Environmental Effect on Fatigue and Lifetime of Silica Optical Fibers


Fiber optics as a transmission lines using for transmitting the signals and datainformation at minimum losses. It is using with modem communication which has thehigh immunity to' electromagnetic interference for transmitting the information, lightweight, low cost, no corrosion , safety because the electric nature which eliminates thespark hazard , wide band width (more channel can be transmitted), low signalattenuation than other propagation systems . It is using the light as a carrier formodulation signals information (l013 – 1014 ) HZ comparing to radio frequencies of(l06 – 109) Hz. Light sources as light emitting diodes (LED) & light Amplification bystimulated emission of radiation (LASER),each one using with proper type of fiberwhich are multi mode (step index), Graded index , single mode. Signal strength losscan occur for several reasons, such as: Attenuation, Rayleigh scattering, fresnelreflection , cracks , connector loss, splice loss…....For the strength and fatigue of fused silica optical fiber on the environmentalparameters temperature, humidity and PH (chemical acid, neutral or alkaline). It isshown that the stress corrosion parameter (n) is not a constant but depends on thenature of the environment. Further, different kinetic forms for the stress corrosionkinetic lead to different interpretations of experimental results? Since life timepredictions are very sensitive to the value of (n) and the kinetic form it is important toknow which form is correct. It is shown that the empirical power law form that isalmost exclusively used by the fiber optics industry provides a good fit to fatigue datafor high strength fiber, but an exponential form provides a more self- consistentdescription of fatigue in different environments . From our research the followingresults are:1. Life time of the optical fiber (silica) obviously affected by the environmentalclimate. The fatigue at the fibers affected by the presence of the chemical materials;(according to that types and concentration) affected directly to the concentration ofthe fiber starting from the external surfaces to the clad and then to the core whichhappening the cracks and these cracks increases continuously by the affect of thatmaterials. That obviously by equation research (part 2).2. the effects of stress or high weight on fiber may be happen the bending or a smallbend inside the fiber then dispersion of the light signal will be take place, then thereflection way cannot becomes write, or cracks can be happens.3. The effects of continuously humidity on strength of the fiber (according to the bellyband),relative fatigue be occurs, and that affected to the construction of fiber.(Table No.1).4. Effected of PH (concentration of hydrogen) on the strength and fatigue of the fiberfollows to the faster fused silica. As we know the limit of PH generally start from(1-14) as a number (acid, passivity or neutral) the No.7 at the middle neutralconcentration of Hydrogen ions will be basic, under to (7) will be acid. Theequations and Fig. 1 noted that.5. The effected of temperature on the strength and construction of the fiber lead tofatigue or fused silica (Eq.9) or increasing of the hardening, then lost the flexibilityand then may be broken or cracks appears on it which lost the specification.