Measurement of crossphase modulation in coherent wavelength-division multiplexing using injection lasers

Light from two InGaAsP injection lasers of different wavelengths was multiplexed into a 15 km-long single-mode fibre. Owing to the nonlinear refractive index, the phase of light in one channel was changed by power changes in the other channel. A 1 mW power charge in one channel produced a 1.4° phase shift in the other channel.