NOTICE This reportwas prepared as an accountof worksponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty,express or implied,or assumesany legal liabilityor responsibilityfor the accuracy, completeness,or usefulness of any information,apparatus, product,or processdisclosed,or representsthat its use would not infringe privately owned rights. Reference herein to any specific commercial

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... uce, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarilyconstituteor imply itsendorsement,recommendation, or favoring by the United States Governmentor any agencythereof. The views and opinionsof authorsexpressedhereindo not necessarilystate or reflectthose of the United States Governmentor any agency thereof. NOTICE This report has been reproducedfrom the best available copy. Availablein papercopyand microfiche. We have subjecteda silica core fiber optic cable to 4 years of low-level neutron and gamma radiation from Princeton's TFTR controlled fusionexperiment The accumulated dosewas 200 Gy. As a result of the radiation, we have measuredincreasedal_nuadons of 100 -300 dB/km in the visible part of _e spectrum,and a decreaseof the numerical aperture. An attempt to decrease this damage by photobleaching failed. We arguethat this failure isnotunexpected, since therate of damage isso slowandthedme scale so longthattheself-annealing process keepstheresidual damage attheirreducible level seeninother experiments. The implications of these findings forcontrolled fusion diagnostics duringupcomingexperiments withhighly reactive deuu:rium-tritium plasmas arediscussed.