Silicon-Based MZI-Embedded Microring Array With Hitless and FSR-Alignment-Free Wavelength Selection

We demonstrate a silicon-based Mach-Zehnder interferometer (MZI)-embedded microring array consisting of four wavelength channels. The embedded MZI in each microring resonator (MRR) works as an ON/OFF key of the resonance, and can offer larger operating wavelength range. The footprint of the core elements is only $180.6\,\,\mu \text{m}\,\,\times 476.1\,\,\mu \text{m}$ . The transmission performances of four wavelength channels keep with good consistency within a 35.2-nm-wide wavelength range. The insertion loss of each channel is less than 3.05 dB. Its rising response time of the ON/OFF status transition is about $4.8~\mu \text{s}$ . Moreover, since the array does not require the free spectral range (FSR)-alignment and the on-chip thermal crosstalk is slight, the hitless wavelength selection can be realized simply without any electronic control assistance. Our experiment results indicate that such compact, and scalable array with the function of easily-implemented hitless wavelength selection may provide another solution for large-scale wavelength division multiplexing (WDM) network.