One limitation of glass fiber optics is the problem of transmitting high-energy laser beams. These attempts usually damage the glass fibers, which in turn scatter the laser beam outside the fibers. No wonder scientists have been working for some time to create an optical fiber completely devoid of fiberglass.
Researchers from the University of Maryland (UMD) Departments of Physics and Electrical and Computer Engineering have just introduced a fiber-optic cable that operates with air instead of glass fibers inside the wire. Most importantly, in this way it was practically possible to remove the aforementioned limitations without any loss in productivity.
Optical fiber, or rather, an antenna waveguide
To efficiently transmit information over an air-filled optical fiber, the scientists added a device to the cable that emits ultrashort laser pulses, which somehow create a waveguide within the cable itself. This pulse creates a ring of high-intensity light, which, as it travels, heats the air molecules it encounters, creating a ring of warmer, less dense air surrounding a core of unchanging air in the center. At the boundary of these two media, the information-carrying light ray is refracted, just as it is in a glass optical fiber. The advantage of this solution is the ability to transmit high-energy laser beams.
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In early 2023, scientists published a scientific paper describing tests that were able to create optical waveguides up to 50 meters long. Such a waveguide exists for a few tens of milliseconds, but during this time it allows you to transmit information. After this time, the heated air loop returns to the ambient temperature. Surprisingly, a single watt laser is enough to produce these rings. The profit is huge, as it allows the transmission of laser beams with a power of up to one megawatt.
In the first tests, the scientists used pulses emitted from the laser every 100 milliseconds to generate the waveguide. The problem is that the waveguide it was created with dissipated after 30ms. Then, for another 70 milliseconds, the laser beam was scattering along with the data. in The latest paper is published in the journal Optica The researchers used laser emitting pulses every 1 millisecond to create the waveguide. As a result, the light tunnel remained unchanged, because subsequent pulses did not allow it to cool. Thanks to this, the laser beam with the data transmitted through it was not subjected to any scattering.
The researchers point out that waveguides that are in the range of kilometers are wider. This, in turn, means that the cooling of this waveguide is slower, so a laser with a pulse generation frequency of less than 1000 Hz will be sufficient to maintain it. Everything indicates that maintaining atmospheric waveguides should be relatively easy with current technology. So it may turn out that optical fiberglass will gradually be replaced by pneumatic waveguides.
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