An Eight-Channel Hybrid Wavelength-/Mode-Division (De)multiplexer Based on LNOI Platform

Multi-dimensional multiplexing technology is pivotal for enhancing on-chip communication capacity. In this paper, we proposed and fabricated an 8-channel hybrid (de)multiplexer chip based on a lithium niobate on insulator (LNOI) platform, which can simultaneously implement mode-division multiplexing (MDM) and wavelength-division multiplexing (WDM). The proposed (de)multiplexer comprises a two-channel mode (de)multiplexer utilizing an asymmetric directional coupler (ADC) and a four-channel WDM (de)multiplexer employing a set of second-order microring resonator (MRR) arrays. To further increase the number of channels, the two ports of the mode demultiplexer are interconnected, thereby doubling the communication capacity while maintaining the same number of MRRs. Experimental results demonstrate that the device achieves intermode crosstalk below -10 dB with a multiplexing bandwidth of exceeding 50 nm. The adjacent channel crosstalk and the non-adjacent channel crosstalk of the multiplexer's eight channels are below -13 dB and -27 dB, respectively, over a free spectral range (FSR) from 1556 to 1562 nm. This research paves new avenues in the field of multi-dimensional multiplexing techniques on the LNOI platform.