Fiber Bend Radius Guide

Fiber Bend Radius Guide

The fiber optic market has witnessed an increase in the use of fiber optic cable assemblies. FTTx networks are the driving force behind the adoption of fiber optic cables. For almost any FOC (fiber optic cable) installer or technician, one of the most important considerations when installing fiber optic cables is maintaining a minimum fiber bend radius. During the installation of these cables, more attention is focused on the effect of the bend radius and the need to maintain the specified cable bend radius. Why? Read on and you might find out why.

What is bend radius?

Bend radius is how sharply a cable can safely bend without causing damage by creating micro cracks on the glass fibers. Bending a fiber cable excessively can also cause the optical signal to refract and escape through the cladding. By interfering with light transmission, attenuation increases and compromises the integrity of the data being transmitted. Every cable will have a minimum radius, but this will vary according to the type being used.
Bend insensitive fiber can be either singlemode or multimode and is designed for better performance in reduced cable bend radius applications. Examples include residential or office buildings, or any space where tight bends and flexibility are needed, such a data center server cabinet. Bend insensitive fiber has a refractive index trench, or a ring index of refraction material. This reflects the lost light caused by the bend so that it comes back into the fiber’s core, minimising data loss.

How do I calculate bend radius?

The manufacturer should specify the minimum radius that your cable may safely be bent.
When the manufacturer has failed to do this, you can go by this general rule of thumb:
The optical minimum bend radius is equal to ten times the outer jacket diameter of that cable.
So if you’re dealing with a fiber cable that has a 2mm outer jacket, then 2mm x 10 = 20mm bend radius.

What Is Bend Insensitive Fiber Optic Cable?

Bend insensitive fiber patch cable is designed to transmit light with minimum loss even if they are bent beyond the bend radius. In these BIF optical cables, an optical “trench” – a ring of lower index of refraction material – is built into the fiber to basically reflect the lost light back into the core of the fiber, thereby minimizing data loss. Bend insensitive fiber cable offers greater flexibility in demanding environments than traditional fiber cable. It is typically used in data centers or any space constrained area where tight bends and flexibility are required. Bend insensitive fibers are available in 50/125 MMF (OM3 and OM4) and 9/125 SMF versions.

Advantages of Bend Insensitive Fiber Optic Cable

  • Flexible Installations: Bend insensitive fiber cables are very useful for indoor fiber cable installations as they can now be taken around walls, pillars, ceilings, ducts, and other uneven surfaces within the buildings without worrying about excessive fiber bends.
  • High Performance: Higher bandwidth applications can be confidently deployed using bend insensitive fibers as accidental excessive bending of fibers does not cause much of performance degradation.
  • Great Resilience: Bend insensitive fibers also show a great deal of resilience in situations where fibers are fixed to surfaces using clamping, tie-wrapping or stapling.
  • Small Incremental Cost: The cost of manufacturing bend insensitive fibers is not very high when compared to the cost of manufacturing normal fiber cables.
  • Same Splicing Methods: Bend insensitive fiber cables can be spliced using the same methods used for normal cables.


Fiber bend radius is always a real issue that we should really need to be concerned about when installing fiber optic cables. Make sure to know the minimum fiber band radius of your installed cables, and do not bend it beyond the specified bend radius. Additionally, if the application needed, you can try to use the bend insensitive fiber.
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