SBIR-STTR Award

Fiber optic distribution of mm-waves is important in phased array antennas, in particular in airborne or mobile phased array antennas because of low weight and compactness. Fiber optic distribution may also be very attractive in future cellular communication systems where frequency bands around 35 GHz and 60 GHz are considered. The low loss of optical fiber is very important in these systems, since signals needs to be transmitted over relative long distances. Compact optical transmitters and receivers covering the 20-60 GHz frequency range are required, but not currently commercially available. In this phase I project, we propose to demonstrate an optical receiver operating up to 45 GHz, and design receivers working up to 60 GHz. The designed receiver module will be analyzed for noise and dynamic range and a fiber optic package will be developed. A compact and simple module will be designed to make a reliable component for mobile systems. A prototype module will be fabricated during this phase I, the module will be tested and measurements will be compared to theoretical results.

Keywords:
optical receivers mm-waves cellular communication phased array antennas photodetectors

Fiber optic distribution of mm-waves is important in phased array antennas, particularly for mobile antennas because of low weight and compactness. Coaxial cables are extremely lossy at these frequencies and the low loss of optical fiber is very important in these systems. Compact optical receivers covering the 20 to 50 GHz range are required, but are not commercially available. In this Phase II project, we-propose to demonstrate receivers optimized for two bands: 6-12 GHz and 2 to 50 GHz. The detector design is optimized for efficiency within each band. The receiver modules will be analyzed for transimpedance, noise, saturation current and dynamic range. The modules will be compact, rugged, low power and packaged with single mode fiber. An exciting new approach is proposed for the 6-12 GHz frequency range, namely the use of InGaAs/Si APDs hybrid integrated with a MESFET amplifier. The use of silicon for the avalanche region has demonstrated gain bandwidth products of 81 GHz and projected gain bandwidth products of 800 GHz. The use of this detector could reduce the gain requirements of present and future optical links by 40 dB, thus allowing significantly smaller size, lower power, improved sensitivity and lower cost. It could have broad impact on virtually every military optical link. The InGaAs/Si APD could reduce SAGM APDs in most commercial links. Further, it eliminates the need for an expensive optical amplifier at a receiver. The high speed receiver modules will find application in SONET systems at 2.5,10 and 40 Gbit/s. These modules should also be useful in cellular communication systems and satellite communication links.