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Automated Pigtail Fabrication Needed for Future Networks

Photonics Spectra
Mar 2002
The "process-centric" automation of fiber pigtail fabrication is a step toward a revolution in fiber optics manufacturing for next-generation networks.

Dr. William L. Emkey

The need to automate the manufacture of fiber optic components is clear. Automation must be embraced if the industry is to fuel the expansion and urban deployment of next-generation networks. The question is how best to implement automation in the manufacture of fiber optics.

Most attempts to date have featured fragmented, single-process automated or semiautomated manufacturing cells that still require extensive manual participation. These “person-centric” approaches, while an improvement on purely manual assembly, fall short in terms of product quality, consistency and cost.

Automating the fiber pigtail fabrication process improves the assembly of fiber optic components by eliminating the problems associated with human intervention. KSaria Corp.’s Prima automated fiber pigtail fabrication system features a throughput of 120 fibers per hour.

True automation is best achieved using a “process-centric” approach that examines each step to determine a way to automate it, with the goal of removing human subjectivity from the system and of establishing measurable parameters for each step of the assembly process. The result is a seamless, in-line system that achieves consistent, repeatable results and lowers manufacturing costs by increasing first-pass yield and throughput.

Until recently, automation of pigtail fabrication had not been considered feasible. Today, however, an automated in-line system can produce a pigtail with no operator intervention. A key component is the fiber work tray, which facilitates movement throughout the automated processes and enables the transportation of processed fiber without touching it. A well-designed fiber work tray:

A well-designed fiber work tray is a key element of automated fiber pigtail fabrication. The tray eases the movement of the fiber through the process and enables the operator to transport the fiber without touching it.

• Never violates the minimum bend radius of the fiber.

• Facilitates the loading and unloading of fiber.

• Includes strain relief to protect the fiber.

• Includes retention mechanisms for fiber coils and ends that hold fiber in place in various positions.

• Withstands the harsh chemicals and high temperatures of a manufacturing environment.

• Eliminates electrostatic buildup.

• Includes registration features for the automated identification of the fiber position.

• Adapts to accommodate various ferrules and end shapes.

• Is stackable for volume handling efficiency.

Preparation and termination

The production of high-quality, high-yield fiber optic components begins with pigtail fabrication, which can be divided into two processing steps: fiber preparation and fiber termination.

Until recently, it was not feasible to automate pigtail fabrication. The process can be divided into two steps: fiber preparation and fiber termination. Preparation consists of dispensing a specific length of fiber onto the work tray and stripping and cleaning the fiber. Termination consists of cleaving the fiber, attaching the ferrule (which involves alignment, fiber insertion and the application and curing of the epoxy) and polishing the surface. Images courtesy of kSaria Corp.

Fiber preparation consists of spooling, stripping and cleaning, each of which must be done consistently and precisely at the start of assembly. The in-line process begins by inserting a cassette of stacked work trays into the system’s tray management module, which loads the trays onto a self-aligning transport mechanism that moves each to the payout and spool tool. The tool extracts a programmed length of fiber from the fiber reel and spools it onto the work tray without violating the minimum bend radius. This is difficult to do by hand and often results in fiber damage that may not be detected until much later in the manufacturing process.

The fiber work tray is then indexed to the stripping tool, where a programmed length of buffer is heated and stripped from the end of the fiber. Automatic stripping has several advantages over manual or benchtop stripping, including the use of controlled and optimized temperature profiles, a more reliable and consistent strip because of the automatic blade positioning, and consistent fiber strip lengths and pull strengths.

Next, the tray is indexed to the cleaning tool, where the fiber is ultrasonically cleaned with a nonalcoholic, noncombustible fluid. The automatic tool provides a rapid cleaning process that results in a consistently cleaner fiber.

After preparation, the ends of the fibers must be terminated. Depending on the application, the fiber cleave operation can be the final termination step, or it can be the step prior to inserting the end into a ferrule. In the latter case, cleaving reduces the possibility of axial crack propagation during subsequent handling, and it facilitates insertion into the ferrule.

This operation has several physical characteristics that must be controlled, including cleave angle, fiber hackle and fiber chipping. In automated cleaving, the tray moves to the tool, which cleaves the fiber to meet or exceed industry standards. Because this process is done automatically with the associated monitoring and control, it achieves extremely consistent cleave angles and better cleave quality than manual or manually assisted processes.

The tray moves on to the ferrule or capillary attach module. At this point, the system must accommodate a variety of ferrule termination options, including ferrule geometries, orientations, materials, epoxy-bonding requirements and buffer distances. Automatic, in-line attachment provides the flexibility and precision control throughout the process to address these options. Automation offers the necessary precision alignment, fiber insertion, bubble-free epoxy application and curing control for consistent ferrule attachment, which is almost impossible to achieve with manually assisted operations.

In the final step, the tray moves to the polishing module to undergo a controlled sequence of polishing operations for a premium surface finish. The polishing station can be programmed to provide a variety of end-face finishes, including normal planar, angled planar and spherical.

The completed assembly is then cleaned, and the tray is indexed to an inspection stage where a vision system determines whether the end face meets polish quality specifications. Rejected pigtails can be recycled through the system for repolishing or removed for disposal. Finished pigtails are loaded into a cassette for the next process.

A fully cued system, beginning with the fiber on a spool, provides one terminated fiber pigtail per minute.

Revolutionary step

The automation of the fiber pigtail fabrication process clearly improves the assembly of fiber optic components, eliminating the problems associated with human intervention. It is a flexible, hands-off, process-centric solution that yields high-quality fiber pigtails quickly and cost-effectively with consistent, repeatable results.

Manufacturers have long recognized that manual and semiautomated methods do not meet the demands of broadband network deployment and that they will limit industry growth and profitability. This is particularly evident in the manufacture of optical components and modules, which make up the core of the sophisticated, next-generation networks — especially those poised for metropolitan deployment. Fiber optics manufacturers must produce components with higher quality and consistency at lower costs to meet future demand and to thrive as an industry.

Automation — full, in-line, process-centric automation — is the solution. It will solve both the cost and quality issues that plague the industry. It represents not an incremental change to current processing methodologies, but a huge first step toward a true revolution in fiber optics manufacturing.

Meet the author

William L. Emkey is chief technology officer at kSaria Corp. in Wilmington, Mass. Prior to joining kSaria, he was an associate professor of physics at Pennsylvania State University, managed optical design and development teams at Lucent Technologies Inc.’s Bell Labs in Murray Hill, N.J., and was vice president of product marketing at Lightchip Inc. in Salem, N.H. He holds seven patents on devices such as optical couplers and isolators, and has a PhD in solid-state physics from Lehigh University.

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