Reducing the Impact of Relative Intensity Noise via Phase-Based Measurement in Raman-Assisted Brillouin Optical Time-Domain Analysis

Relative intensity noise transfer is a widely identified issue limiting the performance of a Raman-assisted Brillouin optical time-domain analysis (BOTDA) fiber sensor. Here, we demonstrate that phase-based measurement can perfectly avoid this problem. Both theoretical analysis and experimental results show that the relative intensity noise (RIN) only affects the amplitude of the Brillouin probe while it has no impact on its phase. As a result, phase-based measurement is inherently insensitive to RIN. This enables the reduction of the measurement uncertainty by similar to 2.5 times compared to the gain-based measurement. In addition, since the designed phase-noise-insensitive coherent detection (PNI-CD) scheme can double the Brillouin phase shift, the phase-based measurement additionally reduces the measurement uncertainty by 2 times. Therefore, a total measurement uncertainty reduction of similar to 5 times is achieved.

Automated summary

Phase-based measurement can perfectly avoid the problem of relative intensity noise transfer by showing that RIN only affects the amplitude of the Brillouin probe and not its phase. This phase-based measurement reduces the measurement uncertainty by about 5 times, through a 2.5 times reduction in uncertainty compared to gain-based measurement and an additional 2 times reduction through the designed phase-noise-insensitive coherent detection scheme.