How does bending effect a Fiber Patchcord?
Fiber optic cables by their nature and the way they are manufactured are designed to be enduring the stress applied to them during their installation and maintenance, however as they are made of glass and are highly fragile it is highly advisable by the manufacturers to lower this stress to a minimum. Bending the fiber cables and the amount of quality loss depends on the type of the cable, if it’s Single- mode or Multi- mode cable, their design, their core diameter and their transmission wavelength. Usually longer wavelengths are more sensitive to stress and bending losses.
The process of bending or pulling loss starts inside the cable as the optical signal within the cable is not guided through the core of the fiber, instead a big part of the light itself is lost and bouncing in the walls and the cladding in the cable thus creating a high loss in optical light. Bending would most probably permanently damage the fiber cable by causing cracks in it. This would compromise the quality of the signal and the integrity of the data transmission. This is easily put to the test with the help of a visible laser put in the fiber itself and bending it at a certain point. The light loss will be visible where the cable is being bent.
During the last couple of years manufacturers and the Fiber Optic Association started developing a new type of cables that are more durable and can withstand higher stress and bending. This was firstly developed for the Single- mode fibers and after a couple of years for the Multi- mode fibers. The way they were testing the bending and the endurance of the cables was with the help of a piece of wood and bending the cable around it in front of a wide audience.
The bending of the fiber optic cables is measured by the bend radius. Only in the last couple of years this bending radius has been industry standardized by the Fiber Optic Association. In contrary before it was standardized the bending radius have been governed by the cable manufacturers. The new standard defined by the ANSI/TIA/EIA-568B.3 named “Optical Fiber Cabling Components Standard” sets exact performance specifications concentrated on the minimum bend radius and the maximum pulling tensions for 50/125 micron and 62.5/125 micron fiber optic cables. With the new standard introduced the manufacturers have the obligation to specify the minimum bending radius to which the cable could be safely bent during the installation. Most commonly the minimum bend radius of 1.6mm and 3.0mm fiber cables is around 3.5cm and the minimum bend radius for patch cable is around ten times the cable diameter. If referring to the manufacturer’s recommended bend radius is not possible, the general guideline for cable bending is no more than 20 times the diameter of the cable itself.