SFP Conversion

[DraconisMaximus]

I’ve used these to plug ethernet cables into SFP ports in the past.

https://techspecs.ui.com/unifi/accessories/uacc-cm-rj45-mg?subcategory=accessories-modules-fiber

I now need to plug an SFP cable into an ethernet port but cannot find a reversed adapter for that other than full converter boxes like these.

https://www.amazon.com/sfp-media-converter/s?k=sfp+media+converter

I’m guessing there is some technical reason why the conversion is harder in that direction that requires an active device. Can anyone confirm if this is true / the technical details of it?

[Electronics Wizardy]

Typically SFP is used so you can put different fiber transivers into a port, so you can pick multimode or single mode for example for each port, instead of having to have different switch models. Generally SFP isn't used for long distance connections in walls like you would with fibre or twisted pair cables.

 

A bit more detail about what exact devices your connection would porbably help, but yea a media converter is often needed.

[AbydosOne]

43 minutes ago, DraconisMaximus said:

I now need to plug an SFP cable into an ethernet port but cannot find a reversed adapter for that other than full converter boxes like these.

Yep, you'll have to rely on a media converter.

 

SFP modules (more specifically, the active chips inside) get their power from the device they're plugged into. If you run SFP to SFP, you need something on the far end of the cable to provide power, and Ethernet devices don't universally provide power. Hence, media converter.

[OhYou_]

its a bit like converting a door into a window and a window into a door.
most doors can be a window, some even support being a window by having glass.
when you try to convert a window into a door, well now you have a serious problem, there are no stairs on the other side, there is no path to get to it, the opening isnt tall enough to walk through.
 

[OddOod]

14 minutes ago, OhYou_ said:

its a bit like converting a door into a window and a window into a door.
most doors can be a window, some even support being a window by having glass.
when you try to convert a window into a door, well now you have a serious problem, there are no stairs on the other side, there is no path to get to it, the opening isnt tall enough to walk through.
 

Strong analogy there

[DraconisMaximus]

On 6/3/2025 at 11:03 AM, Electronics Wizardy said:

A bit more detail about what exact devices your connection would porbably help, but yea a media converter is often needed.

The ISP ran a PON terminated cable into the house. They included a PON to SFP adapter to go into their POS standard gateway. I have a Cloud Gateway Max/UCG-Max that only takes ethernet. While some some people may like the POS standard, I don't and getting a direct WAN connection is the first of many steps to eliminate the POS.

[DraconisMaximus]

On 6/3/2025 at 11:31 AM, AbydosOne said:

Yep, you'll have to rely on a media converter.

Any recommendations for a decent one? The ones I have been seeing run $130 - $200+ USD. I should note that SFP+ and 10GBase-T are necessary to get the full speed out of the system. I currently have a Cloud Gateway Max/UCG-Max and at those prices it may just be worth upgrading to a Cloud Gateway Fiber/UCG-Fiber.

[Lurick]

1 hour ago, DraconisMaximus said:

The ISP ran a PON terminated cable into the house. They included a PON to SFP adapter to go into their POS standard gateway. I have a Cloud Gateway Max/UCG-Max that only takes ethernet. While some some people may like the POS standard, I don't and getting a direct WAN connection is the first of many steps to eliminate the POS.

And your ISP will provide you the information needed to do that and let you bypass their PON gateway?

[DraconisMaximus]

2 hours ago, Lurick said:

And your ISP will provide you the information needed to do that and let you bypass their PON gateway?

I have talked to three different people at the ISP and gotten three different answers. BYOD is not banned but they would prefer you keep using provided hardware and so they don't make it easy. In any case, to even try I need a compatible connection to my own gateway.

[Alex Atkin UK]

50 minutes ago, DraconisMaximus said:

I have talked to three different people at the ISP and gotten three different answers. BYOD is not banned but they would prefer you keep using provided hardware and so they don't make it easy. In any case, to even try I need a compatible connection to my own gateway.

Yeah typically when people do this they will buy a gateway that already has an SFP+ port, or run pfSense/OPNsense on a PC.

Or put the ISPs gateway into bridge mode so it acts as a media converter itself.

[Electronics Wizardy]

4 hours ago, DraconisMaximus said:

The ISP ran a PON terminated cable into the house. They included a PON to SFP adapter to go into their POS standard gateway. I have a Cloud Gateway Max/UCG-Max that only takes ethernet. While some some people may like the POS standard, I don't and getting a direct WAN connection is the first of many steps to eliminate the POS.

Just saying, those SFP connections are typically ethernet too, just a different standard.

 

A media converter is the best option unless you can get a router with sfp ports like the UDM pro.