Full-C-band, sub-GHz-resolution Nyquist-filtering (de)interleaver in photonic integrated circuit

TL;DR

This paper introduces a low-cost, power-efficient on-chip optical Nyquist-filtering (de)interleaver with sub-GHz resolution, enabling high-performance N-WDM systems with simple photonic integrated circuits covering the full C-band.

Contribution

The authors demonstrate a novel photonic integrated circuit using a two-ring-resonator-assisted Mach-Zehnder interferometer for high-resolution, full C-band Nyquist filtering with compact design and sub-picosecond delay accuracy.

Findings

Achieved sub-GHz resolution with near-rectangular passband.

Enabled full C-band coverage with over 160 free spectral ranges.

Demonstrated potential for chip-scale N-WDM transceivers and ROADMs.

Abstract

Nyquist wavelength division (de)multiplexing (N-WDM) is a highly promising technique for next-generation high-speed elastic networks. In N-WDM, Nyquist filtering is an essential function that governs the channel spectral efficiency. However, most Nyquist filter implementations to date require either expensive, power-hungry digital electronics or complex arrangements of bulky optical components, hindering their adoption for important functions such as Nyquist channel shaping and reconfigurable optical add-drop multiplexers (ROADMs) for Nyquist super-channels. Here, we present a distinctive solution with low-cost, power-efficient, and simple-device natures, which is an on-chip optical Nyquist-filtering (de)interleaver featuring sub-GHz resolution and a near-rectangular passband with 8% transition band. This unprecedented performance is provided by a simple photonic integrated circuit comprising a two-ring-resonator-assisted Mach-Zehnder interferometer, which features high circuit compactness using high-index-contrast Si3N4 waveguide, while showing sub-picosecond optical delay accuracy enabling full C-band coverage with more than 160 effective free spectral ranges of 25 GHz across a bandwidth over 4 THz. Such devices show clear potential for chip-scale realization of N-WDM transceivers and ROADMs.