Long range distributed fiber sensing with improved noise performance
AssigneeNokia Solutions and Networks Oy
InventorsMikael Mazur, Nicolas Fontaine
Life of this patent
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Abstract
A method and apparatus of OFDR are disclosed, in which a pair of probe signals are launched, on mutually orthogonal channels, into the optical fiber cable that is to be monitored. In a digital processing circuit, phase noise is cancelled from the return signals after detecting them in their respective mutually orthogonal channels and after demodulating them, by combining them such that noise components of the respective demodulated signals are mutually cancelled. In embodiments, a conjugate pair of probe signals are launched, on mutually orthogonal channels, into the optical fiber cable.
Claims16
An apparatus comprising:
- an optical transmitter configured to inject first and second optical frequency domain reflectometry (OFDR) probe signals into an optical fiber cable on respective, mutually orthogonal first and second probe channels, wherein the optical transmitter is configured to inject the first OFDR probe signal with a first linearly swept frequency modulation envelope, and to inject the second OFDR probe signal with a second linearly swept frequency modulation envelope that is a complex conjugate of the first swept frequency modulation envelope;
- a coherent optical receiver configured to measure portions of the first and second OFDR probe signals received in response to backscattering of the first and second OFDR probe signals at a scatterer in the optical fiber cable;
- and
- a digital processing circuit configured to estimate, from the measured portions of the first and second OFDR probe signals, a time value indicative of a round-trip propagation time for light of said first and second OFDR probe signals in the optical fiber cable.
A method, comprising:
- injecting first and second optical frequency-domain reflectometry (OFDR) probe signals into an optical fiber cable on respective, mutually orthogonal first and second probe channels, wherein the first OFDR probe signal is injected into the optical fiber cable with a first linearly swept frequency modulation envelope, and the second OFDR probe signal is injected into the optical fiber cable with a second linearly swept frequency modulation envelope that is a complex conjugate of the first swept frequency modulation envelope;
- measuring content of the first and second OFDR probe signals that has been backscattered from the optical fiber cable;
- and
- estimating, from the measured backscattered content, a time value indicative of a round-trip propagation time for light of said first and second OFDR probe signals on each of one or more paths within the optical fiber cable.
Dependencies are inferred from the claim text.