Practical Industrial Data Networks:Design, Installation and ...

84Practical Industrial Data Networks: Design, Installation and TroubleshootingCeramic FerruleConnector BodyFiberBayonet Fitting toSpring Loaded CouplingFigure 6.5ST connector6.6.4 Connector handlingMost fiber optic connectors are designed for indoor use. Connectors for outdoor userequire to be hermetically sealed. It is very important to protect the optical faces of theconnectors from contamination. The optical performance can be badly degraded by thepresence of dirt or dust on the fiber ends. A single dust particle could be 10 microns indiameter but it would either scatter or absorb the light and could totally disrupt a singlemodesystem. Connectors and patch panels are normally supplied with protective caps.These should always be fitted whenever the connectors are not mated. These not onlyprotect from dust and dirt but also provide protection to the vulnerable, polished end ofthe fiber. Compressed air sprays are available for cleaning connectors and adapterswithout needing to physically touch the mating surfaces.Take care not to touch the end of the connector ferrules, as the oil from your fingers cancause dirt to stick to the fiber end. Clean connectors with lint-free wipes and isopropylalcohol.Durability of connectors is important throughout their lifetime. Typical fiber connectorsfor indoor use are specified for 500 to 1000 mating cycles, and the attenuation is typicallyspecified not to change by more than 0.2 dB throughout their lifetime. Repeatedconnection and disconnection of connectors can wear the mechanical components andintroduce contamination to the optical path.6.6.5 Optical couplersOptical couplers or splitters and combiners are used to connect three or more fibers orother optical devices. These are devices that split the input power to a number of outputs.While the splitting of the light is done passively, active couplers include opticalamplifiers, which boost the signal before or after the splitting process. Couplerconfiguration depends on the number of ports and whether each of these areunidirectional, so called directional couplers, or bi-directional. Most couplers are foundwithin the equipment for monitoring purposes.6.7 Splicing trays/organizers and termination cabinetsThis section looks at different types of storage units that are used for housing optical fibersplices and end of cable terminations.