4 ch × 30-Gbps/ch Optical Transmission Performance of a Low-Power Transmitter Flip-Chip-Bonded 1.3-μM LD Array-on-Si

This paper presents a four-channel (4-ch) transmitter consisting of a 4-ch 65-nm CMOS cascode shunt laser diode (LD) driver and flip-chip-bonded 1.3-μm membrane LD-array-on-Si that has the highest power efficiency yet reported for 4-ch over-25-Gbps/ch transmitters that use distributed-feedback (DFB)-LDs and vertical-cavity surface emitting lasers. In order to transmit over-25-Gbps/ch NRZ PRBS-31 signals on four channels simultaneously, the driver incorporates electro-optic (EO)-response-improvement functions. It was designed with our photonic-electronic conversion system in SPICE, and the transmitter was implemented with a flip-chip-bonding interconnection between the driver and LD array. The effects of the EO-response-improvement functions were clarified mathematically and the optical output waveforms of a transmitter with and without the functions were simulated and measured. Furthermore, the bit error rate (BER) was measured. It was found that the functions improved the eye openings and reduced the jitter of the simulated and measured optical output waveforms. Moreover, the crosstalk penalties between discrete and simultaneous operation decreased, and 30 (31) Gbps/ch NRZ PRBS-31 signals could be transmitted error-free on four channels over 10-km-long standard single-mode fiber (or in the back-to-back (BtoB) configuration) with a power efficiency of 1.19 (1.15) mW/Gbps. Without the improvement functions, error-free simultaneous 4-ch transmissions were possible in the BtoB configuration for 25-Gbps/ch NRZ PRBS-31 signals but not for higher rates per channel.