Fiber optic cable can be run anywhere from 300 meters up to 80 kilometers (roughly 50 miles) depending on the cable type, transceiver used, and network standard. One type of single mode fiber is known as “G. 652,” which is commonly used in telecommunications networks. Single-mode. LaTeX Go Diameter of Fiber = (Wavelength of Light*Number of Modes)/ (pi*Numerical Aperture) LaTeX Go Power Loss Fiber = Input Power*exp(Attenuation Coefficient*Length of Fiber) LaTeX Go Attenuation Coefficient = Attenuation Loss/4. 343 LaTeX Go Number of Modes = Normalized Frequency^2/2 See. Is there a specific formula to calculate this, for example if the OTDR show 5000 meters of fiber, how long is the actual cable? What you're looking for is called the helix factor and it's usually a few percent. This means the fiber will be a few percent longer than the cable. Using a fiber size chart simplifies cable selection and ensures compliance with industry standards (TIA, ISO, ITU-T).