Fiber Optic Communication Technology

A: A walks through the math cleanly: fiber loss 2.4×0.35, connectors and splices summed once, then +2 minus −20. B feels like plant practice where panels hide losses, but the physics doesn't forgive bookkeeping. C sneaks in an unearned credit; safety factors reduce margin, they don't add it. D is a real DFMEA move for conservatism, yet the question asked for available margin, not a derated one.

A: A is the classic reason people talk about fiber and EMI, so it's tempting to over-credit shielding. C and D stay on the electrical side and are real system risks outside the fiber itself. B slips past because it's not electromagnetic at all; shielding foil won't stop heat, and DFMEA occurrence climbs if routing ignores temperature.

A: A explains loss but not the moisture correlation reversing when dry. C is slow and one-way; it doesn't heal overnight. D would be constant and distance-driven. B nails the reversible loss, clean OTDR, and water-triggered behavior—classic connector interface issue that slips through FAT.

A: A satisfies the safety reflex but skips due process and risks false scrap. C hides outliers that matter for worst-case margin. D assumes drift without evidence. B respects metrology: clean, reference, method compliance. Only then do you argue tolerance versus process capability.

A: A uses the simple bandwidth–distance product straight. B misreads the unit and crushes capacity. C bakes in a safety factor the question didn't ask for. D leans on optimism rather than the given rating, a move that burns you later in validation.

A: A confuses optical isolation with electrical noise control. C assumes a failure mode not guaranteed by the component physics. D jumps domains; there's no voltage path. B tracks cause to effect: reflections destabilize the laser, a known reliability hit that DFMEA should catch.

A: A and B chase power, but the levels check out. C is plausible for electronics, yet the issue appeared with a harness change. D ties the mechanical change, temperature, and signal quality together; shrinkage shifts alignment and the eye takes the hit.

A: A is the knee-jerk move and expensive. C masks the question rather than answering it. D changes hardware without evidence. B checks the basis: sensitivity numbers depend on BER, pattern, and bandwidth. Mismatch those and the comparison is meaningless.

A: A is the classic pushback and ignores that eccentricity drives variability, not just mean loss. C treats symptoms and grows technical debt. D drags in a new failure family late in the game. B addresses the mechanism, lowers occurrence, and actually moves the RPN the right way.