BENDING INDUCED PHASE-SHIFTS IN ARBITRARILY BENT RECTANGULAR-CORE DUAL-MODE WAVE-GUIDES

We examine the variation of the effective indexes of the two modes of an arbitrarily bent dual-mode rectangular-core waveguide, We find that under the large bending radius approximation, which is indeed the pra ctical case for most of the devices, the waveguide bent with bending r adius rho in a plane at an angle theta with the major axis is almost e quivalent to bending it simultaneously in the plane of major and minor axes with bending radii rho sec theta and rho cosec theta, respective ly, The bending-induced phase difference between the two modes is foun d (a) to be maximum when the waveguide is bent along the major axis, a nd (b) to decrease first and then increase in the opposite direction a s the V-number is decreased, The results of our study can be used to i mprove the sensitivity of the dual-mode optical waveguide sensors and devices based on the bending of fiber.