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DS100KR401: Will the DS100KR401 translate a 40GBASE-KR4 interface to a 40GBASE-SR4 that will work with a Samtec Firefly optical module

Kevin Graff
Prodigy 20 points
Part Number: DS100KR401
Other Parts Discussed in Thread: DS100DF410

I would like to connect a 40GBASE-KR4 ethernet interface from an existing switch (nearby, distance is not an issue) and out to an optical interface (Samtec Firefly https://www.samtec.com/products/etuo-b04-10-012-0-1-1-5 )

The Samtec interface requires a 40GBASE-SR4 signal. The Samtec might also support SFI/XFI; I'm waiting to hear back on that. The reason is that the Samtec is fairly simple, it only amplifies the signal for the TX lasers and from the RX diodes.

For now I need a chip that can convert all four lanes of -KR to -SR full-duplex, and I wanted to confirm that the DS100KR401 would do that.

Thanks

  • 0
    Prodigy 20 points

    Is this DS100KR401 a simple repeater? Or does it actually translate -KR to -SR?

    The reply I got from Samtec is that it just needed to be a protocol designed for optical (-SR, -LR, -ER, Fibre Channel, Infiniband, etc...) seems like the link training, handshakes, quiet times are what need to be avoided, or at least optimized for fibre applications.

    Perhaps a PHY is needed here, or a switch?

  • 0 in reply to Kevin Graff
    TI__Mastermind 29650 points

    Hi Kevin,

    DS100KR401 is a repeater which reduces jitter in a signal through the use of equalizers. While it supports 10G-KR, it cannot translate to another protocol since it simply redrives a signal without making any modifications to the data. A PHY might be a better choice for your application.


    Best,

    Lucas

  • 0 in reply to Lucas Wolter
    Prodigy 20 points

    Thanks I was suspecting it wasn't able to translate protocols.

    Can you suggest a simple PHY that would do this?

  • 0 in reply to Kevin Graff
    TI__Mastermind 29650 points

    Hi Kevin,

    After looking more closely at 10G-KR versus 10G-SR, I found that DS100KR401 actually can be used in your application. Both protocols have the same physical layer coding so there are no data modifications necessary.

    10G-SR has the following eye specs. Y1, X1 and X2 can be met by tuning the CTLE setting on the repeater. Y2 shows a maximum peak-to-peak amplitude of 700mV. DS100KR401 has a minimum transmit output voltage setting of 700mV, so there is a possibility the repeater's output voltage amplitude may be too large.

    An alternative part that can be used is the DS100DF410 retimer. This part has an adjustable transmit output voltage down to 600mV, which should be sufficient to meet 10G-SR spec.

    Best,

    Lucas

  • 0 in reply to Lucas Wolter
    Prodigy 20 points

    I think the compatibility issues lie more with -KR link training and quiet times which can play havoc with optics, clock recovery and all that.

    At this point I'd rather go the PHY direction since it's more of a sure thing.

  • 0 in reply to Kevin Graff
    TI__Mastermind 29650 points

    Hi Kevin,

    After discussing with some colleagues, unfortunately we don't have any -KR to -SR PHYs available in our catalog.

    If you are still interested in using a retimer or repeater for your application, I expect that they should work. If you choose to use the DS100DF410 retimer, it should work without issue as long as you disable link training. If you choose to use the DS100KR401 repeater, this supports link training as long as you are using the linear 10G-KR mode.

    Best,

    Lucas

  • 0 in reply to Lucas Wolter
    Prodigy 20 points

    Thank you I believe that's all the info I need