Low-noise receivers for fiber optic communications

Improvements in fiber-optic direct detection receivers are reported. Very-low-noise avalanche photodiodes were developed for use in up to 2-Gb/s transmission rates with noise characteristics of less than 0.6 pA/Hz/sup 1/2/ at a gain of 10. The detectors were coupled to both transimpedance and high-impedance low-noise amplifiers utilizing commercially available HEMT (high-electron-mobility-transistor) devices. The best sensitivity at 1310 nm was -45.75 dBm and -46.75 dBm at 1548 nm for a nonreturn-to-zero pattern at 565 Mb/s.<
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