| As the development of the science technology and industry, the fiber-optic interferometer sensor is attached more attention due to high sensitivity, especially in the accurate measurement field where the Micro-displacement or micro-vibration measurement is needed. Due to the sensitivity of fiber, the phase of internal transmission field is affected by external parameter fluctuation. The measurement signal induces the phase fluctuation of transmission light. Meanwhile, external additional disturbance change the phase information as well. Therefore interference will produce interference sensing system instability, decline of output signal, results in degraded accuracy. At present, the effectively methods we take mainly includes phase tracking technology and PGC modulate and demodulate technology on this matter. What is particular, when the interferometer system except for sensor suffer the disturbance which frequency close to the signal. Co-frequency interference will appear at the interferometric output. What is worse, we can not acquire the signal from disturbance using ordinary methods. These factors influencing the fiber-optic interferometer block the interferometer develop rapidly.To the co-frequency interference question occurred in transmission loop, based on the common-path fiber interferometer previously proposed, a common-path fiber interferometer demodulation system via the digital PGC technique is proposed in this paper. To the structure of common-path interferometer, we compensated the depth of demodulation system to guarantee the amplitude of two signals match and finally achieve elimination effective of external disturbance. The simulation of the demodulation system had been performed based on Lab VIEW Workbench and the simulation results indicated the correctness of the theoretical model.Secondly, based on PGC demodulation technique, a double Michelson interference system had been constructed and the interferometric signals were processed on the LabVIEW Workbench using digital demodulation technique. The experiment results indicated the system had a good performance in suppressing the external disturbance. The probe of the system consisting of small pieces of fiber was relatively simple and has a strong anti-jamming capability, which provides new possibilities for measurement system miniaturization and practical.At last, to the signal crosstalk question induced by the double-Michelson interferometer’s structure, the double Mach-Zender interference system were proposed based on the common-path technique. And in the system the double light sources and bidirectional detection were used to avoid the impact of signal crosstalk on the demodulation. The experiment proved that the system can detect the useful signal and the external disturbances had been reduced by26dB, which could enhance the anti-interference ability and measurement stability of the system, based on the above interference system and wavelength division multiplexing (WDM) technology, a scheme is proposed to realize the quasi-distributed sensing networks and the feasibility of the system has been verified through theoretical analysis. |
