Yuzhao MA^1,2*

¹Tianjin Key Laboratory for Advanced Signal Processing, Civil Aviation University of China, Tianjin 300300, P. R. China
²College of Electronic Information Engineering, Civil Aviation University of China, Tianjin 300300, P. R. China

(Received August 21, 2012; Accepted September 29, 2012)

In the present work two types of low-coherence interferometry are used to estimate the ellipticity of the core of an optical fiber in the cross section. Using the time-domain low-coherence interferometry the group-index difference between the degenerate high-order modes is measured. Because of the usage of a short fiber sample the group-index difference between the degenerate fundamental modes is too small to measure. Secondly, a frequency-domain low-coherence interferometry is presented in details. Since it is an all-fiber setup, longer fiber is allowed to be used. The high-order modes are filtered. The group-index difference between the degenerate fundamental modes is obtained. For each of the methods the experimental results are used to estimate the ellipticity of the fiber core in numerical simulations.

Key words: fiber ellipticity, fiber modes, interferometry, birefringence

^*E-mail address: yzma@cauc.edu.cn