Investigation of Brillouin Properties in High-Loss Doped Silica Waveguides by Comparison Experiment

We propose a novel scheme to investigate the Brillouin properties of waveguides with high loss and severe reflection through comparison experiments with a single-mode fiber (SMF). An optical filter is adopted to filter the reflected pump light. Brillouin scattering is detected with a lock-in amplifier (LIA). To obtain a large Brillouin gain in a short medium, a modulation signal with a time width of 2 ms is applied. With application of the mathematical relationship between the output power and measurement range of the LIA, the measured Brillouin gains of the waveguides and the SMF are normalized to derive the relationship among the Brillouin gain coefficients. This scheme is verified on two doped silica waveguides. The Brillouin scattering properties of the doped silica waveguides are further described and the Brillouin gain coefficients are derived.