657 Class A1 fibers are specified for a minimum bend radius of 10 mm, allowing up to 0. 75dB (at 1550 nm) increase in one turn. That radius varies according to the particular fiber's design, but historically, most fibers are optically unaffected by bends 30 mm radius. As a bend is reduced to a critical value, though, some. The correct bend radius calculation is a fundamental prerequisite for high-quality fiber optic installations and is decisive for long-term network performance and reliability. A common mistake in fiber deployment is treating every curve the same. Exceed it once and you might get away with it.