WINDOW: wideband demodulator for optical waveforms.

Area of Science:

• Electrical Engineering
• Optical Communications
• Signal Processing

Background:

• High-rate optical communication systems face sampling rate bottlenecks, exceeding analog to digital converter (ADC) bandwidth.
• Existing multi-channel sampling methods like interleaved ADCs have limitations including signal distortion and precise timing shift requirements.

Purpose of the Study:

• To propose and evaluate an alternative multi-channel sampling scheme, the wideband demodulator for optical waveforms (WINDOW), for optical communication systems.
• To address the limitations of interleaved sampling in high-rate optical systems.

Main Methods:

• WINDOW employs analog RF demodulation with periodic mixing functions for spectral aliasing before integration and sampling.
• The system intentionally utilizes the ADC's inherent anti-aliasing filter for integration, enhancing signal-to-noise ratio (SNR).
• Theoretical analysis and numerical experiments were conducted to compare WINDOW with interleaved sampling.

Main Results:

• The WINDOW system demonstrates superior signal recovery and symbol estimation compared to interleaved sampling, particularly in the presence of thermal and quantization noise.
• The proposed method shows slightly reduced robustness to timing jitter compared to interleaved sampling.
• The study successfully applies RF demodulation concepts to optical signals in the Nyquist regime.

Conclusions:

• WINDOW provides a viable alternative sampling scheme for optical links where receiver thermal noise is a primary bottleneck.
• The integration of RF demodulation offers improved performance in optical communication sampling.
• This research contributes to overcoming sampling limitations in high-speed optical systems.