Noise transfer characteristics in LD wavelength conversion

Noise transfer characteristics are studied for a laser diode (LD) wavelength converter. The converter has a threshold property in its input relation, which has the effect of improving the signal quality. Results of experiments carried out for various input conditions, where amplified spontaneous emission (ASE) light was intentionally imposed on a signal light, show that allowable ASE level is improved through the conversion process depending on the input condition. Improvement in signals suffering from crosstalk light is also demonstrated. A theoretical discussion on the improvement effect is presented.