Method and device for waveform shaping of signal light

• US 20020003653A1
• Filed: 03/13/2001
• Published: 01/10/2002
• Est. Priority Date: 07/04/2000
• Status: Active Grant

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Watanabe, Shigeki, Takeda, Shinichi
• Granted Patent: US 6,859,307 B2
• Time in Patent Office: Days
• US Class Current: 359/333
• 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 the steps of:

providing a waveform shaper for waveform shaping input signal light and outputting output signal light;

measuring the quality of said output signal light; and

controlling the power of said input signal light so that said quality measured is improved.

2. A method according to claim 1, wherein said controlling step comprises the steps of providing an optical amplifier for amplifying said input signal light, and adjusting the gain of said optical amplifier.

3. A method according to claim 1, wherein said quality is a Q factor of a signal obtained according to said output signal light.

4. A method according to claim 1, wherein said quality is a bit error rate of a signal obtained according to said output signal light.

5. A method according to claim 1, wherein said quality is a spectrum shape of said output signal light.

6. A method according to claim 1, wherein said quality is an eye opening of a signal obtained according to said output signal light.

7. A device comprising:

a waveform shaper for waveform shaping input signal light and outputting output signal light;

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

a power controller for controlling the power of said input signal light so that said quality measured is improved.

8. A device according to claim 7, wherein said power controller comprises an optical amplifier for amplifying said input signal light and a controller for adjusting the gain of said optical amplifier so that said quality is most improved.

9. A device according to claim 7, wherein said power controller comprises an optical amplifier for amplifying said input signal light, an optical attenuator for attenuating an output from said optical amplifier, and a controller for adjusting the attenuation of said optical attenuator so that said quality is most improved.

10. A method comprising the steps of:

providing a waveform shaper having a variable threshold for waveform shaping input signal light according to said variable threshold and outputting output signal light;

measuring the quality of said output signal light; and

controlling said variable threshold so that said quality measured is improved.

11. A method according to claim 10, wherein:

said waveform shaper comprises a semiconductor optical amplifier; and

said controlling step comprises the step of adjusting an injection current to be supplied to said semiconductor optical amplifier.

12. A method according to claim 10, wherein:

said waveform shaper comprises a distributed feedback laser diode adapted to change said variable threshold according to the power of assist light supplied thereto; and

said controlling step comprises the step of adjusting the power of said assist light.

13. A device comprising:

a waveform shaper having a variable threshold for waveform shaping input signal light according to said variable threshold and outputting output signal light;

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

a controller for controlling said variable threshold so that said quality measured is improved.

14. A device according to claim 13, wherein:

said waveform shaper comprises a semiconductor optical amplifier; and

said controller adjusts an injection current to be supplied to said semiconductor optical amplifier.

15. A device according to claim 13, wherein:

said waveform shaper comprises a distributed feedback laser diode adapted to change said variable threshold according to the power of assist light supplied thereto, and a light source for outputting said assist light; and

said controller adjusts the power of said assist light.