Identifying fibers of fiber optic cables

• US 20020076176A1
• Filed: 12/10/2001
• Published: 06/20/2002
• Est. Priority Date: 12/14/2000
• Status: Active Grant

• Current Assignee: Radiodetection Limited
• Original Assignee: Radiodetection Limited
• Inventors: Flatt, David William
• Granted Patent: US 6,643,436 B2
• Time in Patent Office: Days
• US Class Current: 385/100
• CPC Class Codes: G01M 1/32 by adding material to the body to be tested, e.g. by correcting-weights
• CPC Class Codes: H04B 10/07 Arrangements for monitoring or testing transmission systems; Arrangements for fault measurement of transmission systems

Abstract

A method of and apparatus for identifying fibers of fiber optic cables is disclosed. Waveforms may be generated by integer subdivision of a clock, the waveforms for modulation of a laser beam into a set of unique signals. Preferably, however, each waveform has two states and a different integer X associated therewith. The repeat period of the waveforms is preferably set at 2Y cycles of the clock, Y being an integer greater than the highest value of X, and the waveforms can be generated by counting X mod Y and changing the state of each waveform whenever this counting reaches or exceeds Y. The signals may be applied either successively or simultaneously to individual fibers at one end of a fiber optic cable. At another end of the cable, each signal can be detected as having a frequency by taking a Fourier Transform; the frequencies detected preferably being in arithmetic progression, whereby each fiber can be identified individually.

Claims

1. A method of identifying the fibers of a fiber optic cable, comprising:

inputting a set of signals at one end of the fiber optic cable to the fibers of said fiber optic cable; and

detecting the signals at another end of the fiber optic cable;

wherein each signal of the set of signals has a different waveform, and is an input to a respectively different fiber, whereby each fiber has an input signal of a different waveform from the other fibers in the cable.

2. A method according to claim 1, wherein each waveform has a plurality of states and an integer X associated therewith, X being different for each waveform, and the integers X forming a set of integers X_n, wherein the waveforms are generated by:

establishing a generating clock cycle at a generating rate;

defining a repeat period for the waveforms, the repeat period being equal to 2Y cycles of the clock and being the same for each waveform, Y being an integer greater than the highest integer of the set of integers X_n;

counting X mod Y for each waveform at each clock cycle and changing the state of the waveform each time Y is reached or exceeded by said counting.

3. A method according to claim 2, wherein the signals are detected by:

establishing a sampling clock cycle at a sampling rate;

taking a series of samples of each signal, each sample being taken on a cycle of the sampling clock;

performing a Fourier Transform on the series of samples;

wherein the sampling rate is chosen so that the signals are detected as having a frequency, each signal being detected as having a different frequency from the other signals.

4. A method according to claim 3, wherein the sampling rate is the same as or a multiple of the generating rate.

5. A method according to claim 2, wherein the set of integers X_n is composed of members of an arithmetic progression.

6. A method according to claim 2, wherein each waveform has only two states.

7. A method according to claim 1, wherein the waveforms are generated by:

establishing a generating clock cycle at a generating frequency; and

dividing the generating frequency by a set of integers;

wherein a waveform with a different frequency is generated for each integer division of the generating clock, each waveform being a pure tone.

8. A method according to claim 7, wherein the waveforms is generated with frequencies in arithmetic progression.

9. A method according to claim 1, wherein each signal is a laser beam modulated by the required waveform.

10. A method according to claim 1, wherein the signals are for successive inputting to the respective fibers of a fiber optic cable.

11. A method according to claim 1, wherein the signals are for simultaneous inputting to the respective fibers of a fiber optic cable.

13. An apparatus according to claim 12, further comprising:

a generating clock for establishing a generating clock cycle at a generating rate;

light generating means for generating a plurality of optical signals;

modulation waveform generating means regulated by the clock for generating a plurality of modulation waveforms, each waveform having a plurality of states and an integer X associated therewith, X being different for each waveform, and the integers X forming a set of integers X_n;

modulating means for modulating the plurality of optical signals generated by the light generating means with the plurality of modulation waveforms generated by the modulation waveform generating means;

said waveform-generating means being configured to generate said plurality of waveforms by;

defining a repeat period for the waveforms, the repeat period being equal to 2Y cycles of the clock and being the same for each waveform, Y being an integer greater than the highest integer of the set of integers X_n, and

counting X mod Y for each waveform at each clock cycle and changing the state of the waveform each time Y is reached or exceeded by said counting.

14. A apparatus according to claim 13, wherein said detection means comprises:

a sampling clock for establishing a sampling clock cycle at a sampling rate;

means for receiving a series of samples of each signal, each sample being taken on a cycle of the sampling clock; and

means for performing a Fourier Transform on the samples, the sampling rate being chosen so that the signals are detected as having a frequency, each signal being detected as having a different frequency from the other signals.

15. An apparatus according to claim 14, wherein the sampling rate is the same as or a multiple of the generating rate.

16. An apparatus according to claim 13, wherein the set of integers X_n is composed of members of an arithmetic progression.

17. An apparatus according to claim 13, wherein the waveform generating means has

a plurality of adding means,

a plurality of accumulators of size Y,

a plurality of overflow detecting means, and

a plurality of waveform output means for outputting a plurality of waveforms;

each adding means being linked to a respective accumulator and configured to add a given integer X to said accumulator every clock cycle, each adding means adding a different integer X;

each respective accumulator being linked to a respective overflow detecting means, and each respective overflow detecting means being linked to a respective wave output means.

18. An apparatus according to claim 13, wherein the modulating means is one modulator of changing modulating frequency.

19. An apparatus according to claim 13, wherein the modulating means is a plurality of modulators, each modulator at a different modulating frequency.

20. An apparatus according to claim 13, wherein each waveform has two states.

21. An apparatus according to claim 12, further comprising:

a generating clock operating at a generating frequency; and

frequency dividing means for dividing the generating frequency by a set of integers;

wherein the frequency dividing means is arranged to produce waveforms of different frequencies, each waveform being a pure tone.

22. An apparatus according to claim 21, wherein the waveforms are generated with frequencies in arithmetic progression.

12. An apparatus for identifying the fibers of a fiber optic cable, comprising:

inputting means for inputting a set of signals at one end of the fiber optic cable to the fibers of said fiber optic cable;

detecting means for detecting the signals at another end of the fiber optic cable;

characterized in that;

each signal of the set of signals has a different waveform, and is an input to a respectively different fiber, whereby each fiber has an input signal of a different waveform from the other fibers in the cable.

23. A method of generating waveforms for modulating physical signals, each waveform having an integer X associated therewith, X being different for each waveform, and the integers X forming a set of integers X_n, the set of integers X_n being composed of members of an arithmetic progression, comprising:

establishing a clock cycle;

defining a repeat period for the waveforms, the repeat period being equal to 2Y cycles of the clock and being the same for each waveform, Y being an integer greater than the highest integer of the set of integers X_n;

counting X mod Y for each waveform at each clock cycle and changing the state of the waveform each time Y is reached or exceeded by said counting.