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Algorithms usher in a new era for telecom

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DOUGLAS FARMER, SENIOR EDITORSingle-mode optical fibers were a boon when they were introduced in the telecommunications industry 50 years ago, due to their ability to transmit data over extended distances with minimal degradation. Now, advanced multimode optical fibers — which can simultaneously send images and their larger amounts of related data over the line — are affecting the way a variety of industries do business. Multimode optical fibers offer multiple spatial channels in the same fiber conduit. This allows for the transference of not only binary signals but also analog (grayscale) images. Thanks to a capacity to support independent channels — otherwise known as spatial fiber modes — multimode fibers have been able to deliver increasingly complex information.

Up to now, the question has been how to reconstruct it at the other end.

The answer can be found in deep neural networks (DNNs), the subject of this edition’s cover story. Eirini Kakkava, Babak Rahmani, Christophe Moser, and Demetri Psaltis examine how DNNs — essentially, complex algorithms — can be trained to reconstruct or organize various kinds of images, based on amplitude or phase features and the corresponding speckle pattern after propagation through the fiber lines. The relevant data set is thus captured. This progress has profound implications for industries ranging from optical computing and augmented reality to medical instrumentation. Learn more here.

Elsewhere in this edition, Stuart Thomson expounds on the optically pumped terahertz molecular laser, which was first demonstrated at Bell Labs more than 50 years ago. Since those early days, the concept has been further advanced to deliver high-power terahertz radiation over a wide range of frequencies. This radiation lies on the edge of the microwave and infrared regions of the spectrum. The most common construction of an imaging system, which was used to excite a vapor of polar molecules to a higher energy state, involves a CO2 laser, the output of which is coupled into a molecular laser in a single unit. Using this technology, the spectral fingerprint of various materials can be identified spectroscopically. Read about the latest research and its applications here.

Finally, in “EPIC Insights,” Francesca Moglia relates how a wide variety of companies and industries have taken advantage of the combination of additive manufacturing with two-photon polymerization. This direct laser writing technology creates a light-matter interaction within a focused laser spot, which can then be moved through all three spatial dimensions of the light-sensitive material to produce 3D structures along the laser’s trajectory. This allows for the production of complex structures without the need for depositing new material. Discover how the business community is using this technique.

Enjoy the issue!

Summer 2021

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