In Step 5, concept of DWDM, which as we discussed in Step 4, was just introduced, evolved to have possibilities to transmit multiple wavelengths to in both directions using same fiber:
This way, all cost of building the cable and equipment infrastructure were decreased.
In such networks, we use 3 wavelenghts, to send various services over same fiber – 1550 nm is used for the CATV signal, and 1490/1310 nm are used for PON itself.
In this article, which discussed CATV overlay over PON you might get more details on this topic.
Scheme in this case will look anything like this:
Now, you can see that to mix 3 wavelenghts and to send them over single fiber, CATV EDFA is used, more details on CATV EDFA can be found here.
You’ve sure heard about “Triple Play” so this is it – Voice + Internet + TV is triple play.
Figure 3: 4 x Fast Ethernet + Voice FXS POTS + WiFi + CATV GPON ONT HGU type access unit