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Researchers Propose a New Imaging Strategy for Multimode Optical Fibers

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Reviewed by Emily Henderson, B.Sc.Nov 21 2022

As far as light-guiding applications are concerned, multimode optical fibers (MMFs) are known to be universal hair-thin glass strands.

Their advancement has gone side-by-side with the massive growth in the rapid transmission of information worldwide. Also, the small footprint of MMFs makes them intriguing candidates for next-generation micro-endoscopes to provide optical microscopy deep into the body.

But the MMFs’ practical information capacity has been restricted by modal dispersion. This is a mechanism that tussles the spatial information propagating via MMFs. Hence, the direct broadcast of images happening via MMFs seems very difficult: an image projected onto one end is indistinctly scrambled by the time the light extends to the other end.

In the past few years, pioneering research has displayed how the optical scrambling attributable to MMFs could be quantified and ruined. Currently, a research group from the University of Exeter and Leibniz Institute of Photonic Technology have constructed this notion and suggested a new imaging plan known as optical inversion.

The Intelligent Computing journal reported the study on November 17^th, 2022.

The majority of imaging techniques demonstrated so far rely on raster-scanning or sequential pattern projection, essentially meaning that light is unscrambled one spatial mode at a time.

Dr. Unė Būtaitė, Study Lead Author, University of Exeter

Būtaitė added, “This currently precludes the delivery of wide-field imaging techniques through MMFs. For example, there is currently no way to conduct wide-field super-resolution imaging at the tip of an MMF— which would be a very desirable way to gain deeper understanding of biological processes inside the body.”

To defeat this problem, scientists suggest and design a passive optical device, discussed as an optical inverter.

Our inverter can be understood as a bespoke scattering medium, designed to be complementary to an MMF so as to undo its optical effects.

Dr. Unė Būtaitė, Study Lead Author, University of Exeter

The spatial information has been confused following the light emanating from the scene is propagated via MMF. However, the optical inverter tends to scramble the light in precisely the opposite direction to the fiber. This makes it possible to rectify the scene’s image in a passive manner and in an all-optical way in just a few nanoseconds.

Various scenarios were simulated to learn about the performance of the optical inverter design of the researcher. The outcomes display that an optical inverter exhibits the ability to obtain super-resolution imaging and single-shot wide-field imaging via MMFs.

Besides integrating optical memory effects into its design, the optical inverter could adapt in a dynamic manner to see via flexible fibers.

The key advantage of our concept is that it renders possible any form of wide-field microscopy at the tip of a hair-thin strand of MMF— which can potentially be loaded into a needle to view scenes deep inside the body.

Dr. David Phillips, Study Senior Author, University of Exeter

Phillips added, “This includes powerful new imaging techniques such as localization-based super-resolution imaging, along with other emerging forms of parallelized super-resolution microscopy, structured illumination microscopy, and single-objective light sheet microscopy. Furthermore, single-shot wide-field imaging at any distance beyond the distal end of a short length of MMF also becomes possible."

Subsequently, the scientists forecast other applications for this study. Dr. Phillips stated, “The optical inversion strategy we have described here can potentially be extended to unscramble light that has passed through other objects, such as photonic crystal waveguides, photonic lanterns, or biological tissue.”

“Finally, we anticipate that all-optical inversion of scattered light will find an array of applications beyond optical imaging: benefiting the fields of mode division multiplexing for high-capacity optical communications, as well as quantum cryptography and classical and quantum optical computing. We are excited to see where this technology goes!”