64 Gb/s PAM4 VCSEL-based FSO link.

Area of Science:

• Optical Communications
• Free-Space Optics
• Semiconductor Lasers

Background:

• High-speed free-space optical (FSO) links are crucial for next-generation wireless communication.
• Vertical-cavity surface-emitting lasers (VCSELs) offer potential for compact and cost-effective optical transmitters.
• Achieving high data rates like 64 Gb/s in FSO links presents significant technological challenges.

Purpose of the Study:

• To propose and demonstrate a 64 Gb/s free-space optical (FSO) link utilizing a vertical-cavity surface-emitting laser (VCSEL) transmitter.
• To investigate the effectiveness of an external light injection scheme for enhancing VCSEL performance in high-speed FSO applications.
• To analyze the link performance using four-level pulse amplitude modulation (PAM4) and evaluate its suitability for long-distance transmission.

Main Methods:

• A 1550-nm VCSEL transmitter was employed, incorporating an external light injection scheme.
• The system was configured for 64 Gb/s data transmission using four-level pulse amplitude modulation (PAM4).
• Link performance was evaluated through real-time eye diagram analysis and offline bit error rate (BER) calculations using Matlab over a 100-m FSO channel.

Main Results:

• The 11.2 GHz VCSEL with external light injection proved capable of supporting the 64 Gb/s PAM4 FSO link.
• The study achieved good bit error rate (BER) performance and clear eye diagrams.
• Successful demonstration of a 100-m free-space link using the proposed VCSEL-based FSO system.

Conclusions:

• The integration of an external light injection scheme with a 1550-nm VCSEL is a viable approach for high-speed (64 Gb/s) PAM4 FSO links.
• This technology shows promise for enabling high transmission rates over extended distances in FSO communication.
• The demonstrated system represents a significant advancement in VCSEL-based FSO technology.