# US 5,349,465 A · Optical democulator

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- Number: US 5,349,465 A
- Document ID: US5349465A
- Status: Granted
- Kind: A
- Application number: 07/913,661
- Filed: 1992-07-16
- Granted: 1994-09-20
- Earliest claimed: 1991-07-16
- Assignees: Research Development Corporation of Japan
- Inventors: Koji Mizuno
- Web page: https://patentgrep.com/patent/US5349465A

## CPC

- H04B 10/60: Receivers
- H04B: TRANSMISSION

## Abstract

An optical demodulator includes a nonlinear element which responds to both light and a microwave-submillimeter wave (far infrared radiation). An optical signal modulated by a modulating wave in which a subcarrier consisting of the microwave-submillimeter wave is modulated by a signal wave, and a local oscillated signal consisting of a microwave-submillimeter wave the same in frequency as the subcarrier are added to the nonlinear element, to fetch the signal wave by a heterodyne system.

## Claims

### Claim 1

An optical demodulator for demodulating a modulated optical signal wave to obtain a signal wave, said optical demodulator comprising:
a semiconductor diode responsive to light and microwave-submillimeter waves;
a waveguide circuit for applying a local oscillated signal to said semiconductor diode; and
means for fetching a signal wave produced by said semiconductor diode by a heterodyne system,
wherein said semiconductor diode produces the signal wave in response to simultaneous
irradiation of said semiconductor diode with a modulated optical signal wave having a microwave-submillimeter subcarrier wave modulated by the signal wave, and
application, via said waveguide circuit, of a local oscillated signal having the same frequency as the subcarrier wave to said semiconductor diode.

### Claim 2 (depends on 1)

An optical demodulator according to claim 1, wherein said waveguide circuit is a microstrip line.

### Claim 3

An optical demodulator for demodulation of an optical signal by a heterodyne system, comprising:
a waveguide circuit;
a semiconductor diode responsive to light waves and microwave-submillimeter waves for obtaining a signal wave from a modulated optical signal, said semiconductor diode loaded on said waveguide circuit, and generating optical conductive current when irradiated with an optical signal; and
means for fetching the optical conductive current produced by said semiconductor diode by a heterodyne system.

### Claim 4

A method of demodulating a modulated optical signal having a subcarrier microwave-submillimeter wave modulated by a signal wave to obtain the signal wave, comprising the steps of:
irradiating the modulated optical signal on a semiconductor diode, and simultaneously
applying a local oscillated wave having the same frequency as the subcarrier wave to said semiconductor diode.

### Claim 5 (depends on 4)

A method as in claim 4, further comprising the step of fetching the obtained signal wave.