Optical clock signal extraction device and optical clock signal extraction method

Abstract

The present invention is an optical clock signal extraction device, comprising first conversion means and second conversion means for enabling to extract an optical clock signal without depending on the polarization direction of an input optical signal. The first conversion means comprises a first optical converter and a continuous wave light source of which wavelength is λ2, where an input optical signal of which wavelength is λ1 and continuous wave light of which wavelength is λ2 are input to the first optical converter, and an intermediate optical signal of which wavelength is λ2 is generated and output without depending on the polarization direction of the input optical signal. The second conversion means has a second optical converter, where the intermediate optical signal is input to the second optical converter, and an optical clock signal of which wavelength is λ3 is generated and output by the passive mode locking operation of the second optical converter. The input optical signal is input from the end face L1 of the first optical converter, and the continuous wave light of which wavelength is λ2 is input to the first optical converter from the other end face of the first optical converter. The intermediate optical signal is output from the end face of the first optical converter and input to the end face of the second optical converter. The optical clock signal is output from the other end face of the second optical converter.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of the present invention will be better understood from the following description taken in connection with the accompanying drawings, in which:

FIG. 1 is a block diagram depicting an overview of the optical clock signal extraction device according to the first embodiment;

FIG. 2 is a block diagram depicting an overview of the optical clock signal extraction device according to the second embodiment;

FIG. 3 is a cross-sectional view depicting an overview of the passive mode-locked laser diode;

FIG. 4 are diagrams depicting the time-based waveforms of the input optical signal, intermediate optical signal and optical clock signal;

FIG. 5 is a graph depicting the characteristics of the time jitter with respect to the ratio of the wavelength detuning and mode interval;

FIG. 6 are diagrams depicting the operation principle of the passive mode-locking;

FIG. 7 are diagrams depicting the pattern effect;

FIG. 8 is a block diagram depicting an overview of the device used for optical clock signal extraction experiment;

FIG. 9 are diagrams depicting the waveforms in the time domain of the input optical signal and optical clock signal; and

FIG. 10 is a block diagram depicting an overview of the optical clock signal extraction device according to the third embodiment.

Claims

1. An optical clock signal extraction device comprising: first conversion means, comprising a first optical converter and a continuous wave light source of which wavelength is λ2, for inputting an input optical signal of which bit rate is f and wavelength is λ1 and continuous wave light of which wavelength is λ2 into said first optical converter, and generating and outputting an intermediate optical signal which has wavelength λ2 and which does not depend on the polarization direction of the input optical signal; andsecond conversion means, comprising a second optical converter, for inputting said intermediate optical signal into said second optical converter and generating and outputting an optical clock signal of which repeat frequency is f and wavelength is λ3 by passive mode locking operation of said second optical converter.

2. The optical clock signal extraction device according to claim 1, wherein said first optical converter is a semiconductor optical amplifier of which active layer is formed by bulk crystals and of which amplification factor does not depend on the polarization direction of said input optical signal.

3. The optical clock signal extraction device according to claim 1, wherein said first optical converter is a semiconductor optical amplifier of which active layer is formed by a strained-layer quantum-well structure and of which amplification factor does not depend on the polarization direction of said input optical signal.

4. The optical clock signal extraction device according to claim 1, wherein said first optical converter is a saturable absorber of which active layer is formed by a strained-layer quantum-well structure, and of which amplification factor does not depend on the polarization direction of said input optical signal.

5. The optical clock signal extraction device according to claim 1, wherein said first optical converter is an electro-absorption modulator of which active layer is formed by a strained-layer quantum-well structure, and of which amplification factor does not depend on the polarization direction of said input optical signal.

6. An optical clock signal extraction device, comprising: first conversion means, comprising a first optical converter, a continuous wave light source of which wavelength is λ2, and a continuous wave light source of which wavelength is λ4, for inputting an input optical signal of which bit rate is f and wavelength is λ1, continuous wave light of which wavelength is λ2 and continuous wave light of which wavelength is λ4 into said first optical converter and generating and outputting an intermediate optical signal which has wavelength λ2 and which does not depend on the polarization direction of the input optical signal; andsecond conversion means, comprising a second optical converter, for inputting said intermediate optical signal into said second optical converter, and generating and outputting an optical clock signal of which repeat frequency is f and wavelength is λ3 by passive mode locking operation of said second optical converter.

7. The optical clock signal extraction device according to claim 6, wherein said first optical converter is a semiconductor optical amplifier of which active layer is formed by bulk crystals and of which amplification factor does not depend on the polarization direction of the input optical signal.

8. The optical clock signal extraction device according to claim 6, wherein said first optical converter is a semiconductor optical amplifier of which active layer is formed by a strained-layer quantum-well structure and of which amplification factor does not depend on the polarization direction of said input optical signal.

9. The optical clock signal extraction device according to claim 1, wherein said second optical converter is a passive mode-locked laser diode having a gain area and a saturable absorption area.

10. The optical clock signal extraction device according to claim 2, wherein said second optical converter is a passive mode-locked laser diode having a gain area and a saturable absorption area.

11. The optical clock signal extraction device according to claim 3, wherein said second optical converter is a passive mode-locked laser diode having a gain area and a saturable absorption area.

12. The optical clock signal extraction device according to claim 4, wherein said second optical converter is a passive mode-locked laser diode having a gain area and a saturable absorption area.

13. The optical clock signal extraction device according to claim 5, wherein said second optical converter is a passive mode-locked laser diode having a gain area and a saturable absorption area.

14. The optical clock signal extraction device according to claim 6, wherein said second optical converter is a passive mode-locked laser diode having a gain area and a saturable absorption area.

15. The optical clock signal extraction device according to claim 7, wherein said second optical converter is a passive mode-locked laser diode having a gain area and a saturable absorption area.

16. The optical clock signal extraction device according to claim 8, wherein said second optical converter is a passive mode-locked laser diode having a gain area and a saturable absorption area.

17. An optical clock signal extraction method, comprising: a first conversion step of inputting an input optical signal of which bit rate is f and wavelength is λ1 and a continuous wave light of which wavelength is λ2 into a first optical converter, and generating and outputting an intermediate optical signal of which wavelength is λ2 by a cross gain modulation effect, which is manifested by said input optical signal and said continuous wave light, without depending on the polarization direction of the input optical signal; andsecond conversion step of inputting said intermediate optical signal into a second optical converter, and generating and outputting an optical clock signal of which repeat frequency is f and wavelength is λ3 by passive mode locking operation of said second optical converter.

18. An optical clock signal extraction method, comprising: a first conversion step of inputting an input optical signal of which bit rate is f and wavelength is λ1, a continuous wave light of which wavelength is λ2, and a continuous wave light of which wavelength is λ4 into a first optical converter, and generating and outputting an intermediate optical signal of which wavelength is λ2 without depending on the polarization direction of said input optical signal; anda second conversion step of inputting said intermediate optical signal to a second optical converter, and generating and outputting an optical clock signal of which repeat frequency is f and wavelength is λ3 by passive mode locking operation of said second optical converter.

19. The optical clock signal extraction method according to claim 17, wherein said second conversion step is executed by passive mode-locked laser diode having a gain area and saturable absorption area which sets one of longitudinal oscillation modes of said passive mode-locked laser diode to a value close to λ2 which is a wavelength of said intermediate optical signals.

20. The optical clock signal extraction method according to claim 18, wherein said second conversion step is executed by passive mode-locked laser diode having a gain area and saturable absorption area which sets one of longitudinal oscillation modes of said passive mode-locked laser diode to a value close to λ2 which is a wavelength of said intermediate optical signals.