Wavelength division multiplexers can convert multimode

Wavelength division multiplexers can combine or separate multiple optical signals across different wavelengths and spatial modes using multimode interference waveguides.

How Multimode WDM Works

A multimode wavelength division multiplexer (WDM) is designed to handle optical signals that propagate in multiple spatial modes within a waveguide. Each input beam can carry several optical signals at different center wavelengths, and the multiplexer combines these into a single output beam while preserving the mode structure. Conversely, a demultiplexer separates a multimode input beam into multiple output beams, each corresponding to a specific wavelength and mode (WO2023061376A1).

Key Components

Multimode Interference (MMI) Waveguides: These waveguides exploit dispersive self-imaging, allowing multiple input signals to interfere constructively and form distinct output images corresponding to different wavelengths and modes. Angled Multimode Interferometers (AMMI): AMMI structures improve wavelength selectivity and mode separation, enabling hybrid multiplexing for both WDM and mode-division multiplexing (MDM). Asymmetric Directional Couplers (ADCs): These couplers facilitate efficient coupling between input/output waveguides and the MMI waveguide, maintaining low insertion loss and minimal crosstalk.

Advantages and Applications

Increased Data Capacity: By combining WDM with MDM, multimode WDM devices significantly enhance the total transmission capacity of optical fibers beyond single-mode WDM systems. Compact Integration: Silicon-on-insulator (SOI) platforms allow compact on-chip implementations of mode converters and demultiplexers, with low insertion loss (