Method, device, and system for waveform shaping of signal light

• US 6,477,300 B2
• Filed: 02/15/2001
• Issued: 11/05/2002
• Est. Priority Date: 03/03/2000
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Watanabe, Shigeki, Takeda, Shinichi, Hironishi, Kazuo
• Primary Examiner(s): Epps, Georgia
• Assistant Examiner(s): Dinh, Jack
• Application Number:
  US09/783,557
• Publication Number:
  US 20010021288A1
• Time in Patent Office: 628 Days
• Field of Search: 385/24, 385/122, 385/42, 359/140, 359/115, 359/124, 257/107, 327/291, 327/292
• US Class Current: 385/42
• CPC Class Codes: G02F 1/3519 of Sagnac type, i.e. nonlinear optical loop mirror [NOLM]
• CPC Class Codes: G02F 2203/26 Pulse shaping; Apparatus or methods therefor
• CPC Class Codes: H04J 14/0223 Conversion to or from optical TDM
• CPC Class Codes: H04J 14/08 Time-division multiplex systems
• CPC Class Codes: H04L 7/0075 with photonic or optical means

Abstract

The present invention relates to a method for waveform shaping of signal light. This method includes the steps of supplying signal light to a first waveform shaper to obtain intermediate signal light, dividing the intermediate signal light into first and second signal lights, supplying the first signal light to a clock recovery circuit to obtain a clock pulse, and supplying the second signal light and the clock pulse to a second waveform shaper to obtain regenerated signal light synchronous with the clock pulse.

Claims

1. A method comprising the steps of:

supplying signal light to a first waveform shaper to obtain intermediate signal light;

dividing said intermediate signal light into first and second signal lights;

supplying said first signal light to a clock recovery circuit to obtain a clock pulse; and

supplying said second signal light and said clock pulse to a second waveform shaper to obtain regenerated signal light synchronous with said clock pulse.

2. A method according to claim 1, wherein each of said first and second waveform shapers comprises an optical gate using switching by cross-phase modulation.

3. A method according to claim 2, wherein:

said optical gate comprises a nonlinear optical loop mirror;

said nonlinear optical loop mirror comprising a first optical coupler including first and second optical paths directionally coupled to each other, a loop optical path formed of a nonlinear optical medium for connecting said first and second optical paths, and a second optical coupler including a third optical path directionally coupled to said loop optical path.

4. A method according to claim 1, wherein said clock recovery circuit comprises a mode-locked laser.

5. A method according to claim 1, further comprising the step of supplying said clock pulse to an optical filter to stretch the pulse width of said clock pulse.

6. A method according to claim 1, wherein said signal light comprises WDM signal light obtained by wavelength division multiplexing a plurality of optical signals having different wavelengths.

7. A method according to claim 6, further comprising the step of supplying said WDM signal light to an optical delay circuit to change each timing of said plurality of optical signals in the time domain.

8. A method according to claim 7, wherein said optical delay circuit comprises an optical medium providing chromatic dispersion.

9. A method according to claim 7, wherein:

said intermediate signal light comprises an optical time division multiplexed signal having a single wavelength;

said clock pulse comprises a plurality of clock pulses respectively corresponding to said plurality of optical signals; and

said regenerated signal light comprises WDM signal light composed of a plurality of optical signals having wavelengths respectively corresponding to the wavelengths of said plurality of clock pulses.

10. A method according to claim 6, further comprising the step of making the polarization states of said plurality of optical signals constant.

11. A device comprising:

a first waveform shaper for accepting signal light to output intermediate signal light;

an optical branch for dividing said intermediate signal light into first and second signal lights;

a clock recovery circuit for accepting said first signal light to output a clock pulse; and

a second waveform shaper for accepting said second signal light and said clock pulse to output regenerated signal light synchronous with said clock pulse.

12. A device according to claim 11, wherein each of said first and second waveform shapers comprises an optical gate using switching by cross-phase modulation.

13. A device according to claim 12, wherein:

said optical gate comprises a nonlinear optical loop mirror;

said nonlinear optical loop mirror comprising a first optical coupler including first and second optical paths directionally coupled to each other, a loop optical path formed of a nonlinear optical medium for connecting said first and second optical paths, and a second optical coupler including a third optical path directionally coupled to said loop optical path.

14. A device according to claim 11, wherein said clock recovery circuit comprises a mode-locked laser.

15. A device according to claim 11, further comprising an optical filter for accepting said clock pulse to stretch the pulse width of said clock pulse.

16. A device according to claim 11, wherein said signal light comprises WDM signal light obtained by wavelength division multiplexing a plurality of optical signals having different wavelengths.

17. A device according to claim 16, further comprising an optical delay circuit for accepting said WDM signal light to change each timing of said plurality of optical signals in the time domain.

18. A device according to claim 17, wherein said optical delay circuit comprises an optical medium providing chromatic dispersion.

19. A device according to claim 17, wherein:

said first waveform shaper converts said WDM signal light into an optical time division multiplexed signal having a single wavelength;

said clock recovery circuit comprises a plurality of clock recovery circuits for respectively outputting a plurality of clock pulses respectively corresponding to said plurality of optical signals; and

said regenerated signal light comprises WDM signal light composed of a plurality of optical signals having wavelengths respectively corresponding to the wavelengths of said plurality of clock pulses.

20. A device according to claim 16, further comprising a polarization controller for making the polarization states of said plurality of optical signals constant.

21. A system comprising:

a first optical fiber transmission line for propagating signal light;

an optical regenerator connected to said first optical fiber transmission line for converting said signal light into regenerated signal light; and

a second optical fiber transmission line connected to said optical regenerator for propagating said regenerated signal light;

said optical regenerator comprising;

a first waveform shaper for accepting said signal light to output intermediate signal light;

an optical branch for dividing said intermediate signal light into first and second signal lights;

a clock recovery circuit for accepting said first signal light to output a clock pulse; and

a second waveform shaper for accepting said second signal light and said clock pulse to output said regenerated signal light.

22. A system according to claim 21, wherein said signal light comprises WDM signal light obtained by wavelength division multiplexing a plurality of optical signals having different wavelengths.

23. A system according to claim 22, wherein said optical regenerator further comprises an optical delay circuit for accepting said WDM signal light to change each timing of said plurality of optical signals in the time domain.

24. A system according to claim 23, wherein said optical delay circuit comprises an optical medium providing chromatic dispersion.

25. A system according to claim 23, wherein:

said first waveform shaper converts said WDM signal light into an optical time division multiplexed signal having a single wavelength;

said clock recovery circuit comprises a plurality of clock recovery circuits for respectively outputting a plurality of clock pulses respectively corresponding to said plurality of optical signals; and

said regenerated signal light comprises WDM signal light composed of a plurality of optical signals having wavelengths respectively corresponding to the wavelengths of said plurality of clock pulses.

26. A system according to claim 22, wherein said optical regenerator further comprises a polarization controller for making the polarization states of said plurality of optical signals constant.

27. A method comprising the steps of:

converting WDM signal light obtained by wavelength division multiplexing a plurality of optical signals having different wavelengths into an optical time division multiplexed signal;

obtaining a clock pulse having a frequency corresponding to the speed of each of said plurality of optical signals; and

supplying said optical time division multiplexed signal and said clock pulse to a waveform shaper to obtain regenerated signal light.

28. A method according to claim 27, wherein said step of obtaining said clock pulse comprises the step of regenerating a plurality of clock pulses respectively corresponding to said plurality of optical signals.

29. A method according to claim 28, further comprising the step of sequentially delaying said plurality of clock pulses by a predetermined delay time.

30. A method according to claim 28, wherein said step of regenerating said plurality of clock pulses comprises the step of supplying said optical time division multiplexed signal to a plurality of clock recovery circuits.

31. A method according to claim 28, wherein said step of regenerating said plurality of clock pulses comprises the steps of supplying said WDM signal light to a plurality of optical filters having pass bands respectively corresponding to the wavelengths of said plurality of optical signals, and supplying outputs from said optical filters to a plurality of clock recovery circuits, respectively.