Abstract
Mode-division-multiplexing (MDM) can increase the total on-chip transmission capacity. Silicon-on-insulator (SOI) based MDM multiplexer (MUX) and demultiplexer (DEMUX) using asymmetrical directional couplers (ADCs) are promising; however, they usually require long coupling lengths for mode conversion. Here, for the first time up to the authors’ knowledge, we propose, simulate, fabricate and demonstrate a size reduced SOI based $4 \times 4$ MDM MUX and DEMUX using enhanced evanescent-wave coupling (EEC). Here, we illustrate by experiments and numerically analyses that by size reducing the ADC access coupling region, evanescent-wave coupling is enhanced. Significant coupling length reduction of ~80 % can be achieved, while similar MDM MUX and DEMUX performance can be observed. To experimentally evaluate the broadband and high-speed transmission operations of the proposed device, 48 wavelength channels each modulated by >60 Gbit/s orthogonal frequency division multiplexing (OFDM) signals are successfully mode multiplexed and demultiplexed, achieving a transmission capacity of 11.73 Tbit/s.
Highlights
The bandwidth demands are increasing very rapidly due to the popularity of video-based and cloud-based services
In the proposed size reduced evanescent-wave coupling (EEC) mode division multiplexing (MDM) device, the coupling lengths are significantly reduced by 82.2 %, 80.8 % and 76.6 % in CH2, CH3 and channel 4 (CH4) respectively; while the bus waveguide widths are reduced by 20.6 %, 20.1% and 19.1%, respectively
Different DEMUX outputs are measured by using an optical spectrum analyzer (OSA)
Summary
The bandwidth demands are increasing very rapidly due to the popularity of video-based and cloud-based services. Through phase-matching the access and bus waveguides, fundamental mode and higher order modes can be converted efficiently By using this ADCbased MDM MUX and DEMUX, several high throughput demonstrations were reported [27,28,29]. These MDM MUX and DEMUX required relatively long coupling lengths in the directional coupler section for mode conversion. For the first time up to the authors' knowledge, we propose, simulate, fabricate and demonstrate a size reduced semiconductor-on-insulator (SOI) based 4 × 4 mode MUX/DEMUX using enhanced evanescent-wave coupling (EEC). Transmission capacity of 11.73 Tbit/s is achieved, and the hard-decision forward-error-correction (HD-FEC) threshold (bit-error-ratio, BER ≦ 3.8 × 10-3) is satisfied
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