3 min readNew Dynamic Dual-core Optical Fibre Enhances Data Processing, Better Sensing

is image demonstrates the structure of the dual-core nanomechanical optical fiber. Inside the fiber, two cores are shown suspended from above and below. This innovative structure enables the two cores to move and precisely respond to an external mechanical force, moving closer or further apart, depending on data transmission needs. Image: Optics Express

Washington, DC – Optical fibres –the backbone of the Internet–carry movies, messages, and music at the speed of light. But for all their efficiency, these ultrathin strands of pristine glass must connect to sluggish signal switches, routers, and buffers in order to transmit data.

Hoping to do away with these information speed bumps, researchers have developed a new, dual-core optical fibre that can perform the same functions just by applying a miniscule amount of mechanical pressure.

These new nanomechanical fibres, which have their light-carrying cores suspended less than 1 micrometer apart from each other, could greatly enhance data processing and also serve as sensors in electronic devices. The researchers describe their new fibre and its applications today in the Optical Society’s (OSA) open-access journal Optics Express.

“Nanomechanical optical fibres do not just transmit light like previous optical fibres,” says Wei H. Loh, deputy director of the EPSRC Centre for Innovative Manufacturing in Photonics and researcher at the Optoelectronics Research Centre, both at the University of Southampton, U.K. “Their internal core structure is designed to be dynamic and capable of precise mechanical motion. This mechanical motion, created by applying a tiny bit of pressure, can harness some of the fundamental properties of light to give the fibre new functions and capabilities.”

This innovation was achieved by fabricating fibres with two cores―the pathways that carry data in the form of light―that are close enough to each other to be optically coupled, a property of light by which a photon’s influence can extend beyond the fibre’s core, even though the light itself remains inside. By shifting the position of one of the cores by just a few nanometers, the researchers changed how strongly the light responded to this coupling effect.

If the coupling effect is strong enough, the light immediately jumps from one fibre to the other. “Think of having a train travelling down a two-track tunnel and jumping the tracks and continuing along its way at the same speed,” explains Loh. The flexible suspension system of the fibre easily responds to the slightest bit of pressure, bringing the two cores closer together or moving them apart, thereby controlling when and how the signals hop from one core to the other, reproducing, for the first time, the function of an optical switch inside the actual fibre.

This same capability may also enable optical buffering, which, according to the researchers, has been very hard to achieve. “With our nanomechanical fibre structure, we can control the propagation time of light through the fibre by moving the two cores closer together, thereby delaying, or buffering, the data as light,” says Loh. Buffers are essential when multiple data streams arrive at a router at the same time; they delay one stream so another can travel freely.

To create the new fibres, the researchers heated and stretched a specially shaped tube of optical glass with a hollow centre containing two cores suspended from the inside wall. The fibres maintain this original structure as they are drawn and stretched to the desired thickness.

According to the researchers, this is the first time that nanomechanical dual-core fibres have been directly fabricated. Other types of multicore fibres have been fabricated previously, but their cores are encased in glass and mechanically locked. This previous design meant that routing, switching, or buffering data involved taking the light out of the optical fibre for processing in the electronic domain before reinsertion back into the fibre, which is cumbersome and costly. “An implication of our work is that we would integrate more of these functions within the fibre backbone,” says Loh, “through the introduction of MEMS (microelectromechanical systems) functionality in the fibres.”

Since the new process utilizes traditional fibre optic manufacturing techniques, it’s possible to create dual-core fibres that are hundreds of meters to several kilometres long, which is essential for telecommunications.

Loh and his colleagues also expect this introduction of MEMS functionality into the optical fibre to have implications in other fields, such as sensing. “Nanomechanical fibres could one day take the place of silicon-based MEMS chips, which are used in automobile sensors, video game controllers, projection displays, and other every-day applications,” observes Loh. Because the fibres are so sensitive to pressure and can be readily drawn to very long lengths, they also could be integrated into bridges, dams, and other buildings to signal subtle changes that could indicate structural damage.

The next step of their research is to test the fibres at longer lengths and to enhance the precision with which they perform switching and other functions. The researchers hope that nanomechanical fibers could begin to enhance telecommunications and industrial systems within the next three to five years.


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