Optical Fiber Systems and Testing Flashcards

What does an OTDR 'ghost' event indicate?

Answer: A false reflection caused by high-reflectance events creating phantom signals further down the trace

OTDR ghosts are phantom events that appear further along the trace, caused by double reflections from highly reflective connectors or end faces bouncing back and forth.

Why is a launch cable (also called a launch fiber or mandrel) used when performing OTDR testing?

Answer: To allow the OTDR to fully recover from the initial blind zone before measuring the first connector on the fiber under test

A launch cable allows the OTDR to pass its initial dead zone (caused by the strong Fresnel reflection at the output connector) so the first connector on the actual cable under test can be measured accurately.

What is 'macrobending loss' in optical fiber?

Answer: Loss caused by bending the fiber cable below its minimum bend radius, causing light to escape the core

Macrobending loss occurs when fiber is bent beyond its minimum radius, causing the evanescent field to extend beyond the cladding and light to radiate out of the fiber core.

Which standard defines the testing requirements for installed optical fiber cabling systems including insertion loss and return loss?

Answer: ANSI/TIA-526-14 (multimode) and ANSI/TIA-526-7 (single-mode)

ANSI/TIA-526-14 covers optical power loss measurement for multimode fiber, while TIA-526-7 covers single-mode; both are referenced by TIA-568 for acceptance testing.

What is 'modal bandwidth' and why does it matter for multimode fiber?

Answer: The frequency range over which a multimode fiber can transmit; higher modal bandwidth supports faster data rates over longer distances

Modal bandwidth (MHz·km) describes how much information a multimode fiber can carry before intermodal dispersion causes adjacent pulses to overlap; higher bandwidth enables higher data rates over longer spans.

What safety practice is mandatory when working with active optical fiber systems?

Answer: Never look into an active fiber end or connector without using an appropriate optical power meter or fiber inspection scope

Invisible near-infrared laser light from active fiber systems can cause permanent eye damage; always use a power meter or inspection camera, never look directly into an active fiber.