Ultrafast DOD-N Logic Gates for Router Applications

The University of Michigan requests seed funding to research and demonstrate ultrafast, DOD-N logic functions using a platform technology consisting of a semiconductor optical amplifier Mach-Zehnder interferometer. By using a symmetric structure with SOA’s biased at transparency and counter-propagating signals and clock, all of the requirements for a DOD-N logic gate can be satisfied. This configuration of the SOA-MZI can serve as the key enabling building block for modules such as 3R regenerators or wavelength converters, or for DOD-N sub-systems such as label swapping, header processing or error checking. As a subset of the original SAMMI Consortium proposal that was submitted at the end of May, 2003 to DARPA, the University of Michigan (UM) requests seed funding from DARPA to demonstrate and integrate the platform logic gates. The work will focus on fundamental and device aspects of the logic gate platform, along with their potential applications in modules for logic operations, 3R regeneration and wavelength conversion. For a sufficient funding level and duration of the project, the logic gates can also be bench-top integrated into DOD-N subsystems, such as label swapping, header processing and error checking. A. DOD-N Logic Gates (device platform) We propose a semiconductor optical amplifier Mach-Zehnder interferometer (SOA-MZI) building block for all the logic operations, with a particular emphasis on XOR functionality. Beyond the logic functions, the next section describes how the same device platform can be used for modules such as 3R regeneration and wavelength conversion. Finally, the last few sections describe how the device platform may be used for DOD-N sub-systems, including label swapping, header processing and error checking. The requirements on DOD-N logic gates include: ÿ three-terminal devices (clock – CLK – and signals are separable) ÿ cascadable (same wavelength output, minimize pulse distortion) ÿ polarization independent (input is random polarization) ÿ regenerative logic (output is new CLK photons, with either 2R or 3R clean-up) ÿ ultrafast operation (operate at speeds of 100Gb/s or more and avoid inter-symbol interference (ISI) or pattern dependence) ÿ high contrast ratio (low off state, high on/off contrast) ÿ Boolean complete (NOT, AND, XOR, etc.) In the design below, we meet all of these requirements using a particular configuration of the SOA-MZI. In particular, by using counter-propagating CLK and signals, we achieve threeterminal, cascadable and polarization independent operation. Regenerative operation is achieved by replacing the incoming photons with new photons from local CLK source. Ultrafast operation is achieved by using a symmetric structure and biasing at the gain transparency point.