| 摘要 |
Apparatus for measuring the spot size of light emerging from an optical fibre comprises a rotating radial grating which is moved relative to a monochromatic beam of light, passing through the fibre, to vary the spatial frequency of the light entering a photodetector situated at the output end of the optical fibre, thereby obtaining a variation in the modulation amplitude of the light received by the detector, allowing measurement of the spot size to be obtained.
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