Why are telephone cables filled with gel?

In the manufacturing process of communication cables and optical cables, three methods are often used to prevent moisture and water, namely, inflation, filling with petroleum jelly or using super absorbent materials. Among them, petroleum jelly for optical fiber cables is widely used at home and abroad. Petroleum jelly is filled in all gaps in optical fibers and optical cables, playing a role of sealing and waterproofing, so that optical fibers are not affected by the external environment. Extend its service life, and no maintenance is required, and it can maintain the stability and reliability of optical fiber transmission for a long time.
Basic properties
Petroleum jelly for optical fiber cables is a flexible colloidal substance that can be filled and used at room temperature. It has a wide range of applications (-40℃～100℃) and good comprehensive performance. After filling optical fiber cables, it can play a waterproof and buffering role; it has excellent thixotropic properties, moderate viscosity, and can be filled and used at room temperature. It is different from traditional cable petroleum jelly based on vaseline and polybutylene. It overcomes the shortcomings of cable petroleum jelly that needs to be filled at high temperature and shrinks after cooling to produce gaps, and is also easy to process and manufacture. Therefore, petroleum jelly for optical fiber cables has been widely used at home and abroad, and more than a dozen kinds of petroleum jelly are available abroad; but there are only 2 to 3 kinds of petroleum jelly products in China, which is far from meeting the development needs of domestic optical communications.