An optical-feedback transimpedance receiver for high sensitivity and wide dynamic range at low bit rates

A novel transimpedance optical receiver using optically coupled feedback rather than a conventional feedback resistor is described. The 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 Mb/s. The experimental receiver uses InGaAs p-i-n photodiodes and a silicon JFET preamplifier and obtains a maximum sensitivity of -63.8 dBm for an error rate of 1*10/sup -7/. When the receiver is optimized for high level signals, an optical dynamic range of 40 dB is attained with no preamplifier automatic gain control (AGC). The results of a transmission experiment over a length of 303 km of single-mode optical fiber at a wavelength of 1.55 mu m are presented.>