Step 6, were a period where complexity of channel spacing and muxes were further improved and that allowed increase the spacing of adjacent channels to 20 nm. This is a technology we know now as CWDM – Coarse Wavelength Division Multiplexing.
That is to say, that after installation, testing and further commissioning of these links are rather simple – what you need to do, is have some testing equipment in hands, and connect that in both ends of installed transmission path. Measurement of power loss, at the installed wavelenghts, are not hard, and here you can see some of steps what you can do.
However, it needs to be understood, that at these steps, from 1 – 6 all the optoelectronics are restricted and thus limited to the ends of the scheme installed. So, in other words, there is a optical path, and it has an “entrance” and it has “exit”, and electrical signal goes in and at another side goes out.
Of course, testing of these links are easy, but design variations we could do at these steps were rather limited.
What network planner needed know is mostly the wavelengths he will be using and the distance of the optical path, from which he could understand what will be the total bandwidth of the payload he will be sending, and what are future expansion possibilities over that physical optic cable infrastructure installed.
And that is at least not flexible – we know that, market conditions changes fast, bandwidth demands grows exponentially driven by modern applications and plan something in future is hard, and if the installed infrastructure is not flexible then network provider, especially those working in Access Network, or Open Network, have significant challenges in future.
That is why optical networks continue to develop and that’s why we are going to look further next steps in future articles.