Optimizing DC restoration in Kramers-Kronig optical single-sideband receivers

Area of Science:

• Optical communications
• Signal processing

Background:

• Kramers-Kronig (KK) receivers mitigate signal-signal beat interference (SSBI) in optical systems.
• AC-coupling photocurrents for analog-to-digital converter (ADC) range necessitates digital DC restoration for KK algorithms.
• Previous research focused on perfect DC restoration for optimal error rates.

Purpose of the Study:

• Investigate SSBI cancellation in a single photodiode KK receiver.
• Analyze the impact of varying optical carrier-to-signal power ratio (CSPR) and DC offset on signal quality.
• Develop an optimized DC restoration strategy for improved performance.

Main Methods:

• Simulations and experimental validation of the KK receiver algorithm.
• Systematic variation of optical CSPR and DC offset levels.
• Analysis of signal quality metrics post-DC restoration.

Main Results:

• A theoretically perfect DC restoration does not guarantee optimal signal quality, especially at low CSPRs.
• An optimal restored DC level exists for maximum SSBI cancellation, dependent on optical CSPR.
• Defined digital CSPR and established optimal DC offset calculation methods based on optical CSPR.
• Identified system noise levels as a factor influencing the optimal DC restoration strategy.

Conclusions:

• Optimized DC restoration in KK receivers enhances SSBI cancellation and signal quality.
• The optimal DC offset strategy varies with optical CSPR, requiring adjustments for low and high CSPR regimes.
• The findings provide a practical approach to optimizing KK receiver performance without exhaustive DC offset searching.