Integrated SOA-based interferometers for wavelength conversion and photonic signal processing

Integrated SOA-based interferometers have been the focus of considerable attention in recent years. As they offer access to an extremely fast, optically controlled non-linear “gate” functionality, they can be exploited in a variety of application contexts, including wavelength conversion, time (de)multiplexing, and signal regeneration. Wavelength conversion using SOA-based interferometers is accompanied by “2R” (amplitude domain) regeneration, and therefore supports digital (format and bit rate) transparency, with reasonable cascadability, at bit rates of at least 10 Gb/s Some of the application contexts are discussed, and recent achievements and demonstrations are highlighted. Future prospects are discussed through a consideration of the physical and operational parameters promoting high-speed operability. SOA-based interferometers must be (either monolithically or hybrid-) integrated to ensure a practical level of mechanical stability. However, the integration itself imposes substantial technological problems. In principle, the devices should consist of SOA´s “inserted” into a passive interferometer structure. Such “active-passive” integration has been pursued by various laboratories, by both monolithic and hybrid means. Some of the principal published active-passive interferometer technologies are reviewed. We have carried out an optimisation for an all-active Mach-Zehnder wavelength converter based on a bulk-tensile SCH SOA structure; the device and its optimisation are discussed in detail