Analysis and design of a narrowband all-fiber spectral filter made of step-index and W-type fibers

Abstract

An all-fiber spectral filter constructed with step-index and W-type fibers is proposed. A coupled-mode theory based on the interaction of evanescent fields is employed to analyze the transfer of power between the two fibers. The proposed filter on'ers a narrow spectral width on the order of few nanometers. The narrow bandwidth is achieved by exploiting a relatively large slope din'erence between the dispersion characteristics of the step-index and W fibers. Transmission characteristics are plotted versus wavelength. The influence of various fiber parameters as well as fiber separation and coupling length on the spectral response is discussed. The application o f t h e filter in wavelength division multiplexing is addressed.

Effect of cladding layers on the mode of circular optical waveguides

“…The high sensitivity to bending makes the W-fiber useful in fiber optic sensor systems. The existence of an "extinguish" wavelength allows the W-fiber to be used for a low pass filter [15].…”