Optical Sensors

Performance improvement of phase-generated carrier method by eliminating laser-intensity modulation for optical seismometer

[+] Author Affiliations
Qingping Shi

Tsinghua University,Department of Precision Instruments and Mechanology, State Key Laboratory of Precision Measurement Technology and Instruments, Beijing, 100084 China

Qian Tian

Tsinghua University,Department of Precision Instruments and Mechanology, State Key Laboratory of Precision Measurement Technology and Instruments, Beijing, 100084 China

Liwei Wang

Tsinghua University,Department of Electronic Engineering, Optical Fiber Sensor Laboratory, Beijing, 100084 China

Changdong Tian, Huayong Zhang, Min Zhang, Yanbiao Liao

Tsinghua University,Department of Electronic Engineering, Optical Fiber Sensor Laboratory, Beijing, 100084 China

Honghua Wang, Xiang Zeng, Longjun Huang

China Oilfield Services Limited,Yanjiao, SanHe, Hebei Province, 065201 China

Opt. Eng. 49(2), 024402 (March 03, 2010). doi:10.1117/1.3294878
History: Received May 20, 2009; Revised November 19, 2009; Accepted November 30, 2009; Published March 03, 2010; Online March 03, 2010
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An improved demodulation method for the phase-generated carrier (PGC) system by eliminating laser-intensity modulation (LIM) is proposed. The influence of LIM is analyzed theoretically and experimentally. Two parameters are used to describe the effect of LIM: the LIM coefficient (LIMC) and the LIM phase delay (LIMPD). Good stability of the LIMC and LIMPD is confirmed by experimentation with an actual system. The demodulation signal using the traditional method has a much greater higher harmonic component than the improved method due to LIM. The increase of the signal-to-total-harmonic ratio (SHR) using the improved method is >23dB, and there is a corresponding improvement of 19dB to the signal to noise and distortion (SINAD) and signal-to-noise ratio (SNR). A new prototype system using the improved PGC method for marine seismic sensing capable of demodulating multiple channels in parallel, simultaneously, is demonstrated. The SHR is stable at 56dB when the LIMC is <0.5. Similar results are obtained for the SINAD and SNR. The demodulated signal’s upper limit is 100rad at 100Hz and 12rad at 1kHz, giving a dynamic range reaching 130dB at 100Hz. The system’s SINAD is stable within 1dB, whereas the SHR is stable within 2dB in field application.

© 2010 Society of Photo-Optical Instrumentation Engineers

Citation

Qingping Shi ; Qian Tian ; Liwei Wang ; Changdong Tian ; Huayong Zhang, et al.
"Performance improvement of phase-generated carrier method by eliminating laser-intensity modulation for optical seismometer", Opt. Eng. 49(2), 024402 (March 03, 2010). ; http://dx.doi.org/10.1117/1.3294878


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