A: Do I really need to be concerned about bend radius?
B: Yes, bend radius is a real issue.
The question “A” asked is a common question in fiber optic cable installation. And thanks “B” to show us the right answer. To almost every FOC (fiber optic cable) installer or technician, one of the most important considerations when installing fiber optic cable is maintaining the minimum bend radius. Why? Just keep reading, you may find out the reason.
As we know, most of the fiber optic cable is made of glass. It is very amazing that the bundle of fiber can transmit a huge amount of signals and data. But, do you know that the cable can be pretty delicate because of the material itself? Thus, we need to set a standard (e.g. EIA/TIA 568) to define the minimum bend radius in order to keep cables in good working order.
The “bend radius” of a fiber optic cable is the term for how sharply a cable can safely bend at any given point. All cabling has a bend radius, and the bend radius may be different according to different types or different make of cables.
The minimum bend radius for fiber optic cable should be specified both for long-term installation, and for when the cable is subject to tensile load. A typical value for a cable under no load (or “unloaded”) conditions is 10 times the cable’s outside diameter. When a cable is under tensile load (or “loaded”), the minimum bend radius is usually 15 times the cable’s outside diameter. For instance, for most of the premises cables, they require a bend radius of 10 times the cable outside diameter unloaded and 15 times the outside diameter when under the maximum rated pulling tension for that cable.
Bending a fiber optic cable excessively may cause the optical signal to refract and escape through the cladding. It could also cause permanent damage by creating micro cracks on the delicate glass fibers. And when overbending interferes with light transmission, the resulting increased attenuation compromises the integrity of your valuable data. So, always remember that do not bend the fiber beyond it’s specified bend radius.
Bend insensitive fiber cables are designed for improved bend performance in reduced-radius applications, such as residential or office environments which have less bend sensitivity. Optical fiber manufacturers used a refractive index “trench” in bend insensitive fiber, which means a ring of lower refractive index material, to basically reflect the lost light back into the core of the fiber. Compared with the conventional fibers, the bend insensitive fiber employs a moderately higher numerical aperture (NA) and offers improved bend performance for applications in the 1310nm and 1550nm range.
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 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.