# Arbitrarily routed mode-division multiplexed photonic circuits for dense integration

## TL;DR

This paper introduces highly compact, arbitrarily routed mode-division multiplexed photonic circuits using digitized meta-structures, enabling dense integration and high-speed data transmission with minimal chip area.

## Contribution

It presents the first MDM circuits based on digitized meta-structures with extremely small footprints and arbitrary routing capabilities.

## Key findings

- 3-mode bending radius of 3.9 μm
- Crossing footprint of 8x8 μm²
- 3x100 Gbit/s mode-multiplexed signals with low BER

## Abstract

Mode-division multiplexing (MDM) is becoming an enabling technique for large-capacity data communications via encoding the information on orthogonal guiding modes. However, the on-chip routing of a multimode waveguide occupies too large chip area due to the constraints on inter-mode cross talk and mode leakage. Very recently, many efforts have been made to shrink the footprint of individual element like bending and crossing, but the devices still occupy >10x10 um2 footprint for three-mode multiplexed signals and the high-speed signal transmission has not been demonstrated yet. In this work, we demonstrate the first MDM circuits based on digitized meta-structures which have extremely compact footprints. The radius for a three-mode bending is only 3.9 {\mu}m and the footprint of a crossing is only 8x8um2. The 3x100 Gbit/s mode-multiplexed signals are arbitrarily routed through the circuits consists of many sharp bends and compact crossing with a bit error rate under forward error correction limit. This work is a significant step towards the large-scale and dense integration of MDM photonic integrated circuits.

---
Source: https://tomesphere.com/paper/1812.06904