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I have a 40GBASE-SR4 QSFP transceiver which can be used for 4x10G SFP+ communications using a 40G QSFP+ to 4x10G SFP+ multi-mode optical spliter. I am looking for an LR (single-mode) equivalent of this SR transceiver, but can't find any.

I fear that fundamentally 40GBASE-LR4 cannot be used for 4x10G because the data is delivered as four wavelengths over the same fiber, whereas 40GBASE-SR4 can be used for 4x10G because the data is delivered over four parallel fiber lanes.

Can 40GBASE-LR4 be used for 4x10G?

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You are correct. SR4 works because it's four fibres. LR4 doesn't because it's four lambdas. Even if you break out each one -- good luck finding 10G-LR optics at the exact wavelengths LR4 requires, the module itself doesn't support operating at 4x10G -- the data rate on most is 40G only.

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This transceiver can do both 40G-LR4 and 4x40G LR.

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  • I didn't see anything saying it could do qty. 4 10G links. i.e. there's no break-out cable to attach 4 10G LR ports to one.
    – Ricky
    Jun 24, 2014 at 17:20
  • I called up the guys behind this, and confirmed that 4x10G is supported. The connector is standard MPO for which you need a single mode optical breakout cable.
    – Randomblue
    Jun 24, 2014 at 17:40
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Just for people looking at this answer now (close to 3 years after the original answers): today you can get QSFP+ PLR4 transceivers that support 4x10G breakout over SMF (long range).

These transceivers work by using 4 transmitters on the same wavelength but on different fibers.

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  • Product or resource recommendations are explicitly off-topic here, as they are on most SE sites, except Software Recommendations and Hardware Recommendations, and they may be considered spam.
    – Ron Maupin ♦
    Jun 5, 2017 at 14:55
  • Fair enough, I figured direct links were helpful to prove the answer (they weren't intended to be endorsements). But an Internet search for PLR4 finds you plenty of examples quickly enough (making the direct links moot).
    – Jeff Morriss
    Jun 6, 2017 at 16:08

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