Improvement in the measurement of index modulation along an optical fiber grating by movement of the probe spot perpendicularly to the fiber axis

摘要

We demonstrate a large improvement in the efficiency of the method proposed by Krug et al. [Opt. Lett. 20, 1767 (1995)] to measure the amplitude of the refractive-index modulation along a fiber Bragg grating. The basic idea consists of using what to our knowledge is a new modulation scheme for the probe beam that not only allows the user to get a better discrimination of the probe light incoherently scattered by the fiber from that scattered by the grating but also facilitates alignment of the setup.