Optical Transmitter Based on a 1.3-μm VCSEL and a SiGe Driver Circuit for Short-Reach Applications and Beyond

Abstract

Long-wavelength vertical-cavity surface-emitting lasers (LW-VCSELs) with emission wavelength in the 1.3-μm region for intensity modulation (IM)/direct detection optical transmissions enable longer fiber reach compared to C-band VCSELs, thanks to the extremely low chromatic dispersion impact at that wavelength. A lot of effort has been recently dedicated to novel cavity designs in order to enhance LW-VCSELs' modulation bandwidth to allow higher data rates. Another approach to further improve VCSEL-based IM speed consists of making use of dedicated driver circuits implementing feedforward equalization (FFE). In this paper, we present a transmitter assembly incorporating a four-channel 0.13-μm SiGe driver circuit wire-bonded to a novel dual 1.3-μm VCSEL array. The short-cavity indium phosphide buried tunnel junction VCSEL design minimizes both the photon lifetime and the device parasitic currents. The integrated driver circuit requires 2.5-V supply voltage only due to the implementation of a pseudobalanced regulator; it includes a two-tap asymmetric FFE, where magnitude, sign, relative delay, and pulse width distortion of the taps can be modified. Through the proposed transmitter, standard single-mode fiber reach of 20 and 4.5 km, respectively, for 28- and 40-Gb/s data rate has been demonstrated with state-of-the-art power consumption. Transmitter performance has been analyzed through pseudorandom bit sequences of both 2 7 -1 and 2 31 -1 length, and the additional benefit due to the use of the driver circuit has been discussed in detail. A final comparison with state-of-the-art VCSEL drivers is also includedt.