Wavefront Shaping Optimization Algorithms For Focusing Light Through a Multimode Fiber

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2022-5

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TABAK, MEHMET

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Optical fibers are widely used to guide optical signals. Multi-mode fibers offer a greater bandwidth when compared to single-mode counterparts. The intensity at the end of a multi-mode fiber can be affected by mode-to-mode coupling and multi-mode interference. This can reduce the signal throughput. However, the total intensity at the end of the fiber can be modulated by shaping the input wavefront and providing increased signal levels. In our study, we show that focusing light inside the optical fiber is possible by wavefront shaping. There is a unique wavefront that focuses light inside the media at a given location. While the light moves in the particles, we adjust the wavefront dynamically using the spatial light modulator. Here, we experimentally evaluate and develop optimization algorithms for wavefront shaping that focuses light through a multi-mode fiber. These algoritmhs are continuous sequential (C), stepwise sequential (S), segmented (SE), hybrid Monte-Carlo continuous (MCC), hybrid stepwise continuous (SC) and hybrid segmented continuous (SEC). We analyze and compare these algorithms according to their performance: speed, regional enhancement, total enhancement. The continuous algorithm has reached to focus faster than others, the MCC algorithm is slowest with 46% lower than the C algorithm. The ranking of speed is C, SE, S, SC, SEC, MCC, in order. However, focus formation is much faster using the H-MCC algorithm. There is focus formation with enhancement 150 times than the initial value at 357 seconds for MCC. The focus is seen clearly at the target point. For regional enhancement, the C algorithms have higher performance than the stepwise with 1.1% and segmented 2.9%. For the total enhancement, the SC algorithm has increased the total transmisson 5.82 times than initial value. The ranking of total enhancement is follow: the C algorithm: 5.80, the S: 5.61, the SE: 5.47, the SEC: 4.97, MCC: 4.90.

Subject Keywords

Interference, Optical fiber, Optimization, Speckle Pattern, Wavefront Shaping

URI

https://hdl.handle.net/11511/97384

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Graduate School of Natural and Applied Sciences, Thesis

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Citation Formats

M. TABAK, “Wavefront Shaping Optimization Algorithms For Focusing Light Through a Multimode Fiber,” M.S. - Master of Science, Middle East Technical University, 2022.