Lossless 1×4 Silicon Photonic ROADM based on a Monolithic Integrated Erbium Doped Waveguide Amplifier on a Si3N4 platform

During the past years, incorporating ptical Circuit Switches (OCS) in high-bandwidth optical interconnects has outlined the critical challenges of achieving ultra-low fiber-to-fiber losses (FtF) and constantly decreasing costs for Photonic Integrated Circuits (PICs). This work aims to simultaneously satisfy both the low-loss and low-cost requirements by bringing two of the most successful example-technologies in the history of optics, i.e. EDFAs and ROADMs to a common Si<sub>3</sub>N<sub>4</sub> platform. In particular, the proof-of-concept operation of a lossless four-port Silicon Photonic (SiPho) ROADM is experimentally presented for the first time based on two PIC prototypes on a Si<sub>3</sub>N<sub>4</sub> platform, including a monolithic-integrated 5.9cm-long spiral Al<sub>2</sub>O<sub>3</sub>:Er<sup>3+</sup> Erbium Doped Waveguide Amplifier (EDWA) with 15 dB signal enhancement capabilities and a lattice MZI-interleaver ROAM layout with 100 GHz channel spacing. Considering an ultra-low 2.55 dB FtF loss of the ROADM along with 0.5 dB loss for each of the two coupling-interfaces between the Si<sub>3</sub>N<sub>4</sub> and Al<sub>2</sub>O<sub>3</sub>:Er<sup>3+</sup> waveguide layers, a cumulative loss of 3.55 dB is obtained, which can be compensated by the 3.6 dB net gain provided by the EDWA to four incoming WDM signals of -1.7 dBm/channel. Lossless wavelength-routing operation is validated at up to 240 Gb/s WDM (460Gb/s) data traffic, while the cascadability of the proposed device is benchmarked in a realistic two-stage optical bus topology with 10 km single mode fiber that selectively routes 425Gb/s WDM data channels to any of its eight Drop output ports. This work forms the first demonstration of lossless ROADM operation exclusively on SiPho technology, highlighting a promising roadmap for large scale SiPho switching matrices and more complex PICs co-integrated with EDWAs.