Dual Frequency Comb Assisted Analog-to-Digital Conversion of Subcarrier Modulated Signals

TL;DR

This paper introduces a photonic analog-to-digital conversion method using dual frequency combs to enable high-resolution, parallel digitization of broadband signals, overcoming traditional ADC limitations.

Contribution

The paper presents a novel dual frequency comb approach for optical downconversion, allowing high-resolution parallel digitization of broadband signals with demonstrated experimental results.

Findings

Achieved >45dB SFDR in experimental tests

Demonstrated detection of 10-GHz subcarrier signals with 500-MHz bandwidth ADCs

Potential for improved SINAD with better receiver design

Abstract

Photonic analog to digital conversion offers promise to overcome the signal-to-noise ratio (SNR) and sample rate trade-off in conventional analog to digital converters (ADCs), critical for modern digital communications and signal analysis. We propose using phase-stable dual frequency combs with a fixed frequency spacing offset to downconvert spectral slices of a broadband signal and enable high resolution parallel digitization. To prove the concept of our proposed method, we demonstrate the detection of a 10-GHz subcarrier modulated (SCM) signal using 500-MHz bandwidth ADCs by optically converting the SCM signal to ten 1-GHz bandwidth signals that can be processed in parallel for full signal detection and reconstruction. Using sinusoidal wave based standard ADC testing, we demonstrate a spurious-free dynamic range (SFDR) of >45dB and signal-to-noise-and-distortion (SINAD) of >20dB, only limited by the receiver front-end design. Our experimental investigation reveals that this SINAD limitation can be overcome by improved receiver design, promising high resolution ADC for broadband signals.