Threshold dose Levels in Borosilicate Glass Fibers
<50 rad (very low dose)
No detectable changes in structure, optics, or mechanics.
Any induced defects are below detection limits of spectroscopy.
10² – 10³ rad (100–1,000 rad)
Beginning of trace radiation-induced defects.
Very slight increase in UV absorption possible, but not measurable in visible range.
Mechanical and thermal properties remain unchanged.
10⁴ – 10⁵ rad (10,000–100,000 rad)
Color centers become measurable: noticeable darkening in UV and near-UV regions.
Minor refractive index changes (<10⁻⁴) possible.
Still no significant mechanical degradation.
10⁶ – 10⁸ rad (1–100 Mrad)
Strong optical darkening: broad absorption bands in visible and near-IR.
Permanent defects accumulate in the Si–O–B network.
Refractive index changes become measurable.
Some reduction in fiber strength and durability may occur, especially if combined with stress or high temperature.
>10⁸ rad (extreme doses, beyond most practical environments)
Severe optical blackening (loss of transparency).
Glass network suffers radiation-induced compaction, changing density and refractive index.
Mechanical performance is degraded due to bond breakage and defect accumulation.