Apparatus and method for identification of optical cable

• US 20070196058A1
• Filed: 08/23/2006
• Published: 08/23/2007
• Est. Priority Date: 08/23/2005
• Status: Active Grant

• Current Assignee: KT Corporation
• Original Assignee: KT Corporation
• Inventors: Lee, Bong-Wan, Lee, Yong-Gi, Jeong, Ho-Jin, Youn, Kyeong-Mo, Min, Kyoung-Seon, Jeong, Hyun-Ho
• Granted Patent: US 7,505,643 B2
• Time in Patent Office: Days
• US Class Current: 385/100
• CPC Class Codes: G01M 11/3172 Reflectometers detecting the back-scattered light in the frequency-domain, e.g. OFDR, FMCW, heterodyne detection
• CPC Class Codes: H04B 10/07953 Monitoring or measuring OSNR, BER or Q

Abstract

In order to identify an optical cable for optical communication from a remote place, a Sagnac interferometer including two strands of an optical fiber is formed in the optical cable, and a worker in the remote place applies a disturbance of a popping sound to an optical cable to be identified. The disturbance applied by the worker is detected and regenerated in the form of a sound. The optical cable can be easily identified by comparing the regenerated signal and the disturbed signal in the remote place to thereby prevent an incorrect optical cable from being cut. In addition, the optical cable can be more precisely identified by selecting a different light detecting frequency component in accordance with environment conditions.

Claims

1. An optical cable identification apparatus for identifying an optical cable by looping-back one end of each of two strands of optical fiber in an optical cable to be identified and applying a disturbance to the optical cable to be identified, the optical cable identification apparatus comprising:

an optical unit for applying light to the two strands of the optical fiber in the optical cable to be identified after phase-modulating the light at a predetermined modulation frequency, interfering the light applied to the two strands in opposite directions, and detecting and outputting light having a different intensity resulting from a phase difference due to the phase modulation and a phase difference due to the disturbance of the optical cable;

a signal processor for eliminating noise from a signal output from the optical unit, demodulating the signal to a voice signal, and outputting the voice signal; and

a voice output unit for outputting the voice signal of the signal processor as a sound.

2. The optical cable identification apparatus of claim 1, wherein the optical unit comprises:

a light source generator for generating light,

a light detector for detecting light;

an optical directional coupler having two arms in each of a first direction and a second direction,

wherein the first direction is opposite to the second direction, a first arm in the first direction is connected to the light source generator, a second arm in the first direction is connected to the light detector, the two arms in the second direction are connected with the two strands of the optical fiber, and the two strands of the optic fiber are looped -back and form a ring;

a phase modulator connected to the first arm in the second direction, and phase-modulating the light output from the optical directional coupler and applying the phase-modulated light to the optical fiber of the optical cable; and

a depolarizer connected to the second arm in the second direction and stabilizing an interference signal by eliminating a polarization component from input light.

3. The optical cable identification apparatus of claim 2, wherein the phase modulator, the optical directional coupler, the optical fiber of the optical cable, and the depolarizer function as an optical fiber interferometer.

4. The optical cable identification apparatus of claim 3, wherein the optical fiber interferometer is a Sagnac interferometer.

5. The optical cable identification apparatus of claim 2, wherein the signal processor comprises:

a switch for selecting a demodulation frequency;

a controller for controlling an output of a demodulation frequency that corresponds to a selection of the switch;

a function generator for supplying a predetermined modulation frequency to the optical unit and outputting a demodulation frequency that corresponds to a control signal of the controller; and

an amplitude extract unit for extracting an amplitude of a demodulation frequency component from the signal output from the optical unit, the demodulation frequency component being output from the function generator.

6. The optical cable identification apparatus of claim 5, wherein the controller outputs a warning signal when the amplitude of the amplitude extract unit is saturated, and

the signal processor further comprises a first mixer for mixing the warning signal and a signal of the amplitude extract unit and outputting the mixed result.

7. The optical cable identification apparatus of claim 2, wherein the signal processor comprises:

a switch for selecting a demodulation frequency;

a function generator for supplying a constant modulation frequency signal to the optical unit and outputting a demodulation frequency that corresponds to a selection signal of the switch; and

an amplitude extract unit for extracting a demodulation frequency component from the signal detected from the optical unit, the demodulation frequency component being output from the function generator.

8. The optical cable identification apparatus of claim 7, wherein the signal processor further comprises:

an amplitude measure unit for outputting a warning signal when the amplitude extracted by the amplitude extract unit is saturated; and

a first mixer for mixing the warning signal and a signal from the amplitude extract unit and outputting a mixed result.

9. The optical cable identification apparatus of claim 6, wherein the voice output unit comprises:

a first jack connected to a mobile phone;

a second jack connected to a speaker;

a third jack connected to a microphone;

a second mixer for transmitting an output of the mobile phone through the first jack and an output of the first mixer to the speaker through the second jack; and

a third mixer for transmitting the output of the first mixer and an input to the microphone through the third jack to the mobile phone through the first jack.

10. The optical cable identification apparatus of claim 1, wherein the signal processor delays outputting of the signal detected by the optical unit to easily distinguish a regenerated sound transmitted through a communication apparatus from a disturbance signal applied to the optical cable by a worker in a remote site, and regenerates the signal into a voice signal.

11. An optical cable identification apparatus for identifying an optical cable by detecting light that varies due to a disturbance, the disturbance applied to the optical cable after short-circuiting two strands of an optical fiber of the optical cable in one direction and the light applied to the two strands of the optical fiber in the other direction, the optical cable identification apparatus comprising:

an optical unit for phase-modulating and applying light to two strands of an optical fiber of an optical cable to be identified, and detecting and outputting a disturbed light received at the optical unit; and

a signal processor for eliminating noise from a signal output from the optical unit, demodulating the signal into a voice signal, and outputting the voice signal.

12. The optical cable identification apparatus of claim 11, wherein the signal processor comprises:

a switch for selecting a frequency;

a function generator for supplying a predetermined frequency to the optical unit and outputting a frequency corresponding to a selection signal of the switch; and

an amplitude extract unit for extracting an amplitude of a frequency component from the signal detected by the optical unit, the frequency component being output from the function generator.

13. The optical cable identification apparatus of claim 12, wherein the signal processor further comprises:

an amplitude measure unit for outputting a warning signal when the amplitude of the amplitude extract unit is saturated; and

a first mixer for mixing the warning signal and a signal of the amplitude extract unit and outputting a mixed result.

14. The optical cable identification apparatus of claim 11, wherein the signal processor uses a demodulation scheme, and extracts an amplitude of a frequency component that corresponds to a modulation frequency of the optical unit or two times the modulation frequency.

15. A method for identifying an optical cable by looping back one direction of each of two strands of an optical fiber in an optical cable to be identified and applying a disturbance to the optical cable to be identified, the method comprising:

applying light to the two strands of the optical fiber of the optical cable;

phase-modulating the light applied to the two strands of the optical fiber at a predetermined modulation frequency and modulating a phase difference of the interfering lights at the modulation frequency;

additionally generating a phase difference due to an external disturbance between the interfering lights of the optical cable; and

measuring a phase difference due to the disturbance by demodulating a light signal, converting the light signal into a voice signal, and outputting the voice signal, wherein intensity of the light signal is modulated by the disturbance.

16. The method of claim 15, wherein when the light is applied to the two strands of the optical fiber in the optical cable, an optical fiber interferometer having the two strands is formed.

17. The method of claim 16, wherein the measuring of the phase difference due to the disturbance, converting of the light signal into the voice signal, and outputting of the voice signal comprise determining an amplitude component of light detected in accordance with a user'"'"'s choice.

18. The method of claim 15, wherein the measuring of the phase difference due to the disturbance, converting of the light signal into the voice signal, and outputting of the voice signal comprises transmitting the voice signal to a worker at a remote site by outputting the voice signal to a mobile phone.

19. The method of claim 18, wherein the measuring of the phase difference due to the disturbance, converting of the light signal into the voice signal, and outputting of the voice signal comprises delaying outputting of the detected light signal for a predetermined time.