3 × 40 Gbit/s All-Optical Logic Operation Based on Low-Loss Triple-Mode Silicon Waveguide

Information capacity of single-mode fiber communication systems face fundamental limitations imposed by optical nonlinearities. Spatial division multiplexing (SDM) offers a new dimension for upgrading fiber communication systems. Many enabling integrated devices, such as mode multiplexers and multimode bending with low crosstalk, have been developed. On the other hand, all-optical signal processing (AOSP) can avoid optical to electrical to optical (O–E–O) conversion, which may potentially allow for a low cost and green operation for large-scale signal processing applications. In this paper, we show that the system performance of AOSP can be pushed further by benefiting from the existing technologies developed in spatial mode multiplexing (SDM). By identifying key technologies to balance the impacts from mode-dependent loss, crosstalk and nonlinearities, three-channel 40 Gbit/s optical logic operations are demonstrated using the first three spatial modes in a single multimode waveguide. The fabricated device has a broadband four-wave mixing operation bandwidth (>20 nm) as well as high conversion efficiency (>−20 dB) for all spatial modes, showing the potential for a large-scale signal processing capacity with the combination of wavelength division multiplexing (WDM) and SDM in the future.