Thermally induced microbending losses in double-coated optical fibers during temperature cycling

Abstract

The thermally induced microbending losses in double-coated optical fibers during temperature cycling are analyzed. The compressive radial stress at the interface between the glass fiber and primary coating would produce the microbending loss. A simplified closed-form formula to calculate the microbending loss is obtained by the viscoelastic theory. This formula can be extended to calculate microbending losses induced by temperature cycling with any number of stages, if the temperature is linearly raised, linearly dropped, 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 possibly exist. This microbending loss increases with the number of temperature cycles, and finally approaches a constant. To minimize the interfacial radial stress between the glass fiber and primary coating, the radius, Young’s modulus, thermal expansion coefficient, and Poisson’s ratio of polymeric coatings should be appropriately selected, and the relaxation time of the primary coating should be much shorter than the period of the temperature cycle. The condition for the glass transition temperature range of polymeric coatings within the temperature cycling is discussed. Additionally, microbending losses in single-coated optical fibers during temperature cycling are also considered.

Effect of temperature cycling on the static fatigue of double-coated optical fibers

“…Moreover, A 0 and A 2 represent the crosssectional areas of the glass fiber and the secondary coating, respectively. 9,17,[20][21][22][23][24] Accordingly, the long-term stresses in optical fibers can be solved by the viscoelastic theory, as follows. Although the approach stated here is less rigorous than the exact theory-of-elasticity treatment, 18 it often enables easy to use and sufficient accurate solutions to be obtained.…”

Effect of polymeric coatings on the static fatigue of double-coated optical fibers

“…Although the viscoelastic behavior of polymeric coatings is not very clear, polymeric coatings can be simply and reasonably assumed to behave as Maxwell materials. 5,6,9 As a result, long-term stresses in glass fibers can be determined from the viscoelastic theory as follows. 10 First, the Young's modulus of the polymeric coating, given in Eq.…”

“…Although the glass fiber behaves like an elastic medium, polymeric coatings for optical fibers are typically viscoelastic materials. As a result, the stresses exerted on the coating are relaxed, 5,6 and the applied tensile force is gradually transferred from the polymeric coatings to the silica glass fiber over a long time. Equation ͑1͒ shows that increasing the tensile stress, a , applied to the glass fiber accelerates the failure of the glass fiber over a long period.…”

Minimisation of thermally induced microbending losses in dual‐coated optical fibres caused by viscoelastic behaviour of commercial polymeric coatings

“…Thermal or mechanical stresses in optical fibres are important, and have been extensively studied [1–10]. Suhir [11] first paid attention to thermally induced stresses in single‐coated optical fibres at low temperatures, and found that added transmission losses increased with the lateral pressure on the glass fibre.…”