Apparatus for and method of using optical interference of light propagating through an optical fiber loop

• US 20020196447A1
• Filed: 07/25/2002
• Published: 12/26/2002
• Est. Priority Date: 04/28/1998
• Status: Active Grant

• Current Assignee: Fujikura Limited
• Original Assignee: Fujikura Limited
• Inventors: Nakamura, Yasushi, Unami, Yoshiharu, Niimi, Shinichi
• Granted Patent: US 6,825,935 B2
• Time in Patent Office: Days
• US Class Current: 356/483
• CPC Class Codes: G01H 9/004 using fibre optic sensors light guides per se G02B6/00, acousto-optical devices specially adapted for gating or modulating in optical wave guides G02F1/125

Abstract

A signal/vibration detecting technique employs a simple structure to identify a target optical fiber among many and carry out a bidirectional conversation through the target optical fiber.

First ends of optical fibers (202A, 202B), one of which is a target optical fiber, are connected to an optical transceiver (201). Second ends of the optical fibers are connected to each other to form a loop. A local unit (203) is installed at the loop. The local unit vibrates the loop, and the optical transceiver emits lights so that the lights are oppositely propagated through the loop. The propagated lights are coupled together so that they interfere with each other. In the intensity of the interfering lights, a change corresponding to the vibration is detected to identify the target optical fiber. Once the target optical fiber is identified, it is used to carry out a conversation between the optical transceiver and the local unit.

Claims

1. An apparatus for detecting a signal based on optical interference comprising:

a light source;

a photo-detector;

a loop made of a plurality of optical fibers and having open ends; and

a splitter-coupler connected to the open ends of the loop,

wherein the light source emits a light, which is split by the splitter-coupler, the split lights are made incident to the open ends of the loop, respectively, so that the split lights are oppositely propagated through the loop, the oppositely propagated lights are coupled by the splitter-coupler so that they interfere with each other, and the interfering lights are converted by the photo-detector into a signal that indicates the intensity of the interfering lights and is responsive to a change in the phase difference between the lights,

whereby the signal from the photo-detector shows a physical change applied to the loop.

2. An apparatus for detecting a signal based on optical interference according to claim 1, vibration is applied to the loop as the physical change.

3. A method of detecting a signal based on optical interference, comprising the steps of:

emitting a light from a light source;

splitting the light by a splitter-coupler;

making the split lights incident to open ends of a loop of optical fibers, respectively, so that the split lights are oppositely propagated through the loop;

coupling the oppositely propagated lights by the splitter-coupler so that they interfere with each other;

converting the interfering lights by a photo-detector into a signal that indicates the intensity of the interfering lights and is responsive to a change in the phase difference between the lights; and

detecting a physical change applied to the loop according to the signal from the photo-detector.

4. A method of detecting a signal based on optical interference according to claim 3, vibration is applied to the loop as the physical change.

5. A method of detecting a signal based on optical interference according to claim 3, an optical delay unit is inserted to a portion of the loop.

6. A method of identifying a target optical fiber cable among many, comprising the steps of:

connecting each end of a plurality of optical fibers to each other to form a loop having two open ends;

connecting an optical transceiver to the open ends of the loop;

emitting a light from a light source of the optical transceiver;

splitting the light by a splitter-coupler of the optical transceiver;

making the split lights incident to the open ends of the loop, respectively, so that the split lights are oppositely propagated through the loop;

coupling the oppositely propagated lights so that they interfere with each other;

converting the interfering lights by a photo-detector of the optical transceiver into an electric signal that indicates the intensity of the interfering lights and is responsive to a change in the phase difference between the lights; and

detecting in the electric signal a physical change applied to the target optical fiber cable that contains at least a part of the loop, to identify the target optical fiber cable.

7. A method of identifying a target optical fiber cable among many according to claim 6, vibration is applied to the target optical cable as the physical change.

8. A method of identifying a target optical fiber cable among many according to claim 6, an optical delay unit is inserted to a portion of the loop.

9. A method of identifying a target optical fiber among many, comprising the steps of:

connecting each end of a plurality of optical fibers including the target optical fiber to each other to form a loop having two open ends;

connecting an optical transceiver to the open ends of the loop;

emitting a light from a light source of the optical transceiver;

splitting the light by a splitter-coupler of the optical transceiver;

making the split lights incident to the open ends of the loop, respectively, so that the split lights are oppositely propagated through the loop;

coupling the oppositely propagated lights so that they interfere with each other;

converting the interfering lights by a photo-detector of the optical transceiver into an electric signal that indicates the intensity of the interfering lights and is responsive to a change in the phase difference between the lights; and

detecting in the electric signal a physical change applied to the loop to identify the target optical fiber.

10. A method of identifying a target optical fiber among many according to claim 9, vibration is applied to the loop as the physical change.

11. A method of identifying a target optical fiber among many according to claim 9, an optical delay unit is inserted to a portion of the loop.

13. An optical fiber communication method according to claim 12, characterized by using FM-modulation to the light from the light source according to the electric signal from the first microphone;

AM-modulation to the signal from the first photo-detector into the voice signal in the optical transceiver; and

FM-demodulation to the signal from the second photo-detector into the voice signal in the local unit.

12. An optical fiber communication method comprising the steps of:

connecting each end of a plurality of optical fibers to each other through an optical connector to form a loop having two open ends;

connecting an optical transceiver to the open ends of the loop;

attaching a local unit to the loop between the optical transceiver and the optical connector; and

carrying out optical-transceiver steps and local-unit steps, wherein the optical-transceiver steps include;

emitting a light from a light source;

converting a voice into an electric signal by a first microphone;

modulating the light from the light source by a driver according to the electric signal from the first microphone;

splitting the light from the light source by a splitter-coupler;

making the split lights incident to the open ends of the loop, respectively, so that the lights are oppositely propagated through the loop;

coupling the oppositely propagated lights by the splitter-coupler so that they interfere with each other;

converting the interfering lights into an electric signal by a first photo-detector; and

demodulating the electric signal into a voice signal by a first voice unit, and the local-unit steps include;

bending the loop;

receiving leakage lights from the bend by a second photo-detector;

converting the leakage lights by the second photo-detector into an electric signal;

demodulating the electric signal into a voice signal by a second voice unit;

converting a voice into an electric signal by a second microphone; and

vibrating the loop by a vibrator according to the electric signal from the second microphone, thereby establishing a conversation between the optical transceiver and the local unit.