Dual-mode FPA for free space communications

A new dual mode focal plane array integrating both staring and high-speed data reception readout circuits is proposed. This FPA incorporates an indium gallium arsenide PIN photodiode array optimized for high-speed response and a custom CMOS readout integrated circuit (ROIC). The ROIC includes an integrator and a high-speed transimpedance amplifier within each pixel for photosignal detection and also peripheral circuits for controlling the readout operation. These circuits enable the entire pixel array or a smaller, randomly addressable pixel window within the array to be read out in stare mode and also for a single pixel to be selected and read out in high-speed data reception mode. The stare mode features snapshot integration, very high frame rates and continuously adjustable sensitivity over a wide range, and the data reception mode is capable of detecting a high-speed data stream from anywhere within the FPA's field-of-view without the need for mechanical adjustment. The integration of these features into a single FPA enables the development of optical communications networks that can automatically configure themselves without prior knowledge of each transceiver’s location. This paper introduces the architecture, design and functionality of the device. It also outlines some of the design constraints imposed by the dual-purpose functionality.