End-of-cable sensitivity (vertical units: dB re 1V/μPa) of a 150 μm diameter needle hydrophone calibrated up to 40 MHz using the TDS method and up to 100 MHz using both the TGFA and the nonlinear techniques. “Horizontal” line at the -274 dB re 1V/μPa level: preliminary data, up to 40 MHz for 10 micrometers diameter tip, early prototype, uncoated, fiber optic hydrophone (see text for details). Error bars were omitted for clarity; overall uncertainty: 1-40 MHz: ±1dB, 40-60 MHz: ±1.5dB, beyond 60MHz: ±2.5dB.