Optical time domain reflectometry method and apparatus
First Claim
1. An optical time domain reflectometry method in which a plurality of pulses of optical radiation, having different respective wavelengths and delayed by known amounts of time relative to one another such that adjacent pulses do not overlap, are launched into an optical fibre (6) of interest and optical radiation backscattered from the fibre (6) is detected to produce electrical output signals, the said backscattered optical radiation being processed before detection so as to remove the effect thereon of the relative time delays between the said plurality of pulses;
- characterised in that the said plurality of pulses is derived from a pulse of optical radiation in a preselected wavelength band, each of the said pulses having a peak power less than the power at which non-linear effects begin to occur in the said optical fibre (6).
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Abstract
In an optical time domain reflectometry method, in which a plurality of pulses of optical radiation, delayed by known amounts of time relative to one another such that adjacent pulses do not overlap, are launched into an optical fiber (6) of interest and optical radiation backscattered from the fiber (6) is detected to produce electrical output signals the said plurality of pulses have different respective wavelengths and are derived from optical radiation at a preselected wavelength, each of the said pulses having a peak power less than the power at which non-linear effects begin to occur in the said optical fiber (6). The said backscattered optical radiation is processed before detection so as to remove the effect thereon of the relative time delays between the said plurality of pulses.
91 Citations
50 Claims
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1. An optical time domain reflectometry method in which a plurality of pulses of optical radiation, having different respective wavelengths and delayed by known amounts of time relative to one another such that adjacent pulses do not overlap, are launched into an optical fibre (6) of interest and optical radiation backscattered from the fibre (6) is detected to produce electrical output signals, the said backscattered optical radiation being processed before detection so as to remove the effect thereon of the relative time delays between the said plurality of pulses;
- characterised in that the said plurality of pulses is derived from a pulse of optical radiation in a preselected wavelength band, each of the said pulses having a peak power less than the power at which non-linear effects begin to occur in the said optical fibre (6).
- View Dependent Claims (2, 3, 4, 5, 6)
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7. Optical time domain reflectometry apparatus comprising means operable to launch a plurality of pulses of optical radiation, delayed by known amounts of time relative to one another such that adjacent pulses do not overlap, into an optical fibre (6) of interest and detection means (9) operable to produce electrical output signals in response to optical radiation backscattered from the fibre (6);
- characterised by;
source means (1) for emitting a pulse of optical radiation in a preselected wavelength band;
pulse spreading means (3;
22), connected to receive the said optical radiation emitted from the said source means (1) and operable to derive therefrom the said plurality of pulses such that the pulses of the said plurality have different respective wavelengths and a peak power less than the power at which non-linear effects begin to occur in the said optical fibre (6), the said pulse spreading means (3;
22) being connected to launch the said plurality of pulses into the said optical fibre (6); and
pulse re-forming means (7;
22) connected, between the said optical fibre (6) and the said detection means (9), to intercept backscattered optical radiation from the said optical fibre (6), the said pulse re-forming means (7;
22) being operable to process said backscattered optical radiation so as to remove the effect on that backscattered optical radiation of the relative time delays between the said plurality of pulses and to output the processed backscattered optical radiation to the said detection means (9).- View Dependent Claims (8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33)
- characterised by;
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34. An optical time domain reflectometry apparatus usable with a selected optical fiber comprising:
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a radiant energy source for emitting at least one pulse of optical radiation in a preselected wavelength band;
a pulse spreading network coupled to receive the at least one pulse of optical radiation emitted from the source and operable to form therefrom a plurality of pulses such that the pulses of the plurality have different respective wavelengths and a peak power less than the power at which non-linear effects begin to occur in the optical fiber wherein the network couples the plurality of pulses into the optical fiber;
an optical detector; and
a pulse re-forming network coupled between the optical fiber and the detector to intercept backscattered optical radiation from the optical fiber wherein the pulse re-forming network processes the backscattered optical radiation so as to remove the effect on that backscattered optical radiation of the relative time delays between the members of the plurality of pulses and to output the processed backscattered optical radiation to the detector. - View Dependent Claims (35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50)
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Specification