Cisco GainMaker Optoelectronic Node 1GHz with 65 86 MHz Split Technical References

2 

 

4022872 Rev C 

 

The coaxial cables used in HFC networks have greater signal loss at higher 

frequencies. A plot of coaxial cable loss versus frequency has a curved, down-tilted 

shape (provided that the frequency axis uses a linear scale). 
The following illustration shows a sample plot of cable loss versus frequency. 

 

The curved shape associated with the plot is sometimes referred to as a smile shape. 
Cable equalizers are designed to offset both the tilt and the shape associated with 

coaxial cable loss. Thus, a plot of cable equalizer loss versus frequency is the 

opposite of the coaxial cable plot, with greater loss at lower frequencies and a frown 

shape. 
A sample plot of cable equalizer loss versus frequency can be seen in the illustration 

on the next page. 
The dB value of a cable equalizer indicates the equivalent amount of cable loss that 

the equalizer is designed to compensate for in terms of both tilt and shape. Plug-in 

cable equalizers are typically available in a wide range of fixed dB values. Typically, 

most cable equalization is accomplished at the input of the amplifier station (input 

equalization), with additional equalization between amplifier gain stages (interstage 

equalization).