NOISE CHARACTERISTICS OF CROSS-PHASE MODULATION INSTABILITY LIGHT

The noise characteristics of cross-phase modulation instability visibl e light produced in high-birefringence fibres have been investigated. Noise measurements were made on single sidebands, and on the intensity difference between upshifted and downshifted sidebands using single p ass and fibre-laser configurations. The intensity difference noise for the single pass configuration was reduced by more than 25 dB below th e single sideband noise, which was typically 35 dB above shot noise. U nder certain conditions the intensity difference noise of the modulati on instability laser sidebands could be reduced to the shot noise leve l, while the single sideband noise from the modulation instability las er could be reduced to 2 dB above shot noise. Raman gain on the low fr equency sideband and attenuation in the fibre limited the attainable n oise reduction.