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9 steps of Evolution of Fiber Networks – Step 7

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In step 7, we are seeing adding of Fixed Wavelength type add/drop multiplexers (ADM’s), to enable a scheme, which could offer not just simple point to point path, but also add/drop possibilities in middle nodes to extract tributaries and insert them back in main path.


Example of middle add/drop node using OADM


Figure 1: Example of middle add/drop node using OADM


However, as it was mentioned in previous steps, planning of such optical transmission pathes is not easy, as you still can’t predict how much of future bandwidth you will need.


Good example of ADM’s are SDH systems, where you can add/drop E1’s, V.35. Ethernet or other payload, make ring or daisy chain networks.


OADM example using SDH system in ring network


Figure 2: ADD/DROP scheme based on SDH STM-1 optical path using miniSDH system


This is also the main difference between SDH and PDH systems, (at least that moment of the history), when PDH could offer only point to point schemes without add/drop possibilities, while SDH could offer this.


To illustrate the importance of adding OADM concept, just compare for example this scheme:



Figure 3: 8E1’s G.703 + 4 Ethernet using PDH multiplexer, point to point scenario


With the OADM SDH scheme in Figure 2. We can see that we can do much more flexible design in adding optical nodes in between to drop out tributaries.



Lomoveishiy – Finland

I needed those to connect my PC on the third floor to have internet access in that room, and ISP installed their modem on the first floor only. After dropping fiber patch cables, plugged in all cables into these media converters at both sides, and link came up instantly. Was much easier than I thought!

Raymond – USA

Great experience – units worked straight out of the box – just needed plug in cables and we were done. I also like the possibility to enable jumbo frames, while we do not have a need for this feature at the current moment it’s great to have this option.