Brillouin gain spectrum characterization in single-mode optical fibers

TLDR

A novel method for measuring the Brillouin gain spectrum in optical fibers is introduced. The method uses a single‑laser pump–probe scheme with an external modulator to generate interacting lightwaves, and employs two successive polarization measurements to achieve polarization‑insensitive determination of the Brillouin gain coefficient. The technique delivers high accuracy and stability, enabling calibration and reference measurements; it has been validated on fibers with varying refractive index profiles and fully characterizes strain and temperature effects on the Brillouin gain spectrum.

Abstract

A novel method for Brillouin gain spectrum measurements in optical fibers is presented. It is based on the pump and probe technique with the specificity to use a single laser source together with an external modulator 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 in the article and a polarization insensitive determination of the actual Brillouin gain coefficient is made possible through two successive measurements with different polarizations. The effects of strain and temperature on the Brillouin gain spectrum are also fully characterized.