Battle brewing over bend-insensitive multimode fiber

A battle is brewing among makers of optical fiber and fiber-optic cable concerning bend-tolerant or bend-insensitive multimode fiber. Over the past year or so several providers of multimode fiber-optic cable have introduced bend-tolerant/bend-insensitive offerings. The main benefit of this type of fiber-optic cable is that it can withstand tight bends, or even kinks, without suffering significant loss - or any loss in a lot of cases.

Corning Cable Systems was the first to bring this type of cable to market. Corning Optical Fiber - a separate operating unit of Corning Incorporated and a "sister" company of Corning Cable Systems - developed the bend-insensitive fiber that is used in Corning Cable Systems' products. Notably, Corning Optical Fiber also supplies fiber to other cable manufacturers, so its fiber is found in cables from cable suppliers other than Corning Cable Systems.

OFS also manufactures multimode optical fiber, and supplies that fiber to cable manufacturers, including CommScope. Recently, through a white paper, a blog post on its website and other outlets, CommScope has called into question the real value of bend-tolerant/bend-insensitive multimode fiber. In a blog post, Eric Leichter, manager for training and technology with CommScope's enterprise division, openly wonders why bend-insensitive multimode has seen a recent market push. In the post he also raises the issue of compatibility between bend-insensitive and traditional multimode fibers, saying "there are concerns" about such compatibility. He concludes his post by saying, "It might be best to wait for this technology to mature before jumping in."

Speaking of sister organizations, our sister publication Lightwave recently published commentary from fiber-maker OFS that also raised questions about bend-insensitive multimode's compatibility with traditional multimode. (Page 5 of this Lightwave issue.)

In the January issue of Cabling Installation & Maintenance magazine, we're going to publish two sides of this topic. (I'd say "both sides," but for all I know there could be more than two. I'm currently aware of two sides, I guess I'll put it that way.) One article, contributed by researchers from Panduit, will discuss results of an intermateability study conducted by Panduit. The results, the article says, show potentially significant losses when a signal travels from a bend-tolerant multimode fiber into a standard multimode fiber. Panduit's study yielded different degrees of bend-loss improvement among the various manufacturers whose products were tested.

In that vein (and likely in that vein alone) the information from Panduit and that which will be presented by Corning Optical Fiber coincide. Two engineering managers and a product manager from Corning Optical Fiber will contribute a separate article to our January issue. Within that article they say, "Not all bend-insensitive multimode fibers are created equal. Differences in designs of bend-insensitive multimode fiber result in differences in performance." The technical detail in the article boils down to the notion that a well-designed bend-insensitive multimode fiber will not have compatibility or loss-performance issues.

It kind of sounds like they're both saying the same thing, but I don't think that's the case. The organizations I've named here have gone toe-to-toe in the past over issues related to multimode fiber. Most recently, they sparred about the most effective way to measure multimode's bandwidth while the OM4 fiber specifications were under development. Corning Cable Systems and Corning Optical Fiber favored the EMB(c) method while OFS and Panduit favored the DMD mask. Ultimately, the standard recognized both measurement methods as valid.

The current wrangling over bend-insensitive multimode fiber is the latest in a history of companies lining up on opposite sides of technical issues surrounding optical-fiber transmission. Frankly, I see this current spat to be more relevant to fiber-cabling system users than the one over EMB(c)-vs.-DMD mask, because that one was waged primarily in the figurative smoke-filled rooms of standards-making committees. This one focuses squarely on users who are making decisions today about what type of fiber-cabling plant to install. As always in these debates, each side makes a convincing case. If I heard just one side's compelling story, I'd feel well-informed and confident in what the right choice would be. But then I hear the other side's compelling story and am left with a tough choice. That's just hypothetical for me, because I won't have to choose which type of multimode fiber-optic cabling system to install anytime soon. You very well may have to.

My real hope is that providing two sides of the situation in our January issue will do a service, rather than a disservice, to anyone who uses Cabling Installation & Maintenance to help them make decisions about cabling. I'm sure there are more charts, graphs, simulations and the like - on each side - than we could put into the magazine, and these cabling-system providers would be happy to show them to you. In all sincerity, I hope that bringing this topic to your attention equips you with the knowledge that it exists, and helps you prepare to ask the questions you need answered when you are making these important decisions.