Abstract
Mode-division multiplexing (MDM) is an attractive solution for future on-chip networks to enhance the optical transmission capacity with a single laser source. A mode-division reconfigurable optical add/drop multiplexer (ROADM) is one of the key components to construct flexible and complex on-chip optical networks for MDM systems. In this paper, we report on a novel scheme of mode-division ROADM with mode-selective silicon photonic MEMS (micro-electromechanical system) switches. With this ROADM device, data carried by any mode-channels can be rerouted or switched at an MDM network node, i.e., any mode could be added/dropped to/from the multimode bus waveguide flexibly and selectively. Particularly, the design and simulation of adiabatic vertical couplers for three quasi-TE modes (TE0, TE1, and TE2 modes) based on effective index analysis and mode overlap calculation method are reported. The calculated insertion losses are less than 0.08 dB, 0.19 dB, and 0.03 dB for the TE0 mode, TE1 mode, and TE2 mode couplers, respectively, over a wavelength range of 75 nm (1515–1590 nm). The crosstalks are below −20 dB over the bandwidth. The proposed device is promising for future on-chip optical networks with flexible functionality and large-scale integration.
Highlights
The explosive growth of data traffic passing through optical networks has emerged as a critical problem in optical communications [1]
mode-division multiplexing (MDM) appears attractive for future networks-on-chip in computing because it does not require an array of lasers of precise wavelengths like Wavelength-division multiplexing (WDM)
Typical Mode-selective switches (MSSs) and mode-division reconfigurable optical add/drop multiplexer (ROADM) are realized with combined architectures of passive mode-divisionmultiplexers and space switches [23,24,25,26,27,28,29,30] or cascaded mode-selective ring resonators with bus waveguide taper transitions [31,32,33] that are subject to accumulated optical losses and crosstalks with large footprints owing to the requirement for combining various photonic components
Summary
The explosive growth of data traffic passing through optical networks has emerged as a critical problem in optical communications [1]. Wavelength-division multiplexing (WDM) was introduced as a breakthrough to provide high capacity data communications by allowing simultaneous transmissions of multiple wavelength channels in a single optical fiber [4,5]. Mode-division multiplexing (MDM) has emerged as a potential route to increase the data transmission capacity by utilizing the multiple spatial guided-modes in multimode waveguides, which can enhance the optical link capacity many folds using only a single wavelength source [7]. Typical MSSs and mode-division ROADMs are realized with combined architectures of passive mode-division (de)multiplexers and space switches [23,24,25,26,27,28,29,30] or cascaded mode-selective ring resonators with bus waveguide taper transitions [31,32,33] that are subject to accumulated optical losses and crosstalks with large footprints owing to the requirement for combining various photonic components. The total length for three couplers is short (less than 300 μm) and the device exhibits low insertion losses less than 0.08 dB for TE0 mode coupler, less than 0.19 dB for TE1 mode coupler, less than 0.03 dB for TE2 mode coupler over a wide bandwidth of 75 nm
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