A Multi-mode Linear Optical Modulator Driver Circuit in 130 nm SiGe BiCMOS Technology

This paper presents a multi-mode linear driver operating as 64 Gbps non-return-to-zero to duobinary encoder, 55 GHz bandwidth transparent amplifier or 32 Gbps 1-Tap feed-forward equalizer. The driver, implemented in a 130 nm SiGe BiCMOS technology featuring fT/fMAX of 300/500 GHz, utilizes the traveling-wave topology to deliver a large output signal in both transparent mode, and superposing two consecutive input bits in duobinary mode, enhancing in this way the spectral efficiency. Moreover, the TWA cores provide the possibility to shape the signal in its equalizer operation mode. The present amplifier exhibits 24 dB gain with an output voltage swing up to 4 Vppd in duobinary mode. Measurement results indicate that the total harmonic distortion is better than 5.5% at the 1 dB compression point. To the best knowledge of the authors, this driver is the only one among the state-of-the-art linear large output swing drivers offering multi-mode functionality and, consequently, high system flexibility while preserving state-of-the-art performance.