Silicon Photonic Integrated Devices for Space-Division Multiplexing

Space-division multiplexing (SDM) is seen as a promising technique to further enhance the capacity of optical transmission systems. In SDM, different spatial paths are used as parallel channels to transmit independent data streams. Different orthogonal modes inside a multimode fiber can also be such spatial paths.

This thesis explores devices on silicon photonic chips for the use of SDM, especially for directly coupling from a chip into different modes of few-mode fibers. The use of silicon photonics can make such devices compact, reliable, low-priced and capable of being integrated with other silicon photonic devices.

First, a concept of a vertical off-chip emitting device that uses silicon oxynitride waveguides and total internal reflection is presented. Calculations about its coupling are made and first fabrication results are shown. This device is designed to have a wide-bandwidth operation. Furthermore, the multiplexing and demultiplexing of data into different linearly polarized modes of a few-mode fiber using two silicon photonic mode multiplexers is experimentally demonstrated.

This presents the capability of chip-to-chip operation of mode-division multiplexing. Finally, the design, fabrication and characterization of a mode multiplexer that is capable of coupling to different orbital angular momentum (OAM) modes of an OAM fiber is comprehensively described. The successful coupling to OAM fiber modes with topological charges of L = 5, 6, 7 is demonstrated.