First my assumptions (possibly wrong):

  • 100BASE-FX -> Multi-mode fiber
  • 100BASE-LX -> Single-mode fiber

In fact, if I check some online information from CISCO regarding SFPs, it confirms my assumptions: https://www.cisco.com/c/en/us/products/collateral/interfaces-modules/fast-ethernet-sfp-modules/product_data_sheet0900aecd801f931c.html

But the situation is that I found some products on the web that are designed for single-mode fiber but they use the 100BASE-FX designation. Is this wrong? Is any 100BASE-FX SFP capable of communicating trough both multi-mode and single-mode fibers? If not, how can I know that a 100BASE-FX SFP will work with multi-mode or single-mode if it is not clearly stated?

  • There is no such thing as 100base-LX, I assume you mean 1000base-LX or 100 base-LX10? You can always check cisco's compatibility matrix: tmgmatrix.cisco.com – Lenniey Jan 14 at 16:29
  • Yes, you are right, but my question is if 100BASE-FX will work with single-mode and multi-mode fibers and how (I assume that the laser should be different)? – soyxan Jan 16 at 11:12

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