Abstract
Multimode optical switch is a key component of mode division multiplexing in modern high-speed optical signal processing. In this paper, we introduce for the first time a novel 2 × 2 multimode switch design and demonstrate in the proof-of-concept. The device composes of four Y-multijunctions and 2 × 2 multimode interference coupler using silicon-on-insulator material with four controllable phase shifters. The shifters operate using thermo-optic effects utilizing Ti heaters enabling simultaneous switching of the optical signal between the output ports on four quasi-transverse electric modes with the electric power consumption is in order of 22.5 mW and the switching time is 5.4 µs. The multimode switch exhibits a low insertion loss and a low crosstalk below − 3 dB and − 19 dB, respectively, in 50 nm bandwidth in the third telecom window from 1525 to 1575 nm. With a compact footprint of 10 µm × 960 µm, this device exhibits a relatively large width tolerance of ± 20 nm and a height tolerance of ± 10 nm. Furthermore, the conceptual principle of the proposed multimode switch can be reconfigurable and scalable in multifunctional on-chip mode-division multiplexing optical interconnects.
Highlights
Multimode optical switch is a key component of mode division multiplexing in modern high-speed optical signal processing
Since each mode is an independent channel potentially makes a myriad of single channel capacity for optical communications systems and optical interconnects when it combines with the wavelength division multiplexing (WDM) technique[6,7]
In order to couple the switch with the WDM–mode division multiplexing (MDM) system, grating couplers[49,50] or edge-couplers[51,52] are required to couple high-order modes from the few-mode fibers to the silicon waveguides for realizing the functionality of a wavelength division multiplexed few-mode fiber switch
Summary
Multimode optical switch is a key component of mode division multiplexing in modern high-speed optical signal processing. The mode division multiplexing (MDM) technique has been considered as a promising solution for increasing communication bandwidth In this method, the data was carried out using spatial orthogonality of guided modes. Zhang et al have successively demonstrated a silicon 2 × 2 four-mode dual polarization optical s witch[27] and a silicon 1 × 2 four-mode dual polarization optical s witch[28] Both of those structures need asymmetric adiabatic couplers for realizing the (de)multiplexing functionalities in a multimode bus waveguide and Mach–Zehnder interferometers (MZI) for switching operation leading a large footprint and relatively complicated mechanism. Some other proposals for multimode switches either based on multiplexers/demultiplexers and waveguide crossing structures following Benes topologies[29,30] or use lots of relatively complicated microring resonators and waveguide crossing elements
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