Network installers usually meet the situation that device you have in your network does not always fit and work perfectly with the fiber. They plan to make a cable plant based on the multimode fiber cabling. But owing to the link limitation or other reasons, they have to connect multimode equipment with single-mode devices. Is it feasible? In other words, can I use the multimode SFP over single-mode fibers or vice versa? This article will give you a clear explanation about the feasibility of the solutions, and introduce two relevant devices: mode conditioning cable and multimode to single-mode fiber media converter.

Multimode Fiber SFP Over Single-mode Fiber – You Can If You Are Lucky

This is the question that has been asked so many times, but no one can give the exact answer—yes or no. Hence, let’s explain it in details.

Most people think single-mode and multimode fiber are not interchangeable. Because the wavelength of the laser and core size of the fiber are different. Single-mode fiber (MMF) uses a laser as a light source. While multimode fiber (MMF) uses an LED to generate the signal. This would require two significantly different devices to generate the signal.

The core sizes are different between SMF and MMF. SMF is 9 µm and multimode fiber is 62.5 or 50 µm. If users try to mix the single-mode and multimode cabling in the same network, they might have trouble in dealing with the two different types of signal.

However, it is possible to interconnect two devices using SMF interfaces at one end and MMF receiver at the other end. Keep in mind that it depends on the devices, so you can if you are lucky. When plugging LC single-mode duplex fibers on the multimode fiber module in the network, you will find the link came up (the light on the switch turns green). Therefore, the multimode fiber transceiver connected by the single-mode fibers works for the short-reach application. The following image is the real screenshot of the single-mode fibers inserting into the 1000BASE-SX SFP.

While it should be stressed that the link is not reliable and it only works for typical brand devices with a very short link length. Many famous vendors like Huawei or Cisco do not support it. Nevertheless, owing to the differential mode delay (DMD) effect, signal loss of this connection is not acceptable, either.

To sum up, this might be feasible but not advisable. If you need to make a connection between single-mode and multimode interfaces, you’d better use the intermediate switch that is able to convert the signals between single-mode and multimode fibers. The following part will introduce two solutions that might be helpful for the multimode and single-mode conversion.

Conclusion

It doesn’t make much sense to use the single mode fibers with multimode fibers in your network or vice versa, although the link will come up. Just as said above, you can if you are lucky. MCP cables and fiber to fiber converter are the two available options for single-mode and multimode connection. If you bought the wrong fiber optic cables, just replace it into the right one. Fiber optic cable and optical transceiver module nowadays are very cheap. You won’t need to risk of mixing them in the same network.