Ultrabroad tunable wavelength conversion with uniform efficiency and signal-to-noise ratio

Abstract

ABSTRACT By using two orthogonally-polarized pump beams, an ultrabroad tunable wavelength converter is demonstrated with uniform efficiency and equalized signal-to-noise ratio (SNR) through four-wave mixing (FWM) in an 1500-nm semiconductor optical amplifier (SOA). This device allows the conversion of the input data signal to lower or higher frequencies with nearly-constant conversion efficiency and SNR over a 10.66 THz tuning range. This result is a significant improvement of both the conversion efficien cy and the SNR as compared with the conventional FWM-based wavelength converters. We have also investigated the effect of parameters of both input power and wavelength of pump P 2 on conversion efficiency and SNR of the wavelength-converted signals. Key words: All-optical wavelength conversion; Semiconductor optical amplifiers; Four-wave mixing; Two orthogonally-polarized pump beams. 1. INTRODUCTION The growing demand for voice and data telecommunications, such as high-definition television, multimedia services, and the world-wide web, is driving the use of wavelength division multiplexing (WDM) technologies for greater utilization of the available fiber bandwidth. An important element for implementation of all-optical WDM networking systems is an optical wavelength converter, since it makes possible many useful system functions in the optical domain such as wavelength reuse, dynamic wavelength routing and switching, and optical network reconfigurability [1]. Several mechanisms have been demonstrated for the implementation of all-optical wavelength conversion using semiconductor optical amplifiers (SOAs) [2]. These include cross-gain modulation (XGM) [3], cross-phase modulation (XPM) [4] and four-wave mixing (FWM) [5-6]. The XGM and XPM methods directly exploit the gain or phase modulation produced in the SOA by the injected signal, while the FWM technology is based on the generation of a replica of the data signal through a nonlinear interaction involving the optical signal and pump fields injected in the SOA. The XGM and XPM wavelength converters are simple to implement and offer higher conversion efficiency compared to FWM. However, FWM has the advantage of being transparent to both the modulation format and the bit rate, which are of critical importance when handling anal og or digital signals with speed of hundreds gigabit per second [7]. Data transparency is also offered by different frequency generation (DFG). Demonstrated DFG performance has been improved in r ecent years through use of quasi-phase matching in AlGaAs or LiNbO