BRILLOUIN GAIN SPECTRUM CHARACTERIZATION IN SINGLE-MODE OPTICAL FIBERS

A novel method for Brillouin gain spectrum measurements in optical fib ers is presented. It is based on the pump and probe technique with the specificity to use a single laser source together with an external mo dulator to generate the interacting lightwaves. The high accuracy and inherent stability of the technique makes it suitable for calibration and reference measurements. Different fibers with different refractive index profiles have been tested and characterized. The problem of the evolution of the polarization of the interacting waves is addressed i n the article and a polarization insensitive determination of the actu al Brillouin gain coefficient is made possible through two successive measurements with different polarizations. The effects of strain and t emperature on the Brillouin gain spectrum are also fully characterized .