The protection against the penetration of water in optical cables is a very important feature for the performance and useful life of the optical fibers, directly changing the aspects of their installation.

THE EFFECT OF WATER ON OPTICAL CABLES

There are conditions were, circumstantially, the core of the optical cable and fibers may be exposed to water, which is a substance that degrades the component material of the fiber (silica) over time.

This humidity is responsible for the increase in micro-cracks, a factor that reduces the mechanical resistance of the fibers, and which may cause the rupture in a short period of time or damage the adhesion of the primary coating of the fiber, causing micro-bends that over time result in an increase in the optical attenuation.

Therefore, it is important for the optical fibers to be effectively protected from contact with water. The optical cables are thus produced with materials that protect them against these risks / aggressions.

OPTICAL CABLES

Most of optical cables are built using the loose tube technology, which represents the loose optical fibers packed inside the tubes protected from the penetration of humidity and coated by a thermoplastic jacket.

Two types of materials are currently used to protect cables from the penetration and propagation of water: Gel and Superabsorbent (water blocking) materials.

The first generation of optical cable uses gel in its entire construction (both in the core of the cable and inside the loose tube) with the purpose of providing a physical protection barrier against the migration of water, filling the interstitial spaces through which water could propagate.

In the beginning of the 1990s, the water blocking technology started to be introduced in the optical cable industry. This technology uses superabsorbent polymers that expand when in contact with water, changing to a gelatinous state, which blocks the propagation of water.

It is normally said that there are 3 generations of loose optical cable in terms of protection against humidity.

1ST GENERATION – GEL FILLED OPTICAL CABLE (G)

It has a gel derived from petroleum in its entire construction that fills up the inside of the optical units (loose tube) and the interstitial spaces of the core.

2ND GENERATION – DRY OPTICAL CABLE (S)

It has gel only inside the loose tube, while the gel in the optical core is replaced by tapes and/or yarns impregnated with superabsorbent powder (water blocking).

3RD GENERATION – TOTALLY DRY OPTICAL CABLE (TS)

It completely eliminates the presence of gel compounds derived from petroleum in its entire construction, where both the optical units (loose tube) and the interstitial spaces of the core are replaced by water blocking tapes/yarns.

This complete removal of the gel from the construction of the cable is part of the technological evolution of optical cables. The totally dry cable technology has been spread worldwide since 1997, and it is commonly known as “Totally Dry” or “Gel-free”.

In summary

This latest generation of the product was very well received (market, customers, installers) due to the elimination of the viscous compound (gel) that requires cleaning the cable. The preparation time of the cable ends was also significantly reduced once the need to clean them was eliminated.

It is worth emphasizing that new prerequisites or standards were not created for qualifying these products. The totally dry cables are subjected to the same tests as the cables of the other generations and fully comply with all the requirements.

WATER BLOCKING YARNS (WB)

Materials called Water Blocking are those impregnated with polymer in the form of moisture superabsorbent powder (SAP - Superabsorbent polymers).

Classified as hydrogel, they absorb aqueous solutions through the hydrogen bond with water molecules. These plastic polymers have very high absorption capacity, which may retain very large quantities of liquid in relation to their own masses (500 times their weight and from 30 to 60 times their volume).

REASONS FOR USING TOTALLY DRY OPTICAL CABLE

• Compliance with the Standards: They fully comply with the performance requirements of the international standards like TELCORDIA GR-20 and ICEA;
• Dimensional reduction: The total elimination of the gel reduces the linear weight by up to 40% and the outer diameter by up to 20%;
• Transport Agility: Reels with smaller weight and dimension reduce costs and facilitate the transport and handling of the cable during installation;
• Environment-friendly: Eliminates the need to use organic solvents (degreasers) and cleaning cloth to remove the gel;
• Faster installations: Reduces the preparation time of the cable ends to execute optical splices by up to 80%.
• Cost: New technology available with similar prices in comparison to the conventional gel-filled optical cable technology;
• Easy installation: Optimization of anchoring accessories, eliminating the use of thimbles, BAP, eyelet, etc. Simplification in the installation and reduction of mechanical impacts on the infrastructure.

WHAT PRODUCTS ARE AVAILABLE?

The Totally Dry optical cable technology is available for a wide variety of applications networks: aerial, underground in ducts, underground directly buried, intrabuilding, as well as premises networks.

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