We have an optical tap (https://www.fs.com/products/73675.html) that provides an LC connector providing two TX instead of RX/TX. enter image description here As you can see, there is a conflict.

What I think I need: enter image description here A splitter from one LC connector RX/TX to two LC connectors TX to be able to connect two NICs.

How is this done in the industry?

1 Answer 1


For starters: you can split a Tx into multiple Txs (transmitting to receiving direction) but you can't possibly join multiple fibers into one (transmitting to receiving as well).

The Tx on the tap goes into the Rx on the NIC. The NIC needs to be able to "link" to the Tx only, without negotiation.


From your diagrams, you need to use either two simplex LC patches or a splitable one (many are) to connect the dual LC tap-out to two monitor ports (Rx side). Each port's Tx side stays empty (you should put on a dust cover though).


The diagram you linked to enter image description here shows that the link's signal (LC port 1-2 to 3-4) is split by direction to LC port 5 and 6 - both are Tx. 4→1 is split to 6 and 2→3 is split to 5.

  • I didn't get it. How this is done in the real life? The optical TAP provides two TXs in a single LC connector. If I connect a patch cable, the NIC's TX will receive the second TAP's RX.
    – None
    Jul 27, 2019 at 9:16
  • Generally, you connect a Tx to an Rx. The Tx of a NIC goes to the Rx of a switch and vice versa. You can split a signal (Tx) to two or more Rx but you cannot combine multiple Tx into one Rx. If you need to monitor two Tx lines (or both directions of a single link) you need two NICs or a dual-port one.
    – Zac67
    Jul 27, 2019 at 11:16
  • That's why I don't understand, if you click on the link I provided, you'll see the diagram of the tap providing 2xTX single LC connector.
    – None
    Jul 27, 2019 at 11:30
  • Thank you for confirming what I thought. I wasn't sure what's the proper way to do it.
    – None
    Jul 27, 2019 at 22:45

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