Ultra‐High Bandwidth Density and Power Efficiency Chip‐To‐Chip Multimode Transmission through a Rectangular Core Few‐Mode Fiber

Abstract Optical interconnects have emerged as promising solutions for assisting electrical interconnects in short‐reach scenarios, where high bandwidth density and energy efficiency are of particular importance. Mode‐division multiplexing (MDM), capable of enhancing the bandwidth density and energy efficiency of optical systems, has drawn tremendous interest. However, the chip‐to‐chip MDM optical interconnects are impeded by the multimode chip‐fiber interfaces, where the transverse modes on the MDM chip mismatch with the linear polarization modes in the circular core few‐mode fiber (CCF). Moreover, the high differential group delays (DGDs) of a conventional CCF make the digital signal processing (DSP) computation complex thus consuming high power. To overcome these bottlenecks, a new multimode coupling solution based on a rectangular core few‐mode fiber with ultra‐low DGDs and an integrated multimode coupler is proposed. Based on this coupling scheme, a chip‐to‐chip MDM transmission experiment is performed on the TE 00 , TM 00 , TE 10 , and TM 10 modes, and the highest bandwidth density of 19.4 Tb s mm −1 is realized at the chip facet. The DSP power consumption is ≈6% of a conventional CCF‐based system. It is believed that this work will pave the way for ultra‐compact, high density, low cost, and low computation‐complexity optical interconnects, such as data centers, cloud computing, and telecommunications.