Nondegenerate four-wave mixing efficiencies in DFB laser wavelength converters

The salient parameters affecting nondegenerate four-wave-mixing (FWM) conversion efficiency in distributed-feedback (DFB) laser wavelength converters are examined analytically. Both the maximum attainable, and typical gain saturated, FWM efficiencies are derived. Typical DFB lasers cannot achieve maximum conversion efficiency due to gain saturation, while laser-amplifier combinations potentially can. The ratio of efficiency to spontaneous emission noise is also addressed, where it is found that this ratio increases quadratically with net unsaturated gain.