I have been reading a lot about modern fiber networking recently and I have a clarifying semi-hypothetical question:
Imagine I have two 3-foot sections of Multi Mode Fiber, and four SFP+ 10G transceiver modules. I have two servers, each with an SFP+ slot, mounted 5 feet apart. I can't connect them with one of my cables, but if I could use both cables I could pull it off. I could use an optical connector of some kind and that would probably work, but I don't have one of those.
Does such a device exist that would accept my two extra SFP+ modules, and provide a direct connection? Like a switch, but without the switching. It doesn't really need to know anything about Ethernet Frames, so I don't need a MAC layer. If the configuration was possible, I could use two PHY ICs back to back blindly passing data. But do I need PHYs? I read the SFF-8418, and the SFI interface is quite bare bones. I also saw an SFP+ module app note, and it looks like the module isn't much more than a laser and conditioning circuits. the SFP+ does no buffering, etc.
So can I just make a board with two SFP+ slots wired directly together? Both modules would need power. There are those I2C pins, which probably need to be used to turn on the laser. What SFF document has information on that protocol? Do SFP+ modules need a clock signal?
Assuming I can build a board with properly impedance matched traces, how close to impossible is this?
If it is possible, what are boxes like this doing? some kind of signal reconditioning for long hauls?