Chromatic Dispersion (CD) is a fundamental transmission impairment in optical fibers. It occurs because the refractive index of the silica glass fiber is dependent on the wavelength of the light passing through it. Consequently, different wavelengths (or "colors") of light propagate at different group velocities. For a light pulse composed of multiple wavelengths, this difference in speed causes the pulse to spread out, or disperse, as it travels along the fiber. This pulse broadening can lead to inter-symbol interference (ISI) at the receiver, limiting the transmission distance and bit rate.

A. CD is dependent on the wavelength, not the channel bandwidth. Different channels experience different CD because they operate at different center wavelengths.

B. CD is caused by the wavelength-dependent refractive index of the fiber, a property known as material dispersion, not by changes in fiber attenuation.

D. Fiber attenuation is the reduction of signal power. Inter-channel interference is typically caused by non-linear effects like Four-Wave Mixing (FWM), not attenuation.

1. Nokia, "Nokia Optical Networking Fundamentals, Student Guide," (Course Code: TTP31001-1-1), Module 2: Optical Fiber Transmission, Section 2.3.1: Chromatic Dispersion, pp. 2-15. The guide states, "Chromatic dispersion (CD) is the phenomenon where different wavelengths of light travel at different speeds in an optical fiber... This causes the different spectral components of the pulse to arrive at the end of the fiber at different times."

2. Agrawal, G. P. (2010). Fiber-Optic Communication Systems (4th ed.). Wiley. In Chapter 2, Section 2.4, "Group-Velocity Dispersion," p. 45, it is explained that "the refractive index n(ω) of the fiber material depends on the optical frequency ω... As a result, different spectral components of a pulse travel at slightly different group velocities. This phenomenon is known as group-velocity dispersion (GVD) or simply fiber dispersion." (Note: GVD is the formal term for what is commonly called Chromatic Dispersion in this context).

3. Saleh, B. E. A., & Teich, M. C. (2019). Fundamentals of Photonics (3rd ed.). Wiley. Chapter 9, Section 9.1.B, "Dispersion in Optical Fibers," p. 336. The text describes material dispersion: "Since the refractive index n(λ₀) of a dielectric medium is a function of the wavelength λ₀, the group velocity vg is also a function of λ₀... This results in pulse spreading."