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Chen X.-F.,Zhejiang University | Zeng X.-C.,Research Institute of Beijing Aerospace Control Instrument | Zhou H.,Zhejiang University | Wang L.,Zhejiang University
Zhejiang Daxue Xuebao (Gongxue Ban)/Journal of Zhejiang University (Engineering Science)

By employing the time delay modulation characteristic of the fiber optical Sagnac interferometer, a closed loop measurement method for half-wave voltage (HWV) of an eletrooptical phase modulator was designed. Such closed loop method eliminates the influence of optical signal drift on the measure result. The digital function of the closed control loop for modulation and demodulation was designed for simulation, which shows good HWV tracking performance. Simulation results also confirm its immunity to low frequency drift error in the system, and the measure accuracy depends on the noise power only. An experiment system was set up to implement the algorithm. The test results show that: the HWV measure precision is better than 1.8×10-5 under 200 Hz sampling frequency, and it is better than 1.1×10-5 for one second average, which is restricted by the temperature sensitive of the modulator and the unstability of the test environment. The proposed method can measure the HWV of phase modulator with good precision, thus improving the performance of the fiber optical sensor, which can be also employed in precise temperature measurement with fast speed. Source

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