Ultra-low noise phase measurement of fiber optic sensors via weak value amplification

The noise floor is a vital specification that determines the minimum detectable signal in the phase measurement. However, the noise floor in optical phase measurement conducted via conventional optical interferometry tends to approach the intrinsic limit. In this study, a low noise phase measurement of a fiber optic sensor conducted via weak value amplification is experimentally demonstrated. The system has a flat, wideband frequency response from 0.1 Hz to 10 kHz, as well as adequate linearity. The operating band is wider than the present sensor using the same mechanism. In particular, the system noise floor is measured to be -98 dB at 1 Hz and -155 dB at 1 kHz. The results indicate that the minimum detectable signal can reach as low as 5.6 × 10^-6 rad at 1 Hz and 8 × 10^-9 rad at 1 kHz. In addition, it is demonstrated that the noise result of the proposed system is two-order of magnitude lower than that of the typical interferometric fiber optic sensors through the comparison experiment. With the characteristic of low-noise, the system is promising in the field of weak signal detection such as underwater acoustic signal detection, seismic wave detection, and mineral resource exploration.