40GB to 10GB optical power

[nixcraft]

I'm ordering QSFP+ modules from fs.com for connecting an Extreme switch 40GB ports to a SonicWall firewall 10GB ports through a MPO breakout cassette.

Has anyone ran into trouble using transceivers with TX power over -1 dBm with 10GB SR with any gear? The Extreme module has TX power of -1 but RX max of 2.4. I've asked SonicWall their specifications, but in general could this be an issue?

[Gabriel_G · Accepted solution]

As always, your mileage may vary when using 3rd party optics.

That said, as long as the specifications match and/or fall within mutual ranges on both sides, it should be fine from a physical standpoint.

You can check 'show port transceiver info detail' to get DDMI information from the optic on reported Rx and Tx power levels to verify, assuming the optic supports DDMI.

You've likely already found our optics webpage: https://optics.extremenetworks.com/

You may not have found this large guide with more specs for many optics which may be helpful for you:

https://documentation.extremenetworks.com/pluggable/downloads/Pluggable_Transceivers_Installation_Gu...

[WillyHe]

Hello,

For all FO transceivers (SFP/SFP+/SFP28/QSFP+/QSFP28/....) there are standard specifications for min/max TX/RX powers and more.

In my experience the switch manufactures have better specifications for their selected (supported) transceiver models.

The "Pluggable Transceivers Installation Guide" document is also nice to have.
It provides more information but is now +1 year old.

On the webpage there is the up to date transceivers list, also the "obsolete" (old/very old) marked models, it also gives information about the compatibility per network device type (switch, router, ...).
For the FO transceivers the TX/RX values are also provided.

regards
WillyHe

[nixcraft]

The issue was that the old Extreme 10319 module has a high TX output max of 2.4 dBm. This seems to be too high in a 10GB breakout installations because most 10GB SFP+ modules are overloaded with higher than -1 dBm RX power.

The newer Extreme 40G-SR4-QSFP150M module has lowered the TX output to -1 dBm perhaps because of this very issue. But the FS module I was looking at was modeled based on the Extreme 10319 module and has that high output power as well. They are bringing out a revised version with lowered output power in the fall. That was a bit late for me so I found another compatible module from BlueOptics that according to specs has that more suitable -1 dBm TX power.

[WillyHe]

In this case, another solution is, if you like it, to insert an attenuator in the high power TX path, they are available in various connector types.

regards
WillyHe