Can the SFP port be used to feed to a device, like a Lumin U2 or a Rose RS130, or is it only on the intended “input” side of the switch? And if it is output capable, does it mean that if used, the number of wired RJ45 ports is decreased by 1?
Not sure excatly what you are asking but
the main reason I see SFP ports are used on hi end streamers is the theory that fiber optics can get around ground loops and shielding issues associated with copper wires.
You can certainly use the SFP ports with a DAC cable or a SFP copper ethernet transiever in a SPF port, so the cable between the device is copper and RJ45 to RJ45, even though you are using the SFP ports.
one example:
This module can but put into a SFP port and use a copper ethernet cable to connet to your switch of choice be LHY or whatever RJ45
a DAC cable for shorter runs between 2 SFP ports:
On many network switches there is sometimes one port that is only on the “A” side, and can’t be used to interface to an endpoint like a streamer.
as far as I know sfp(+) are bi directional.
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Understood. But some of these switches are weird. The EtherREGEN comes to mind, where while all ports are bi-directional, some claim the RJ-45 on the “B” side of the moat is the better choice for the audio endpoint. It’s even marked as such.
Melco S100 same thing. 4 for streaming things… 100M and 4 for high speed 1G. No idea why they do that but they say it makes a diff. Noise???
Yes SFP are bi directional. they are same as ethernet, just different connection and wire.
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I know the fundamentals. 
I’ve been playing with fiber since the late ‘80, for both hobby and in a professional capacity. But I don’t care to guess how the guts of these so called audiophile switches are built. Especially when I can’t find a manual online for some of them. 
I edited my OP to make it a bit more clear.
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Both LHY-6 and LHY-10 can connect to Lumin U2 by FB without problem, and they can connect to each others as well such as in my case.
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Thanks Donald! That’s what I was hoping to hear!
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Only speculation, probably some manufacture is doing the same thing as Audioquest Marking cables as directional. There is a difference, depends on use case. But for network connectivety, no.
Rob from Network Acoustic (Tempus switch and Muon Pro) gave me and advice. He said that after many tests they still prefer electrical connection over fiber between 2 SFP ports. Sonically speaking.
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I used the SFB port on my EtherREGEN to feed a Pink Faun server which fed my Grimm MU1 and didn’t sweat the magic B port. I still use the EtherREGEN, but no longer use the B port.
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It’s weird how this network stuff is so system synergistic, like everything else. A friend with a very impressive system was using an EtherREGEN. We asked him to bypass that and hook directly into his streamer. It sounded better to pretty much everyone who was listening. No knock on the EtherREGEN - it could have been “fill in the blank” network device. But it seems sometimes they help, and sometimes not. Just like everything else. All systems are different. It an be a frustrating hobby.
Without experiencing Frustration you can’t get audiophile Nirvana, that’s all in this hobby! That’s this hobby!
Sorry, my friend. I’ve learned a long time ago that there is no such thing as audio nirvana, and that forgetting about what’s making the music - and just listening to music - is the true happiness that so few in this hobby seem to find.
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Was he talking about FB link right before the streamer, or anywhere in the chain?
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Not only to add to what Donald said about full compatibility with a Lumin U2 but these things also accept the good Finisar modules (1475s/1471s). I actually have a 1471 (10G) in the LHY and a 1318 in my U2 since it will not accept a 10G transceiver and it sounds best to me. I was surprised when I initially connected these two that they would communicate. And no issues in two different switches with the combo. They definitely sound better than 1318s at each end (Switch and U2). Not exactly sure why but it is what it is. Experimenting is fun.
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