Splicing fiber requires the right fusion splicer

Fusion splicing has become the preferred method of joining optical fibers in communication systems. A fusion splice has many attractive characteristics that have made it the joint of choice, including long-term reliability, low loss, no significant reflectance, and minimal cost per splice.

Before browsing the Internet or calling distributors or manufacturers, take the time to answer some questions to help determine your needs, including the following:

  • What are the loss specifications of the typical jobs I will be working?
  • Will I need to know the exact splice loss on-site before leaving the splicing site?
  • What is the fiber type I will most often be splicing?
  • Will I be splicing ribbon fibers or only loose strands of single fibers?
  • Will I work in a controlled environment or outside?
  • Will I be splicing in confined areas or open areas?
  • Will I be splicing in remote areas without an AC power source?

After answering these questions, you can direct yourself toward the machine with the right features. Considering the different categories of splicers also will help narrow the selection.

Core-aligning splicers have the ability to position two fibers' cores precisely, so that the lowest possible splice loss is achieved. The two common technologies used in these splicers are LID (local injection and detection) and PAS (profile-alignment system) with core detection. In a LID system, an optical signal is coupled into one fiber, and the fibers are aligned until the detected power level in the other fiber is at a maximum, indicating good core alignment. In a PAS unit, a sophisticated imaging system "sees" the core/cladding interface and moves each fiber to align the cores.

The core-aligning machines splice only single fibers, not ribbons. Their strengths include consistent low-loss splices and accurate loss estimation. These machines are also recommended when splicing any dispersion-shifted specialty fibers.

Automatic fixed V-groove micro splicers are significantly smaller, lighter, and less expensive than most of the top-end core-aligning units. But they only align fibers based on the outside cladding and do not provide any fiber positioning other than pushing the fibers together during the splice. The alignment is solely based on the fibers' position in a fixed V-groove. The splice process is completely automatic, and an estimated loss is displayed at the end of fusion.

These units are not as precise as core-aligning units and do not provide consistent low-loss and estimator accuracy; however, they are more than adequate for many singlemode and multimode jobs. Micro splicers traditionally have been single-fiber units only, but in 1998, every major manufacturer offered a micro mass-fusion splicer capable of splicing up to 12 fiber ribbons.

Manual fixed V-groove splicers have the least features and are the least expensive of the fusion splicer categories. Like the micro splicers described above, these units employ a fixed V-groove for single-fiber alignment. Prior to fusion, the operator must position the fibers and inspect them to determine if the alignment and cleave are acceptable. The splicer then pushes the fibers together during fusion. No estimated loss is provided. In the hands of an experienced operator, these units can perform as well as the automatic micro splicers.

Mass fusion splicers are generally based on the automatic, fixed V-groove splicers described above. They are capable of splicing single fibers or ribbons of up to 12 fibers. Smaller, lightweight mass splicers have become popular as a result of the recent drive to install fiber ribbon cables. The mini-mass units are as capable as older, larger mass splicers, but can also operate in confined areas and by battery power in remote locations.

Determining which splicer best suits your application depends on how much loss is acceptable and how much money you can afford to spend. Consider some of the common applications for splicing communication systems: cable television, local telephone, long-haul telephone, and traffic-control systems. The splice-loss requirement is typically defined based on the system-fiber lengths: the longer the system (and therefore the weaker the signal at the system end), the lower the required splice-loss specification. These applications often define maximum acceptable loss values.

The top-end machines can easily meet any of the less-stringent specifications, but the fixed V-groove machine may not always be able to meet tight loss requirements. If you are splicing in many different applications, the selection of your splicer should be based on the lowest splice-loss requirement you anticipate.

Marty Anderson is a product specialist at Siecor Corp. (Hickory, NC.)

This article is reprinted courtesy of Cable Foreman, now OSP Engineering and Construction, a PennWell publication.

For more information, see the "Splices and Splicing" product comparison table in this issue.

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