Efficiency of broadband wavelength conversion by four-wave mixing in semiconductor traveling-wave amplifiers

Four-wave mixing in traveling-wave amplifiers (TWA´s), when used for wavelength conversion, has several advantages. Owing to their traveling-wave operation, these devices offer the potential for very high speed operation as well as continuous tuning of the input and output wavelengths. In addition, since the converted signal is the phase-conjugate replica of the input signal, the conversion is transparent to the modulation format, and provides the possibility for fiber-dispersion-compensation in lightwave communication systems. In this paper, we present measurements of wavelength conversion efficiencies in TWA´s for Δλ-shifts as large as 27 nm. We show that wavelength up-conversion is less efficient than down-conversion and show that the effect results from phase interference between the interband and intraband mechanisms causing four-wave mixing