Photonic Integrated Circuits for Self-Routing in Packet Switching

A GaAs based integrated circuit is proposed as a means to implement optical network switching technology for phased array antennas (PAA) and ATM switching functions. The integrated technology offers a family of components in monolithic form and combinations of these devices can be used with an optical fiber input, to strip the header from the incoming optical signal and to use this routing information to set up a path for the optical data of the payload without O/E conversion. This technology has produced vertical cavity surface emitting lasers (* 2 mA threshold), vertical cavity resonant detectors (0.6 A/W responsivity), high performance heterostructure field effect transistors (ft > 40 GHz) and waveguide absorption modulators (35:1 contrast) all using a common fabrication sequence. This technology is realized with a single epitaxial growth upon a GaAs substrate, and uses a single set of fabrication steps to realize a monolithic integrated circuit with electronics, emission, detection and modulation capability. A essential component for the all optical switching function is the HFET waveguide directional coupler switch. Using this switch for optical routing and controlling it with HFET logic, a high speed switching network can be realized. The other essential component for the self-routing function is the HFET modulator/detector which is able to remove the header by O/E conversion and then use the resulting electronic code to set up the optical switching path. These photonic circuits can implement a complete III-V chip set for an optical switching network. With this device compatibility, it is possible to implement the header removal, the header decode logic, the switch set-up circuits and the optical switching network within the area of a single integrated circuit. For the PAA, the headers contain the phase delay data for routing optical RF signals through a True Time Delay network and with sub-micron scaled devices, this function can be performed at data rates approaching 100Gb/s. In this program the integrated circuits for all optical signal routing with optoelectronic header conversion, decode and set-up for an optical switching network system with fiber inputs and outputs will be developed.