Mechanical/Dynamic Fatigue is a rarely acknowledged value within the IEC60793-1-33 standard for fiber optics.

Ninety percent of the fibers available in the market today all meet the requirement value of Nd=18, while the more durable fibers in the market typically meet a value of Nd = 20. So what does it mean? How is it derived? What does it mean to have a value of Nd = 30 vs. Nd = 20?

Mechanical/Dynamic Fatigue is a value determined by three primary tests that simulate fiber under duress or stress for an extended period of time. The purpose of these tests to determine a standard value indicating whether a cable or fiber can meet the requirements of an installation and survive under adverse conditions of that installation for a given period of time.

These three tests include:

  • Repeat Bending Test – where the fiber is bent over a mandrel 200 times to determine if the fiber will illustrate micro fractures, or surface fractures.
  • Hot Water Tight Bend Test – where the fiber is bent to 3.0mm between two metal plates, submerged in 90 degree Celsius water, and timed to failure/breakage.
  • Elongation / Tensile Strength Test – where the fiber is stretched and tested to maximum capacity.

The values of these tests are put into a series of complex formulas to determine the ultimate value Nd= X.