Filtering-free complex-valued DSB-16QAM generation for a 100 G direct detection optical interconnection

Area of Science:

• Optical Communications
• Signal Processing
• High-Speed Interconnects

Background:

• Intensity Modulation/Direct Detection (IM/DD) systems are crucial for optical interconnects.
• Conventional Quadrature Amplitude Modulation (QAM) schemes face limitations in spectral efficiency and complexity.
• Existing methods often require complex optical filtering or additional hardware components.

Purpose of the Study:

• To propose and experimentally demonstrate a novel complex-valued double-sideband 16QAM (CV-DSB-16QAM) signaling scheme.
• To achieve high spectral efficiency and simplify hardware in 100 Gb/s IM/DD systems.
• To offer an alternative for advanced complex-valued direct detection systems.

Main Methods:

• Generation of CV-DSB-16QAM signals by combining two independent sideband modulated QPSK signals.
• Utilizing a single intensity modulator without requiring sharp-edged optical filtering.
• Experimental validation using a 25-GBaud CV-DSB-16QAM signal over 2-km standard single-mode fiber.

Main Results:

• Achieved a net bit rate of 100 Gb/s.
• Occupied a narrow electrical bandwidth of 25.1 GHz with a 4% guard band.
• Demonstrated an optical filtering-free profile, saving hardware components like photodiodes and ADCs.

Conclusions:

• The proposed CV-DSB-16QAM scheme is a viable and efficient solution for high-speed optical interconnects.
• This approach offers a compelling alternative for complex-valued direct detection systems demanding high spectral efficiency.
• The demonstrated method simplifies system architecture and reduces hardware costs compared to existing schemes.