Tunable ring-assisted MZI interleavers for CWDM applications

This paper proposes a ring-assisted Mach–Zehnder interferometer (RAMZI) design for filtering odd and even channels in coarse wavelength division multiplexing systems. The interleaver design is scalable and can be used in 1×4 or 1×8 multiplexers/demultiplexers. Device fabrication was carried out using GlobalFoundries’ state-of-the-art monolithic silicon photonics process. Thermo-optic phase shifters were incorporated in the MZI arm to compensate for any fabrication variations, resulting in a nearly ideal response. Additionally, optimized bent-coupler designs were implemented to achieve high coupling, yielding a uniform 1 dB channel bandwidth of ∼19.6nm and crosstalk of ∼−12dB across the entire O-band. These parameters can be further improved by optimizing the coupling coefficient between the ring and the MZI arm. The interleaver response was measured across eight dies and demonstrated consistent performance when optimally operating the thermo-optic phase shifters. The proposed RAMZI is a promising candidate for CWDM systems due to its compact footprint and reconfigurability.