Analysis and Design of Acoustic Fiber Coupler

Abstract

A coupled-mode theory for two parallel cylindrical acoustic waveguides with a common cladding is presented. The theory illuminates the mechanism responsible for the oscillation of power between the two waveguides. The method of analysis is based upon the expansion of the fields of the composite waveguide in terms of the modal fields of the individual guides. The analysis is then applied to the problem of an acoustic fiber coupler made of two identical weakly guiding fibers. Coupling coefficient and its variations with guides separation and the frequency response of the coupler are examined. Design of 3 dB couplers as power dividers is addressed. A bandpass filter constructed with acoustic fiber couplers is proposed.