Please to create posts and topics.

How to Calculate the Tensile Strength of Optical Cable?

Hello guys,

do you have somebody experiences with mathematic calculate tension strength (cable with yarn, wire….) optical cable? Is ti different max. fiber strain for MLT, CLT, distribution, drop, adss….. cable? OR max fiber strain is max. 0,33% every cases?
Thank you.

Refer this article written by me. Good luck!


You are kindly, so I calculate Ts for every tensile member in cable and I do sum all?
Ep is 1% ?
A = is the cross section area one member from whole cabel? (for example cable has 18 mm2 cross section area and aramid has cross section area is 3 mm2)
How unit you use in this formula?


An addition to my comments, which was sent by one of my contacts Mr. Bourkeb Souheib by mail yesterday. Originally, this article was written by me in Fiber Optic Social Network Site.

Ts = Sum of ( Yx Ax Ep )
Ts = Tensile Strength of Optical fiber cable
Y = Young’s modulus of cable materials
A = Area of cross section of cable components
Ep = Permissible elongation of cable

Thanks Souheib for resending this.

Thank you very much!

You can buy the IEC specs from here

If your fiber proof test value is 1%, then your fiber in the cable can allow a maximum fiber strain of 0.6% as per the latest IEC standards.

For CLT design; You need to know the percentage of excess fiber length in your CLT. For example, if the excess fiber length in CLT is 0.2%, then the maximum allowable cable elongation will be 0.2 + 0.6 = 0.8%.

Now, you need to calculate the tensile strength provided by the strength members such as aramid yarns, FRP or Steel wires etc. For Aramid yarns, you can take the LASE – Load At Specified Elongation. In fact, you need to know the Young’s modulus of strength members and calculate the strength provided by them by multiplying with area of cross section and permissible elongation, which in the example is 0.8%.

Thank you so much ? , I calculate cable for 0,33%; 0,5%; 0,6% so it’s all right, so dosen’t metter on type of cable( Simplex, CLT, MLT, drop, distribution…….) values 0,6% is base + excess fiber lenght. So it is?

Very thanks

“0.333% is the maximum allowable fibre strain (ITU-T) for 1% proof strain fibre”

I think ITU-T spec doesn’t specify 0.333%. Mr.Tom, could you please show me the ITU-T spec mentioning the above criteria?. Just for my study and reference only. I know IEC specification puts the criteria of 60% of proof test strain of fiber. This is applicable for underground cables mainly and some customers wants lower permissible strain for aerial cables.

Please refer to the latest IEC specs. You may need to buy it as it is copyright protected.

ok thanks and how IEC specs you think? Can you send me link to massege?

I am a beginner, so every fiber producer guarantee proof test >100 kpsi(0,69Gpa), so how values is 60% proof strain of fiber?

For example, when I calculate tensile for CLT cable with 6 x aramid yarns, which values I use?? (tensile strength yarn 0,3% or 0,5% or what??

For MLT cable is very more difficult, which values i mustn’t exceed?

I know that for MLT, CLT, Drop…. cables are different mathematic metods 🙂, but how values max. fiber strain mustn’t exceed, when I calculation tensile strength?

“0.333% is the maximum allowable fibre strain (ITU-T) for 1% proof strain fibre”

This is the same for all types optical cables?

Tom, are you asking for the mathematical calculations?

Hi Tom, Calculation methods are different for MLT, CLT and drop cables. The max. Fiber strain allowed is 60% of the fiber proof test value as per the new IEC standard. Hence the allowed fiber strain depends on the fiber type. For G.652 fibers, 0.6% and for G.657 fibers, around 1%.