Anyone familiar with SFP Fiber Optic Modules?

[A.J.710]

I have a question regarding the minimum operating speed of new SFP+ fiber modules. In my line of work, I'm most commonly seeing 10GBASE SFP+ modules installed for network data. Can these modules operate at low speed? Specifically with a PHY capable of only a fraction of the data rate?

Further detail:
I have programmed a 10/100BASE capable microcontroller connected to a PHY and standard ethernet port to host a DHCP server and send ping requests with feedback. This was in attempt to create a quick tester for network ports, mainly to verify internal connections from the network ports to the CPU of a closed product.

I'd like to design a battery powered PCB to make this device handheld for quick portable checks. It's my understanding that with a lower speed SFP module, it would be as easy as the current setup and just replacing the ethernet magnetics with the SFP cage connector and adding all final support circuitry. Is this even possible with a 10GBASE SFP+ modules?

I know it's physically impossible for it to communicate to the MCU at that speed, but would it still be able to function at the lower speed in order to just send the simple pings or other custom data packets? The pinouts for the SFP vs. SFP+ modules look the same. I'm hoping to be able to make this universal for copper or fiber inserts. Are there any fundamental hardware differences that make the port SFP+ compatible besides being able to handle the higher speed?

Any help would be appreciated. I'm fairly familiar with these ports at a computer network system level, but this is the first time I'm attempting to really dive into the low level electronics of their direct communication.

 

[Tom.G]

The one datasheet I looked at shows minimum data rate of 1Gbs.
Data sheets for several models can be found here:
https://www.fs.com/c/16g-10g-8g-transceivers-56

(above found with: https://www.google.com/search?q=sfp++fiber+transceiver)

Cheers,
Tom

 

[Adrian Alexander]

Good Day. I am having a similar issue with low data rates. 9.8304Mbps runs fine but 4.096Mbps runs errors. Did you have any luck resolving the issue? Thank you.

 

[brian_au]

I am also interested in this, for a fibre/fiber conversion from MM to SM, with an old protocol that runs at only 1Mbps. I would have _thought_ that a 'non-smart' SFP that does simple clock recovery and electrical to light (and reverse) conversion in a transparent way should work at any low speed? But if it is a 'smart' device and only expects Ethernet-type signals then I guess it will not work, and it is too smart for its own good.
Would love for someone who really knows how these things work to chip in here... thanks in advance.

 

[berkeman]

I am also interested in this, for a fibre/fiber conversion from MM to SM, with an old protocol that runs at only 1Mbps. I would have _thought_ that a 'non-smart' SFP that does simple clock recovery and electrical to light (and reverse) conversion in a transparent way should work at any low speed? But if it is a 'smart' device and only expects Ethernet-type signals then I guess it will not work, and it is too smart for its own good.
Would love for someone who really knows how these things work to chip in here... thanks in advance.

Welcome to PF, Brian.

I'm not that familiar with this FO module, but if it has a minimum datarate, I'm guessing that there is a highpass filter structure somewhere in the circuit (for whatever reason). Hopefully you can find a low-speed alternative.