If the multimode optical module is connected to the sin […]
If the multimode optical module is connected to the single mode fiber jumper, the interface between the optical transmitter and the single mode fiber will have a large loss, which will significantly reduce the transmission distance, and probably increase the loss by 6dB-10dB. And the general 100M or Gigabit Ethernet system budget is only so much. As a result, the bit error rate is high and the system is prone to failure. The actual transmission distance will be very short or not working directly.
If it is: the single-mode optoelectronic module is connected to the multimode fiber jumper, the coupling efficiency of the transmitter is obviously improved. However, due to the increase of the mode, the introduction of inter-mode dispersion is caused, which indirectly reduces the bandwidth and the maximum transmission distance. The 1300nm band single-mode laser module + single-mode fiber defined in the ITU Gigabit Ethernet 1000BASE-LX can transmit 5 kilometers. If the wrong connection is OM1 or OM2 multimode jumper, Gigabit Ethernet can transmit about 300 meters. If it is connected to OM3 jumper, it can transmit up to 500 meters. 100 megabit Ethernet can even be transmitted to a maximum of more than 1,000 meters.
In summary, a multimode module misconnected to a single-mode fiber will result in a very short transmission distance (depending on the actual signal light intensity) or inactivity due to increased losses. Single-mode module misconnected multimode fiber will reduce bandwidth and transmission distance due to the introduction of inter-mode dispersion, but it is still available in short distances (within 300 meters).