Which of the following transmitter light sources has a MINIMUM bandwidth of 4700 MHz/km (EMB) at 850 nm">

Question

Options

• AOM1 (62 50/125 multimode)
• BOM2 (50/125 multimode)
• COM3 (50/125 laser optimized multimode)
• DOM4 (50/125 laser optimized multimode)

• A
  5% (2)
• B
  2% (1)
• C
  12% (5)
• D
  80% (33)

Explanation

OM4 is the correct answer because it is specified with a minimum Effective Modal Bandwidth (EMB) of 4700 MHz·km at 850 nm, making it the highest-performing standard multimode fiber in the list and the only one meeting that threshold.

Why the distractors are wrong:

• OM1 (62.5/125) has a much lower bandwidth (~200 MHz·km) and uses a larger core designed for LED sources, not lasers.
• OM2 (50/125) improves on OM1 (~500 MHz·km) but is still far below 4700 MHz·km and is not laser-optimized.
• OM3 (50/125 laser-optimized) is laser-optimized like OM4 but only specifies a minimum EMB of 2000 MHz·km - roughly half of OM4's requirement.

Memory tip: Think of the OM grades as a staircase - each step doubles or more the bandwidth. OM4 is the top step with 4700, and OM3 is just below at 2000. The "4" in OM4 pairs with 4700 MHz·km - the number in the name hints at the higher tier.

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