Multimode equipment will not launch (inject) enough light into a single-mode fiber since the light carrying core of this fiber is only 9 microns in diameter compared to 62.5 microns in diameter for multimode fiber. It's like connecting 50 ohm coax cable to a 75 ohm coax cable. The impedence mismatch basically kills the signal and you could end up damaging equipment over time as a result.
Your only true course of action would be to get SM to MM converters and then you would be ok.