In a RFI, an ICT distribution designer instructs the contractor to test all the fibers In a PON Installation. Which of the following testing requirements does the designer include?

Question

Options

• AUni-directional 850 nm and 1300 nm
• BBi-directional 850 nm and 1300 nm
• CUni-directional 1310 nm and 1550 nm
• DBi-directional 1310 nm and 1550 nm

• A
  7% (3)
• B
  5% (2)
• C
  16% (7)
• D
  73% (32)

Explanation

Option D is correct because PON (Passive Optical Network) installations use single-mode fiber, which operates at 1310 nm (upstream) and 1550 nm (downstream). Testing must be bi-directional - run from both ends - because some fiber faults (poor splices, microbends, faulty connectors) can appear asymmetrically and may only be detected from one direction; bi-directional OTDR testing per TIA/EIA standards ensures complete characterization of end-to-end loss.

Why the distractors are wrong:

• A & B (850 nm / 1300 nm): These are multimode fiber test wavelengths. PON uses single-mode fiber, so these wavelengths are simply wrong for this installation type.
• C (Uni-directional 1310/1550 nm): The wavelengths are correct for single-mode/PON, but uni-directional testing only - one pass from one end - can miss faults that are direction-dependent or understate actual loss at splice points.

Memory tip: Think "PON = Single-mode = 1310/1550, and always go BOTH ways." The "bi" in bi-directional mirrors the "both" in PON's two-wavelength operation (upstream and downstream), reminding you that you need both directions AND both wavelengths covered.

No community discussion yet for this question.