Explain the impact of chromatic dispersion on signal quality in a high-speed fiber optic system, and how it can be mitigated.

Chromatic dispersion, also known as group velocity dispersion (GVD), is a phenomenon in fiber optic systems where different wavelengths of light travel at slightly different speeds through the fiber. This difference in speed causes the different wavelength components of a signal pulse to spread out as they propagate, leading to pulse broadening. In high-speed fiber optic systems, where data is transmitted at very high rates, chromatic dispersion can significantly degrade signal quality. Pulse broadening causes adjacent pulses to overlap, making it difficult for the receiver to distinguish between them. This phenomenon is known as intersymbol interference (ISI), and it increases the bit error rate (BER) of the system. The impact of chromatic dispersion increases with both the data rate and the distance of transmission. Higher data rates mean shorter pulse widths, making the signal more susceptible to pulse broadening. Longer distances mean more time for the pulse to spread. Several techniques can be used to mitigate the effects of chromatic dispersion. One technique is dispersion compensation, which involves using a dispersion-compensating fiber (DCF) or a fiber Bragg grating (FBG) to introduce dispersion of the opposite sign to the fiber, effectively canceling out the accumulated dispersion. Another technique is electronic dispersion compensation (EDC), which uses signal processing algorithms at the receiver to compensate for the effects of dispersion. EDC is often implemented in high-speed transceivers. A third technique is to use dispersion-shifted fiber (DSF), which is designed to have minimal chromatic dispersion at the operating wavelength. However, DSF can have other nonlinear effects that limit its use in some systems. By using these mitigation techniques, the impact of chromatic dispersion on signal quality can be minimized, allowing for reliable high-speed data transmission over long distances. For example, in a 100 Gbps system, dispersion compensation is essential to achieve the desired reach and performance.