Wavelength-locked low-noise Brillouin ring laser for Brillouin sensing

In this work we expand the previous report on the performance of an enhanced version of a Brillouin ring laser (BRL) based on a short-cavity layout that is resonant for both pump and Brillouin signal and implementing an active heterodyne wavelength-locked technique for the tuning operation, which was compared with a previously demonstrated long-cavity (LC) (~ 2 km) BRL pump-probe source. We provide a detailed analysis of the technique required to achieve double resonance, evaluate the relative intensity noise in the 0-50 kHz range (which is shown to still be below ~-100 dB/Hz) and use the previous relative intensity noise comparison of the two sources to estimate the potential temperature/strain resolution improvement in BOTDA measurements.