Get the answers to the top 11 most frequently asked fiber questions.


1) I have been hearing many good things about OM5 wideband multimode fiber. What can it do to cover my future bandwidth needs?

The advantage of OM5 cabling is its ability to extend the reach of applications that use short wavelength division multiplexing (SWDM) while retaining support for all legacy applications. The existing and emerging SWDM applications permit transmission of high-rate applications over one-quarter of the number of multimode fibers needed by the usual parallel fiber approaches, thus allowing 40G, 100G and even 200G data rates over a single MMF pair. With OM5, customers can retain the use of familiar duplex LC connector circuit administration for many generations beyond current 10G data rates, at reaches of 150-200 meters.


2) Will fiber be the best solution to connect cellular network radios in the future?

Industry consensus is that 5G radio networks will opt for fiber as the preferred technology for backhaul and fronthaul, because of bandwidth. The density of radios for 5G will drive the requirement for network convergence between wired and wireless traffic, increasing the requirement for fiber network solutions that focus on providing the density, accessibility and flexibility to support multiple applications needed for the future.


3) For in-building applications, are fiber-optic cables subject to new European CPR regulations? This is a hot topic in Europe now for in-building, with new regulations instated July 1, 2017.

Yes, CommScope cables will be classified. Local regulations will determine what cable should be used and when—responsibility is with the building owner. All permanent fiber cable is subject to regulations—meaning trunks. Patch cords are not considered permanent.


4) I hear that 400G is right around the corner. Do I need to use singlemode fiber to run that application?

Most Enterprise customers do not plan to implement 400G any time soon; but, for some very large DC operators (hyperscale, for example) 400G can’t come soon enough. The IEEE 802.3bs standard for 200/400G Ethernet has already been approved. This standard includes options for both SM and MMF. Additional work is underway to add new PMDs based on SWDM options that are currently available for 40 and 100G on MMF. It is most likely that future support for 400G in the enterprise DC will be available and cost effective on MMF for Enterprise DCs. Meanwhile, it is most likely that hyperscale DCs will deploy 400G on SMF as soon as it becomes practical.


5) How do I design an ultra-low-loss data center infrastructure?

An ultra-low-loss fiber infrastructure conserves the optical signals by reducing the losses associated with cabling and apparatus. The design focuses on every component of the link—end to end. The design will also include the exact loss requirements for each link. Ultimately, assuring that high-speed optic applications will work reliably can only be based on low-loss and high-quality components. CommScope’s design tool set—the Link Loss Calculator and Application Assurance guide—make DC design for high speed easy, error free and guaranteed.


6) There appears to be discussion around 200-micrometer optical fiber. What does it mean for me?

In today’s high-performance networks, the most economical way to distribute large volumes of information is to utilize very high-fiber-count cables.

In most instances, ducts and pathways are installed prior to the need for these high-fiber-count cables. The cost to replace these items is often high—and sometimes not attainable.

Singlemode fibers with a 200-micrometer outer coating versus a 250-micrometer outer coating enable much smaller cables. As an example: a cable with 288 fibers that is manufactured with conventional 250-micrometer diameter fiber has a dimension of 14.0 millimeters; utilizing a 200-micrometer diameter fiber reduces the cable dimension to 9.6 millimeters. The design with the smaller diameter fiber is 36 percent smaller.


7) I have heard about eight-fiber connectivity. I use 12-fiber MPOs. Do I need to switch?

Parallel fiber applications often require eight fibers, with each fiber carrying one-quarter of the total data per direction. Parallel fiber transceivers, such as the QSFP, are directly compatible with both eight-fiber and 12-fiber MPOs. An eight-fiber MPO connector provides only the necessary subset of the fibers to support the application. Thus, cabling infrastructure using eight-fiber units is matched to the needs of these applications. A 12-fiber cabling infrastructure also easily supports these applications and offers options on how to use the available fibers. One way deploys the 12-fiber infrastructure so the eight-fiber application is assigned to operate over a 12-fiber cabling unit, leaving four fibers dark. Another way combines two 12-fiber cabling units together to carry three eight-fiber applications. The eight-fiber cabling solutions are relatively new. Existing preterminated array cabling infrastructures are mostly based on 12-fiber MPOs deployed with devices that transition to six duplex LCs to support six two-fiber applications. This cabling can be converted to support parallel applications by removing the transition devices. So there are several options to support parallel applications, but it is not necessary to switch from 12-fiber to eight-fiber cabling to do so.


8) How long of a span can I suspend self-supporting fiber?

A self-supporting fiber cable is defined as a cable that was purposely designed to support itself without attaching it to a supporting strand. Each self-supporting fiber cable will have its own specification for maximum span length.

While most of the self-supporting fiber-optic cables can mechanically withstand the loads of longer distances than are typically specified for each cable, the span lengths are often limited by the strain placed on the fiber-optic glass inside the cable and/or by the minimum clearance requirements provided by the NESC (National Electric Safety Code). A great example to highlight this is the M-MN-109 self-support drop fiber, which has a maximum span length under NESC heavy loading conditions of 128 feet when attached at an 18-feet height and a minimum clearance for areas accessible by vehicles is 15 feet. Whereas, if there was enough clearance to allow for 18.6 feet of sag, the span length under NESC heavy, it could extend to 420 feet. This would require an attachment height of 33.6 feet in an area accessible by vehicles. This is not very common, which is why CommScope refers to this type of length as an “infinity” span.

Some manufacturers only provide their customers with infinity span lengths regardless of NESC clearances. CommScope provides span lengths in three categories—NESC vehicular access, NESC pedestrian access, and infinity—within each NESC loading category: heavy, medium, and light.

When a self-supporting fiber cable is lashed to a support strand such as a one-quarter-inch 6.6-meter EHS strand, the self-support span limitations no longer apply since the load is all being placed on the strand—not the cable.

The only sure way to know the limitations is to look at the specifications for the cable.


9) Can I bend a fiber around a sharp corner?

All fiber-optic glass cables, patch cords, jumpers and pigtails have a bend radius that must be maintained for good signal transmission. Typically a sharp corner will bend the cable to the point of bend attenuation and loss of optical signal. However, with just a little curve around the corner there are many fiber-optic cords that will have enough radius to keep a good, clean signal. Fiber-optic cables and cords that meet ITU-T G.657 are termed bend-insensitive or reduced bend radius fibers. The fiber cables have glass construction technology to allow for a reduced bend radius. The minimum bend radii are specifically:

    • G.657.A1: 10 millimeters
    • G.657.A2 and G.657.B2 (G.657.A2/B2): 7.5 millimeters
    • G.657.B3: 5 millimeters

Note that regular nonbend insensitive fiber is guided by G.652 and has a specification of 30 millimeters (a two-inch bend radius is commonly used). Also, larger count inside and OSP cable will often have a manufacturer’s specification of 15x OD during installation and 10x OD during standard operations.


10) I hear that loss budgets for future applications are stringent. What are the loss characteristics of your connectors?

As optic applications increase in speed, the total link loss budget allocated to the physical cabling is reduced. More budget is allocated to signal impairments due to the transmission though the MMF. Supporting these high-speed links requires high-performance fiber that minimizes signal impairment and low-loss connectors that conserve as much signal as possible. The total link performance must be designed as a system to ensure that future higher speed applications will be supported. Looking at individual connector losses is not enough. The CommScope guaranteed loss performance includes all components as they are assembled and installed as a working link. The link performance is far superior to the worst-case sum of the components. When you need high performance, you should know that each and every component is the best it can be. Using the CommScope Link Loss Calculator requirements ensures you get the performance you need—and paid for. Better link performance means longer distance support with the structured connectivity DCs need to ensure scale and availability.


11) What types of cabling are needed to support metrocell/small cell deployments?

Although on a smaller scale than macrosites, metrocells need to connect to similar equipment. Ruggedized optical fiber cables, typically singlemode, are used to connect the remote radios to the backhaul fiber. RF jumpers and power cables are also needed to connect to the antennas and power the radios. There are many innovations in this space, including smaller, more flexible cables, as well as hardened and weatherproofed connectors to make installation easier.


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