What do attenuation and dispersion refer to in fiber optics, and how do they affect signal?

• A. Attenuation is power loss per distance; dispersion is pulse broadening due to different speeds for wavelengths; both limit reach and data rate and may require amplification or dispersion compensation.
• B. Attenuation is frequency shift; dispersion reduces signal power; these degrade signals.
• C. Attenuation increases signal strength; dispersion reduces power.
• D. Attenuation is a form of modulation; dispersion is noise.

Answer: (C)

Attenuation is the loss of optical power per unit length as light travels through the fiber. It happens because some light is absorbed, scattered, or lost at imperfections and bends. As distance increases, the signal at the far end gets weaker, which can worsen the ability to detect the information reliably. To keep signals strong over long spans, systems use optical amplifiers or repeaters to boost the power along the link.

Dispersion is the spreading of a light pulse in time as it propagates, because different wavelength components travel at different speeds inside the fiber. This pulse broadening causes adjacent bits to overlap, leading to errors and limiting how fast data can be sent and how far the signal can travel without distortion. Dispersion management techniques—such as using dispersion-compensating fiber, special fiber designs, or signal processing at the receiver—help keep pulses tight and maintain higher data rates over longer distances.

So both effects constrain reach and data rate, and each has its own methods to mitigate its impact.