Photoelectric oscillator

• US 20050211875A1
• Filed: 02/18/2005
• Published: 09/29/2005
• Est. Priority Date: 02/19/2004
• Status: Active Grant

• Current Assignee: National Institute of Information and Communications Technology
• Original Assignee: Nat'L Institute of Info & Comm Tech Incorporated Admin Agency
• Inventors: Shinada, Satoshi, Kawanishi, Tetsuya, Izutsu, Masayuki, Sakamoto, Takahide
• Granted Patent: US 7,425,696 B2
• Time in Patent Office: Days
• US Class Current: 250/208.100
• CPC Class Codes: G02F 1/2255 controlled by a high-frequency electromagnetic component in an electric waveguide structure
• CPC Class Codes: G02F 2201/58 Arrangements comprising a monitoring photodetector
• CPC Class Codes: H04B 10/505 using external modulation

Abstract

A photoelectric oscillator includes a laser beam projection unit; an optical modulator on an optical path extending from the projection unit, which optical modulator outputs a modulated signal or an optical signal containing a harmonic of the modulated signal and includes a modulation electrode whose resonant frequency band includes the frequency band of the modulation signal; a photoelectric converter for converting the output of the optical modulator to an electric signal; a feedback circuit for selecting from the radio-frequency electric signal obtained from the photoelectric converter an electric signal to be re-supplied to the optical modulator; and an output section for outputting an optical signal containing the modulation signal or a harmonic of the modulation signal or outputting the modulation signal or a harmonic of the modulation signal. A laser beam of sufficient intensity is input from the projection unit to produce a radio-frequency electric signal in the feedback circuit, and the radio-frequency electric signal or an optical signal containing the radio-frequency electric signal or the radio-frequency signal is output from the photoelectric oscillator.

Claims

1. A photoelectric oscillator comprising:

a laser beam projection unit;

an optical modulator on an optical path extending from the projection unit, which optical modulator outputs a modulated signal or an optical signal containing a harmonic of the modulated signal and includes a modulation electrode whose resonant frequency band includes the frequency band of the modulation signal;

a photoelectric converter for converting the output of the optical modulator to an electric signal;

a feedback circuit for selecting from the radio-frequency electric signal obtained from the photoelectric converter an electric signal to be re-supplied to the optical modulator; and

an output section for outputting an optical signal containing the modulation signal or a harmonic of the modulation signal or outputting the modulation signal or a harmonic of the modulation signal,

a laser beam of sufficient intensity being input from the projection unit to produce a radio-frequency electric signal in the feedback circuit, and the radio-frequency electric signal or an optical signal containing the radio-frequency electric signal or the radio-frequency signal being output from the photoelectric oscillator.

2. A photoelectric oscillator according to claim 1 wherein the feedback circuit is provided with an amplifier having a frequency characteristic that partially overlaps the resonant frequency band of the optical modulator.

3. A photoelectric oscillator according to claim 1, wherein the feedback circuit is provided with a delay circuit capable of delay time adjustment.

4. A photoelectric oscillator according to claim 1, wherein the output from the optical modulator is amplified in an optical amplifier and supplied to the photoelectric converter.

5. A photoelectric oscillator according to claim 1, further provided with means for adjusting the temperature of an optical modulator having a resonant electrode structure, which temperature adjusting means is used to regulate the oscillation frequency of the photoelectric oscillator.

6. A photoelectric oscillator according to claim 1, wherein the optical modulator is a Mach-Zehnder interference modulator on two constituent optical paths of which are provided multiple phase modulators having resonant electrode structures of differing resonant frequency, each of the phase modulators being applied with a signal obtained by regulating the amplitude or phase of the optical modulator output and further provided with means for varying said amplitude or phase to control the transmission frequency characteristic of the Mach-Zehnder interference modulator with respect to the radio-frequency electric signal.

8. A photoelectric oscillator according to claim 1, wherein optical modulator is a reciprocating optical modulator whose the resonant frequency band of the modulation electrode of the modulator includes the frequency band of the modulation signal and that repeats modulation every reciprocation on a reciprocal optical path.

9. A photoelectric oscillator according to claim 1, wherein the optical modulator is formed using an optical modulator that has an optical path of loop structure and repeats modulation every circuit of the optical path.

10. A photoelectric oscillator according to claim 1, wherein the feedback circuit is provided with an electrical amplifier having a characteristic such as to selectively amplify the frequency band of the feedback signal.

11. A photoelectric oscillator according to claim 1, wherein the optical modulator is an optical phase modulator and an optical filter is provided between the optical modulator and the photoelectric converter to suppress those radio-frequency signal components of the optical spectrum spread by the modulation by the optical phase modulator that are not to be fed back as modulation signals.

12. A photoelectric oscillator according to claim 1, further provided on the optical path between the optical modulator and the photoelectric converter with a delay circuit capable of delay time adjustment.

13. A photoelectric oscillator according to claim 1, wherein a second radio-frequency electric signal is injected into the feedback circuit to output a radio-frequency signal synchronized with the second radio-frequency electric signal or an optical signal containing a multiplied second radio-frequency electric signal.

14. A photoelectric oscillator according to claim 1, wherein an optical signal superimposed with a radio-frequency electric signal is input to output a radio-frequency electric signal synchronized with the radio-frequency electric signal or an optical signal containing a radio-frequency electric signal synchronized with the radio-frequency electric signal.

7. A photoelectric oscillator according to 6 wherein the phase modulators provided on the first optical path of the two constituent optical paths of the Mach-Zehnder interference modulator and the phase modulators provided on the second optical path thereof have a common resonance band and a radio-frequency signal belonging to the common resonance band is applied to the phase modulators of the two paths at a predetermined phase, the radio-frequency signal being the output signal of the photoelectric converter.