Imagine a computer that does not rely only on electronics but uses light to perform tasks faster and more efficiently. Collaboration between two research teams from Tampere University in Finland and Université Marie et Louis Pasteur in France, have now demonstrated a novel way for processing information using light and optical fibers, opening up the possibility to build ultra-fast computers.
The study performed by postdoctoral researchers Dr. Mathilde Hary from Tampere University and Dr. Andrei Ermolaev from the Université Marie et Louis Pasteur, Besançon, demonstrated how laser light inside thin glass fibers can mimic the way artificial intelligence (AI) processes information. Their work has investigated a particular class of computing architecture known as an Extreme Learning Machine, an approach inspired by neural networks.
"Instead of using conventional electronics and algorithms, computation is achieved by taking advantage of the nonlinear interaction between intense light pulses and the glass," Hary and Ermolaev explain.
Traditional electronics approaches their limits in terms of bandwidth, data throughput and power consumption. AI models are growing larger, they are more energy-hungry, and electronics can process data only up to a certain speed. Optical fibers on the other hand can transform input signals at speeds thousands of times faster and amplify tiny differences via extreme nonlinear interactions to make them discernable.
Towards efficient computing
In their recent work, the researchers used femtosecond laser pulses (a billion times shorter than a camera flash) and an optical fiber confining light in an area smaller than a fraction of human hair to demonstrate the working principle of an optical ELM system. The pulses are short enough to contain a large number of different wavelengths or colors. By sending those into the fiber with a relative delay encoded according to an image, they show that the resulting spectrum of wavelengths at the output of the fiber transformed by the nonlinear interaction of light and glass contains sufficient information to classify handwritten digits (like those used in the popular MNIST AI benchmark). According to the researchers the best systems reached an accuracy of over 91%, close to the state of art digital methods, in under one picosecond.
What is remarkable is that the best results did not occur at maximum level of nonlinear interaction or complexity; but rather from a delicate balance between fiber length, dispersion (the propagation speed difference between different wavelengths) and power levels.
"Performance is not simply matter of pushing more power through the fiber. It depends on how precisely the light is initially structured, in other words how information is encoded, and how it interacts with the fiber properties," says Hary.
By harnessing the potential of light, this research could pave the way towards new ways of computing while exploring routes towards more efficient architectures.
"Our models show how dispersion, nonlinearity and even quantum noise influence performance, providing critical knowledge for designing the next generation of hybrid optical-electronic AI systems," continues Ermolaev.
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