S.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical wavelength conversion device that converts and outputs the optical wavelength of intensity-modulated signal light.

[0002]

2. Description of the Related Art As a conventional wavelength conversion method, there is a method of wavelength conversion using injection locking for a semiconductor laser oscillator having a residual side mode ("Bistability and Wav").
eformReshaping in a DFB-LD with Side-Mode Light In
jection ", IEEE PHOTONICS TECHNOLOGY LETTERS, vol.
7, no.2, pp.164-166).

It is assumed that this semiconductor laser oscillator has a residual side mode in its oscillation spectrum and is in an oscillation state at a wavelength λ _C. When the signal light of wavelength λ _{S in} the vicinity of one of the residual side modes is input as injection-locked light from the outside, the oscillation of wavelength λ _C stops due to the injection-locking phenomenon,
It oscillates in the side mode that is drawn to the wavelength λ _S. That is, the semiconductor laser oscillator oscillates at the wavelength λ _S or the wavelength λ _C depending on whether the input signal light is on or off. By extracting only the oscillation light of the wavelength λ _C among them, the wavelength conversion from the wavelength λ _S to the wavelength λ _C is effectively realized. However,
The oscillation light of wavelength λ _C has a complementary relationship (on / off inversion) with the input signal light.

[0004]

By the way, the wavelength conversion method using injection locking has a significant threshold effect in the input / output relationship, and one of the major advantages is that it has a waveform shaping action. On the other hand, however, the injection locking phenomenon has wavelength dependency, and the conversion operation and conversion efficiency change only when the wavelength of the input signal light changes by sub-nanometers. Therefore, in order to put such an optical wavelength conversion device into practical use,
There is a demand for wavelength independence that allows constant operation regardless of the wavelength of the input signal light.

It is an object of the present invention to provide an optical wavelength conversion device which realizes wavelength conversion without wavelength dependency while taking advantage of the injection locking type wavelength conversion.

[0006]

The optical wavelength conversion device of the present invention receives an intensity-modulated signal light having a wavelength λ _S , and has a wavelength λ _i corresponding to ON / OFF without depending on the input wavelength. a control circuit for outputting a control light, and the first semiconductor laser oscillator synchronized injection same by the control light having a wavelength lambda _i, the oscillation wavelength in response to turning on and off the control light varies with the wavelength lambda _i or wavelength lambda _C, And a wavelength selecting means for extracting the output light of the wavelength λ _C of the first semiconductor laser oscillator as the wavelength-converted light for the signal light of the wavelength λ _S.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION

(First Embodiment) FIG. 1 shows a first embodiment of the present invention. In the figure, a control circuit 10 includes a semiconductor laser oscillator 11, an optical circulator 12, and a polarization maintaining optical fiber 1.
3. The signal light of wavelength λ _S is input to the semiconductor laser oscillator 11 via the optical circulator 12. The control light of the wavelength λ _i output from the semiconductor laser oscillator 11 is output from the optical circulator 12 via the polarization maintaining optical fiber 13. The semiconductor laser oscillator 1 is
Enter the control light of wavelength lambda _i as injection locking light, the wavelength lambda _i
Alternatively, it outputs the oscillation light of wavelength λ _C. The optical filter 2 blocks the oscillation light of wavelength λ _i and outputs the oscillation light of wavelength λ _C as wavelength conversion light (signal light).

Here, the feature of the present invention is that the semiconductor laser oscillator 11 of the control circuit 10 outputs the control light of the wavelength λ _i according to the ON / OFF of the input signal light without depending on the wavelength of the input signal light.
The semiconductor laser oscillator 1 is injection-locked with the control light and outputs the oscillation light of the wavelength λ _i or the wavelength λ _C according to the on / off state. As the semiconductor laser oscillator 11 having no wavelength dependence, for example, a semiconductor laser oscillator 11 in which end face residual reflection is sufficiently reduced and side modes caused by reflection can be ignored may be used. The semiconductor laser oscillator 11 outputs control light having a wavelength λ _i which causes injection locking of the semiconductor laser oscillator 1 when the input signal light is off. On the other hand, the oscillation is suppressed when the input signal light is on. That is, some of the carriers used for oscillation of the wavelength λ _{i in} the semiconductor laser oscillator 11 are consumed by stimulated emission of the input signal light, and the refractive index in the laser associated therewith changes. As a result, the power of the output control light is reduced to the extent that injection locking is lost in the semiconductor laser oscillator 1, or the wavelength of the control light is shifted from the wavelength λ _{i at} which injection locking occurs.

FIG. 2 shows the relationship between the oscillation spectrum of the semiconductor laser oscillator 1 and the wavelength λ _i of the control light. The semiconductor laser oscillator 1 is a single mode laser having a residual side mode for injection locking. For example, distributed Bragg reflection (DBR) semiconductor laser or distributed feedback (DFB)
A semiconductor laser can be used. The oscillation wavelength of the semiconductor laser oscillator 11 is a wavelength λ _{i in} the vicinity of one of the residual side modes of the semiconductor laser oscillator 1. In the semiconductor laser oscillator 1, when the control light of the wavelength λ _i output from the semiconductor laser oscillator 11 is input, the oscillation at the free oscillation wavelength λ _C is stopped and the side mode pulled to the wavelength λ _i by the injection locking. Oscillates at. That is, the semiconductor laser oscillator 1 outputs an oscillation light having a wavelength lambda _i or wavelength lambda _C in accordance with the control light of the on-off wavelength lambda _i.

The wavelength conversion operation in this embodiment will be described based on the above configuration. The semiconductor laser oscillator 11 of the control circuit 10 oscillates at a wavelength λ _i near one of the residual side modes of the semiconductor laser oscillator 1. The signal light of the wavelength λ _S that has been on / off modulated is input to the semiconductor laser oscillator 11 via the optical circulator 12. When the signal light is off, the semiconductor laser oscillator 11
Outputs control light having a wavelength and power sufficient for injection locking the semiconductor laser oscillator 1. On the other hand, when the signal light is on, the oscillation light power of the semiconductor laser oscillator 11 decreases or the oscillation wavelength λ _i changes, and the injection locking condition for the semiconductor laser oscillator 1 is no longer satisfied. Here, when the control light output from the semiconductor laser oscillator 11 satisfies the injection locking condition for the semiconductor laser oscillator 1, it is turned on, and when it is not satisfied, it is turned off.
The control light is modulated complementarily (on / off inversion) with the on / off of the signal light. The modulation operation does not depend on the wavelength of the signal light.

The control light having the wavelength λ _i output from the semiconductor laser oscillator 11 is input to the semiconductor laser oscillator 1 via the optical circulator 12 and the polarization maintaining optical fiber 13. In the semiconductor laser oscillator 1, injection locking is turned on / off according to on / off of the control light, and oscillated light of wavelength λ _i or wavelength λ _C is output. Of the oscillated light, only the oscillated light of the wavelength λ _C corresponding to the turning off of the control light is extracted by the optical filter 2. As a result, signal light modulated in a complementary (on / off inversion) to the on / off of the control light is obtained.
Here, the control light so are complementarily modulated to the signal light of the wavelength lambda _S, the signal light of the wavelength lambda _C is the wavelength converted light having the same logic waveform of the signal light of the wavelength lambda _S.

The wavelength conversion operation (λ _i → λ _C ) using injection locking of the semiconductor laser oscillator 1 depends on the wavelength λ _i of the input control light. However, since the control light is generated from the semiconductor laser oscillator 11 provided in the device, it is possible to input it to the semiconductor laser oscillator 1 with a stable wavelength λ _i . Therefore, the semiconductor laser oscillator 1 can perform a stable wavelength conversion operation with a predetermined injection locking characteristic. On the other hand, since the wavelength conversion operation of the semiconductor laser oscillator 1 has no wavelength dependence, the wavelength conversion to the wavelength λ _C is stably performed even if the input wavelength λ _S of the signal light varies as a whole. That is, the wavelength λ of the input signal light
Wavelength conversion from wavelength lambda _S not depend on _S to the wavelength lambda _C is realized. Moreover, the advantage of wavelength conversion by injection locking of the semiconductor laser oscillator 1 can be utilized as it is.

The polarization-maintaining optical fiber 13 connecting the semiconductor laser oscillator 11 and the semiconductor laser oscillator 1 is arranged for the purpose of preventing a change in the injection locking state due to polarization fluctuation. The optical circulator 12 may be replaced with an optical coupler. Further, in the present embodiment, it is assumed that the semiconductor laser oscillator 11 has no end face reflection. However, since there is residual reflection, the semiconductor laser oscillator 1
When a part of the signal light of wavelength λ _S input to the optical circulator 12 returns to the optical circulator 12, a wavelength λ s may be provided between the optical circulator 12 and the semiconductor laser oscillator 1 as necessary.
An optical filter that blocks the _S signal light may be inserted.

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention.
An embodiment will be described. The feature of this embodiment is that, in the control circuit 10 of the first embodiment, the signal light is input to one end face of the semiconductor laser oscillator 11 and the control light is output from the other end face without using the optical circulator 12. It is in. At this time, the semiconductor laser oscillator 11 having no end face reflection due to the wavelength independence transmits the input signal light of the wavelength λ _S as it is. Therefore, the optical circulator 12
In the configuration not using, the optical filter 14 that blocks the transmitted signal light of the wavelength λ _S and transmits only the control light of the wavelength λ _i is inserted. Other configurations are the same as those of the first embodiment.

(Third Embodiment) FIG. 4 shows a third embodiment of the present invention.
An embodiment will be described. The feature of this embodiment lies in that the input / output end faces of the semiconductor laser oscillator 1 of the first embodiment are made the same by using the optical circulator 3. That is, the control light output from the polarization maintaining optical fiber 13 of the control circuit 10 is input to the semiconductor laser oscillator 1 via the optical circulator 3, and the wavelength λ _i or λ _C output from the same end face of the semiconductor laser oscillator 1. The signal light is input to the optical filter 2 via the optical circulator 3. Other configurations are the same as those of the first embodiment. The optical circulator 3
May be replaced with an optical coupler.

(Fourth Embodiment) FIG. 5 shows a fourth embodiment of the present invention.
An embodiment will be described. The feature of this embodiment is that the input / output end faces of the semiconductor laser oscillator 1 of the second embodiment are made the same by using the optical circulator 3. That is, the control light output from the polarization maintaining optical fiber 13 of the control circuit 10 is input to the semiconductor laser oscillator 1 via the optical circulator 3, and the wavelength λ _i or λ _C output from the same end face of the semiconductor laser oscillator 1. The signal light is input to the optical filter 2 via the optical circulator 3. Other configurations are the same as those of the second embodiment. The optical circulator 3
May be replaced with an optical coupler.

(Fifth Embodiment) FIG. 6 shows a fifth embodiment of the present invention.
An embodiment will be described. In the first embodiment, a single mode laser was used as the semiconductor laser oscillator 1, but in the present embodiment, a multimode laser is used. It is known that a multimode laser oscillates into one of its modes with external light to cause single mode oscillation with a residual side mode. Therefore, by inputting the external light having the wavelength λ _C to the semiconductor laser oscillator 1, the oscillation is made into a single mode.

In this embodiment, a polarization maintaining type optical coupler 1 is provided between the optical circulator 12 and the semiconductor laser oscillator 1.
5, and external light of wavelength λ _C is input to the semiconductor laser oscillator 1 via the optical coupler 14. Other configurations are first
It is similar to the embodiment. The position of the optical coupler 15 may be between the semiconductor laser oscillator 1 and the optical filter 2 or on the output side of the optical filter 2, and external light may be input from the output side of the semiconductor laser oscillator 1.

(Sixth Embodiment) FIG. 7 shows a sixth embodiment of the present invention.
An embodiment will be described. A feature of this embodiment is that the semiconductor laser oscillator 1 in the second embodiment is a multimode laser, and external light is input using the optical coupler 15 as in the fifth embodiment. Therefore, the basic operation is similar to that of the second embodiment.

(Seventh Embodiment) FIG. 8 shows a seventh embodiment of the present invention.
An embodiment will be described. A feature of this embodiment is that the semiconductor laser oscillator 1 in the third embodiment is a multimode laser, and external light is input using the optical coupler 15 as in the fifth embodiment. Therefore, the basic operation is similar to that of the third embodiment. The semiconductor laser oscillator 1 does not use the optical coupler 15 for coupling external light.
On the other hand, the input may be performed from the end face opposite to the optical circulator 3 side.

(Eighth Embodiment) FIG. 9 shows an eighth embodiment of the present invention.
An embodiment will be described. A feature of this embodiment is that the semiconductor laser oscillator 1 in the fourth embodiment is a multimode laser, and external light is input using the optical coupler 15 as in the fifth embodiment. Therefore, the basic operation is similar to that of the fourth embodiment. The semiconductor laser oscillator 1 does not use the optical coupler 15 for coupling external light.
On the other hand, the input may be performed from the end face opposite to the optical circulator 3 side.

[0022]

As described above, the optical wavelength conversion device of the present invention does not depend on the wavelength of the input signal light, and has the advantage of the injection locking type wavelength conversion (for example, the threshold effect between input and output). It is possible to convert to a predetermined wavelength while making full use of it.

[Brief description of drawings]

FIG. 1 is a block diagram showing a first embodiment of the present invention.

FIG. 2 is a diagram showing the relationship between the oscillation spectrum of the semiconductor laser oscillator 1 and the wavelength λ _i of control light.

FIG. 3 is a block diagram showing a second embodiment of the present invention.

FIG. 4 is a block diagram showing a third embodiment of the present invention.

FIG. 5 is a block diagram showing a fourth embodiment of the present invention.

FIG. 6 is a block diagram showing a fifth embodiment of the present invention.

FIG. 7 is a block diagram showing a sixth embodiment of the present invention.

FIG. 8 is a block diagram showing a seventh embodiment of the present invention.

FIG. 9 is a block diagram showing an eighth embodiment of the present invention.

[Explanation of symbols]

 1 Semiconductor Laser Oscillator 2 Optical Filter 3 Optical Circulator 10 Control Circuit 11 Semiconductor Laser Oscillator 12 Optical Circulator 13 Polarization-Maintaining Optical Fiber 14 Optical Filter 15 Optical Coupler

Claims (4)

[Claims] 1. A control circuit for inputting intensity-modulated signal light of wavelength λ _S and outputting control light of wavelength λ _i according to ON / OFF without depending on the input wavelength, said wavelength λ _i the synchronized injection same by the control light, and the first semiconductor laser oscillator oscillating wavelength changes the wavelength lambda _i or wavelength lambda _C according to the on-off of the control light, the wavelength lambda _C of the first semiconductor laser oscillator An optical wavelength conversion device comprising: a wavelength selection unit that extracts output light as wavelength conversion light for signal light of wavelength λ _S. 2. The control circuit outputs the control light of wavelength λ _i when the signal light of wavelength λ _S is off, and does not satisfy the injection locking condition of the first semiconductor laser oscillator when the signal light is on. The optical wavelength conversion device according to claim 1, further comprising a wavelength-independent semiconductor laser oscillator that outputs control light whose power is reduced to a certain degree or control light whose wavelength λ _i is changed. 3. The optical wavelength conversion device according to claim 1, wherein the first semiconductor laser oscillator is a single mode laser having a residual side mode. 4. The optical wavelength conversion device according to claim 1, wherein the control circuit includes means for holding the polarization of the control light having the wavelength λ _i and coupling it to the first semiconductor laser oscillator.