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Registered: ‎10-28-2019

10G Ethernet

Design 10g Ethernet with Xilinx IP 10g Ethernet subsystem,use sfp+ optical module is ok,change to 10g sfp+ t electrical module,it doesn’t work.IP PCS/PMA block is 10gbase-R, 10g sfp+ t electrical module phy type is 10gbase-T,but I have checked 10g sfp+ t electrical module datasheet,the host interface is XFI,so why  sfp+ optical module can work,10g sfp+ t electrical module fail.

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Registered: ‎01-08-2012

There are several reasons why this can fail.  In no particular order:

  • Some SFP electrical plugins do not correctly implement the LOS pin functionality.  Some reflect the status of the electrical interface on LOS; others have LOS permanently low (= indicating the link is always up, even when it's not).
  • Most SFP electrical plugins draw a lot more power supply current than their optical siblings.  This may lead to current limit or heat issues if the hardware designer didn't allow for the extra current or heat.
  • Some 10G SFP electrical plugins will downshift to (e.g.) 5Gb/s or 2.5Gb/s or slower depending on the cable quality.  N.B. Most only specify a 30m span of CAT6a at 10G.  Unless you know your PCS/MAC can handle the downshift, you should disable it by writing to the appropriate SFP registers (or get shorter or better cable).
  • FEC is done in the SFP plugin.  You should disable FEC in your PCS.
  • Different 10G SFP electrical plugins may use different I2C addresses.  I have seen up to three different I2C addresses used on a single plugin.  Make sure you have the correct settings for the particular plugin you are using.