Multimode fiber is designed to operate at 850 and 1300 nm, while singlemode fiber is optimized for 1310 and 1550 nm. The difference between 1300 nm and 1310 nm is simply a matter of convention, harking back to the days when AT&T dictated most fiber optic jargon. Among the most commonly used fiber types are single-mode fiber (SMF) and multimode fiber (MMF), often paired with 1310nm SFP modules for high-speed data transmission. In this guide, we will explore the distinctions between 1300nm and 1310nm transceivers, examine the characteristics of SMF and MMF. That value determines whether the module is designed for multimode fiber (MMF) or single-mode fiber (SMF), how much attenuation the signal will experience, how dispersion behaves over distance, and whether optical amplification or DWDM systems are possible. Although they can do the same job in some instances, the different construction methods make each of them better suited to certain tasks and budgets.