In single-mode fiber, which dispersion mechanism primarily causes pulse broadening?

In single-mode fiber, which dispersion mechanism primarily causes pulse broadening?

• A. Modal dispersion
• B. Chromatic dispersion
• C. Material dispersion
• D. Waveguide dispersion

Answer: (B)

In single-mode fiber, pulse broadening is mainly caused by chromatic dispersion. Since only one spatial mode propagates, modal dispersion is essentially absent. Chromatic dispersion arises because different wavelengths travel at different speeds in the fiber: material dispersion comes from the glass’s refractive index varying with wavelength, and waveguide dispersion comes from the fiber’s geometry affecting the mode’s effective index. The combination means the various spectral components of a pulse arrive at different times, broadening the pulse as it travels. Material and waveguide dispersion are parts of chromatic dispersion, but the overall effect that broadens the pulse in SMF is chromatic dispersion.

In single-mode fiber, pulse broadening is mainly caused by chromatic dispersion. Since only one spatial mode propagates, modal dispersion is essentially absent. Chromatic dispersion arises because different wavelengths travel at different speeds in the fiber: material dispersion comes from the glass’s refractive index varying with wavelength, and waveguide dispersion comes from the fiber’s geometry affecting the mode’s effective index. The combination means the various spectral components of a pulse arrive at different times, broadening the pulse as it travels. Material and waveguide dispersion are parts of chromatic dispersion, but the overall effect that broadens the pulse in SMF is chromatic dispersion.