| 摘要 |
When an optical fiber ( 1, 1 ') is heated by an electrical discharge generated between electrodes ( 3 ) thermal light emission from the core and cladding of fiber forms a hot image which can be observed by an optical imaging system ( 9, 15, 17 ). Since the concentration of dopants in the core is significantly higher than in the cladding, the light emitted from the core gives a peak structure in the light intensity profile of a hot image. The peak width of the core image increases significantly when dopants diffuse out of the core such as in heating the fiber. The increase of peak width is found to be highly correlated to the expansion of the mode field diameter (MFD) of fiber. This correlation can be experimentally determined at well-defined fusion conditions for any given type of fiber and thereby used to give a measure of the MFD by observing the peak width in hot images. Measures of MFD can be used for improving the quality of estimation of losses in splices of optical fibers.
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