| 摘要 |
There is disclosed a photodetection device comprising: a photodetector having detection sensitivity at a first wavelength; a first optical fiber propagating light in a plurality of modes at the first wavelength, the first optical fiber having an entrance end on which light at the first wavelength falls; and a second optical fiber propagating light in a plurality of modes at the first wavelength, the second optical fiber having a product of a core diameter and a numerical aperture at the first wavelength that is greater than a product of a core diameter and a numerical aperture at the first wavelength of the first optical fiber, the second optical fiber having one end and another end, the second optical fiber being optically coupled to the first optical fiber at the middle of the first optical fiber in a longitudinal direction of the first optical fiber, and the one end of the second optical fiber being optically coupled to the photodetector.
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