Atlanta Fiber System Experiment: Optical Detector Package

This paper describes the design, packaging, and performance characteristics of the optical detector packages used in the receiver portion of the regenerator employed in the Atlanta Fiber System Experiment recently completed in Atlanta, Georgia. The goal of this development effort was to design a self-contained optical detector package containing the photodetector along with the associated preamplifier which would operate at the DS3 transmission 1809 rate (44.7 Mb/s), achieve good sensitivity, possess a wide dynamic range, and be easily interfaced both optically and electrically to the printed circuit board and backplane. The design was also to produce a level of performance representative of a manufacturable unit. This latter constraint affected several of the engineering choices made during this development. The optical detector package, to be described in detail below, employs an avalanche photodiode as the optical detector and a transimpedance amplifier as the interface between the detector and the remainder of the linear channel. The combination is enclosed in an EMI shield and potted in plastic to provide mechanical rigidity. Optical interfacing is accomplished by use of a short piece of optical fiber connected on one end to the APD and on the other end to an optical connector. Electrical interfacing is achieved via pins designed to fit either into a socket or on to a printed circuit board. The performance of 53 detector packages fabricated and evaluated for this project includes a measured optical sensitivity of --54.1 dBm with a standard deviation of 0.3 dB for a bit error rate of 10 - 9 and a dynamic range of 38 dB of optical power compared to design goals of --53 dBm and 30 dB, respectively.