Researchers from Bell Laboratories in New Jersey have discovered a method to improve data speeds using twin, mirrored beams of light to strengthen data signal quality over longer distances.
Typical fiber optic cables use a single beam of light to transmit information and are limited in power and consequentially, distance. While larger distances require more power to transmit across, high power transmissions using light interact more with the material of the fiber optic cable, which can add noise to the beam and affect the ease and clarity with which data can be transmitted.
However, lead by Dr. Xiang Liu of Bell Laboratories, the research team sent a signal of 400Gb/s—four times faster than any currently available commercial speeds—down a single 12,800 km fiber optic cable using a mirrored pair of light beams. To date, trans-oceanic cables as long as 6,000 km have been used to transmit data.
The team employed a technique known as phase conjugation to “remove” the noise gathered during transmission using the inverse of the incoming waves, Liu said. However, while the concept of using phase conjugation to remove noise in data transmitted via fiber link is not new, current techniques involve installing devices at certain, possibly inconvenient, points along the cables—even in the middle of the ocean.
“Sometimes you may send data from London to New York, sometimes you may send it from London to Paris. The links are changing and you cannot keep sending people to the middle of the link,” Liu told BBC News.
To combat this issue, Liu and his colleagues instead used a pair of phase-conjugate light beams, each carrying the same data. During transmission, each beam gathers noise, essentially the mirror image of one another.
“At the receiver, if you superimpose the two waves, then all the distortions will magically cancel each other out, so you obtain the original signal back,” he said.
With the ability to undo the noise on the beams, the power, and distance, of fiber optic transmission could be drastically increased. The new phase conjugation method can also allow data to transmit at higher speeds, since less repetition of information is needed in a given beam for error correction.
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