CWDM-MUX8A

Hardware MikroTik hardware general
1

Hi,

can this mux be used crosspatched to let it work on single strand fiber (obviously halving the capacity)? We’ll use this technique with other products and it’ll work fine, but I see that mikrotik’s one explicitly distincts mux from demux. Is it just an indication, or is the demux side physically different from the mux side ?

BR,
Simone.

2

Yes, you can, but

  • You’ll need an additional splitter to combine both RX and TX, since you’re planning using single strand.
  • You’ll have additional losses due to the combined RX/TX and connectors
  • You’re only using half of the wavelengths, since you need the others at the other side to be demuxed.

It can be done, but I recommend a seperate mux/demux when you’re planning on using a single strand. Especially when you’re having issues its much easier to debug a ‘build-for-it’ setup instead of ‘misusing’ a 2-strand mux/demux.

Also, I recommend to use 2 adjecent channels for a link, eg 1270/1290 for a link, and not 1270/1610. Since CWDM uses a wide range of optical spectrum this can cause some issues, especially on longer links.
Finally, make a good design. Most fibers are specified on either 1310 or 1550nm (or both) and when using 1270 or 1610nm they have a much higher attenuation. this, along with your mux losses, has to be taken into account when calculating your power budget as well.
Nowadays, I would only consider CWDM on

  • Links where you need to mix 1 and 10Gbit (1Gbit DWDM is pretty expensive compared to CWDM)
  • Short links (<30-40km)
  • Links which you’re 100% sure they never need to be extended in the future.

Also make some calculations for DWDM. This is more expensive, but gives you much more future options:
Upgrade to higher link speeds, more channels (40 instead of 16 when using 2-strand), ability to amplify when you need to cover a longer fiber span, and much more equal attenuation on all wavelenghts.

3

So the CWDM-MUX8A need 2 fibers to transmision between locations right?

4

That would be usual application since most commonly CWDM SFPs use same wavelength for both TX and RX … at least they are declared as such. However I’ve seen CWDM systems which used single fibre strand between the sites … MUXes and SFPs came in complementary pairs. Not MT one though.

OTOH I’ve seen many SFPs with no affinity for RX wavelength (e.g. standard 1310 nm wide-band and a 1590 nm CWDM SFPs cross-connected to each other worked just fine) and if your SFPs are this kind, then you could build setup with single strand between sites and using standard (dual-strand) MUXes and SFPs … you only have to be careful to use SFPs with different TX wavelengths on both sites.