Improvement on measuring optical nonlinear phase shift by self-aligned interferometer

The measuring mechanism of the self-aligned interferometer (SI) is analyzed in detail in the paper. The expression Δ φ of nonlinear phase shift and its error expression δ_φ are derived. The reasons of influencing on the measuring accuracy of the nonlinear phase shift are analyzed theoretically. The influences of the SI structure parameters on measuring the nonlinear phase shift are simulated and calculated. Properly selecting structure parameters in the SI, the optimal value Δφ and δ _φ are obtained. A measuring system using the optimal structure parameters is set up. The measured nonlinear phase shift Δφ coincides with the theoretical value. When compared the measured Δφ with other testing values from reference [2], the deviation Δ_φ obtained in our experiment is smaller. The experimental results show that the measuring method with simulating and optimizing the structure parameters in the SI is effective and convenient. The measuring method improved will be applied widely in optical fiber communications and optical precise measurements.