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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.

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Synthesized poly(pelargonamide) membranes are shown to be a ferroelectric polymeric material based on the demonstration of the D‐E hysteresis curves of the oriented and unoriented samples. Dipole switching required a lower electric field excitation with increasing stretching ratio caused by a better orientation of the dipoles upon the uniaxial stretching of the membranes. The ferroelectric response of the samples could be greatly enhanced by uniaxial cold‐drawn. When T was >Tg , and d31 was kept constant then e31 increased non‐linearly with Pr for the samples within the range of the stretching ratio. However, both d31 and e31 increased nonlinearly with Pr for the samples within the range of the stretching ratio if T < Tg. Scanning electron microscopy photographs illustrate the stretching and poling effects on the packing of the macrofibrils of the specimens. The origin of the piezoelectric response of the poly(pelargonamide) membranes was considered to account for the effect of the dipoles reorientation under the electric field poling and was evidenced by polarized infrared spectroscopy examinations.