100Gbit/s all-optical wavelength conversion with integrated SOA delayed-interference configuration

Introduction: All-optical wavelength converters with 2R regeneration capabilities, that allow operation at speeds beyond the limits of electronic devices, will be essential in future wavelength division multiplexing (WDM) networks. Of particular interest are simple and compact wavelength converters that help to avoid wavelength blocking and facilitate WDM network management. All-optical wavelength conversion has successfully been demonstrated with semiconductor optical amplifier (SOA) devices exploiting the cross-gain modulation (XGM) effect as well as the cross-phase modulation effect (XPM). In the XGM scheme a strong input signal is used to saturate the gain of an SOA and thereby to modulate a CW signal carrying the new wavelength. Although XGM is limited by the relatively slow carrier recovery time within the SOA, impressive wavelength conversion of up to 40Gbit/s [1], and with some degradation even up to 100Gbit/s [2], has been demonstrated. Unfortunately, XGM is accompanied by large chirp and low extinction ratios [3]. To overcome these disadvantages, SOAs have been integrated in interferometric configurations, where the intensity modulation of the input signal is transferred into a phase modulation of the CW signal and exploited for switching. These XPM schemes enable wavelength conversion with lower signal powers, reduced chirp, enhanced extinction ratios and ultrafast switching transients that are not limited by the carrier recovery time. Subsequently wavelength conversion with excellent signal quality up to 40Gbit/s has been demonstrated [4, 5]. However, the simplest XPM wavelength converter is based on an SOA followed by a delayed-interference loop [5 – 7]. Here, we report for the first time 100Gbit/s wavelength conversion exploiting the efficient XPM effect in an SOA. We use a fully integrated and packaged SOA delayedinterference configuration (SOA-DI) that comprises a monolithically integrated delay loop, phase shifter and tunable coupler. Only one input and one output fibre is needed to operate the device, which simplifies packaging. In addition, we believe that we report the best results for any SOA based wavelength conversion scheme at 100Gbit/s.