Enhanced performance low-noise Brillouin ring laser for Brillouin sensing

In this work, we present an enhanced design for a Brillouin Ring Laser (BRL) based on a doubly-resonant cavity (DRC) with short fiber length, paired with a heterodyne-based wavelength-locking system, to be employed as pump-probe source in Brillouin sensing applications. The enhanced source is compared with the long-cavity (LC) (~ 2 km) BRL pump-probe source that we have recently demonstrated, showing a significantly lower relative intensity noise (~-145 dB/Hz in the whole 0-800 MHz range), a narrower linewidth (10 kHz), combined with large tunability features and an excellent pumpprobe frequency stability (~200 Hz) which is uncommon for fiber lasers. The measurement of intensity noise on the novel BRL signal yielded an improved signal-To-noise ratio (SNR) of about 22 dB with respect to LC-BRL schemes that is expected to lead to a temperature/strain resolution enhancement in BOTDA applications up to 5.5 dB.