Wavelength channel data rewriter using semiconductor optical saturator/modulator

A wavelength channel data rewriter (WCDR) is a device that erases the data on an incoming signal by utilizing the saturation characteristic of a semiconductor optical amplifier (SOA) and then modulates it with new data to generate an upstream signal. This paper describes a theoretical and experimental investigation designed to improve the performance of the WCDR. Through numerical calculations, this paper shows that an SOA with a long waveguide with a large small-signal gain better suppresses optical bit patterns. This paper also uses calculated and experimental results to show that the amplified-spontaneous-emission noise in the SOA input signal degrades the bit-pattern suppression. This paper then describes the semiconductor optical saturator/modulator (SOSM), which this paper has developed for use in the WCDR based on the results of the author´s theoretical investigations. This paper outlines the SOSM specifications and provides experimental results that confirm the improved WCDR performance obtained using the SOSM.