Specification of Glass Yarns

Glass yarns provide strength to an optical fiber cable. Glass yarns are bundles of thin glass filaments grouped together for ease of processing and handling. Glass yarns are generally used to provide additional strength to the optical fiber cable by applying on the periphery of cable core or over the inner sheath. Thus, they are also known as peripheral strength members. Uncoated glass yarns split easily from their yarn group and may cause pollution to the surroundings in its processing area. Hence, wax or similar material is applied to discipline glass yarns.

Weight of glass yarns is calculated in kg. However, suppliers specify glass yarns in tex. Tex is a unit for yarns. Tex is the weight of one kilometer yarn. Thus one kilometer of 600 tex glass weigh 600 grams or 0.6 kg. It is often confused with the dtex, the unit for Aramid yarns in fiber optic cable industry.

Let us see the important parameters for glass yarn and learn how to specify them in a typical raw material specification that we submit to the material supplier. Here will discuss the specification requirements of glass yarns for use as peripheral or sheath strength members in Optical Fiber Cables. The nominal required Tex shall be specified in the inquiry /purchase order document. Note that the tex may vary from supplier to supplier and accordingly you need to consider when using the values in cable design.


S # Attribute Value
1 Linear Density in tex, nominal 600 1200 1800 2400
2 Force at specified elongation in N, Min. at 0.5% 75 150 225 300
3 Force at specified elongation in N, Min. at 1.0% 150 325 500 650
4 Maximum elongation at break in % 4 4 4 4
5 Youngs modulus GPa 50 50 50 50

The Glass yarns shall have a high chemical and thermal resistance.

The material shall be easily processable and shall not degrade during extrusion at high temperatures.

Each incoming delivery/ batch shall be accompanied by a test certificate

Test Certificate: The winding quality shall be even and it shall be easy to unwind during processing

Packing: Material shall be packed to provide adequate protection during normal handling and transportation.

Author: Fiber

Chief Editor of Fiber Optic Mania Magazine

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