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WHITE PAPER Fiberstore (FS.COM) | Does Bend Insensitive Multimode Fiber Make Sense? Page 1 As we all know, when optical fiber exceeds a certain bend radius, some amount of light can be lost, causing signal loss. This can happen during installation or anytime during fiber handling, and is often a concern within the tight spaces of high-density fiber patching areas in the data center. Today, a bend insensitive multimode fiber (BIMMF) was introduced, which can withstand tight bends, or even kinks, without suffering significant loss or any loss in a lot of cases. However, there are no standards around BIMMF and there are concerns about compatibility between BIMMF and traditional fibers. Besides, there are also questions around bandwidth measurements in the factory and actual performance in the fields. So, does BIMMF really make sense? Let’s find the answer together. What Is Bend Insensitive Multimode Fiber? Bend insensitive multimode fiber, first introduced in 2009, is quickly becoming the fiber of choice for high-performance enterprise LANs and data centers. With the introduction of BIMMF, installers were finally able to deploy fiber networks without fear of over-bending the fiber and degrading performance. Compared with standard fibers, BIMMF has a specially engineered optical “trench” added between the core and cladding. This trench contains the propagating modes within the fiber core, even in an extreme bend. It retains more of the light that would have escaped the core of a traditional multimode fiber. BIMMF enables more compact fiber management systems and to improve space utilization in modules, enclosures, cabinets and patch fields. Today, BIMMF is widely deployed in data centers and much has been published about its design and benefits. Does Bend Insensitive Multimode Fiber Make Sense?

Does bend insensitive multimode fiber make sense

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As we all know, when optical fiber exceeds a certain bend radius, some amount of light can be lost, causing signal loss. This can happen during installation or anytime during fiber handling, and is often a concern within the tight spaces of high-density fiber patching areas in the data center. Today, a bend insensitive multimode fiber (BIMMF) was introduced, which can withstand tight bends, or even kinks, without suffering significant loss or any loss in a lot of cases.

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WHITE PAPER

Fiberstore (FS.COM) | Does Bend Insensitive Multimode Fiber Make Sense? Page 1

As we all know, when optical fiber exceeds a certain bend radius, some amount of light can be lost,causing signal loss. This can happen during installation or anytime during fiber handling, and is oftena concern within the tight spaces of high-density fiber patching areas in the data center. Today, abend insensitive multimode fiber (BIMMF) was introduced, which can withstand tight bends, oreven kinks, without suffering significant loss or any loss in a lot of cases. However, there are nostandards around BIMMF and there are concerns about compatibility between BIMMF andtraditional fibers. Besides, there are also questions around bandwidth measurements in the factoryand actual performance in the fields. So, does BIMMF really make sense? Let’s find the answertogether.

What Is Bend Insensitive Multimode Fiber?Bend insensitive multimode fiber, first introduced in 2009, is quickly becoming the fiber of choicefor high-performance enterprise LANs and data centers. With the introduction of BIMMF, installerswere finally able to deploy fiber networks without fear of over-bending the fiber and degradingperformance. Compared with standard fibers, BIMMF has a specially engineered optical “trench”added between the core and cladding. This trench contains the propagating modes within the fibercore, even in an extreme bend. It retains more of the light that would have escaped the core of atraditional multimode fiber. BIMMF enables more compact fiber management systems and toimprove space utilization in modules, enclosures, cabinets and patch fields. Today, BIMMF is widelydeployed in data centers and much has been published about its design and benefits.

Does Bend InsensitiveMultimode Fiber MakeSense?

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Fiberstore (FS.COM) | Does Bend Insensitive Multimode Fiber Make Sense? Page 2

Is BIMMF Compatible with Non-BIMMF?The preceding core diameter and numerical aperture discussions revealed that there are mode-fieldshape differences between traditional MMF and BIMMF. These differences fundamentally reducethe match between these fiber types and can lead to elevated connection loss. However, modelingand testing on BIMMF has shown that an optimized BIMMF is backward compatible and can bemixed with non-BIMMF without inducing excess loss. There isalso evidence that connector incompatibility and fibergeometry differences (core diameter) may cause directiondependence regardless of fiber type. In fact, according tomost fiber manufacturers, BIMMF is fully compatible withOM2, OM3 and OM4 standards for laser-optimized multimode fibers and is also backwardcompatible with the installed base of non-laser-optimized 50µm multimode fibers.

What Are the Issues?Except the compatibility of BIMMF, there still exist some other issues. All BIMMF designs exhibit alength dependency if an overfilled launched is used. Higher-order modes that get launched into thetrench can remain there for some distance until they attenuate. These modes that are captured andpropagate within the trench area are referred to as “leaky modes.” This phenomenon affects spliceand connector loss. On the other hand, non-BIMMF does not have a length dependency. Anencircled flux launch mitigates the core diameter and numerical aperture length dependency for allBIMMF designs. Further, an encircled flux launch accurately depicts the system performance.

ConclusionBIMMF allows cabling installers to deploy a network with less worry about inducing bend loss dueto workmanship. Besides, it is also comparable and compatible with other non-bend insensitivemultimode fiber such as OM3 and OM4. For proper operation of BIMMF links, either homogenousor mixed with legacy fiber, it is important to use a more tightly controlled launch—encircled flux. Anoverfilled launch will trap more high-order modes in the trench and performance will becompromised. With more and more fibers are being installed in smaller areas, requirements for ahigher bend radius become crucial. BIMMF helps mitigate link failures when optical cables undergo

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Fiberstore (FS.COM) | Does Bend Insensitive Multimode Fiber Make Sense? Page 3

small-diameter bends, particularly when applied in data center jumpers/modules and forhigh-performance computer applications, which really makes sense.

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Notice: This document is for informational purposes only and does not set forth any warranty, expressed orimplied, concerning any equipment, equipment features, or service offered or to be offered by Fiberstore.Fiberstore reserves the right to make changes to this document at any time, without notice, and assumes noresponsibility for its use. This information document describes features that may not be currently available.Contact a Fiberstore sales team for information on feature and product availability.

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