A silica-on-silicon integrated optic interface for microwave sub-systems

The integrated optic interface reported in this paper is designed to provide the capability of wideband analogue channel and bidirectional digital signal distribution over a single optical fibre when operated with suitable equipment. The range of applications based on this technology could be for inter-equipment rack interconnection, cross site links or phased array antenna RF and control/receive data signal distribution. It is the latter application that is specifically reported in this paper and the integrated optic interface has been developed for a phased array antenna signal distribution network. The compact device is for mounting at the sub-array level or within the solid state transmit/receive (T/R) modules located at the array face and the size advantages offered by this optical technology are particularly relevant in this case. Phased array antennas may require typically 10 to many 1000s of T/R modules and the potential low cost and high performance of an optical interface is extremely attractive. In operation the integrated optic interface would route a microwave reference and control signal to the T/R module via an optical fibre splitter network. In the reverse direction the individual digitised receive channels are distributed back to the digital beam forming network for appropriate signal processing. The technology used for the manufacture of this integrated optic interface is silica-on-silicon based and the device developed has a number of optical and electronic functions. This includes WDM and thermo-optic tuning capability as well as digital and RF component integration. How these are incorporated into the integrated optic interface with a general description of the manufacturing details are reported in this paper.