In this article we will consider the problems of optical fiber including splicing, cleaning connectors, fiber bending, fiber identification and Connector loss.
• Splicing –common problems
• Cleaning and Inspecting connectors
• Avoiding Micro and Macro-bending losses
• Mismatched Connector loss
• Live fiber identification –Don’t unplug!
• I just cleave fibers with a pair of scissors –that works fine.
• No need to clean connectors –I always pull them out of the bag directly from the manufacturer and they are ready to go.
• Watch me strip off the cladding.
• I still hand polish my SM APC connectors in the field.
• My shirt cleans connectors just fine –“field clean” so to speak!
• “So, if I run over a length of cable with my chair, should I tell someone?”
Many customers bring their test equipment to class asking for help because it does not work right. We often find the connector at the source to be damaged.
• Lack of understanding about how fiber works
• Limited experience or time in the field
• OJT only allows bad habits to be passed along
• Feeling of expertise because no one has corrected you or your test results pass
• Doing things the way it ‘has always been done’ is easier than change
• Limited training for staff –often product specific, not general knowledge, process, technology training
• Training is not always followed by practice
Excerpts from process and best practices documents…
• CISCO: “Inspection and Cleaning are Critical –One of the most basic and important procedures for the maintenance of fiber optic systems is to clean the fiber optic equipment.”
• ARISTA: “Contaminated fiber optic connectors can often lead to degraded performance and costly, but preventable failures.”
• AT&T: “Inspect, Clean if Necessary, Inspect -One important thing to remember in handling fiber optic connectors is that the fiber end face and ferrule must be absolutely clean before connections are made.”
•JUNIPER NETWORKS: “Note: Improper cleaning can result in high attenuation due to dirt or dust, or can cause mechanical damage to the fiber end face, resulting in decreased performance.”
• Poor cleaving and splicing practices:
– Cause excess loss (misalignment, air bubble, poor cleave)
– May cause excess reflection (air bubble or air gap at poor cleave or break)
– Poor cleaves create rework and add time to a splice job
– Clean V-grooves, maintain splicer electrodes, use correct splicer settings
– Strip and thoroughly clean fiber beforecleaving & splicing
– Use a good cleaver and maintain it! Do not clean fiber after cleaving.
Left:Scissor cleave Right: Stripping tool cleave
Dirty connectors = high insertion loss and high reflectance
Clean connectors =low insertion loss and low reflectance
One-Click Cleaners (dry cleaning)
• Easy, fast & effective; Low cost per clean
• Cleans jumper connector ends
• Cleans through patch panels
Solution & Wipes (wet cleaning)
• Effective on stubborn contamination
• Use solution which leaves no residue
• Wipes or absorbent sticks to dry
• Use sticks to clean through bulkheads
• Field-installable, factory-polished mech. splice connector
– Index matching gel & high quality cleave
– Few tools needed, fast assembly
– Visual connection verification with VFL
– Available for single-mode & multimode
– 900μm standard; 2 and 3mm boot kits available
• Field-installable, factory-polished fuse-on connector
– Fusion splice connector; Eliminates splice trays
– Performance less dependent on technician skill
– Splicer required
– No index matching gel, crimping, polishing or epoxy
– Available for both single-mode & multimode
– 2 and 3 mm cordage available
• Test network using OTDR at short (1310 nm) and long (1550 or 1650 nm) λs
– Distinguish macro-bends from poor splices by higher loss at longer λ
– For long-haul networks, detect macro-bends by testing at 1550 & 1650 nm
– Use VFL (visible red laser) to pinpoint bends in closures & cabinets
• Remove any detected tight bends found during testing
• Ensure fibers not pinched when closing splice closure or sliding in splice trays
• Be sure cable ties are not too tightly cinched
• Looks for fiber pulled tightly over the edge of a panel/tray
• Don’t hang large coils of cable/fiber over an edge
• Test with an OTDR and/or VFLto verify bends have been resolved
• FTTH networks usually built with angle-polished (APC) connectors
– Minimizes connector reflections –a source of noise in 1550 nm RF networks
– Ensures unused (open) PONsplitter ports won’t create strong reflections
• CAUTION: Do not mate UPCconnectors to APC connectors!
– Mated UPC - APC results in excess reflection and loss
– Poor OTDR results will be obtained when mismatched connectors mated
– Use SC-UPCto SC-APC hybrid jumpers or launch cables as necessary to connect test equipment with UPC to APC
• Connecting PC to APC connectors = high loss & excess reflection
• Optical Fiber Identifiers (OFI) clamp-on to detect light in fiber
– Do not require disconnecting fiber to test
– Works on 250μm bare fiber, 900μm buffered, 2 & 3 mm jacketed fiber
– Detects & reports Traffic or Tone and direction
– Use Tone (270, 330, 1k, 2k Hz) for positive ID of specific out-of-service fiber
• Look for an OFI that works on bend-insensitive fiber!
• Train staff on proper procedures and WHY they are important.
• Clean and Inspect fiber optic connectors before mating –every time!
• Use the right materials to clean your connectors.
• Properly clean & cleave fibers & follow process steps for good splicing results.
• Use care when managing fiber in closures, trays, cabinets –avoid sharp bends and pinch points.
• Be aware of connector types –Avoid connecting UPC to APC.
• Get the right tools for troubleshooting live links –Fiber Identifiers are useful but should work with BI fiber.