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Optical Vortexes Could Help Meet Network Traffic Demands of Tomorrow

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TOKYO, March 14, 2019 — A multiplexer/demultiplexer module based on an optical vortex, built by scientists at Tokyo Institute of Technology, could be used to strengthen optical networks so they can meet increasingly heavy traffic demands.

Using optical vortexes for optical communications, Tokyo Institute of Technology.

The multiplexing/demultiplexing module fabricated (a,d) employs a property of light called the optical vortex to transmit and receive multiple signals simultaneously through a shared optical medium. The required light waves with different optical vortexes are generated using a combination of a star coupler (b) and an optical-vortex generator (c). Courtesy of the Optical Networking and Communication Conference & Exhibition 2019.

The Tokyo Tech team developed an optical-vortex multiplexer/demultiplexer using vertically curved silicon waveguides. Multiplexing/demultiplexing with the lowest crosstalk of 23 decibels was demonstrated for five multiple optical vortexes.

To encode signals into light waves with different optical vortexes and then transmit them, the researchers first required circuitry for both the multiplexing and demultiplexing operations. They designed and fabricated an orbital angular momentum (OAM) multiplexing/demultiplexing module that was able to take five independent signals as input. Using a combination of two tiny circuit structures called a star coupler and an optical-vortex generator, the researchers gave each of the five signals a unique OAM. The five signals were packed into a single output signal and a receiver circuit was used to execute the multiplexing operation in reverse (demultiplexing), resulting in output of five independent signals.

The application of the optical vortex for signal multiplexing shows potential, according to the team. “The optical vortex carries the orbital angular momentum of light and can be used to multiplex signals by assigning each signal to a light wave of different momentum,” said professor Tomohiro Amemiya.

The research was presented at the Optical Fiber Communication Conference, March 3-7, 2019, in San Diego, Calif. (https://doi.org/10.1364/OFC.2019.M1C.7).

Photonics.com
Mar 2019
GLOSSARY
coherent communications
A fiber optic communications system that works on the principles of homodyning or heterodyning. The transmitting laser produces an optical wave that is modulated in amplitude, phase or frequency by the signal; at the receiver end, the incoming signal is mixed with a laser beam tuned at or near the wavelength of the transmitter (a local oscillator) and downconverted in detection to the radio-wave domain for further signal processing. Coherent transmission is expected to increase sensitivity more...
multiplexing
The combination of two or more signals for transmission along a single wire, path or carrier. In most optical communication systems this is referred to as wavelength division multiplexing, in which the combination of different signals for transmission are imbedded in multiple wavelengths over a single optical channel. The optical channel is a fiber optic cable or any other standard optical waveguide.
coherent communicationsoptical networksoptical vortexorbital angular momentummultiplexingResearch & TechnologyeducationAsia-PacificCommunicationsTokyo Institute of Technologyfiber optics

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