Fiber-optic cable cassettes target FTTD, Ethernet applications
Telescent (Santa Monica, CA) recently introduced its SureLink family of fiber-optic cable cassettes. The company says the cassettes are designed to conveniently dispense duplex and simplex fiber-optic patch cords of variable length up to 5 m and to safely store unused lengths of cabling on a spool within a protective housing. The ruggedly designed cassette is suitable for use in fiber Ethernet, fiber-to-the-desktop (FTTD), fiber-to-the-home, and critical testing scenarios. The company says its cassette format simplifies the deployment and management of fiber-optic cables at all points within a network infrastructure.
“We’ve always had a lot of frustration with the problems in dealing with fiber, and that’s in a lab-type environment, where you have very extensive test equipment to try to debug problems [arising from] a damaged cable or a damaged or dirty connector,” explains Anthony Kewitsch, president of Telescent. “We felt that as fiber gets closer to the consumer and relatively inexperienced users, there was a need to develop ways of dispensing cable that would reduce the headaches. We felt one key element would be a way to dispense fiber to keep it off the floor...and a retractable or cassette-type cable seemed to be ideal.”
The SureLink cassette dispenses 2-mm jacketed cabling; a magnetic locking feature allows the cassette to be stacked and attached to equipment or a wall adapter plate. The cassette can also be installed within industry-standard LX-type enclosures using an optional face plate. Applications, according to the company, include fiber Ethernet access points, fiber patch panels, wall- or desk-mounted interface plates, fiber-optic modems with detachable cable cassettes, and reference patch cord deployments.
Kewitsch notes that, in designing the cassette, the company focused on two key requirements. “One was an approach that wouldn’t physically interrupt the fiber, a way to produce a variable length cable which doesn’t have an interruption such as a collimator or a lens,” he says. “The other was having a cable where one end is fixed, and the other end is extendable.”
Kewitsch continues, “There are approaches, for example, in the electronics industry, where retractable cables are essentially wound pairwise on a spool, where you pull two ends out, and the enclosure ends up being in the middle. We didn’t feel that was particularly useful in a fiber approach, because now this housing is somewhere mid-span, probably in a very visible location, and not very functional.”
The cassette’s design is based on the company’s patent-pending LightHelix core technology, which enables a continuous length of optical fiber to be embedded within a composite spiral spring structure attached to a rotating “take-up” spool. Continuity of the optical fiber is maintained during the spool’s rotation as the compliant core winds or unwinds.
“The LightHelix structure is a continuous length of one or more optical fibers, depending on whether it’s a simplex, duplex, or ribbon cable,” explains Kewitsch. “Using a unique manufacturing process, that fiber is laminated with, essentially, a clock spring-it’s much like winding up a spring for a watch or a clock, except in this case, it’s a composite including one or more optical fibers. That helical structure is continuous, and as you wind up this spring, one end is rotating and the other end is fixed.”
The company says the cassette’s “tension-buffering” functionality significantly enhances the reliability and ruggedness of exposed optical cables. Additional cabling is released from the cassette should the cable be accidentally pulled. According to the company, for a 5-m length of cable pulled from the cassette, the helix structure contains twice that length that never exits the cassette.
“This design is for a simplex Corning SMF-28 type fiber, for example, or it could be a multimode duplex type fiber-it could be any combination of these,” maintains Kewitsch. “At present for the 5-m extendable length, this cassette is about 5.75 inches on a side.” However, Kewitsch points out that the cassette “can be reduced rather straightforwardly to half that size” through the use of bend-insensitive fiber.
He concludes, “For the SureLink product, we maintain a bend radius of greater than 1 inch for the bare fiber within the helix; the jacketed fiber has a minimum bend radius of 1.5 inches, so it follows the typical guidelines in designing a fiber-optic component, to maintain an adequate bend radius.”