Compact and Fully Packaged Wavelength Converter with Integrated Delay Loop for 40 Gbit/s RZ Signals

摘要

High-speed optical translators will become key elements in WDM networks. In particular, simple and cost effective wavelength converters that can handle RZ format will be very important due to the superior transmission performance of RZ. Monolithically integrated interferometric structures based on semiconductor optical amplifiers (SOAs) are strong candidates for wavelength-conversion applications because they allow for high-speed switching by exploiting the fast carrier-depletion related refractive-index changes in the SOAs [1][2]. In these configurations the maximum speed is only limited by the slow carrier-recovery time of the SOAs. To overcome these carrier-recovery constraints, a scheme with two consecutive control pulses was introduced to set and reset the refractive-index changes [3], subsequently enabling RZ wavelength conversion up to 40 Gbit/s [4]. However, these schemes require external delay loops to create the two consecutive control pulses. This makes it necessary to pigtail whole fiber arrays to a chip in order to introduce and extract all the signals, which makes these hybrid configurations costly and impractical because of the external delay loops. Recently, a hybrid wavelength converter has been demonstrated, using only one SOA followed by a delay-interference section, formed by a calcite crystal, [5]. This delay-interference-signal wavelength-converter (DISC) scheme is much simpler than previously published wavelength converters [1]-[4].