Assessment of Dynamic Range in Interferometric Fiber Optic Hydrophones Based on Homodyne PGC Interrogator

One of the important criteria in underwater acoustic sensing using fiber-optic sensors is to have an interrogator with wide dynamic range. Interferometric sensors with Phase Generated Carrier (PGC) based interrogators offer wide dynamic ranges compared to other techniques. Typically, a dynamic range of 100 to 140 dB is desirable for underwater surveillance and is mainly limited by the interrogator design. Today, several variants of PGC are available, but differ in their implementation and hardware. These aspects play a critical role in deciding the dynamic range of the system. Interrogators limit the dynamic range through the phase detection thresholds either at the lower or upper or both the ends. This paper covers a detailed investigation of the dynamic range possible with the most widely used variants of homodyne PGC techniques. Simulation and experiments were conducted, the results are discussed. This investigation benefits researchers in selecting an efficient interrogation scheme, which can give an optimum dynamic range for a given operational scenario.