Diagnosing fiber cabling faults - DSP FTA Series

If the loss measurement FAILs: 

  • There could be one or more dirty, damaged, misaligned, or unseated connections in the cabling. Check all connections and clean all fiber end faces; then retest. 
  • There could be a kink or sharp bend/break in a patch cord or the fiber under test. A visual fault locator could help to reveal these faults. An OTDR, such as the Fluke Networks OF-500 OptiFiber Certifying OTDR, can help you locate faults not revealed with a visual fault locator. 
  • The number of adapters or splices on the Setup menu was too low (for standards that use a calculated loss value). 
  • For multimode fiber, the wrong mandrel size was used for testing. Smaller mandrels create tighter bends in the fiber, resulting in more loss. 
  • A patch cord or fiber segment had the wrong core size. 
  • The cabling had a bad fusion or mechanical splice or a sharp bend.

If your loss reading is negative: 

  • The fiber ends may have been dirty during referencing. 
  • The connections to the tester may have been disturbed after referencing. 
  • There may have been a kink in a reference patch cord during referencing. 
  • The testers may have been colder during referencing than during testing.

A known length of cable measures too long or too short: 

  • The wrong fiber type may have been selected on the Setup menu.
  • The index of refraction might need adjustment. Change n on the Setup menu. 

Power meter measurement is too low: 

  • Fiber end face was dirty or damaged. 
  • Wavelength selected on tester may not match source wavelength. 
  • Source may have been set to modulated output. 
  • Patch cord or adapter is the wrong type (SM or MM) or patch cord has the wrong core size. 
  • Cabling was cracked or broken. 

Power meter measurement is too high 

  • Tester is connected to an active CATV fiber.