Which factor describes the spreading of a signal as it travels through a fiber?

Which factor describes the spreading of a signal as it travels through a fiber?

• A. Dispersion
• B. Attenuation
• C. Reflection
• D. Absorption

Answer: (A)

Dispersion is the spreading of a pulse in time as it propagates through an optical fiber. A pulse isn’t a single color but a mix of many wavelengths. In a fiber, those wavelengths don’t travel at the same speed because the refractive index varies with wavelength (material dispersion) and, in some fibers, the guiding structure affects different wavelengths or modes differently (waveguide or modal dispersion). Over distance, these speed differences cause parts of the pulse to arrive at different times, broadening the pulse and potentially causing intersymbol interference. Attenuation describes loss of signal power, absorption is energy converting to heat, and reflection involves light bouncing at interfaces; none of these explain the time spreading of the pulse. That’s why dispersion is the factor describing the spreading of a signal in a fiber.

Dispersion is the spreading of a pulse in time as it propagates through an optical fiber. A pulse isn’t a single color but a mix of many wavelengths. In a fiber, those wavelengths don’t travel at the same speed because the refractive index varies with wavelength (material dispersion) and, in some fibers, the guiding structure affects different wavelengths or modes differently (waveguide or modal dispersion). Over distance, these speed differences cause parts of the pulse to arrive at different times, broadening the pulse and potentially causing intersymbol interference. Attenuation describes loss of signal power, absorption is energy converting to heat, and reflection involves light bouncing at interfaces; none of these explain the time spreading of the pulse. That’s why dispersion is the factor describing the spreading of a signal in a fiber.