Distributed light delivery and detection via single optical fiber and tilted grating

Abstract

A passive fiber-optic-based device is designed and analyzed, capable of delivering and detecting light separately or simultaneously at discrete points of interest along the optical axis of a fiber. This goal is achieved by implementation of multiple finite-length tilted gratings inside the core of a single-mode fiber. Each grating is tuned to function as a leaky electromagnetic resonator that resonates at particular wavelength and partially radiates the optical power to the medium surrounding the fiber. First, the basic element of such radiators is theoretically analyzed and a sequence of justifiable approximations are presented to measure the characteristic parameters of the system. Next, a set of equations are developed to provide a logical procedure for the design. This device has several potential applications in the field of fiber optic sensors. Few practical examples of such applications, particularly for optical stimulation of cells and fluorescence signal recording in sensitive tissues including the brain, are studied.