What is Bend Insensitive Fiber?

One of the challenges in the usage of optical fiber is loss of input light due to bending or twisting. Optical fiber is often affected by various kinds of stress, such as bending. Although their coating and design is engineered such that the losses can be minimized, such a loss is almost inevitable in regular optical fiber.

Bend Insensitive fiber is a modern kind of fiber that is completely insensitive to bending and prevents the loss of input otherwise caused due to bending. This fiber was earlier introduced only in its singlemode form but recently, multimode bend insensitive fiber has become available in the market as well.

How Is Bend-Insensitive Fiber Designed?

A bend-insensitive fiber uses an optical trench. An optical trench is a ring of low refraction index material. The fiber uses this trench such that the lost light is reflected into the core again. This way, most of the loss is covered and the input light remains within the core itself instead of being lost. In cases of a multimode fiber, a glass layer is added around the fiber core. This layer of glass has a low refractive index that reflects the light from the weakly guided modes into the core. The reflection of light into the core by the lower refractive index material works on the principle of Total Internal Refraction (TIR), which is the primary phenomenon used in construction of a bend insensitive fiber.

Advantages of Bend Insensitive Fiber

There are many advantages and applications of the bend insensitive fiber. The places where installing optical fiber often results in high losses, bend insensitive fiber can be successfully used. For instance, in patch panels or buildings, this fiber can be molded conveniently and reliably around the ceiling, floors, doors, windows or other structures without suffering loss of signal. It also protects from the issues occurring due to improper installation of the optical fiber.

The cost of manufacturing the bend insensitive fiber is a very small overhead given the value it delivers. It can also be used in the OSP cables as it helps manufacturing of high fiber count cables with smaller sizes and lighter weight.

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