The knock on plastic fiber optic cables is that they aren't tough enough for industrial use. But the more rugged glass fiber cables are usually more expensive and, unlike plastic, can't be bent enough for tight applications without flaking fiber coatings, resulting in attenuation losses, according to Banner Engineering Product Manager for Fiber Optics Chris Dales.
The company has combined the best of both materials in its STEELSKIN™ armored plastic fiber optic cable. Key is the DURA-BEND™ fused multicore plastic optical fiber, now double-metal sheathed for ruggedness. The inner sheath consists of a stainless steel wire wrapped around a polyethylene enclosed fiber core. Jacketing this inner layer is a braided stainless sheath. This design allows a 10-mm minimum bend radius—tighter than with glass fiber—but resists further bending to prevent damaging the core. The full metal jacket also provides crush, impact, repeated flexing, and abrasion and cutting resistance for the cable. Dales says, "Crush strength is 250 lbs per inch of fiber, an order of magnitude greater than ordinary plas-tic fiber."
The STEELSKIN cable is available in bifurcated (twin fiber pigtails at the sensor input/output) or individual (single pigtail) models. The twin-fiber type allows sensing in a diffuse mode (fibers in the same cable conduct the light out from the sensor and back from a target, for example). Two of the individual cables are used for opposed-mode sensing—where, for instance, a fiber cable out of the sensor projects a beam into the separate signal return cable, thus detecting any object breaking the beam.
Standard cable lengths are 1 and 2m, but custom sizes are available. The cable can be terminated with plastic ferrules for interfacing with Banner's FP-style plastic fiber-optic sensors and amplifiers, and there are options for stainless steel sensing tips and hardware and custom end tips. The company has also developed the IP67 rated low-profile FI22FP mini-sensor made with ABS and polycarbonate for use in tight applications with the metal jacketed or plastic cable.
Banner Engineering Corp., www.bannerengineering.com Enter 623