Long-period fiber-grating devices based on leaky cladding mode coupling

Fiber gratings allow great flexibility in the design of all-fiber devices by enabling control over the wavelength, direction, polarization, and mode characteristics of light. In particular, long-period, or transmission, fiber gratings produce devices based on co-directional mode coupling which naturally result in a desirable transmissive rather than reflective output. In a single-mode fiber, coupling to cladding modes can be utilized for various functions, especially wavelength-dependent loss filtering [1]. In this paper we describe alternative applications of transmission fiber grating devices based on coupling to leaky cladding modes.