Influence of optical fiber diameter on thermoluminescence response

Detailed investigation is made of the thermoluminescence (TL) response of various sizes of optical fiber, fibers being developed with either a fixed core-to-cladding ratio or various core-to-cladding ratios. Two Ge-doped optical fiber preforms have been used to reconfirm the experimental findings. For further clarification, a pure silica rod has also been used to fabricate different diameter rods. Experimental investigations show the main TL signal to be generated from the fiber core within which the Ge is doped, the fiber cladding producing insignificant TL signal. Prior to normalization, the results show that in doubling the fiber diameter the TL signal quadruples. Conversely, subsequent to normalizing the different sizes of optical fiber to their mass or fiber cross sectional area, the smaller diameter fibers show slightly greater sensitivity compared to the larger diameter fibers. Relating to the fiber drawing-down process, this is due primarily to the greater shearing effect that the smaller fibers experience compared to the larger fibers within the fiber preform neck-down region.