Superiority of a Square-core Multimode Fiber for Imaging and Spectroscopy

An optical fiber is a promising tool for remote imaging [1]. A multimode fiber (MMF) offers multiple advantages: compactness, flexibility as well as the ability to transmit a large amount of information via multiple spatial modes. There are several methods to do optical imaging through a MMF. One can use wavefront shaping (WFS) to compensate for the modal dispersion and mode mixing so that the incident light can converge to a desired pattern at the fiber output [2]. By using WFS, we can sequentially generate focal spots at the distal fiber facet to scan the sample. Another imaging method through a MMF is compressive imaging (CI). The interfering fiber modes create a speckle pattern, which varies with wavelength and input light position, which. can be used as a basis for CI [3]. CI allows to reconstruct the image with a resolution beating the Abbe limit with fewer measurements than the number of pixels [4]. Finally, the decorrelation of the speckle patterns with wavelength encodes the spectral information of input light, which enables MMF spectroscopy applications [5].