Compact 4 × 4 multi-mode interferometer-based silicon photonics switch unit with thermal crosstalk mitigation

We propose a compact 4 × 4 multi-mode-interferometer (MMI)-based silicon photonics (SiPh) switch unit with thermal crosstalk resiliency. The thermal crosstalk resiliency is achieved via genetic algorithm (GA) optimization for obtaining the bias condition of each phase shifter in the MMI-based photonics switch unit. Experimental results revealed that an extinction ratio (ER) improvement of >17.5 dB can be achieved after the GA optimization. Additionally, the calibrated operating bias voltage condition remains stable for over three weeks as evaluated by experiment. In this proof-of-concept demonstration, each channel under test can successfully support > 80 Gbit/s orthogonal frequency-division multiplexing (OFDM) data rate and meets the hard-decision forward error correction (HD-FEC) threshold. We also discuss how the proposed scheme can be applied to a larger MMI optical switch. The proposed compact design can enable large-scale SiPh photonics switch realization needed for the optical neural network and artificial intelligence (AI) applications.