Time-Delay Measurement Method Based on the Frequency-Spectrum Distribution of Laser Intensity or Phase Noise Signal

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Abstract
Frequency-domain measurement method of time-delay based on laser intensity or phase noise as multi-frequency signal source is proposed. The frequency-spectrum distribution of noise signal caused by the time-delay is analyzed to extract the characteristic frequencies, for derive the time-delay. The experimental results with intensity noise source show that for the time-delay fiber ranging from 0.5 km to 15 km in length, the measurement deviation compared to OTDR results ranges from -0.0514% to 0.0949%, demonstrating good measurement accuracy. For multiple measurements of 5 km-long time-delay fiber, the measurement deviation range with intensity noise source is from 0.0417% to 0.0689%, with a characteristic frequency fluctuation of 11 Hz, corresponding to time-delay measurement resolution of 6.69 × 10 -9 s. The deviation range of the measurement with phase noise source is from -0.2437% to 0.1257%, with a characteristic frequency fluctuation of 150 Hz, corresponding to time-delay measurement resolution of 9.11 × 10 -8 s. Therefore, the time-delay measurement resolution for the two noise sources are lower than the minimum interval of 2 × 10 -6 s, corresponding to sample rate of 500 kHz. It also meets the precision requirements of shifting discrete-signal timing needed for common-mode suppression on phase or intensity noise in optical fiber sensor arrays.
Funding Information
  • Anhui Provincial Key Research and Development Program in Basic Field Projects (2023z04020012)
  • Hefei Comprehensive National Science Center
  • National Natural Science Foundation of China (62275001)
  • University Synergy Innovation Program of Anhui Province (GXXT-2023-016)

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