True or False: All wavelengths travel at the same speed through the fiber.

True or False: All wavelengths travel at the same speed through the fiber.

• A. True
• B. False
• C. Sometimes
• D. Not sure

Answer: (B)

Not all wavelengths travel at the same speed inside a fiber. The glass has a refractive index that changes with wavelength, so the group velocity that carries a light pulse also changes with wavelength. As a result, different spectral components move at different speeds, causing pulse spreading and chromatic dispersion. While the fiber's geometry can add some dispersion through waveguide effects, the core idea is that dispersion makes speeds wavelength-dependent, not universal for all wavelengths.

Not all wavelengths travel at the same speed inside a fiber. The glass has a refractive index that changes with wavelength, so the group velocity that carries a light pulse also changes with wavelength. As a result, different spectral components move at different speeds, causing pulse spreading and chromatic dispersion. While the fiber's geometry can add some dispersion through waveguide effects, the core idea is that dispersion makes speeds wavelength-dependent, not universal for all wavelengths.