Error-Free Three-Dimensional Multimode Crossover Graded-Index Polymer Waveguides for Board-Level Optical Circuitry

Abstract

In this paper, we experimentally introduce a low-loss

3-dimensional (3D) symmetric crossover multimode optical waveguides

realized with parabolic graded-index (GI) profiles using the

Mosquito method. This compact crossover multimode waveguide

is comprised of two S-bend core groups (6 Ch. × 6 Ch.), where

the last six cores cross over the first six cores, maintaining a

height gap at the crossover section to avoid the smudging from

needle scan. The suitable height gap for this crossover multimode

structure is 0.7 mm. The insertion loss of this multimode crossover

waveguide is 1.64 dB at 850 nm wavelength. The insertion losses of

this multimode crossover waveguide are compared with separately

fabricated 3D S-bend waveguides, and it indicates that multimode

crossover structures do not exhibit remarkable excess loss. The

interchannel crosstalk of this waveguide is less than −45 dB.

This crossover multimode waveguide demonstrates sharply open

optical and electrical eye diagrams and transmits error-free data at

26 Gb/s.