Splicing, Termination and Connector Cleaning
The splicing and termination domain tests making a permanent, low-loss joint and a clean connector end face. Questions cover fusion splicing, mechanical splices, connector polish types, and the cleaning discipline that prevents most field loss problems.
Fusion splicing
- Strip, clean with 99% isopropyl alcohol and lint-free wipes, then cleave. A good cleave is square, typically within 0.5 degrees, with a cleave length matched to the holder.
- Set the arc with a calibration or test splice; the splicer's estimated loss should be around 0.02-0.05 dB. A field splice target is typically 0.1 dB or better.
- Center the protection sleeve, let it cure, and route the fiber in the tray at the specified bend radius. Remove gel completely from gel-filled cables before splicing.
Termination
- Common OSP connectors are SC and LC, in UPC (blue) or APC (green, 8-degree angle) polish; ST is still found in older plants.
- Never mate APC to UPC; the air gap and misalignment cause high loss and can damage the end face.
- Options are factory pigtails fusion spliced in a closure or panel, field-installable connectors, and preterminated assemblies.
- Typical connector loss is 0.3 dB or less; UPC reflectance is about -50 dB or better, APC about -60 dB or better.
Cleaning
- Inspect first with a scope; clean dry, then wet with IPA and dry with a lint-free wipe; use one-click cleaners in bulkheads.
- Clean both sides of a mated pair, and never touch an end face.
Worked example
A splice reads 0.12 dB from one direction and 0.08 dB from the other on the OTDR. The true splice loss is the bidirectional average, (0.12 + 0.08)/2 = 0.10 dB. Do not record the higher value as the splice loss; the difference comes from mode-field mismatch and backscatter direction. If the splicer estimated 0.02 dB, the OTDR value still includes fiber mismatch and is the number the link budget uses.
Traps
- Dirty connectors, the largest single cause of field loss.
- Touching or dragging an end face, or mating APC to UPC.
- Reusing a protection sleeve or forgetting to slide it on before splicing.
- A poor cleave or wrong arc, which shows as a high splice estimate.