Stabilizing device for optical modulator

• US 5,907,426 A
• Filed: 06/27/1997
• Issued: 05/25/1999
• Est. Priority Date: 06/28/1996
• Status: Expired due to Term

• Current Assignee: Kabushiki Kaisha Toyota Chuo Kenkyusho (Toyota Motor Corporation)
• Original Assignee: Kabushiki Kaisha Toyota Chuo Kenkyusho (Toyota Motor Corporation)
• Inventors: Ichikawa, Tadashi, Hioki, Tatsumi, Kato, Naohiko, Ito, Hiroshi, Motohiro, Tomoyoshi
• Primary Examiner(s): Epps, Georgia
• Assistant Examiner(s): BURKE, MARGARET A
• Application Number:
  US08/884,661
• Time in Patent Office: 697 Days
• Field of Search: 359/181-184, 359/239, 359/187, 385/2, 385/3
• US Class Current: 359/239
• CPC Class Codes: G01D 3/028 mitigating undesired influences, e.g. temperature, pressure
• CPC Class Codes: G01R 15/241 using electro-optical modulators, e.g. electro-absorption probes containing electro-optic elements G01R1/071
• CPC Class Codes: G01R 29/0885 using optical probes, e.g. electro-optical, luminescent, glow discharge, or optical interferometers
• CPC Class Codes: G02F 1/0123 Circuits for the control or stabilisation of the bias voltage, e.g. automatic bias control [ABC] feedback loops

Abstract

A device for stabilizing a modulation operation of an optical modulator is provided, the optical modulator having an optical waveguide provided on a substrate and an electrode provided so as to correspond to the optical waveguide, modulating light inputted to the optical waveguide by a voltage corresponding to a physical amount to be measured which is inputted to the electrode, and outputting the modulated light. The device includes: an optical detecting device for outputting signal corresponding to intensity of light outputted from the optical modulator; a control signal outputting device for, on the basis of the output signal of the optical detecting device, outputting a control signal which compensates a phase bias fluctuation of the optical modulator; a light source device for outputting control light corresponding to the control signal; and a voltage applying device, provided in contact with the electrode of the optical modulator, for applying voltage corresponding to the control light to the electrode. Accordingly, the light source device illuminates to the voltage applying device a control light corresponding to a driving signal which negatively feeds back a phase bias fluctuation signal. In this way, the voltage applying device applies a voltage which is set so as to offset variation in phase bias fluctuation in accordance with bias fluctuation, and the phase bias fluctuation is offset.

Claims

1. A device for stabilizing a modulation operation of an optical modulator, the optical modulator having an optical waveguide provided on a substrate and an electrode provided so as to correspond to said optical waveguide, said device comprising:

optical detecting means for outputting a signal corresponding to the intensity of light outputted from said optical modulator;

control signal outputting means for, on the basis of the output signal of said optical detecting means, outputting a control signal which compensates for a phase bias fluctuation of said optical modulator;

light source means for outputting control light corresponding to said control signal; and

voltage applying means, provided in contact with said electrode of said optical modulator, for applying voltage corresponding to said control light to said electrode.

2. A device according to claim 1, wherein said control signal outputting means includes an oscillator for outputting a predetermined constant frequency signal which is used to modulate said optical modulator, and extracting means for, on the basis of the output signal of said oscillator, extracting a signal component of said predetermined constant frequency from the output signal of said optical detecting means and outputting a signal corresponding to the intensity of the extracted signal, said control signal outputting means superimposing the signal, which corresponds to the output signal of said extracting means and compensates for a phase bias fluctuation of said optical modulator, upon said predetermined constant frequency signal to output the superimposed signal as the control signal.

3. A device according to claim 1, wherein said voltage applying means is formed by a photoelectric converting means which is formed by an anomalous photovoltaic film which contacts and is integrated with the electrode.

4. A device according to claim 1, wherein said light source means includes:

a light source portion which emits said control light; and

an illuminating portion which illuminates onto said voltage applying means the control light from said light source portion.

5. A device according to claim 4, wherein said illuminating portion is formed by one of a reflecting means, an optical guide means, or a combination thereof.

6. A device according to claim 3, wherein said anomalous photovoltaic film is formed by two-source oblique simultaneous deposition with two deposit sources of an electrically-conductive substance and a semiconductor having a photovoltaic effect.

7. A method for stabilizing a modulation operation of an optical modulator, the optical modulator having an optical waveguide provided on a substrate and an electrode provided so as to correspond to said optical waveguide, said method comprising the steps:

outputting a signal corresponding to the intensity of light outputted from said optical modulator;

outputting a control signal which compensates for a phase bias fluctuation of said optical modulator on the basis of said output signal corresponding to intensity of light;

outputting control light corresponding to said control signal; and

applying voltage corresponding to said control light to said electrode.

8. A method according to claim 7, wherein said control signal outputting step includes the steps of:

modulating said optical modulator with a predetermined constant frequency signal;

extracting a signal component of said predetermined constant frequency from the output signal of said light intensity signal outputting step on the basis of said predetermined constant frequency signal to output a signal corresponding to intensity of the extracted signal; and

superimposing the signal, which corresponds to the output signal of said extracting step and compensates for a phase bias fluctuation of said optical modulator, upon said predetermined constant frequency signal to output the superimposed signal as the control signal.

9. A method according to claim 7, wherein said voltage applying step includes generating a voltage corresponding to said control light using a photoelectric converting means which is formed by an anomalous photovoltaic film which contacts and is integrated with