Overcoming issues with optical cabling

May 1, 2011
A service provider, whether a carrier or data center operator, can find solutions to service-turnup challenges with the right fiber-cabling systems.

A service provider, whether a carrier or data center operator, can find solutions to service-turnup challenges with the right fiber-cabling systems.

by Pat Thompson

Ongoing demand for new services and capacity are putting pressure on network managers to turn up existing capabilities more quickly, while budget constraints are forcing them to do so with existing resources. Often, turning up new revenue streams means connecting new optical equipment. This is an area that traditionally has caused network managers a number of issues. This article will look at how time and cost savings can be achieved in this area.

Issues associated with turning up new optical equipment range from network engineering to product installation. Here is an explanation of some of the most common issues.

Engineering time. Every time cabling is being run to a new piece of electronic equipment with optical interfaces, the operator must measure the distance between the equipment and the fiber distribution frame so a fiber cable can be ordered. Measurements must be fairly precise. If the cable ends up being too short, the connection cannot be made and a new, longer cable needs to be ordered. If the cable is too long, the excess slack must be stored somewhere in the environment, which can lead to congestion and future challenges.

Product selection. Once the length of cable is known, the network engineer needs to determine what catalog number to actually order. To do this, they need to know the fiber count of the cable they need and more importantly, the cable breakout configuration needed to allow the cable to be loaded into the panels that it is connecting to. Getting the wrong cable configuration can result in difficult routing processes for the installers or even worse, damaged connectors, bend-radius issues or broken fibers.

Ordering delays. Because each cable is a custom length, it can take two to three weeks to receive the cable, which delays service turnup. Expedited production and air freight delivery can speed up this process, but will add cost.

Product installation. The configuration of the office, the distance the cable needs to be run and the number of fibers being installed will have a significant impact on how long the installation process will take. The process of loading the individual connectors and dressing the fibers into the back of the panels can be time-consuming and sometimes leads to connectors or fibers being damaged. Installing a 72-fiber tie cable means that 144 individual connectors need to be routed and connected into the back of the panels. This process alone can take a full day of labor.

Slack storage. Any leftover slack in a cable must be stored, and this can be problematic in a crowded fiber raceway or ladder-rack system.

All of these issues combine to make the process of adding fiber capacity a time-consuming and expensive process. Addressing these pain points will have a significant impact on speeding service delivery and improving profitability.

Traditional solutions

Several workarounds have evolved over the years in attempts to solve these issues, but typically they end up just moving the pain point from one place to another, rather than solving the problem entirely.

One strategy is to install a fiber raceway, between the equipment lineups and the fiber distribution frame lineups, capable of accommodating a large number of fiber patch cords. When new equipment needs to be turned up, individual jumpers are connected and routed in the fiber raceway. In these cases, slack is often managed in a designated area at the fiber frame. While this reduces the criticality of precisely measuring the cable distance and delays capital spend on fiber cables, it results in more engineering and installation time as new jobs are needed every time new fibers need to be turned up. Another issue is that there may be custom breakouts at the end of the raceway to manage bend radii and other physical issues, so the user will need to have custom-length cables.

Another strategy is to deploy a small bundle of fibers across the raceway and have an intermediate distribution panel (IDP) at the end. The IDP is connected to the fibers coming from the distribution frame, and technicians then use patch cords to connect individual pieces of optical equipment to the IDP. As with the first workaround, however, this one simply relocates the engineering time from the long-run cables to the patch cords.

Single-device solution

Another approach is to find a way to deal with cable lengths, slack storage and connections in one device. This points to a new type of intermediate distribution panel that incorporates preconnectorized intrafacility fiber cable (IFC) and allows it to be pulled to the precise distance required to connect each piece of optical equipment.

With this solution, the fiber is stored on a reel inside the IDP and can be pulled to the length required. Any leftover fiber (slack) remains stored on the reel.

Each cable contains 12 fibers, each of which is preconnectorized with multifiber push-on (MPO) connectors. In addition, the solution incorporates micro cable, which puts 12 fibers inside a cable that is 3mm in diameter—80 percent smaller than standard cabling—to save space inside the IDP and provide a more flexible cable for routing.

This new type of IDP has a single fiber connector on the front and a 12-fiber connector on the back, so users can connect 72 fibers with six connectors. Compared to having to manually make 144 connections, this represents a 92 percent reduction in labor. By pulling six MPO cable assemblies from the IDP to the fiber distribution frame, the 72-fiber link would be up and ready to go.

This new type of IDP addresses all of the pain points inherent in traditional cabling.

It eliminates precision cable engineering time because cable can be pulled to the precise length needed. The excess cable remains stored on the reel inside the IDP, so there are no slack-storage issues. The use of MPO connectors eliminates the need for specialized fiber connection expertise. The use of thin micro cable makes the cable easier to route in crowded raceways or ladder racks.

Stocking the IDP can reduce equipment deployment lead times by two to three weeks, because users can order and stock 100- and 200-foot versions along with a selection of standard-length patch cords to handle 90 percent of connections.

By deploying a new type of IDP that delivers precise amounts of preconnectorized fiber, operators including service providers and data centers can speed equipment turnups, streamline inventories and reduce costs.

This intermediate distribution panel includes preconnectorized intrafacility fiber cable, which enables the quick deployment of fiber and therefore quick turnup of new services.

TIA standards cover optical-fiber issues

This article by TE Connectivity’s Pat Thompson informs us of a type of fiber-optic cabling system that can shorten the time required to deploy optical communications systems and by doing so, speed up the rate at which new services can be activated. The system described in the article may be attractive to service providers for use in central offices and to data center operators for use in their facilities.

In North America, the voluntary standards that govern the manufacture and use of structured cabling systems are written by the Telecommunications Industry Association’s (TIA; www.tiaonline.org) TR-42 Telecommunications Cabling Systems Engineering Committee. Within the TR-42 umbrella are a number of other committees constantly working on numerous standards, addenda to those standards, and informative telecommunications systems bulletins (TSBs).

During a recent conversation with us, the chair of TR-42 Robert Jensen discussed some of the activities taking place in TR-42, including several that affect optical-fiber cabling systems.

Jensen explained that several years ago a separate committee, called FO-4, existed outside of TR-42. The former TIA FO-4 Fiber Optics Engineering Committee merged into TR-42 and now TR-42 handles all optical-fiber standards for TIA. “Some people have come into TR-42 as part of FO-4,” Jensen explained. Those who previously were part of FO-4 and longer-term TR-42 members “work together to ensure standards are accurate. They do a fabulous job.”

Among the current and recent activities involving optical-fiber systems are the following.

562-14-B: This new standard was adopted from a specification published by the International Electrotechnical Commission (IEC; www.iec.ch) and uses the encircled flux metric for the launch condition when measuring installed multimode fiber-optic cabling. The TIA’s adoption of this standard was detailed in the April 2011 issue of Cabling Installation & Maintenance, beginning on page 21.

568-C.3: The Optical Fiber Cabling Components Standard will have its first addendum. That addendum will add OM4 cabled fiber to the specification, and also have information about 24-fiber array connectors. Jensen explained this effort “will coincide with the 568-C.0 ballot. As C.0 explains how to implement polarity, this addendum will tell you, here are the components for putting those polarity systems together.”

TIA-607: The TIA-607-B Generic Telecommunications Bonding and Grounding (Earthing) for Customer Premises standard was approved for publication in February 2011. It specifies grounding procedures from the entrance facility all the way to equipment racks. “The previous 607 standard did not have anything from the TR to the racks,” Jensen said. The “B” version of the standard will include “environments like computer rooms and data centers,” he added. While bonding and grounding/earthing is most often associated with twisted-pair copper cabling—and shielded copper cabling at that—as the article that begins on page 11 of this issue reminds us, some armored fiber-optic cable is also subject to grounding and bonding.

TIA-942: The “A” revision of the Telecommunications Infrastructure Standard for Data Centers is currently out for ballot. Detail on the revised standard was provided in the same article that discussed TIA-526-14-B. The standard will recognize LC connectors for one or two optical fibers and MPO connectors for more than two fibers. The recognized multimode optical-fiber cable for horizontal and backbone cabling has been changed to OM3 and OM4. OM1 and OM2 will not be recognized in the revised standard.

Also, a task group has been formed within TR-42.11 Optical Systems to look at optical loss budgets. In essence, the group is examining attenuation across an entire link and studying the practicalities of the amount of loss in each connection. One reality in many optical systems is that the first fiber connection contributes more loss than the link’s subsequent connections. The task group is looking at ways of addressing this reality in a standards-based document that acknowledges it while continuing to ensure a standard-compliant link will perform as expected.

Pat Thompson is a market development director for TE Connectivity’s (www.teconnectivity.com) central office fiber and carrier data center solutions.

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