Certified Fiber Optics Practice Exam

Which type of source is typically used in multimode fiber optic systems?

1. Laser

2. Copper

3. LED

4. Fiber

The correct answer is: LED

In multimode fiber optic systems, Light Emitting Diodes (LEDs) are commonly used as the light source. This is mainly due to their ability to emit light over a relatively wide area, allowing multiple modes of light to propagate through the fiber simultaneously. LEDs generate less coherent light compared to lasers, which makes them more suitable for short-distance communication typically associated with multimode systems. Multimode fibers have a larger core diameter than single-mode fibers, which aids in the acceptance of light from the broader emission pattern of an LED. This characteristic enables better light coupling into the fiber and helps to minimize losses due to modal dispersion over shorter distances. Thus, for applications that don't require the high performance and distance capabilities of lasers, such as within buildings or campuses, LEDs are the preferred choice due to their cost-effectiveness and efficiency for the distances involved.