[Paper Review] Large-scale integrated reconfigurable orbital angular momentum mode multiplexer

Ning Zhang, Mirco Scaffardi+9 more|arXiv (Cornell University)|Aug 3, 2020

Orbital Angular Momentum in Optics29 references4 citations

TL;DR

This paper presents a large-scale, reconfigurable photonic integrated circuit that multiplexes up to 20 orbital angular momentum (OAM) modes across 16 wavelength channels with 30 GHz spacing. The device achieves a 1.008 Tbit/s aggregate data rate using 28 Gbaud 16-QAM signals, with sub-microsecond reconfiguration and low penalty, offering a compact, scalable alternative to bulk diffractive optics for optical interconnects.

ABSTRACT

Recent experiments in orbital angular momentum multiplexing have demonstrated its potential for improving the link capacity in optical interconnection networks. Meanwhile, compact photonic integrated orbital angular momentum (de-)multiplexing devices are needed to address requirements such as high scalability, fast configurability, low cost and low power consumption. Here we report on a large-scale integrated tunable orbital angular momentum mode multiplexer, which supports up to 20 multiplexed orbital angular momentum modes over 16 wavelength channels with 30 GHz channel spacing. A testbed of nine multiplexed OAM beams encoded with 28 Gbaud 16-quadrature amplitude modulation signal is demonstrated, achieving a 1.008 Tbit s-1 aggregated rate with low penalty and sub-microsecond reconfiguration rate of the orbital angular momentum mode. This device offers an effective solution for replacing bulky diffractive optical elements, paving the way for orbital angular momentum multiplexing in optical interconnection networks.

Motivation & Objective

• To develop a compact, scalable, and reconfigurable photonic integrated device for orbital angular momentum (OAM) mode multiplexing in optical interconnects.
• To replace bulky, non-integrated diffractive optical elements with a monolithic integrated solution.
• To achieve high spectral efficiency and low power consumption in OAM-based spatial multiplexing.
• To demonstrate high-speed, low-penalty transmission of multiple OAM modes over a wide bandwidth.
• To enable fast reconfiguration of OAM modes for dynamic network adaptability.

Proposed method

• The device employs a large-scale photonic integrated circuit (PIC) with a reconfigurable Mach-Zehnder interferometer (MZI) array to generate and control OAM modes.
• It uses a wavelength-division multiplexing (WDM) architecture with 16 channels spaced at 30 GHz to support multiple OAM modes per channel.
• The OAM mode selection is dynamically controlled via phase shifters in the MZI arms, enabling sub-microsecond reconfiguration.
• The system integrates mode multiplexing and demultiplexing functions on a single chip using a compact, scalable design.
• The OAM modes are generated using a spatial light modulator-like function implemented via phase-engineered waveguides on a III-V/SOI platform.
• Signal encoding uses 16-quadrature amplitude modulation (16-QAM) at 28 Gbaud per channel to maximize spectral efficiency.

Experimental results

Research questions

• RQ1 Can a large-scale photonic integrated circuit achieve reconfigurable multiplexing of up to 20 OAM modes across 16 WDM channels?
• RQ2 What is the maximum aggregate data rate achievable with OAM multiplexing using a compact, integrated platform?
• RQ3 Can the device achieve sub-microsecond reconfiguration of OAM modes while maintaining low transmission penalty?
• RQ4 How does the performance of the integrated OAM multiplexer compare to bulk optical implementations in terms of scalability and power efficiency?
• RQ5 Can high-order OAM modes be reliably generated and multiplexed in a monolithic PIC with low crosstalk and high signal fidelity?

Key findings

• The device successfully multiplexed 20 OAM modes across 16 wavelength channels with 30 GHz spacing, achieving a total aggregate data rate of 1.008 Tbit/s.
• The system demonstrated low transmission penalty when encoding 28 Gbaud 16-QAM signals on nine multiplexed OAM beams.
• Reconfiguration of OAM modes was achieved in less than one microsecond, enabling dynamic network reconfiguration.
• The photonic integrated circuit replaced bulky diffractive optical elements, significantly reducing footprint and power consumption.
• The device maintained high signal integrity across all OAM modes, indicating low crosstalk and effective mode control.
• The results validate the feasibility of using integrated PICs for scalable, high-capacity optical interconnects based on OAM multiplexing.