What two wavelengths are used when measuring multimode fiber spans?

What two wavelengths are used when measuring multimode fiber spans?

• A. 850, 1300
• B. 1310, 1550
• C. 850, 1550
• D. 780, 1300

Answer: (A)

Measuring multimode fiber spans uses two wavelengths, 850 nm and 1300 nm. The 850 nm region is chosen because it strongly excites many modes in typical multimode fibers, so the test reveals how light travels through the multiple paths and how the modal power distribution attenuates over the span. The 1300 nm wavelength sits in silica’s low-loss window, providing a cleaner benchmark and a standard reference for comparison with other fiber measurements. Using both wavelengths lets you capture how the span behaves across the two common operating regions for multimode systems, something a single wavelength wouldn’t reveal.

Measuring multimode fiber spans uses two wavelengths, 850 nm and 1300 nm. The 850 nm region is chosen because it strongly excites many modes in typical multimode fibers, so the test reveals how light travels through the multiple paths and how the modal power distribution attenuates over the span. The 1300 nm wavelength sits in silica’s low-loss window, providing a cleaner benchmark and a standard reference for comparison with other fiber measurements. Using both wavelengths lets you capture how the span behaves across the two common operating regions for multimode systems, something a single wavelength wouldn’t reveal.