An Elimination Method of Polarization-Induced Phase Shift and Fading in Dual Mach–Zehnder Interferometry Disturbance Sensing System

We proposed an improved polarization control method to reduce polarization-induced phase shift (PIPS) and polarization-induced fading (PIF) in a dual Mach–Zehnder interferometry (DMZI) disturbance sensing system. PIPS and PIF will seriously affect the positioning accuracy of the DMZI sensor. This polarization control method uses two PCs to control the state of polarization at the inputs of clockwise Mach–Zehnder interferometer and counter-clockwise Mach–Zehnder interferometer, respectively, based on chaotic particle swarm optimization algorithm, which has advantages of high speed and easy implementation. We experimentally demonstrated that the polarization method can overcome the effect of PIPS and PIF, improve the positioning accuracy of the DMZI sensor efficiently with positioning error of ±20 m after polarization control. Compared with the traditional polarization control method in DMZI based on the criterion of visibility, the positioning error of the sensor using our proposed method has been reduced at least an order of magnitude.