An Optical Feedback Transimpedance Receiver for High Sensitivity and Wide Dynamic Range at Low Bit Rates.

We describe a new type of transimpedance optical receiver employing optically-coupled feedback rather than a conventional feedback resistor. Optically-coupled feedback has a number of advantages, including 1) elimination of feedback-resistor Johnson noise for higher sensitivity, 2) elimination of feedback capacitance for higher bandwidth, and 3) the capability of large feedback current with low output voltage for wide dynamic range. A theoretical analysis is presented, along with experimental results for a long-wavelength optical feedback receiver at a bit rate of 1.5 Mbit/s. The experimental receiver uses InGaAs PIN photodiodes and a silicon JFET preamplifier, and has obtained a sensitivity of -63.8 dBm for an error rate of 1x10 sup (- 7), plus an optical dynamic range of 40 dB with no preamplifier AGC. The receiver was used to conduct a transmission experiment over a length of 303 km of single-mode optical fiber at a wavelength of 1.55micron.