“Twisted” Light Could Dramatically Increase Fiber Bandwidth

Since they were first deployed by telephone companies in the 1970’s, fiber optic cables have become the gold standard for transmitting large quantities of data over long distances. Without fiber optic infrastructure, the Internet could not have become the technological marvel that it is today.

Fiber optics may have gotten us this far, but that doesn’t mean researchers have stopped looking for creative new ways to transmit even greater volumes of data around the globe. Conventional fiber optics can carry a great deal of information, but every technology has its limits.

“Twisted” Light Could Dramatically Increase Fiber BandwidthToday’s fiber optic cables use a series of different light wavelengths to transmit large quantities of data at once. This allows designers to use multiple wavelengths to transfer a whole lot of data across one cable. Each of these wavelengths acts as a different “channel” for data. Unfortunately, there are only so many different wavelengths that can be used in tandem at once. Eventually, channels that are on similar wavelengths will start leaking data into one another, reducing transfer efficiency and corrupting communications. With more and more data being transmitted across the Internet every day, this is likely to become increasingly problematic in the future.

That’s why scientists are working to overcome these limitations and increase the bandwidth potential of optical fibers.

One promising avenue of research involves manipulating light to impart a spiraling motion on photons that grants them “orbital angular momentum” (OAM). This type of momentum allows the photons to “orbit” around a central axis, rather than “spin” in a straight line. When we send light through conventional fiber optic cables, it modulates in linear waves. By “twisting” light, scientists hope to make it modulate in a circular pattern instead.

“Twisted” Light Could Dramatically Increase Fiber Bandwidth

So what are the benefits of circularly polarized light?

It all has to do with the way different wavelengths of light interact with one another. Whereas nearby linear wavelengths can easily interfere with one another other, circular beams of light with OAM can be laid on top of each other without interference. This unique property of twisted light with OAM could effectively eliminate the current bandwidth restrictions of conventional fiber optics.

Of course, harnessing the power of OAM is easier said than done.

To support OAM states, scientists need to develop a new kind of optical fiber that has a core with a low refractive index and an inner cladding with a high refractive index. This type of construction is basically the exact opposite of today’s optical fibers. The difference in the refractive index between core and cladding will also need to be more substantial, which means that the ideal material for the core would be air. Needless to say, creating optical fibers with cores made of air is, well, challenging.

The second step in creating OAM-compatible fiber optics is to create a new type of laser that distributes light in a spiral pattern. Scientists at the University at Buffalo are already making progress on this front. This month, the scientists unveiled a design for a vortex laser beam designed specifically for OAM applications.

The obstacles that face the scientists working on OAM-compatible fiber optics are significant, but not insurmountable. Given enough time, resources and ingenuity, these are solvable problems. And given the potential payoff, researchers aren’t likely to give up anytime soon. Someday, a transition to OAM-compatible optical fibers could transform the world in much the same way that the switch from copper to fiber optics did at the dawn of the Information Age.

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