Abstract
This paper reviews the recent progress in long-wavelength photodetectors and integrated photoreceiversdeveloped for long-distance and large-capacity optical transmission systems. The InGaAsavalanche photodiodes (APDs) successfully operating in the 1.6 Gb/s systems are now being developedfor the 10 Gb/s range, where the reduction of avalanche buildup time is crucial. In InGaAsPIN photodiodes, flip-chip bonding structure shows ultra-low diode and stray capacitance suitablefor PIN/FET integrations. Monolithically integrated Twin-PIN photodiodes of dual balanced opticalreceivers (DBORs) for coherent optical transmission systems exhibit the high-sensitivity much betterthan direct detection. For the future devices, possibility of the very high-speed and low-noise operationof the staircase APDs is discussed as well as a new PIN photodiode in the wavelength range largerthan 2μm, where the theoretical loss of a fluoride fiber is minimized.
