Compact, low-cost, and highly sensitive optical fiber hydrophone based on incident angle sensing.
A compact, low-cost, and highly sensitive optical fiber hydrophone (OFH) based on an incident-angle sensing mechanism (IA-OFH) was demonstrated. An off-center positioned collimator was used for light emitting and receiving, which is very sensitive to the incident angle due to the very small beam divergence of the collimator. Moreover, owing to the angle-sensitive detection (without using any optical interference effect), precise control on the light wavelength and the cavity length is no longer needed, which can greatly simplify the device fabrication and the interrogation system. A quartz IA-OFH with a detection limit of 0.7  mPa/Hz1/2, a dynamic range of ∼110  dB, and a response bandwidth over 1.0 MHz was experimentally demonstrated.