Optical fibers are an attractive solution for meeting the ever-growing demand for high-bandwidth, low-loss, reliable technology. They are at the heart of many day-to-day technologies, such as data transfer and medical endoscopes. Studying the physics of such systems is key for overcoming the inherent challenges they present. 

Fiber piano

Light that propagates through a multimode fiber (MMF) results in a speckle pattern at its distal end. However, by carefully shaping the optical wavefront, it is possible to obtain a desirable output. In this project, we present, develop and demonstrate a new approach for tailoring light at the output of multimdoe fibers, by controlling the fiber itself rather than the incident wavefront. This approach is shown to achieve focusing in MMFs and mode conversion in few-mode fibers, while also allowing for more control over the output (e.g. in multiple wavelengths simultaneously). Further reading

Machine learning for image transmission 

When perturbations are applied on multimode fibers their transmission properties change, and as a result the output speckle pattern (for a specific input) is also altered. Alas, perturbations are an inevitable part of fiber-based applications, such as medical imaging (endoscopy) and telecommunications, and can result from mechanical, thermal, acoustic, or other types of strains. In this project, we use a deep learning model to overcome the effects of strong perturbations, and for the first time (to our knowledge) show reconstruction of the inputs to unknown fiber conformations based on the intensity of the output speckle patterns. We show that even when fibers are strongly perturbed, hidden correlations in the speckle remain. Further reading

Optical cryptography

The dynamics of light in multimode fibers is extremely sensitive to external perturbations, making it an ideal platform for studying optical cryptography. We are developing key distribution methods for optical encryption that rely on propagation of light through multimode fibers. We show that by virtue of time-reversal symmetry,  and the chaotic nature of light in multimode fibers, two remote users can establish a common key that is inaccessible to an eavesdropper. Further reading