Developing reports that accurately break down the SONET and WDM equipment markets is challenging at best. The best way to understand the breakout is to ask the company that developed the report what piece of equipment makes up each category.
In the not too distant past, SONET was run directly over dark fibers, so breaking out the categories were easy.
When WDM technology was introduced, most WDM systems used transponders, which took the grey optical signal output by the SONET equipment and put it on a frequency of light in the WDM system. Breaking out SONET versus WDM was fairly straightforward.
But now, SONET equipment (and data networking equipment) incorporates the colored optical interfaces within their systems; feeding the colored light directly into the WDM systems muxes (no transponder). So, breaking out SONET vs WDM is a little more challenging. Should the colored optical interface within the SONET (or data equipment) be counted in the SONET or WDM category? A lot of it depends on what the report author is trying to show the reader.
Just my 2 cents.
