Optical fiber coatings: High modulus coatings for fibers with a low microbending sensitivity

Abstract

An important function of a n optical fiber coating is to prevent optical losses due to microbending induced by lateral forces on the fiber. To protect the fiber over a wide temperature range the modulus of the primary and the secondary coating should be low and high, respectively, and temperature independent.However, selecting the most appropriate organic coating materials introduces a new source of optical losses. Since the linear thermal expansion coefficients of silica and the organic coatings differ by about two orders of magnitude, thermal fluctuations will cause axial stresses. Cooling may then induce bending or buckling of the glass fiber in the soft primary coating, resulting in increased transmission losses. This effect is especially pronounced when a high-modulus secondary coating is selected with a glass transition temperature above 80°C. For this type of coating the difference in radial shrinkage between the buffer and the top coating during cooling from the curing temperature becomes important. The influence of primary coating thickness is discussed.

On the History of Reactive Mesogens: Interview with Dirk J. Broer

“…The first coating is soft, the second has a high elastic modulus. This combination of coatings provides maximum protection against abrasion and normal forces (Figure b) . The drawing speed exceeded 10 m s −1 ; therefore, the viscosity of the coating prior to curing must be low and curing should proceed in sub‐seconds.…”

Photomechanical effects in liquid crystalline polymer networks and elastomers

“…Photoinitiated polymerization (photopolymerization) is advantageous as it decouples the reaction from the thermotropic nature of the starting materials . A wide range of liquid crystalline monomers can be mixed with one another and even small concentrations of non‐liquid crystalline crosslinkers to prepare materials with mixed side‐ and main‐chain mesogen connectivity . Liquid crystalline polymer networks with side‐on mesogens have also been reported .…”