The FC connector is a fiber-optic connector with a threaded body, which was designed for use in high-vibration environments. It is commonly used with both single-mode optical fiber and polarization-maintaining optical fiber. Although both carry data through light signals, they differ significantly in transmission mechanism, bandwidth-distance capability, deployment cost, and typical. The secret lies in fiber optic technology, and understanding the basics—1-core, 2-core, Single Mode (SM), and Multi-mode (MM)—is key to mastering this field. Let's break down these terms in simple, clear language with practical examples.