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Are all cable lines alike?

wayneI’ve heard this many times before and typically it’s from operations type folks who have seen both copper and fiber cable operations recognize the similarity of the process but do not understand the subtle differences between processing a malleable material such as copper and a crystalline structure such as glass.
I’ve heard many folks tell me they don’t understand why you cannot produce optical fiber cable and copper cable side-by-side on the same equipment.

In order to look at this accurately, let’s start with some of the physics involved.

Copper is a malleable metal that can be drawn or stretched, is relatively strong, has a relatively low thermal expansion and acts as a heat sink to the polymer during the extrusion process.

Glass optical fiber on the other hand is an engineered crystalline structure consisting of many layers and materials. We have glass and optical index of refraction additives in the core and cladding surrounded by the various ultraviolet cured acrylate polymers that make up the optical fiber coating. This engineered assembly does not like stretch and in fact any strain shortens the optical glass lifetime. Due to the crystalline nature of glass there is no sheer strength in the fiber.

Ever see how delicate a stemmed glass is if you knock it the wrong way? Because most optical fiber is typically UV coated, which acts as a thermal insulator, there is almost no absorption of heat by the fiber. This physically causes many problems with polymer extrusion as differential cooling causes many issues in post extrusion stress.

With these physical differences in mind we need to recognize that many of the components look the same. You have an extruder which is a plastic melting pump a water trough which cools the plastic and a capstan that pulls the material through at a fixed rate. And there is typically a form of diameter control with some form of controlled pay off and take up devices.

In copper manufacture, the copper conductors are the strength members in many of the cable designs. The optical fibers on the other hand while very high tensile strength glass, are extremely small and highly susceptible compressive and to off axis stress.

When we look at optical fiber processing, we recognize that in both copper and fiber we are basically squirting plastic over a conductor. Iin one case, an electrical conductor, and in the other an optical conductor. To the untrained eye this looks like the same process. In reality we are actually doing totally different processes. In most copper extrusions we are insulating or coating the copper conductor using a direct contact application of plastic.

In optical fibers we are mechanically buffering the optical fibers from outside handling. While these differences seem almost academic in nature they make a significant difference in how the process line is configured and operates.

In addition the environment in which copper and optical cable are produced is different. Dust and contaminants for optical fiber as well as moisture can create problems for material that does not restrain polymer shrinkage. In copper insulation, thermal heating (preheating) helps maintain a good mechanical bond to the surface since the copper material itself acts as a heat sink and controls shrinkage without affecting its ability to conduct electrons. The same effect in optical fiber will cause compressive strain on the glass which is an engineered component. This would cause significant stain and attenuation increase over cooling and subsequent thermal cycling.

As a result other than the extruder, water trough, capstan combination, very little is held in common between copper and optical fiber process lines. And even these have subtle differences such as in screw, cross head, and tooling design. There are many differences in the water trough processes and location as well as subtle differences in the control logic and surface finish of the capstans.

The pay off and take up equipment may look similar in that we are paying off material and taking up material under controlled tensions but in reality the design and properties used for optical fiber and copper vary widely. In this instance we are using two different properties to correctly handle the different materials.

As we compared copper and fiber process lines we also need to recognize that premise or tight buffer cable and loose tube cable are processed on significantly different process lines. The ancillary equipment and methodologies are drastically different and while many manufacturers have adjustable components to make the process lines capable of producing both loose tube and tight buffer, in doing so, one or the other product line is sub optimized.

When looking at adding optical fiber processing to a cable plant or adding a different product line such as tight buffer, one needs to be very thoughtful in several categories such as which product will be optimized, Product run time or change over time and what the environment will be required for manufacturing. For example will temperature and humidity need to be controlled and will the process be continuous or Job Shop.

So what looks like the same thing under the surface has many differences.

Wayne will be presenting at IWCS in Atlanta October 5th-8th.  If you wish to schedule an appointment with Wayne, contact Kathleen (kskelton@focenter.com) to do so.  Wayne will also be at the Fiber Optic Center booth at IWCS.

Follow Wayne @TechHorsepower

You can find his Twitter feed and easy follow option at the FOC Twitter page: http://focenter.com/twitter-feeds/

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Wayne Kachmar

About Wayne Kachmar

Wayne Kachmar, President, Technical Horsepower Consulting, LLC Mr. Kachmar has been in the optical cable industry for over 37 years. He has participated in many innovations and seen the maturing of the industry. Over the years, Wayne has been involved in many unique projects to provide optical cable in diverse environments such as the underwater ROV that penetrated the Titanic, as well as cable that is in service sensing sub-atomic particles in the Antarctic ice. Wayne developed a number of unique concepts and products using optical fibers as both information carriers and sensors where the cable became the sensor. These have included fiber laser ring gyroscope components and distributed acoustic sensors for terrestrial and underwater applications. As a principal investigator for many government sponsored projects, he has developed methods that push the state of the art in optical cable design and manufacture. Over his career, Wayne has been able to fuse this state of the art knowledge with conventional fiber cable design to significantly cost reduce both materials and processes. With over 50 granted patents in fiber optic cables, connectors and tools and over 60 patents published or in process, Wayne’s path to TE Connectivity started when he founded and ran Northern Lights Cable, Inc. in 1988. He sold the company to Prestolite Wire in late 1997 continuing as division CEO until 2000. In 2000, Prestolite Wire was packaged with other holdings of the owner to become GenTek (a publicly held company), which also acquired Krone that year. Wayne’s position transitioned to Director of R&D, managing the RD&E center. In 2004, all Krone divisions were acquired by ADC who itself was acquired by TE in December 2010. In 2012, Wayne was named a TE Fellow in electro-optic engineering based on the length and depth of his technical knowledge and accomplishments. This is the highest technical title within the TE structure with less than 20 persons worldwide out of 8000 scientists and engineers within TE. In 2015, Wayne incorporated his consulting company Technical Horsepower Consulting, LLC. And joined Fiber Optic Center, Inc. as their Optical Cable Technical Expert. Follow @TechHorsepower