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The Toolbox — Troubleshooting
Fiber Optics
Symptom-based diagnostic guides for fiber optic link faults and OTDR analysis.
Fiber Optic Link
High insertion loss
Possible Causes
- •Contaminated end face
- •Damaged connector
- •Tight bend
- •Wrong fiber type
Diagnostic Steps
- 1.Inspect and clean both end faces with proper fiber cleaning tools
- 2.Re-test with optical power meter after cleaning
- 3.Check for tight bends exceeding minimum bend radius
- 4.Verify fiber type matches system requirements (single-mode vs multimode)
Intermittent loss / signal dropping
Possible Causes
- •Loose connector
- •Mechanical stress on cable
- •Thermal expansion at splice point
- •Partially cracked fiber
Diagnostic Steps
- 1.Wiggle cable at each connector while monitoring power meter — loss that changes indicates connector problem
- 2.Run OTDR to locate intermittent fault
- 3.Check cable routing for areas subject to vibration or repeated flexing
- 4.Inspect all connectors for physical damage
OTDR shows unexpected reflection
Possible Causes
- •Poor fusion splice
- •Connector with air gap
- •Fiber break
- •Connector contamination
Diagnostic Steps
- 1.Locate event on OTDR trace by distance
- 2.Clean connector at that location and re-test
- 3.If loss exceeds 0.5 dB at a connector, clean and re-test or replace
- 4.If reflection is at a splice, re-splice and re-measure