St. Shiue et Cs. Hsu, Thermally induced microbending losses in double-coated optical fibers during temperature cycling, J APPL PHYS, 88(7), 2000, pp. 3840-3847
The thermally induced microbending losses in double-coated optical fibers d
uring temperature cycling are analyzed. The compressive radial stress at th
e interface between the glass fiber and primary coating would produce the m
icrobending loss. A simplified closed-form formula to calculate the microbe
nding loss is obtained by the viscoelastic theory. This formula can be exte
nded to calculate microbending losses induced by temperature cycling with a
ny number of stages, if the temperature is linearly raised, linearly droppe
d, or fixed in each stage of the cycle. Although the temperature change is
zero at the end of the temperature cycling, the microbending loss will poss
ibly exist. This microbending loss increases with the number of temperature
cycles, and finally approaches a constant. To minimize the interfacial rad
ial stress between the glass fiber and primary coating, the radius, Young's
modulus, thermal expansion coefficient, and Poisson's ratio of polymeric c
oatings should be appropriately selected, and the relaxation time of the pr
imary coating should be much shorter than the period of the temperature cyc
le. The condition for the glass transition temperature range of polymeric c
oatings within the temperature cycling is discussed. Additionally, microben
ding losses in single-coated optical fibers during temperature cycling are
also considered. (C) 2000 American Institute of Physics. [S0021-8979(00)073
20-5].