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Making the Right Connections for Fiber-to-the-Home Deployment

Thu, 06/26/2014 - 11:30pm
Cheryl Liu, 3M Communication Markets Division

A renewed interest in fiber-to-thehome (FTTH) networks has swept over the telecommunications industry. With continuing demand for high-bandwidth services and new players entering the market, service providers large and small are revitalizing efforts to pull fiber optics all the way to the doorsteps of individual subscribers.

The drop cable connection serves as a key component in FTTH networks.

Subscriber drops must be affordable, easily installed and stable in order to ensure reliable service and cost-effective deployment.

The chosen method for terminating fiber cable at the neighborhood fiber distribution hub and at the subscriber’s optical network terminal (ONT) has a significant impact on installation cost and service reliability. Factory-terminated and field-terminated connectivity methods are both widely used for drop cable installations. Each alternative has its pros and cons. How to choose? Initial capital costs, reliability, deployment ease and speed, cable management and the deployment environment should be considered when choosing connectivity products.

Using factory-terminated jumpers requires an inventory of multiple lengths of patch cords for different installation scenarios. It also requires a slack cable management system for each subscriber when too long of a cable is used – it is nearly impossible to always have all necessary lengths on hand. In fact, technicians run the risk of being caught in the field without the proper length of patch cord, causing installation delays and adding to labor costs.

Field termination, on the other hand, uses reels of bulk cable cut to the appropriate length on-site, saving cost and rendering slack cable management systems moot. Fusion splicing has been the de facto standard method for fiber feeder and distribution construction projects for many years, and it was naturally adopted for FTTH drop installations.

Outside plant services are often connected using fusion splicing, which in general can be time consuming and requires special training. Fusion splicedon pigtails consist of factory-terminated connectors with fiber pigtails attached.

These assemblies are fusion spliced onto drop cables by a technician in the field.

The splices are usually stored in splice trays or organizers, further adding to costs.

Fuse-on connectors, which incorporate a fusion splice inside a connector, evolved from the pigtail approach. Also called fusion splice field-installable connectors, they incorporate a pre-installed fiber stub which, along with the ferrule end face, is pre-polished. They are comprised of several tiny parts that are assembled after the fusion splicing process, demanding a good amount of dexterity and skill.

The initial capital expenditures, maintenance costs and installation speed of fusion splicing hinder its staying power as the preferred solution. Fusion splicing involves the purchase and maintenance of expensive fusion machines for each job site. The machines sell for thousands of dollars each, requiring a heavy investment to equip technicians in the field. And they require an electrical power source, such as a battery that can run out of charge in the field, adding time and cost to the process.

The need for new solutions

Some service providers prefer to use field-termination methods for the operational flexibility, simplified engineering and reduced inventory they offer compared to using factory-terminated jumpers.

The market has responded to these challenges by developing a broader array of field-terminated mechanical splice-on products that offer the same level of reliability as fusion spliced alternatives, yet are easier and less costly to install.

One specific example of a mechanical splice-on (or no polish) connector is fitted with a pre-installed fiber stub that, along with the ferrule end face, is pre-polished.

It also includes an integral splice with index matching gel inside. A typical mechanical splice-on connector includes a small plastic housing with an aluminum alloy element used to precisely align and clamp fibers together. The index matching gel at the fiber splice point maintains a low loss and low reflectance optical interface.

Mechanical connectors without a splice, gel, or adhesive simplify field installation and offer similar performance compared to fusion-spliced alternatives.The connector can be used at a fiber distribution hub or an ONT.

Unlike fusion spliced-on pigtails and fuse-on connectors, mechanical spliceon connectors are installed with a simple handheld tool that does not require electrical power. Terminating fiber cable using these connectors is fast, easy and therefore requires little training. A sin- gle-fiber termination can be completed in just a few minutes with a no polish connector, decreasing installation time compared to fusion splicing.

Extensive third-party optical, environmental and mechanical tests have demonstrated that the connectors are a highly reliable, cost-effective product for FTTH deployments. In fact, service providers in Japan have deployed more than 30 million mechanical splice connectors both indoors and outdoors with proven reliability. As world leaders in FTTH deployment, Japanese service providers have completed laboratory and field analyses that affirmed that the connectors are a viable long-term answer to fiber optic outside plant requirements.

Providers beyond Japan are now choosing mechanical splice-on connectors as an alternative to fusion spliced-on pigtails and fuse-on connectors in order to achieve lower total installed cost with similar reliability.

Letting go of the splice

A field-finished connector that does not contain a splice, gel or adhesive has been developed to serve providers that prefer connectors without a splice joint.

The simple, one-piece connector design combines the performance achieved by fusion splicing with the speed of mechanical connectors, potentially helping providers reduce installation costs. A major U.S. provider that deployed the spliceless connectors in 2011 realized equipment savings of up to 75 percent and labor savings of 20 percent to 50 percent, depending on the deployment environment, compared to using the incumbent fusion spliced-on pigtail.

Installation of the spliceless connector is quick and easy. It typically takes 5 minutes or less using simple tools that do not require a power source. This can allow for much faster installations than with fusion splicing, which requires time to set up and tear down of the fusion spicing equipment. The connector delivers on performance and reliability, too.

It can be installed in indoor or outdoor locations while maintaining reflectance of less than -60 dB (APC version). Test results show that its optical performance remains stable at temperatures between -40 and 167 degrees F.

Mechanical field-terminated connectors, both with and without a splice, offer many advantages over fusion spliced-on or factory-terminated products for drop cable installations. Chief among them is inventory and planning cost savings.

Mechanical field-installed connectors can make installations faster, easier and more cost effective. They require minimal technician training and utilize simple tools. These products have been used successfully outside of the U.S. for years. Now, U.S. providers are beginning to discover the benefits of these field-termination alternatives. ■

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