The core diameters (9 µm vs. 5 µm) are fundamentally incompatible—attempting to splice or connect them results in massive insertion loss (often 10+ dB) that will fail every optical power budget test. Always confirm your existing infrastructure before ordering pigtails. When you build or upgrade a fiber network, the same four words pop up everywhere— fiber optic (bare fiber), pigtail, patch cord, optical cable. They're related, but they are not interchangeable. Mixing them up drives costs higher, increases loss, and slows your rollout. Fiber optic pigtails. In contrast, fiber pigtails have a connector on one end and a broken end of the fiber core on the other.