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  _____     _____     _  __    _____    _    _   
 / ____||  |  ___||  | |/ //  |  ___|| | \  / || 
/ //---`'  | ||__    | ' //   | ||__   |  \/  || 
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 \_____||  |_____||  |_|\_\\  |_____|| |_|\/|_|| 
  `----`   `-----`   `-` --`  `-----`  `-`  `-`

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Text this: Periodic structure in graded-index multimode fiber