40 Gb/s postamplifier and p-i-n/preamplifier modules for next generation optical front-end systems

Postamplifier and p-i-n/preamplifier modules suitable for 40-Gb/s short-haul and long-haul optical communication systems are presented. The postamplifier module consists of two stages of pseudomorphic high-electron mobility transistor (PHEMT) GaAs amplifiers mounted in a housing. A test fixture is used to provide bias supplies that control the output signal. The postamplifier has a 20-dB gain and 4.5-dB noise figure. The input voltage swing of the postamplifier can be varied from 10 to 148 mV p-p while providing an open output eye-pattern response over the complete range. The p-i-n/preamplifier module consists of a waveguide p-i-n/photodetector, with a polarization insensitive spot-size converter and a PHEMT-based GaAs transimpedance amplifier. The components are integrated inside a hermetically sealed compact package using hybrid techniques. The p-i-n/preamplifier module having 150-Ω transimpedance exhibits a linear output voltage swing over 800 mV p-p and a responsivity of 0.8 A/W. The receiver module has a 3-dB bandwidth as high as 45 GHz, and the input equivalent noise current density is less than 15 pA/√(Hz). The electrical sensitivity of the postamplifier is found to be 7.8 mV p-p for a 40 Gb/s, 2⁷-1 pseudorandom binary sequence nonreturn-to-zero signal. When used in combination with a 150-Ω 40-Gb/s p-i-n/preamplifier module, a sensitivity of less than -11.2 dBm is achieved. These results indicate that the postamplifier module, in combination with the p-i-n/preamplifier module, can be used in 40-Gb/s short-haul systems, while the p-i-n/preamplifier module itself can be used for long-haul front-end receiver systems.