[OPTICAL REVIEW Vol. 12, No. 6 (2005) 467-471]
© 2005 The Optical Society of Japan

A New Method of Solving Multimode Coupled Equations for Analysis of Uniform and Non-Uniform Fiber Bragg Gratings and Its Application to Acoustically Induced Superstructure Modulation

Fatemeh ABRISHAMIAN*, Shinya SATO and Masaaki IMAI

Department of Electrical and Electronic Engineering, Muroran Institute of Technology, 27-1 Mizumoto-cho, Muroran, Hokkaido 050-8585, Japan

(Received July 19, 2005; Accepted September 12, 2005)

A new and simple mathematical formulation that is employed to analyze numerically coupled-mode equations modeling uniform and non-uniform gratings in optical fiber is investigated. This method would be straightforward and thus beneficial to solve multimode coupled equations in comparison with a previously used fundamental matrix method, and the Runge–Kutta algorithm. The new formulation proposed in this study is applied to calculate transmission and reflection spectra of core mode and higher-order cladding modes of acoustically induced superstructure modulation caused by microbending through fiber Bragg gratings (FBGs). Co-directional and contra-directional couplings based on acoustically induced modulation in FBGs have been discussed for a variety of induced coupling coefficients.

Key words: fiber Bragg grating (FBG), acoustically induced microbending, coupled-mode theory, n × n coefficient matrix, similarity transformation

*E-mail address: s1354040@mmm.muroran-it.ac.jp