Ultrafast all-optical signal processing with Symmetric Mach-Zehnder type all-optical switches

We present Symmetric Mach-Zehnder (SMZ) type all-optical switches: an SMZ a ll-optical switch, a polarization-discriminating SMZ (PD-SMZ) all-optical s witch, and a delayed interference signal wavelength converter (DISC). These switches are capable of ultrafast, low control power, and low chirp switch ing, which is not restricted by slow relaxation of highly efficient nonline arities. High repetition operation unrestricted by slow relaxation is also possible for these switches. This is because of a push-pull modulation sche me or sometimes called a differential phase modulation scheme. These three devices are similar, but different in some important aspects, thus a compar ison is made among the three. Then semiconductor optical amplifiers (SOAs) are discussed as a nonlinear phase shifter for these devices. Then, ultrafa st all-optical signal processing using SOA based SMZs is demonstrated. Erro r-free demultiplexing from 168 to 10.5 Gbit/s is presented, in which a hybr id-integrated SMZ (HI-SMZ) is used as a demultiplexer. In pulse regeneratio n experiment, the signal pulses at 84 Gbit/s are regenerated by the PD-SMZ and the regenerated pulses are demultiplexed to 10.5 Gbit/s by the HI-SMZ t o verify error-free operation. The retiming capability of this scheme is qu antitatively demonstrated. Also presented is error-free all-optical wavelen gth conversion at 168 Gbit/s using the DISC. These results represent the fa stest error-free operations reported to date in each category.