ABSTRACT
We investigate modal crosstalk in silicon photonic MDM-based interconnects using tapered multiplexers. Crosstalk from coherent optical interference originates from variation in the physical structure and alters the transmission link performance. Through simulations and experimental work, optical crosstalk as a function of wavelength is analyzed to understand its impact in MDM and MDM-WDM dual-multiplexing applications. The detrimental effects are validated in the frequency and time domains through fabricated MDM interconnects of various lengths. Results indicate modal crosstalk must be < -22 dB to maintain a BER of 10-12. The experimental methodology assesses the optical modal crosstalk's impact on the data, towards a mitigation approach to improve the payload signal integrity and enable system-level optimization such as channel wavelength allocation.
ABSTRACT
We propose and experimentally demonstrate a reconfigurable mode division multiplexing (MDM) silicon photonics three-mode switch (3MS) in C-band using a 120° optical hybrid based unbalanced Mach-Zehnder interferometer (UMZI) and Ti/W metal heater phase-shifter. The novel 3MS enables reconfigurable switching of the first three transverse electric (TE) modes by exploiting the relative phase difference of the 120° hybrid. A proof-of-concept realization of this 3MS demonstrates <12.0 µs switching time and >12.3 dB switching extinction ratio at 1560 nm wavelength with 94.8 mW average heater power consumption. Simultaneous (de)multiplexing and switching of 10 Gb/s non-return-to-zero (NRZ) PRBS31 optical payload over three spatial channels experimentally demonstrates 3 ×10 Gb/s aggregated bandwidth. Open eye diagrams in all output channels with >9.6 electrical signal-to-noise ratio (SNR) exhibits reliable data transmission. The 3MS has potential applications in MDM silicon photonics interconnects for the implementation of high throughput switch matrix.
ABSTRACT
A novel mode selecting switch (MSS) is experimentally demonstrated for on-chip mode-division multiplexing (MDM) optical interconnects. The MSS consists of a Mach-Zehnder interferometer with tapered multi-mode interference couplers and TiN thermo-optic phase shifters for conversion and switching between the optical data encoded on the fundamental and first-order quasi-transverse electric (TE) modes. The C-band MSS exhibits a >25 dB switching extinction ratio and < -12 dB crosstalk. We validate the dynamic switching with a 25.8 kHz gating signal measuring switching times for both TE0 and TE1 modes of <10.9 µs. All channels exhibit less than 1.7 dB power penalty at a 10-12 bit error rate, while switching the non-return-to-zero PRBS-31 data signals at 10 Gb/s.
