What two types of transmitting light sources can a multimode fiber use?

What two types of transmitting light sources can a multimode fiber use?

• A. LED and VCSEL (laser)
• B. LED and Laser diode
• C. VCSEL (laser) and LED
• D. Laser diode and VCSEL

Answer: (A)

Multimode fiber needs a light source that can efficiently fill its large core and tolerate launching light into many propagation paths. LED sources fit this well because they emit broad-spectrum, spatially broad light that couples softly into the fiber and minimizes sensitivity to exact alignment, which keeps costs down for short-range links. VCSELs provide a laser-like, yet highly-couplable beam with high modulation speeds, making them ideal for higher-bandwidth multimode systems while still matching the fiber’s core well. Together, these two options—LED and VCSEL—are the common, practical choices for transmitting light over multimode fiber. Laser diodes designed for single-mode or edge-emitting style aren’t as well suited to the multimode core, so they’re less typical in MMF deployments.

Multimode fiber needs a light source that can efficiently fill its large core and tolerate launching light into many propagation paths. LED sources fit this well because they emit broad-spectrum, spatially broad light that couples softly into the fiber and minimizes sensitivity to exact alignment, which keeps costs down for short-range links. VCSELs provide a laser-like, yet highly-couplable beam with high modulation speeds, making them ideal for higher-bandwidth multimode systems while still matching the fiber’s core well. Together, these two options—LED and VCSEL—are the common, practical choices for transmitting light over multimode fiber. Laser diodes designed for single-mode or edge-emitting style aren’t as well suited to the multimode core, so they’re less typical in MMF deployments.