Sensitivity enhancement in interferometric fiber sensors by using the optical Kerr effect

Sensitivity enhancement in fiber interferometric sensors was achieved by connecting a balanced nonlinear Mach-Zehnder fiber interferometer to the sensing interferometer. Taking advantage of the phase-sensitive nature of this nonlinear interferometer, the improvement of the sensitivity for each output of the interferometer was found to be proportional to the nonlinear phase shift due to the optical Kerr effect, induced by the total power in the fiber. Since high power is needed to induce a large nonlinear phase shift, it is assumed that a high peak-power pulse train is used, with a pulse repetition rate greater than the minimum sampling frequency. This is required by the Nyquist criterion for the reconstruction of the sensed signal. The theory is also extended to remote fiber sensing systems