Assessing the Interplay between Probe Power and Pulse Width in Enhancing Performance of Phase-OTDR Fiber Sensor

We discuss the performance of the distributed fiber optic sensor (DFOS) interrogation unit based on the phase-optical time domain reflectometry (ϕ-OTDR) principle. This experiment focuses on improving the performance of ϕ-OTDR by controlling two selective parameters: probe power and laser pulse width. These parameters were chosen due to their significant impact on the signal-to-noise ratio (SNR), which directly influences the sensitivity and accuracy of the system. Two experiments were conducted using 10 and 40 km standard ITU-T G.652D telecom grade bare fiber optic connected to the ϕ-OTDR setup. For each experiment, two sets of probe laser parameters (launched optical power and pulse width) were varied, and the SNR was calculated as an indicator of performance. An SNR of 13.99 dB was achieved from a 10 km ϕ-OTDR setup with a pulse width of 300 ns (launched optical power fixed at 100 mW). With launched optical power fixed at 100 mW, an SNR of 12.76 dB was obtained from a 40 km ϕ-OTDR setup when the pulse width was set to 500 ns. Data analysis revealed that SNR values in both ϕ-OTDR setups (10 and 40 km) approached saturation as the probe power launched and optical power increased. This study highlights that the best signal performance can be achieved by carefully optimizing these selective parameters, as their interplay determines the balance between spatial resolution and signal strength in the ϕ-OTDR system.