Fibre non-linear coefficient measurement based on four-wave mixing method with two-tone optical source

In this paper, we present the novel two-tone non-linear coefficient meter achieves high peak power using pulsed operation. Both the two-tone generation and the pulse modulation are obtained from a single LiNbO₃ modulator, driven by standard microwave pulse generator. The obtained two optical signals have inherently the same linear polarisation. The frequency spacing is precisely set by the modulation signal and no adjustment is required during the measurement because there is no wavelength difference drifting. The systematic errors produced by either stimulated Brillouin scattering or the spectral component coincidence are eliminated. The measurement scheme without expensive optical equipment is simple and well applicable to field measurement. It has long-term stability and good measurement repeatability. The introduced measurement scheme is applicable to all currently available fibre types including photonic crystal fibres.