Low-coherence Brillouin optical correlation-domain reflectometry based on periodic pseudo-random modulation

Brillouin optical correlation-domain reflectometry (BOCDR) is a technique for measuring the distribution of strain and temperature along an optical fiber, offering advantages such as operation with light injection from one end of the sensing fiber, relatively high spatial resolution, and random-access capability to sensing points. However, it faces a trade-off between spatial resolution and measurement range. In response, low-coherence BOCDR using a randomly modulated light source has been proposed, but this method requires a variable delay line for scanning the measurement position, limiting the measurement range. This paper proposes low-coherence BOCDR based on periodic pseudo-random modulation to address this issue and demonstrates its proof-of-concept operation. First, the dependence of the light source output spectrum on modulation parameters is investigated using a delayed self-homodyne method, showing the potential to resolve the trade-off between spatial resolution and measurement range. Subsequently, we demonstrate the capability of measuring strain distribution along optical fibers without a variable delay line under multiple conditions. Further, we show through simulation that this method can perform more accurate distributed strain measurements than standard BOCDR.