Phase noise of the near-infrared single-mode fiber Mach–Zehnderinterferometer and its stabilization technology

We present an estimation method and an investigation on the phase-noise stabilization for a near-infrared fiber Mach–Zehnder interferometer (MZI) using a laser diode at 1530 nm as the light source. Based on the theoretical analysis, the phase noise is mainly produced by the tiny fluctuations of external temperature, whose amplitude is proportional to the optical path difference (OPD) between two arms of optical fibers in the interferometer. By minimizing the length difference between two fibers in the MZI and specifying the compensation signal applied to the piezoelectric transducer (PZT) modulator actively, the interferometer worked stably at different phase differences. When the interferometer was working at the 90° phase difference, which is usually necessary for practical application, the RMS noise was minimized to 0.47°. By quantitative analysis, the magnification ratio of noise amplitude at room temperature per unit OPD of the MZI was 132.29°/m ( = 0.73 r a d / m ). In this experiment, a good linear correlation between the initial OPD and the phase signal intensity was successfully observed. Using this estimation method, an optical fiber interferometer of different wavelengths can be built more conveniently in practical engineering applications.