The cable of the outer plastic sheath, which is a metal sheath, then there is water swellable layer, a fiber cable core ointment and stick together. The fiber has four water points, namely: the plastic protective layer and a metal sheath, water resisting layer, ointment. So the question is, why this fiber was afraid of the water, the fish tank at home Glass The window glass, why not afraid of water glass is also waterproof, why so different?
Is generally believed that the fiber is not afraid of the water, because the glass of water is excellent. But actually is very harmful to the cable. If the fiber optic cable into the water, in the cold water freezing and expansion will damage the fiber optic fiber, so need to use cream filled, preventing water from entering.
experiment Show that the long-term moisture into the cable will make the fiber attenuation increases, especially in 1.55pm wavelength As shown in Figure:
The reason is: if the water fiber is glass fiber (Si04) silicon oxygen tetrahedron are connected with each other, as shown in figure 1. In a Si – O – Si network In the oxygen atom to form oxygen bridge. But in water environment, the surface of the glass after water vapor adsorption, slowly hydrolysis reaction, thus leading to the silicon oxygen bond cleavage network Si 0 Si in the bridge oxygen into non bridge oxygen as shown in Figure 2, the result of glass crack, and the crack growth.
Whether it is the glass, window glass or glass fiber are afraid of water, which is different in the glass, window glass is very thick, the thickness of 3mm, 5mm, l0mm, even 0.05mm crack does not affect the strength of the glass, the naked eye can not see the change. While the glass fiber is different, the glass fiber diameter of only 0.125mm, as thin as hair, if there is a 0.05mm crack, fiber diameter only 0.075mm, so easily broken fiber fiber, also OH root will also increase the absorption loss of optical fiber. This is why the glass window, not afraid of water, afraid of the water glass fiber causes.
Thus, cable breakage, joint box seal is not good, because the water will be exposed bare fiber and fiber due to shortened life, natural fiber broken.