**2.1 Analog fiber**

**Figure 2(a)** shows the architecture of an analog fiber link. DOCSIS and video signals are aggregated in the hub and delivered to the fiber node in analog waveforms. Then at the fiber node, the received analog signals are delivered to CMs via cable distribution networks. An analog fiber link features simple, low-cost implementation, and high spectral efficiency, but imposes high linearity requirements on channel response. Since it does not perform any data reformation, an analog fiber link is a waveform/service agnostic pipe, and can be used for various services, e.g., DOCSIS, MPEG, and analog TV. On the other hand, it suffers from noise and nonlinear impairments, limited signal-to-noise ratio (SNR), short fiber distance, and small number of WDM wavelengths. It also requires complex RF amplifiers and bi-annual calibration of fiber nodes.
