Numerical Analysis of Current Measurement Error due to Vibration in Reciprocal Fiber-Optic Polarimetric Current Sensor

Accuracy of current measurement in optical fiber current sensors is affected by environmental perturbations to the sensing fiber such as mechanical vibrations, acoustic perturbations, and iemperature changes. Experimental results [],[2] and mathematical model [1] for mechanical vibrations were shown to have effects on the accuracy of the current measurement in unidirectional fiber-optic polarimetric current sensors. This paper presents the development of the mathematical model from Ref. I for numerical analysis of the vibration effects on current measurement error in reciprocal f iber-optic urrent sensors. The results ofnumerical analysis ofthe variation ofpolarization along the sensing fiber used to define theoretical accuracy l imit are demonstrated' Vibration at the (single-mode fiber) sensing part causes the variation ofstress and strain and in turn the variation of linear birefringence. This variation influences the amplitude and phase of optical wave and also limits the accuracy of the system. The vibration was uniformly distributed along the sensing part. The parameters such as static and vibration-induced linear and circular birefringences are included in this investigation. It is widely believed that the analysis of the theoretical accuracy l imit by symbolic calculation and its characteristic 3D plots of current measurement error (as a function of all birefringence parameters) for RFOS are shown for the first time. Results of this analysis will be useful in the design of dimension of torus ring around which sensing fiber is wrapped. This wil l lead to design procedures for the configuration of the sensing fiber part to achieve RFOS with vibration immunity