Fiber Optic Cable Testing Tools PDF

2.6.8 Fiber Optic Cable Testing Tools When you are working with fiber optic cabling, it is important to understand that any mismatch between the cables coupled together will result in data loss. This can occur if the fiber cables are not properly...

2.6.8 Fiber Optic Cable Testing Tools When you are working with fiber optic cabling, it is important to understand that any mismatch between the cables coupled together will result in data loss. This can occur if the fiber cables are not properly aligned, are different sizes, or may have suffered damage (broken/misshaped fiber strands) during transport. If you connect single mode fiber to multimode fiber, you will introduce a catastrophic signal loss of up to 99%. Even connecting fiber cables of the same type but with different diameters can cause a loss of up to 50% of the signal strength. Whenever a connector is installed on the end of fiber optic cables, a degree of signal loss occurs. This is called insertion loss. In addition, some of the light that is lost is reflected directly back down the cable toward the source. This is called back-reflection, reflectance, or optical return loss (ORL). Ultra Physical Contact (UPC) and Angled Physical Contact (APC) polishing reduce ORL reflections, and reflectance loss values improve from UPC to APC. Mating an APC connector to a non-APC port causes major insertion loss. Because of this, APC connectors are always colored green to keep you from mixing them with non-APC connectors. Visual Fault Locator If a break is identified in an installed cable, the location of the break can be found using a visual fault locator. There are different models for short and long link distances, and they can be supplied with adapters for different connector types (ST, SC, or LC). The tool shines visible light down the cable and glows brightly at the point where a cable is broken, excessively bent, or improperly spliced. Dirty Optical Cables Dirt, dust, or grease in the transmission path will greatly reduce signal strength or block transmission completely. Most commonly, this occurs at a connector. Connectors should be covered with a dust cap when removed, and the surrounding area should be dust free before performing a disconnection. Connectors should be cleaned using solvent designed for fiber optics, taking care not to apply excess solvent. The wet-to-dry method applies a drop of solvent to a lint-free cloth and moves the connector from the wet drop across a dry part. Contamination could also be introduced when a cable is spliced. Ensure splicing equipment is cleaned according to the manufacturer's instructions before every splice operation. The powerful light sources used by fiber optics are a hazard. Wear appropriate safety goggles, and never look directly at an active transceiver port or the end of a fiber cable. Point a cable at a flat surface to confirm whether visible light is being transmitted, or use a smartphone camera to detect whether infrared light is being transmitted. Copyright © The Computing Technology Industry Association, Inc. All rights reserved.