[Paper Review] Integrated switch for simultaneous mode-division multiplexing (MDM) and wavelength-division multiplexing (WDM)

Brian Stern, Xiaoliang Zhu+5 more|arXiv (Cornell University)|Feb 16, 2015

Optical Network Technologies55 references3 citations

TL;DR

This paper presents an integrated photonic switch on a silicon chip that enables simultaneous mode-division multiplexing (MDM) and wavelength-division multiplexing (WDM) by individually routing spatial modes using single-mode components. It achieves low crosstalk (< -20 dB), bit-error rates below 10⁻⁹, and power penalties under 2.4 dB when routing four 10 Gbps channels simultaneously, demonstrating a scalable solution for high-bandwidth on-chip optical networks.

ABSTRACT

Leveraging the spatial modes of multimode waveguides using mode-division multiplexing (MDM) on an integrated photonic chip allows unprecedented scaling of bandwidth density for on-chip communication. Switching channels between waveguides is critical for future scalable optical networks, but its implementation in multimode waveguides must address how to simultaneously control modes with vastly different optical properties. Here we present a platform for switching signals between multimode waveguides based on individually processing the spatial mode channels using single-mode elements. Using this wavelength-division multiplexing (WDM) compatible platform, we demonstrate a 1x2 multimode switch for a silicon chip which routes four data channels with low (

Motivation & Objective

• To address the challenge of routing multiple spatial modes in multimode waveguides while maintaining signal integrity.
• To enable simultaneous operation of mode-division multiplexing (MDM) and wavelength-division multiplexing (WDM) on a single photonic platform.
• To design a scalable, low-crosstalk switching architecture for on-chip optical interconnects using individual mode processing.
• To demonstrate high-speed, low-power, and low-error-rate operation across multiple channels in a single integrated device.

Proposed method

• The switch uses a platform that processes each spatial mode independently via single-mode waveguide components to enable selective routing.
• It leverages wavelength-division multiplexing (WDM) compatibility by assigning different wavelengths to different spatial modes for parallel transmission.
• A 1x2 switching configuration routes four data channels (two modes per waveguide, two wavelengths per mode) using integrated thermo-optic phase shifters.
• The design employs a Mach-Zehnder interferometer-based architecture to control mode-specific switching with low crosstalk.
• Each channel is routed separately and then combined at the output, minimizing interference between modes.
• The system is fabricated on a silicon-on-insulator (SOI) platform, enabling CMOS-compatible integration and high-density photonic circuits.

Experimental results

Research questions

• RQ1 Can a single integrated switch simultaneously manage multiple spatial modes and wavelengths in a multimode waveguide system with low crosstalk?
• RQ2 How can individual spatial modes in a multimode waveguide be selectively routed while preserving signal quality?
• RQ3 What is the crosstalk and bit-error rate performance when all four channels are routed simultaneously at 10 Gbps?
• RQ4 What power penalty is introduced when all channels are active compared to single-channel operation?
• RQ5 Can the switch maintain low error rates and high bandwidth efficiency in a scalable on-chip photonic network?

Key findings

• The switch achieves crosstalk below -20 dB across all four channels, indicating effective isolation between spatial modes.
• Bit-error rates are below 10⁻⁹ for all channels when routed individually at 10 Gbps, confirming high signal integrity.
• The power penalty for each channel is less than 1.4 dB when routed separately, indicating low signal degradation.
• When all four channels are simultaneously routed, the additional power penalty is less than 2.4 dB, demonstrating robust multi-channel operation.
• The system maintains low crosstalk and error performance under full-load conditions, validating its scalability for on-chip optical switching.
• The platform enables simultaneous MDM and WDM, offering a path to high-bandwidth, energy-efficient on-chip optical interconnects.