The modes propagation characteristics and modular interference beat length in Elliptical-core Polarization Maintenance Fiber(E-core PMF) are very important parameters for designing optic-fiber sensors based on modular interference.They play an important role in deciding the work wavelength

dynamic range and linearity of optic-fiber sensors.This paper calculates the modes propagation characteristics and modular interference beat length theoretically.The propagation characteristics of several low order modes in E-core PMF are calculated

and as a result

the modular interference beat length of LP

01

and LP

e

11

is obtained.An experiment is designed to investigate the modular interference beat length in an E-core PMF

and the experiment result shows that the beat length is about several hundreds micron

wh

ich is very suitable for designing applicable and reliable optic-fiber sensors.