Bob J. Overton

Influence of stress relaxation in primary coatings on low-temperature attenuation in optical fibers

The attenuation of signal in dual coated optical fibers is sensitive to a number of parameters related to glass design (mode field diameter, cutoff wavelength, etc.), to environment (temperature, stresses), to cable design and fabrication (loose tube, ribbon, crossovers, point stresses, etc.), and to coating properties. The coating properties, principally the temperature dependent modulus of the primary (buffer) coating, and geometry are shown to determine the sensitivity of the attenuation to many of these variables.

Effects of coating moisture permeability on the mechanical reliability of optical fiber

A method to measure the permeability to moisture of fiber optic coatings is presented along with the results of such tests. The resistance of optical fibers to fatigue and strength degradation with high temperature and humidity is shown to be strongly dependent of the permeability of the secondary coating in a dual coating system.

Normal and Weibull probability distribution applied to test results of ribbons under two-point bending

The fiber to the home technology is already in use and more fibers are necessary to carry all the demanded information. Ribbon optical cable, present in the market since the seventy’s, is the right technology to support those needs. Ribboned fiber mechanical strength is currently characterized using tensile tests, where the required handling affects the results. In this study, we demonstrate the use of two-point bending tests to characterize ribbon strength. By this method, handling was minimized and samples aged in harsh environments could be tested. Normal and Weibull Probability Distributions were used to characterize and compare the strength of two ribbons, and of the fibers used to construct them. Both distributions were efficient in describing the strength during an aging process done in harsh environment. Keywords: Ribbon Cable, Two-Point Bending, Dynamic Fatigue, Weibull, Normal.

Kinetics of photopolymerization of acrylates studied with a cure monitor and photoDSC

Photopolymerization of a number of neat acrylate monomers used in polymer coatings of optical fiber was studied with photoDSC and with a cure monitor using a fluorescent probe. Acrylates had functionality from one to six. PhotoDSC results show that conversion of monomers ranges from 40 to 100% depending upon functionality and structure of a monomer. Kinetics of hardening of a sample under light at ambient temperature was nicely fit into two-exponential law; rate constants k1 and k2 in this empirical analysis are in the range 0.5 - 35 min-1. Dependence of rate of polymerization and conversion upon functionality of a monomer is discussed. Both cure monitor and photoDSC can be successfully used for testing of liquid coatings. It was demonstrated, that an application of a moderate permanent magnetic field increases rate of cure of coating up till 20%.