Environmental effect on fatigue and lifetime of silica

الملخص EN

Fiber optics as a transmission lines using for transmitting the signals and data information at minimum losses.

It is using with modem communication which has the high immunity to' electromagnetic interference for transmitting the information, light weight, low cost, no corrosion, safety because the electric nature which eliminates the spark hazard, wide band width (more channel can be transmitted), low signal attenuation than other propagation systems.

It is using the light as a carrier for modulation signals information (l013–1014) HZ comparing to radio frequencies of (l06–109) Hz.

Light sources as light emitting diodes (LED) & light Amplification by stimulated emission of radiation (LASER), each one using with proper type of fiber which are multi mode (step index), Graded index, single mode.

Signal strength loss can occur for several reasons, such as : Attenuation, Rayleigh scattering, fresnel reflection, cracks, connector loss, splice loss…....

For the strength and fatigue of fused silica optical fiber on the environmental parameters temperature, humidity and PH (chemical acid, neutral or alkaline).

It is shown that the stress corrosion parameter (n) is not a constant but depends on the nature of the environment.

Further, different kinetic forms for the stress corrosion kinetic lead to different interpretations of experimental results? Since life time predictions are very sensitive to the value of (n) and the kinetic form it is important to know which form is correct.

It is shown that the empirical power law form that is almost exclusively used by the fiber optics industry provides a good fit to fatigue data for high strength fiber, but an exponential form provides a more self- consistent description of fatigue in different environments.

From our research the following results are : 1.

Life time of the optical fiber (silica) obviously affected by the environmental climate.

The fatigue at the fibers affected by the presence of the chemical materials ; (according to that types and concentration) affected directly to the concentration of the fiber starting from the external surfaces to the clad and then to the core which happening the cracks and these cracks increases continuously by the affect of that materials.

That obviously by equation research (part 2).

2.

the effects of stress or high weight on fiber may be happen the bending or a small bend inside the fiber then dispersion of the light signal will be take place, then the reflection 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 fiber follows 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 neutral concentration of Hydrogen ions will be basic, under to (7) will be acid.

The equations and Fig.

1 noted that.

5.

The effected of temperature on the strength and construction of the fiber lead to fatigue or fused silica (Eq.

9) or increasing of the hardening, then lost the flexibility and then may be broken or cracks appears on it which lost the specification.