Modified square timing error detector with large chromatic dispersion tolerance for optical coherent receivers

Area of Science:

• Optical Communications
• Digital Signal Processing
• Signal Synchronization

Background:

• Clock recovery is crucial for coherent optical receivers, utilizing timing error detectors (TEDs) for sampling synchronization.
• Conventional TEDs struggle with impairments like chromatic dispersion (CD) and polarization rotation, necessitating pre-processing.
• Accurate clock recovery is essential for reliable data transmission in high-speed optical networks.

Purpose of the Study:

• To introduce a modified square timing error detector (TED) with improved tolerance to chromatic dispersion (CD).
• To provide a time-domain solution for CD-tolerant clock recovery in digital signal processing (DSP).
• To reestablish the equivalence between time-domain and frequency-domain TEDs within spectral correlation theory.

Main Methods:

• Development of a modified square TED based on the signal's cyclic autocorrelation function (CAF).
• Implementation of a time-domain approach for chromatic dispersion (CD) tolerant clock recovery.
• Analysis using spectral correlation to link time-domain and frequency-domain TED behaviors.
• Performance evaluation through numerical simulations and experimental validation.

Main Results:

• The proposed modified square TED demonstrates significantly enhanced tolerance to chromatic dispersion (CD).
• The new TED provides a generalized, time-domain solution for clock recovery, simplifying the DSP chain.
• The equivalence between time-domain and frequency-domain TEDs is confirmed under spectral correlation.
• Minimal additional complexity is required for the modified TED implementation.

Conclusions:

• The modified square TED offers a robust and efficient solution for clock recovery in optical systems facing chromatic dispersion.
• This approach simplifies receiver design by mitigating the need for separate CD compensation.
• The findings contribute to advancing digital signal processing techniques for coherent optical communications.