Single-mode optical modules are best for long distances and fast speeds. The optical module serves as a crucial component in optical fiber communication systems, operating at the physical layer, which is the lowest layer in the OSI model. Its primary function is to achieve optoelectronic conversion by converting electrical signals into optical signals and vice versa. Fiber is not "auto sensing" and you're currently using fast ethernet / 100mbps. If the other side is also 100mbps, get a 100mbps sfp multimode lc module. Think about distance, speed, fiber you have. The right optical transceiver module can enhance your network performance; you will enjoy superior data flow speeds and reliable connectivity for little or no additional cost.