Study of the polarization maintaining optical fiber beat length variation with external force

Abstract

The polarization maintaining fiber has been playing an important role in the fields of optical fiber sensing, communication, and so on. The beat length is one of the main parameters of polarization maintaining fiber, and it usually represents its polarization maintaining performance. In this paper, the beat length variation of Panda fiber with external force is investigated. The simulation results indicate that the beat length variation was determined both by the external force value F and the angle θ between the external force direction and the slow axis of Panda fiber. When F is a constant, the beat length of polarization maintaining fiber is changed in sinusoidal form whose various cycle is π with the variation of θ. Meanwhile, the minimum and maximum values of beat length will be obtained when the angles are even multiple of π/2 or odd multiple of π/2, respectively. When θ is a constant, the beat length is changed in linear form with the increasing of external force value. Finally, the experimental system of beat length measurement based on Sagnac interferometer loop is illustrated, and the result shows an excellent agreement with the theoretical analysis.