CNX ANIXTER

Bend insensitive multimode fibers (BIMMFs) utilize an innovative core design allowing to significantly reduce macrobends loss, even in the most challenging bend scenarios. But not all bend insensitive multimode fibers are built the same, and differences in BIMMFs designs have resulted in some misunderstandings about the operation of these fibers.

CNX Anixter brings you the answers for some questions you may have about bend insensitive multimode fiber technology:

1) Do bend insensitive multimode fibers meet standards?
Yes, Corning® ClearCurve® multimode fiber meets the following industry standards:
- IEC 60793-2-10 for multimode fiber 50/125 class A1a
- TIA/EIA 492AAAB (OM2), 492AAAC-A (OM3) and 492AAAD (OM4)
- ITU-T Recommendation G.651
- ISO/IEC 11801 Grade OM2, OM3 and OM4

These are some of the standards we have commonly used for measuring our traditional multimode fibers in the past.

2) Why is it important to rely on standard-based bend insensitive multimode fibers?
Fiber standards ensure compatibility among the different product manufacturers. Incompatibility problems can result in larger losses than expected in splices and connections. Therefore, whether you choose to use bend insensitive multimode fibers or not, you must always ask the manufacturer whether the fiber is compliant with industry standards.

By ensuring the multimode ClearCurve fiber meets existing fiber standards, we can ensure our customers they will have no compatibility issues when combined with any other 50-micron multimode fiber that meets industry standards (whether they are bend insensitive or conventional fibers).

3) Has Corning retired from bend insensitive multimode fibers standard-related activities?
Corning retired from standard activities for a short period of time while we determined our position over copyrights, but we are now actively participating and have decided to license the technology if we get the essential IP. The ClearCurve multimode fiber is fully compatible with current standards and standard-compliant previous and current multimode fibers, so there’s no need to create a new standard to determine whether the ClearCurve multimode fiber is compatible or not. There are now some available bend insensitive multimode fibers offered by other manufacturers that are not  compatible with existing standards, a reason that may drive these manufacturers to create a new standard.

4) Have bend insensitive multimode fibers been tested in the field, or are there any risks to be considered?
ClearCurve multimode fiber has been thoroughly field-tested, and no problems have been reported. Over the last year, all Corning Cable Systems 50-micron products have used the ClearCurve multimode fiber – so we can clearly establish we have found no issues nor complaints on the part of customers.
Before launching this product, Corning made exhaustive trials in order to understand and explore the potential risks for our customers, including compatibility and interoperability with other manufacturer’s multimode standard-compatible fibers. No problems were observed. Only after these trials and analysis were performed, did we give the green light to turn ClearCurve multimode fiber into the new standards-compliant 50-micron fiber.

5) Is there really a benefit in the best performance of multimode fiber in bends?
Definitively. There are very few network installations or movements, additions and changes (MACs) where cables are at very low risk. The conduit or cabletray can become saturated as new splices are added on the network, thus compressing or squeezing cables. Cables can be pinched by a too tight lace. The minimum bend rate for a cable inside a distribution conduit may not be the recommended diameter, although the proper components for cable management are used. Jumpers can get caught between hardware doors (ODF) during installation or maintenance, or movements, additions and changes.
The intention is not, of course, to encourage an underrated management of the ClearCurve multimode fiber or field practices. But we also have a team of experienced field engineers across our company who are aware that mistakes or setbacks may always come up. We see ClearCurve multimode fiber as an insurance policy, with no additional costs, covering the whole extent of the network. And this policy can make the difference between a call and a network breakdown.
With the use of the ClearCurve multimode fiber, there’s also an additional benefit from utilizing improved products.
ClearCurve multimode fiber was an essential component in the new Corning Cable Systems data center solution Pretium EDGE®, which enables totally innovative performance and improved density. Therefore, the ClearCurve multimode fiber provides direct benefits for our customers by adding robustness to the network and, at the same time, allowing for the use of new, innovative products.

6) How are bend insensitive multimode fibers different from traditional multimode fibers?
Like any other fiber optic, information travels from end to end in light form through multimode fiber conventional cores. These cores are all the same size, and work the same way both in insensitive multimode and traditional fibers.
This is where BIMMFs differ: there is an optical trench around the fiber core. Why? If a conventional fiber is bent too hard, for example when tightly coiling the remains of a cable reel,  light modes have difficulties “during coils” and can escape out of the core, resulting in a signal degradation. But optical trenches in BIMMFs act almost as an armour to keep light modes within the core during excessive bending. This is the point where the design of bend insensitive multimode fibers and engineering expertise come into place. Many manufacturers find it difficult to find a careful trench design within the fiber. BIMMFs that are not carefully dealt with in the optical trench design can result in a multimode fiber which is not compliant with standards and/or a fiber that has trouble meeting transmission performance requirements.

 

7) Can I really use a bend insensitive multimode fiber with other multimode fibers without having performance issues?
Yes, as long as both fibers meet all standards, you can have confidence about using them. Our own trials, as well as our customers’ experience, who have already been using this fiber as their standard for about a year in all Corning Cable Systems products, have shown no related issues with the use of the ClerCurve multimode fiber and previous Corning or other fiber manufacturers’ multimode fibers meeting these standards.

8) Do I need to use special tools or processes to terminate or connectorize bend insensitive multimode fibers?
No, not with the ClearCurve® multimode fiber. Remember, it meets all standards and it’s compatible with conventional and previous 50-micron multimode fibers, which means it can be connectorized with the same methods you have used in the past. The only difference you’ll see is a multimode fiber cable which can be bent much harder than cables you’ve worked with so far!

9) Do I need to use special tools or processes to test bend insensitive multimode fibers?
No, not with the ClearCurve® multimode fiber. The mediation method recommended by Corning Cable Systems for an end-to-end test on a multimode system is the one-reference jumper method with a coiling mandrel, in agreement with accepted standards.
There are two options for testing a ClearCurve multimode system, and this should apply for any bend insensitive multimode fiber.
Corning Cable Systems has all the mandrels and jumpers you need to test your system. These products, and much more information on tests, can be found at Corning Cable Systems website. It is important that the customer chooses the most appropriate option based on available test equipment.

10) Does the 4 mm diameter mandrel offer the proper condition for the launching of tests as defined in standards?
Yes, tests performed by Corning® have determined that a ClearCurve multimode fiber reference jumper  and a 4 mm diameter mandrel will offer the desired launching condition for proper tests at 850 nm. Corning is working within these standards in order to ensure that a 4mm diameter mandrel is incorporated within the standards of existing tests.
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