Method and device for waveform shaping of signal light

• US 6,859,307 B2
• Filed: 03/13/2001
• Issued: 02/22/2005
• Est. Priority Date: 07/04/2000
• Status: Expired due to Fees

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Takeda, Shinichi, Watanabe, Shigeki
• Primary Examiner(s): Hellner, Mark
• Assistant Examiner(s): Hughes, Deandra M.
• Application Number:
  US09/803,978
• Publication Number:
  US 20020003653A1
• Time in Patent Office: 1,442 Days
• Field of Search: 359/337, 3593414-34142, 359/337.13, 398/175
• US Class Current: 359/337
• CPC Class Codes: G02F 1/3519 of Sagnac type, i.e. nonlinear optical loop mirror [NOLM]
• CPC Class Codes: H01S 3/005 Optical devices external to the laser cavity, specially adapted for lasers, e.g. for homogenisation of the beam or for manipulating laser pulses, e.g. pulse shaping shaping laser beam for working metal or other materials B23K26/06; optical elements, systems or apparatus in general G02B
• CPC Class Codes: H01S 5/0683 by monitoring the optical output parameters
• CPC Class Codes: H01S 5/50 Amplifier structures not provided for in groups H01S5/02 - H01S5/30
• CPC Class Codes: H01S 5/5018 using two or more amplifiers or multiple passes through the same amplifier
• CPC Class Codes: H04B 10/299 Signal waveform processing, e.g. reshaping or retiming

Abstract

Disclosed herein is a method and device for waveform shaping of signal light. The method includes the steps of providing a waveform shaper for waveform shaping input signal light and outputting output signal light, measuring the quality of the output signal light, and controlling the power of the input signal light so that the quality measured is improved. According to this method, a substantially optimum threshold can be obtained to allow a good regenerating operation.

Claims

1. A method comprising:

inputting a signal light to an optical regenerator;

shaping a waveform of the input signal light by the optical regenerator to thereby output a shaped signal light; and

controlling a power level of the signal light input to the optical regenerator so that a quality measurement of the signal light output by the optical regenerator is improved, the quality measurement being one of a Q factor, a bit error rate, a spectrum shape and an eye opening, wherein said controlling comprises

optically amplifying the signal light with an optical amplifier before being input to the optical regenerator, and

adjusting gain of the optical amplifier to thereby control the power level of the signal light input to the optical regenerator.

6. The method of claim 1, wherein the signal light is a wavelength division multiplexed signal.

22. A method according to claim 1, wherein the optical regenerator is one of an interference type optical regenerator and a nonlinear optical loop mirror (NOLM) optical regenerator.

2. A device comprising:

an optical regenerator inputting a signal light and shaping a waveform of the input signal light to thereby output a shaped signal light; and

a power controller controlling a power level of the signal light before the signal light is input to the optical regenerator so that a quality measurement of the signal light output by the optical regenerator is improved, the quality measurement being one of a Q factor, a bit error rate, a spectrum shape and an eye opening, wherein said power controller comprises an optical amplifier amplifying the signal light before being input to the optical regenerator, and a controller adjusting gain of the optical amplifier to thereby control the power level of the signal light.

23. A device according to claim 2, wherein the optical regenerator is one of an interference type optical regenerator and a nonlinear optical loop mirror (NOLM) optical regenerator.

3. A device comprising:

an optical regenerator inputting a signal light and shaping a waveform of the input signal light to thereby output a shaped signal light; and

a power controller controlling a power level of the signal light before the signal light is input to the optical regenerator so that a quality measurement of the signal light output by the optical regenerator is improved, the quality measurement being one of a Q factor, a bit error rate, a spectrum shape and an eye opening, wherein said power controller comprises an optical amplifier amplifying the signal light before being input to the optical regenerator, an optical attenuator attenuating the amplified signal light before being input to the optical regenerator, and a controller adjusting attenuation of the optical attenuator to thereby control the power level of the signal light.

4. A method comprising:

providing an optical regenerator having a variable threshold for waveform shaping input signal light according to said variable threshold and thereby outputting waveform shaped signal light, the optical regenerator comprising a semiconductor optical amplifier (SOA), and the threshold being variable by changing an injection current of the SOA;

measuring quality of said output signal light; and

controlling said variable threshold by controlling the injection current in accordance with the measured quality so that the measured quality is improved.

5. A device comprising:

an optical regenerator having a variable threshold for waveform shaping input signal light according to said variable threshold and outputting output signal light, the optical regenerator comprising a semiconductor optical amplifier (SOA), and the threshold being variable by changing an injection current of the SOA;

means for measuring the quality of said output signal light; and

a controller controlling said variable threshold by controlling the injection current in accordance with the measured quality so that the measured quality is improved.

7. A method comprising:

inputting signal light to an input of an optical regenerator;

shaping a waveform of the input signal light by the optical regenerator to thereby output a shaped signal light;

measuring a Q factor of said output signal light; and

controlling a power level of the signal light at the input of the optical regenerator by an optical amplifier or optical attenuator positioned at the input of the optical regenerator, the power level being controlled in accordance with the measured Q factor to improve the measured Q factor.

24. A method according to claim 7, wherein the optical regenerator is one of an interference type optical regenerator and a nonlinear optical loop mirror (NOLM) optical regenerator.

8. A method comprising:

inputting a signal light to an optical regenerator;

shaping a waveform of the input signal light by the optical regenerator to thereby output a shaped signal light;

measuring a bit error rate of said output signal light; and

controlling a power level of the signal light before being input to the optical regenerator in accordance with the measured bit error rate to improve the measured bit error rate.

25. A method according to claim 8, wherein the optical regenerator is one of an interference type optical regenerator and a nonlinear optical loop mirror (NOLM) optical regenerator.

9. A method comprising:

inputting signal light to an optical regenerator;

shaping a waveform of the input signal light by the optical regenerator to thereby output a shaped signal light;

measuring a spectrum shape of said output signal light; and

controlling the power of said input signal light in accordance with the measured spectrum shape to improve the measured spectrum shape, wherein the optical regenerator is one of an interference type optical regenerator and a nonlinear optical loop mirror (NOLM) optical regenerator.

20. A method as in claim 9, wherein said controlling comprises:

controlling gain of an optical amplifier which amplifies the input signal light, to thereby control the power level of the input signal light.

10. A method comprising:

inputting a signal light to an optical regenerator;

shaping of waveform of the input signal light by the optical regenerator to thereby output a shaped signal light;

measuring an eye opening of said output signal light; and

controlling a power level of said signal light before being input to the optical regenerator in accordance with the measured eye opening to improve the measured eye opening.

11. An optical repeater comprising:

an amplifier that amplifies a first signal to produce a second signal;

an attenuator that attenuates the second signal to produce a third signal;

an optical regenerator that shapes a waveform of the third signal to produce a fourth signal;

a quality monitor that measures a quality of the fourth signal; and

a controller that controls the attenuator to change a power level of the third signal in accordance with the measured quality to thereby improve the measured quality of the fourth signal, wherein the first, second, third and fourth signals are optical signals.

26. An optical repeater according to claim 11, wherein the optical regenerator is one of an interference type optical regenerator and a nonlinear optical loop mirror (NOLM) optical regenerator.

12. A device comprising:

means for amplifying a first signal to produce a second signal;

means for attenuating the second signal to produce a third signal;

means for shaping a waveform of the third signal by an optical regenerator to produce a fourth signal;

means for monitoring a quality of the fourth signal; and

means for controlling the attenuation by said means for attenuating in accordance with the monitored quality to change a power level of the third signal and thereby improve the monitored quality of the fourth signal, wherein the first, second, third and fourth signals are optical signals.

27. A device according to claim 12, wherein the optical regenerator is one of an interference type optical regenerator and a nonlinear optical loop mirror (NOLM) optical regenerator.

13. An apparatus comprising:

an optical regenerator inputting a signal light at an input of the optical regenerator and shaping a waveform of the input signal light to thereby output a shaped signal light;

means for measuring a Q factor of said output signal light; and

means for controlling a power level of said signal light at the input of the optical regenerator by an optical amplifier or optical attenuator positioned at the input of the optical regenerator, the power level being controlled in accordance with the measured Q factor to improve the measured Q factor.

28. An apparatus according to claim 13, wherein the optical regenerator is one of an interference type optical regenerator and a nonlinear optical loop mirror (NOLM) optical regenerator.

14. An apparatus comprising:

an optical regenerator inputting a signal light and shaping a waveform of the input signal light to thereby output a shaped signal light;

means for measuring a bit error rate of said output signal light; and

means for controlling a power level of said signal light before being input to the optical regenerator in accordance with the measured bit error rate to improve the measured bit error rate.

29. An apparatus according to claim 14, wherein the optical regenerator is one of an interference type optical regenerator and a nonlinear optical loop mirror (NOLM) optical regenerator.

15. An apparatus comprising:

an optical regenerator inputting a signal light and shaping a waveform of the input signal light to thereby output a shaped signal light;

means for measuring a spectrum shape of said output signal light; and

means for controlling a power level of said input signal light in accordance with the measured spectrum shape to improve the measured spectrum shape, wherein the optical regenerator is one of an interference type optical regenerator and a nonlinear optical loop mirror (NOLM) optical regenerator.

16. An apparatus comprising:

an optical regenerator inputting a signal light and shaping a waveform of the input signal light to thereby output a shaped signal light;

means for measuring an eye opening of said output signal light; and

means for controlling a power level of said signal light before being input to the optical regenerator in accordance with the measured eye opening to improve the measured eye opening.

17. A method comprising:

inputting a signal light to an optical regenerator;

shaping a waveform of the input signal light by the optical regenerator to thereby output a shaped signal light; and

controlling a power level of the signal light input to the optical regenerator so that a quality measurement of the signal light output by the optical regenerator is improved, the quality measurement being one of a Q factor, a bit error rate, a spectrum shape and an eye opening, wherein said controlling comprises;

controlling gain of an optical amplifier which amplifies the input signal light, to thereby control the power level of the input signal light.

18. A method comprising:

inputting signal light to an optical regenerator;

shaping a waveform of the input signal light by the optical regenerator to thereby output a shaped signal light;

measuring a Q factor of said output signal light; and

controlling a power level of the signal light input to the optical regenerator in accordance with the measured Q factor to improve the measured Q factor, wherein said controlling comprises;

controlling gain of an optical amplifier which amplifies the input signal light, to thereby control the power level of the input signal light.

19. A method comprising:

inputting a signal light to an optical regenerator;

shaping a waveform of the input signal light by the optical regenerator to thereby output a shaped signal light;

measuring a bit error rate of said output signal light; and

controlling a power level of the input signal light in accordance with the measured bit error rate to improve the measured bit error rate, wherein said controlling comprises;

controlling gain of an optical amplifier which amplifies the input signal light, to thereby control the power level of the input signal light.

21. A method comprising:

inputting a signal light to an optical regenerator;

shaping of waveform of the input signal light by the optical regenerator to thereby output a shaped signal light;

measuring an eye opening of said output signal light; and

controlling a power level of said input signal light in accordance with the measured eye opening to improve the measured eye opening, wherein said controlling comprises;

controlling gain of an optical amplifier which amplifies the input signal light, to thereby control the power level of the input signal light.