Metrological aspects of symmetric double frequency and multi frequency reflectometry for fiber Bragg structures

In paper metrological aspects of symmetric double frequency and multi frequency reflectometry for Bragg structures are considered. Basics of this method is amplitude phase conversion of coherent single frequency radiation to double frequency and its distinguished features are frequency-shifted spectral components symmetrical position relatively suppressed frequency of initial radiation, high level of spectral purity, stable output radiation, and high conversion ratio. In paper are considered the metrological aspects of following systems: a) symmetric multi frequency reflectometry system for Bragg structures control, and b) symmetric double frequency reflectometry system for Bragg structures.