Arista QSFP-40G-U 40G QSFP+ BiDi $25

[llowrey]

There's only 3 left at the first listing, which is the seller I bought from, but it's a good price for these modules. I can't vouch for the modules from the second seller.

These are LC BiDi 40G modules that work with both MMF and SMF (can confirm). Moreover, with SMF, they also work when paired with a (super cheap) KAIAM LR4 module.

Arista QSFP-40G-U 40G 1310NM Fibre Channel QSFP+ Transceiver Module XVR-00071-01 | eBay
Arista QSFP-40G-UNIV 1310NM Channel QSFP+ Transceiver Module XVR-00071-01 | eBay

Cisco BiDi modules can be had for around the same price but I was never able to get them to work with my CX3 cards. Thanks to a tip from @CPNXP I was able to get them to work with my CX4 Lx cards. The Aristas work just fine with my CX3s. The Ciscos are MMF only.

Folks with Mellanox SX6016, SX6018 or SX6036 switches need a few firmware and config tweaks to get them to work but these modules work well and make good use of existing duplex MMF fiber.

 

[Layla]

How are these BiDi modules? They appear to be LC Duplex CWDM; BiDi would be additional wavelengths (e.g
dual wavelength) LC Simplex?

 

[tinfoil3d]

I use Arista's QSFP-40G-UNIV in mlx3 354, they work on OS/2 and OM4 in my case between two nearby buildings with no issues, full speed.
But I bought them at ~60 bucks a piece(new) last year I think.

https://www.arista.com/assets/data/pdf/Whitepapers/QSFP_40G_UNIV_FAQ.pdf

 

[tinfoil3d]

I also don't think cisco's modules are able to operate on OS/2, but yeah they do have both 40 and 40/100 LC MM modules. That are vastly more expensive than arista too.

 

[ArthurA]

These aren't BiDi XCVRs, BiDis will only have a single LC port with Tx & Rx MUXed onto a single fibre. They will specify Tx/Rx wavelengths requiring more attentive sparing since each end will have a different specific part number required to link.

The links you've provided are colour coded for multimode, I've honestly never seen a MMF QSFP XCVR that uses LC connectors only MPO. It's been my experience that 1GbE SX MMF XCVRs won't link over 3m SMF with ~21dB of attenuation due to the 1310nm LED emitters not hitting the smaller SMF core correctly. Typically -6dBm launch, -21dBm attenuation for a realized -27dBm falling far short of the typical -18dBm receiver sensitivity. However with short enough fibre and the higher aggregate TX power of 40G/100G XCVRs (upto +8dBm launch) it's not inconceivable for a short enough fibre to fall within the receiver sensitivity margin.

 

[ArthurA]

It looks like I may be mistaken though since a quick search turns up SWDM MMF BiDi QSFPs with two LC connectors, we just have no use for these odd ball devices in DWDM transmission networking.

 

[NablaSquaredG]

These aren't BiDi XCVRs, BiDis will only have a single LC port with Tx & Rx MUXed onto a single fibre.

Sadly the terminology isn't clear

fs.com calls those BiDi (presumably because some vendor started with it)

https://www.fs.com/de/products/135557.html

 

[ArthurA]

Sadly the terminology isn't clear

fs.com calls those BiDi (presumably because some vendor started with it)

https://www.fs.com/de/products/135557.html

That tracks, FS was the only source I'd found to make me doubt my initial assertion and it does look like they're referencing/matching someone else's PN but in their graphic none of these things are actually BiDi.