40G options between Nexus 9k and Intel NIC

I have a few Nexus 9300 (48 SFP+, 6 QSFP28 - vPC with 100G DAC, Uplink with 100G IR4), and now a server should be connected with 2x 40G instead of 10G links (about 25 meters apart)

The card in the server is a Intel XL710. The first guess was using the Cisco 40G MM BiDi optics, because we have those laying around - but, of course, this seems to be a Cisco thing only? Intel card does not want to use BiDi.

So researching further, it seems that there is no common ground on 40G in just using a pair of MM fibres using LC connector? Between nexus and server rack are 5 free MM pairs which could be used, but would not be enough then.

• BiDi - LC MM, but Cisco only?
• SR4 - MPO-12, so 8 pairs of MM
• LR4 - no SM to Rack, also expensive transceiver
• CSR-S - LC MM, but Cisco only? I saw this only in connection with Cisco, others are CSR4 and also need MPO-12
• AOC - always the question, would cisco work in intel or would intel work in cisco?
• DAC - too far

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So unless there is a common ground I missed, I'm between a rock and a hard place.

I think the best way to go would be SR4 or LR4. Cable would be needed in both cases, SM cable would be way cheaper but transceivers much more expensive to set off the cost of the MPO-12 cables.

Any pointers or ideas greatly appreciated.