Conditions for measuring n2 of various single-mode method nonlinear refractive index fibres using cw-SPM

The conditions for accurately measuring the nonlinear refractive index n₂ of various single-mode fibres utilising the cw self-phase modulation (SPM) method are described. It is demonstrated theoretically that the appropriate measurement conditions can be determined by taking account of the required accuracy and dynamic range of the measurement system. It is also shown that one can approximate the optimum fibre length and minimum input power for a dispersion compensating fibre as a function of the absolute chromatic dispersion value. Moreover, it is confirmed from experimental results that the calculated measurement conditions are reasonable, and that the accuracy of the n₂ measurement strongly depends on the fibre length and wavelength difference of the input lights for a 1.3 μm zero-dispersion fibre and a dispersion compensating fibre