Wide temperature range high-speed VCSEL interconnects using FEC and pre-emphasis.

Area of Science:

• Optoelectronics and Photonics
• Optical Communications Engineering

Background:

• High-speed optical interconnects are crucial for data centers and high-performance computing.
• Vertical-cavity surface-emitting lasers (VCSELs) are key components in these interconnects due to their low cost and integration capabilities.
• Operating VCSEL-based interconnects reliably across extreme temperatures is a significant challenge.

Purpose of the Study:

• To evaluate the performance of 850 nm VCSEL-based optical interconnects using PAM-2 and PAM-4 modulation.
• To assess the operational temperature range of these interconnects from -60°C to 140°C.
• To demonstrate the effectiveness of signal processing techniques in maintaining high data rates.

Main Methods:

• Utilized two distinct multiple quantum well VCSEL designs.
• Implemented advanced signal processing: forward error correction (FEC), electronic pre-emphasis, and receiver-side equalization.
• Employed a three-tap feed-forward equalizer for pre-emphasis and a least-mean-square equalizer at the receiver.

Main Results:

• Achieved successful PAM-4 transmission at 70 Gb/s across the temperature range of -60°C to 100°C.
• Demonstrated 50 Gb/s PAM-4 transmission at 125°C and 42 Gb/s at 140°C.
• The FEC overhead was maintained at a low 3.1%.

Conclusions:

• 850 nm VCSEL-based optical interconnects with PAM-4 modulation exhibit robust performance over an extended temperature range (-60°C to 140°C).
• Signal processing techniques, including FEC and equalization, are effective in overcoming temperature-induced impairments.
• These findings support the viability of VCSELs for high-speed, wide-temperature optical interconnect applications.