Fast Sinusoidal Frequency Scan OFDR for Long Distance Distributed Acoustic Sensing

Lihi Shiloh; Avishay Eyal

doi:10.1117/12.2265403

23 April 2017 Fast Sinusoidal Frequency Scan OFDR for Long Distance Distributed Acoustic Sensing

Lihi Shiloh, Avishay Eyal

Proceedings Volume 10323, 25th International Conference on Optical Fiber Sensors; 103230P (2017) https://doi.org/10.1117/12.2265403
Event: 25th International Conference on Optical Fiber Sensors, 2017, Jeju, Korea, Republic of

Abstract

Implementation of Optical Frequency Domain Reflectometry (OFDR) requires a source whose instantaneous frequency can be accurately scanned over a sufficiently wide frequency range. Achieving high repetition rates of accurate linear frequency sweeps can be rather challenging. In contrast, fast and accurate Sinusoidal Frequency Scan (SFS-OFDR) can be easily implemented via direct or external optical frequency modulation. While enabling high spatial resolution measurements of a sensing fiber at high scan rates, SFS-OFDR requires a special processing algorithm to convert the detector output to fiber profiles. Previous implementation of the algorithm involved O(N²) complexity and prohibited real time operation. In this work a novel algorithm for processing SFS-OFDR raw data is introduced. Based on two consecutive FFT operations, the algorithm produces the fiber profile with O(NlogN) operations and lends itself for real time applications. The new method was tested via simulation and experiment. It enabled static detection with high resolution (~3m) at 64km and highly sensitive dynamic detection (stretching amplitude of 70nm) near the end of a 64km sensing fiber with spatial resolution <10m and with 400Hz scan repetition rate.

Citation Download Citation

Lihi Shiloh and Avishay Eyal "Fast Sinusoidal Frequency Scan OFDR for Long Distance Distributed Acoustic Sensing", Proc. SPIE 10323, 25th International Conference on Optical Fiber Sensors, 103230P (23 April 2017); https://doi.org/10.1117/12.2265403

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