Certified Fiber Optics Practice Exam

Increasing the wavelength of the transmitter is a method to reduce which type of dispersion?

1. Chromatic dispersion

2. Modal dispersion

3. Material dispersion

4. Polarization mode dispersion

The correct answer is: Modal dispersion

Increasing the wavelength of the transmitter primarily helps to reduce chromatic dispersion, which is the spreading of light pulses due to different wavelengths traveling at different speeds through a medium. In optical fibers, chromatic dispersion occurs because the refractive index of the fiber material varies with the wavelength of light. By operating at longer wavelengths, the differential in speed between various wavelengths can be minimized, effectively reducing the effects of chromatic dispersion on signal integrity. While modal dispersion, material dispersion, and polarization mode dispersion are important considerations in fiber optic communications, they do not decrease significantly through a change in transmitter wavelength. Modal dispersion pertains to different light paths (modes) in multimode fibers, material dispersion refers to the effects within the fiber material that cause dispersion based on the material’s properties, and polarization mode dispersion involves variations in speed of polarization states of light. These forms of dispersion are influenced more by the design and physical properties of the fiber rather than the wavelength of light being transmitted.