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Bend Insensitive Fiber Optic Cables: Advantages & Compatibility
Optical fiber is made by glass or plastic, so it is easy to be bent. As is known to all, the main function of optical fiber is transmitting light. Once the fiber has been bent, there must be fiber loss during the process of transmission. New type of “bend-insensitive” singlemode and multimode fiber were introduced in 2007 and in 2009 respectively. This kind of fiber is specifically manufactured for the fibers could be bent in what seemed like impossibly small radii without significant light loss. This article would introduce the advantage and compatibility of bend insensitive fiber optic cables.
As being mentioned, bend insensitive fiber optic cables provide a effective solution for accidentally twisting or bending the cable. But what are they? "Bend Insensitive" or BI cable is designed to be resistant to bend related damage. BI fiber cable has a flex cycle count in the thousands, sometimes as high as 7,500 or more cycles. In addition, it has a much smaller bend radius, meaning it can tolerate tighter corners or being wrapped around cable management equipment.
Different from the regular fiber, bend-insensitive fiber adds a layer of glass around the core of the fiber which has a lower index of refraction that literally "reflects" the weakly guided modes back into the core when stress normally causes them to be coupled into the cladding. Some early singlemode fibers (depressed-cladding fibers) used a similar technology to contain the light in the core of the fiber but this design has a much stronger effect. The following picture shows the technique of bend-insensitive multimode fiber.
Compared to the normal fiber, bend-insensitive fiber has absolute predominance. In buildings, it allows fiber to be run inside molding around the ceiling or floor and around doors or windows without inducing high losses. It is also insurance against problems caused by careless installation. In patch panels, it should not suffer from bending losses where the cables are tightly bent around the racks. BI fibers are also available in 50/125 MM (OM3 and OM4) and SM versions. Considering the advantages of BI fiber and the small incremental cost to manufacture it, some manufacturers have decided to make all their 50/125 MM fiber bend-insensitive fiber.
The answer is yes for SM fibers. Since only one mode is guided in the core, the trench has a minimal impact on system performance and measurement. It seems you can mix and match regular and BI SMF fibers with no problems. For MM fibers, it is still needed to be proved. Owing to the limitation of the current technology, the compatibility with MMF is not so sure so far. Measurement of core size, NA, differential mode delay (DMD) and bandwidth were developed prior to the introduction of BI MMF designs. These measurements are in the process of being evaluated and updated so measurement results may depend on the manufacturer of the BI MMF.
Bend-insensitive fiber has been widely applied in premises installations like apartment buildings or for patch cables, where it simplifies installation and use. BI SMF is also used in OSP cables since it allows fabrication of smaller, lighter high fiber count cables. Using bend-insensitive fiber cable, it is unnecessary to worry about the accidentally twisting or bending the cable.
Post je objavljen 11.10.2017. u 08:16 sati.