Method of and device for measuring the kerr non linearity coefficient in a single mode optical fibre

摘要

A train of rectangular pulses is sent into a fibre (5), which pulses have such a wavelength that fibre (5) operates under anomalous dispersion conditions, such a peak power as to cause modulation instability in the fibre and such a ratio between duration and repetition period that the average power is lower than the threshold at which stimulated Brillouin effect takes place. The maximum value of instability gain is measured in the spectrum of the pulses exiting the fibre and the kerr non linearity coefficient is obtained from the maximum measured value of modulation instability gain by minimising the error, in the range of power values used for the measurement, with respect to a theoretical curve expressing such maximum gain as a function of the peak power. The device to realise the method is also provided.