Experimental comparison of a germanium avalanche photodiode and InGaAs PINFET receiver for longer wavelength optical communication systems

Optical receivers for lightwave communication systems

“…Comprised of a quartz cube with an integral fiber pigtail, it provided a simple means of actively aligning the InGaAs/ InP photodiode with the fiber core to give very high coupling efficiency, while the lower dielectric constant of quartz reduced the stray capacitance [62]. With the total input capacitance reduced to less than 0.5 pF, p-i-n FET hybrid -receivers were able to demonstrate better sensitivities at up to 565 Mbit/s than the Ge APD's then available [29], [63], with very little variation with temperature. These early p-i-n FET hybrids used a FET/bipolar cascode preamplifier which provided a -3-dB bandwidth of 350 MHz.…”

“…At 1.3-pm wavelength, receiver sensitivities obtained using n+-pstructured devices were initially poor and varied by several decibels between 20" and 60°C [29], due to the high level of multiplied shot noise on the bulk leakage current [72]; this has been reduced by cooling the detector [138] and, with the widespread adoption of monomode fiber, by reducing the junction area of the APD [ 1391. Hybrid-in- tegration is also being applied to improve sensitivity [ 1401, since the high k-value limits the ability of the APD to offset the thermal noise of the preamplifier [25].…”

“…Integrating receivers have demonstrated good sensitivities at up to 1.2 Gbit/s in both the 1.3-and 1.55-pm wavelength windows, with negligible temperature dependence (except at the lowest bit rates) [29], [30]; and the structure and electrical bias requirements for the detector are relatively simple. Their main drawback is a limited dynamic range, except where a low-disparity line transmission code can be used.…”