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Preconnectorized solutions: For state-of-the-art optical access deployments

Sat, 02/28/2009 - 7:00pm
Mark Conner, market development manager at Corning Cable Systems

Multiple system operators (MSOs) have been offering commercial services over an all-fiber network for several years, but now it is viewed as an increasingly important part of their growth strategies. Because of the number of small- to medium-size businesses (SMBs) and the range of communications services that they now require, this market has become a ripe opportunity for MSOs.

When commercial services first started taking off, customers typically were larger and were served via a coarse wavelength division multiplexing (CWDM)-based network. The filters and drop cables needed to connect a subscriber were often spliced into existing closures, leveraging optical cables already in place for residential broadband services. As long as customers remained few and far between, this one-at-a-time method worked well.

However, successful initiatives to capture SMBs bring new challenges. MSOs now face a larger volume of subscription orders to fill, which requires increased labor, better management of connectivity and, in some cases, the addition of new fiber into the network. Multi-tenant unit (MTU) commercial buildings in large metro areas represent significant opportunities, but smart deployments must match initial revenue opportunities with the scalability required to capture future growth over time.

As technologies such as Ethernet – P2P, EPON and 10G EPON, and radio frequency over glass (RFoG) – fill out the all-fiber access tool box, MSOs will automatically be building the skills and efficiencies needed to leverage all-fiber access networks for residential services, too. With these technologies, business and residential services over fiber become synergistic, allowing both services to be delivered over the same, or similar, platforms.

For commercial services now, and residential services in the future, preconnectorized assemblies enable very rapid network deployment, usually at similar or better total installed cost compared with current methods. Ultimately, the design methods and solution sets will be similar for both commercial and residential services.

SERVICE DELIVERY PLATFORMS
Current MSO architectures include hybrid fiber/coax (HFC) mostly for residential and all-fiber solutions using CWDM and point-to-point approaches for business services. Splitter-based, all-fiber platforms are of increasing interest, with the evolving RFoG specification.

The splitter-based platform, when built to recognize specifications, can support RFoG, EPON, 10G EPON and GPON technologies, making it a flexible approach for delivery to SMBs, and potentially residential customers. This presents a unique and powerful opportunity, in that the splitter-based, single-fiber physical layer can be used universally for many business and residential applications.

Without a doubt, CWDM and P2P will continue to play a crucial role for service delivery to existing customers, and especially to large enterprises. Established HFC will continue to deliver residential services for some time. However, the evolution of transport platforms is bringing a whole new set of choices for new business and residential builds. The physical layer components needed to support these technologies is established and will continue to evolve and solve the challenges that MSOs face as they expand their businesses.

PHYSICAL LAYER STRUCTURES
Depending on the transport technology, the passive physical layer elements may be structured around these key considerations:

  • Fiber count per subscriber: Both one-fiber and two-fiber solutions can be used. Point-to-point and CWDM generally use two fibers, while splitter-based solutions generally are a single-fiber per subscriber.
  • Architecture: PON-type and CWDM solutions can be deployed using centralized and distributed approaches for placement of splitters and filters. Predominantly, the PON-type networks use a centralized splitter placement strategy to better scale splitters and provide common configuration and testing points. CWDM has used a mix of the two approaches, often placing filters where needed to capture subscribers while conserving existing fiber counts.
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(Click Image to Enlarge)

Regardless of the technology used and the number of fibers per subscriber, similar design methods and solution sets can be used. Totally spliced, blended splice-and-preconnectorized, and highly preconnectorized solutions can be used to deploy these networks. Preconnectorized solutions have the added benefit of better leveraging the available labor pool, allowing more networks to be created with the same resources.

Preconnectorized assemblies are nothing new to MSOs. Operators have used preconnectorized node assemblies successfully for years, splicing one end to the transport cable and feeding the connectorized end into the node housing to connect the electronics. Deployment of residential, all-fiber networks over the last five to six years has helped to evolve and perfect hardened connectors for field use, and has enjoyed a very high success rate for both single and multi-fiber connectors.

To capture new subscribers in developed commercial areas, existing transport cables and node closures can be used to add new business terminals, from which businesses can be connected via preconnectorized drop cables. This approach separates commercial services from existing residential network elements for individual management. Preconnectorized drops make subscriber connections faster and can leverage technicians from a wider range of backgrounds, since splicing is no longer required at the time service is turned on.

For new-build areas – either general commercial areas or dedicated business parks – terminals may be spliced in during initial construction, or terminal distribution systems (TDSs) can be used, allowing terminals to be added later (without splicing), when needed, to make service connections. For existing plant, picking up a business here and there, the added business terminal – be it for CWDM or a PON solution – is a valid approach. For business parks, the density and volume can take advantage of more preconnectorization and a centralized architecture. In both cases, preconnectorized drop cable assemblies complete the link to the customer.

High-rise MTUs offer a very unique situation where there can be as few as one tenant for multiple floors or, more often, several tenants per floor. Each tenant represents a sales opportunity, but a high take-rate may only exist after some time. Because physical access may be limited or only available at certain times, it is desirable to cable the entire building and have it ready to go when services are requested.

Traditionally, this has meant that a riser cable is placed and accessed periodically along its length to add terminals (interconnection points) every few floors. This is a time-consuming process, so the access is sometimes left until the time of service turn-up, when it again requires building access privileges, and requires special skills and tools. Placing a terminal distribution system vertically in a building riser can solve both near- and long-term issues.

In the near term, a cable assembly is placed in the riser, with factory-installed preconnectorized access points at pre-selected locations, usually every one to three floors. The assembly is quickly installed, and the only splicing required is at the headend-facing cable end. This splicing is usually in a telecom closet, basement or outdoor closure and is accomplished quickly, since it is just one location. As soon as the riser assembly is placed, the access points are, by default, already in place, too. Terminals can be quickly connected (without splicing) at the locations where they are needed to activate initial subscribers; additional terminals are only connected when needed to fill subsequent new orders.

Not only is this method fast and easy for the network operator, but it is highly desirable for the building owner, due to its minimum install time. For the network operator, the cost to pass (pre-position) for commercial services is minimized, and the total cost for complete connections is scaled to actual network revenues.

A HIGH-RISE EXAMPLE
Using a real deployment as a basis, in which a preconnectorized solution was selected over a conventional spliced solution, is a great way to illustrate how effectively a preconnectorized approach can be in an MTU setting. The objectives for the project were to "pass" each floor – meaning that a service terminal and equipment can be added without the need for further splicing at service turn-up – in the least amount of time, due to access restrictions and associated costs.

Before installation began, each floor had been core-drilled to allow passage of the cable assembly, as would be done for a conventional deployment. The cable reel was set up on the top floor, with the headend-facing part of the cable paying off and down the riser. The assembly was pulled down through all 38 floors until the first position alignment marker (PAM) lined up with the first floor. The cable was secured in place, and a length of leader cable was routed to the termination point.

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(Click Image to Enlarge)

At this time, the crew can be subdivided, with one person focused on preparing the cable end for termination, mounting hardware and splicing the active fibers, while the remaining crew members continue to secure the cable assembly up through the riser. PAMs, which included a floor designation, were checked and secured. Additional cable was paid off to allow pre-assigned slack to be stored. The two tethers at each access point were separated from the main cable and secured. One tether was left coiled next to the access point, and the second tether was routed up to the next floor, ready to accept a plug-in terminal. Terminals may be placed during installation of the main assembly, but most have been delayed until service is needed to save on initial installation costs. While the riser cable assembly in this example has a raw end for splicing, this, too, can be preconnectorized, eliminating splicing and allowing the end to be plugged into patch panel modules in a matter of minutes.

The total time needed to install the assembly was approximately 10 clock hours (30 technician hours, assuming a crew of three). At completion, all floors are ready to receive a terminal and connect service. Terminal installation requires approximately 10 to 15 minutes. In a conventional deployment, where a riser cable is placed with periodic slack loops for terminal splicing, it is necessary to mount hardware, perform a midspan access on the cable, and splice pigtails or terminal stub cables.

The table below summarizes the time needed for both the preconnectorized TDS and an all-spliced solution. Where terminals must be spliced, a splicing technician is required in addition to personnel to install the electronics needed to complete the service connection. However, with the TDS approach, the technician placing electronics and making the service connection can be trained in a matter of minutes to install the terminal, allowing highly trained splicing technicians to support other projects.

While this example shows new construction in a high-rise environment, the same TDS solution (using outside plant cable assemblies and terminals) can be used for reaching individual businesses, especially in business parks, and residential customers.

LEVERAGING EXISTING CABLES FOR NEW OPPORTUNITIES
Where existing optical cables can be leveraged, business terminals can be added. In this example, similar to Network A above, three terminals are to be added with planned capacity for three customers (CWDM mux/demux filters) in the first and last terminals, and two customers in the second terminal, for a total of eight customers, and therefore eight wavelengths.

Two approaches are considered – a "classic" spliced solution and a preconnectorized solution. The classic solution splices all elements, including access to an existing fiber pair, necessary filters and drops. The initial build is for three terminals/three wavelengths active, which means that adding capacity requires fibers to be broken and re-spliced (up to five times). The preconnectorized approach requires initial splicing into the existing closure – all other connections at the business terminal and customer are completed via connectors. The addition of another filter set into the path requires only a minor reconfiguration and is completed in a matter of minutes by disconnecting and reconnecting. A summary of time/cost information and assumptions is shown.

At first glance, two things stand out. First, the time needed to pass and offer service to the initial subscribers is far less using preconnectorized solutions than with the all-spliced solution, as it also is for incremental adds. In fact, the time spent deploying the spliced solution is as much as four times that required for the preconnectorized solution. And, each incremental add requires a splicing technician for the spliced solution, whereas preconnectorized adds do not.

Second, the total installed cost for the two solutions is nearly the same. Comparing the two approaches, using the preconnectorized approach means that the network can be deployed and services can be marketed to approximately four times as many SMBs, for the same amount of calendar time and installation cost invested. The fact that subsequent service can be connected in less time without need for splicing skills or equipment means splicing technicians can be leveraged for higher-value opportunities, and a wider range of technicians can do service connections. Furthermore, a preconnectorized solution provides convenient and easy access points for testing and network configuration without the need to break and re-splice connectors.

RESIDENTIAL – A LOGICAL PROGRESSION
While commercial services are certainly front and center for MSOs, bandwidth demand in residential services continues to increase. A plethora of available activities on the Internet – audio/video streaming, large file up/downloads, gaming, telecommuting, to name a few – are steadily increasing the amount of bandwidth needed to provide a quality online experience. HFC networks, with regular enhancements, can handle this for a while but will inevitably run out of steam and become increasingly complex to manage.

For new builds and upgrades to much older networks, deploying a network that may need to be replaced before its technical and accounting life cycle has completed may not be the best choice. An all-fiber solution can support an electronics solution with a longer initial horizon before changes are needed. Technologies already exist to offer even more bandwidth when the time comes, using the same physical layer with virtually no changes. Not only does fiber offer a very long bandwidth horizon, but it minimizes or eliminates electronics and power supplies in the field and has been shown to experience as little as one-fifth the service calls as a copper access network, further reducing costs.

Residential deployments over the last five to six years have driven – and continue to drive – the optical fiber and hardware industry to perfect solutions that minimize installation time, maximize workforce efficiency, and reduce total installed and operating costs. Preconnectorized solutions are the state of the art when it comes to optical access deployments for their ability to enhance all of these areas.

CONCLUSION
Preconnectorized optical access solutions offer MSOs an opportunity to use proven technology to more quickly realize their goals in building their commercial services business. As the focus increases on small-to-medium businesses, there will be an increased volume of subscribers to be added, making preconnectorized solutions the best way to handle and manage that volume. The skill set and comfort level developed in commercial services, because of growing similarities in network technology, will make it possible to leverage an all-fiber solution for residential services as well. Where developers require an all-fiber solution, or where a new network is being created, a preconnectorized optical assembly can be placed just as easily, using the same crews, as can a coax cable. Compared to more traditional forms of optical network deployment, preconnectorized optical assemblies will save time and money in terms of total installed cost.

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