Macrobend

Macrobend refers to a relatively large-radius bend of an optical fiber or cable that causes loss of guided light due to leakage from the core into the cladding or surrounding media. It contrasts with microbends, which are small-scale distortions producing scattering losses along the fiber length. Macrobend losses arise when the curvature reduces the optical confinement of the fundamental guided mode; for sufficiently tight bends, light leaks out of the core and is attenuated along the path or escapes the fiber entirely.

Loss from macrobends depends on the bend radius, wavelength, fiber design, and construction. Generally, shorter bend radii and longer wavelengths increase attenuation. The effect is often specified as an attenuation per bend at a given wavelength in dB/bend, or as a bend-induced loss per unit length for a specified bend geometry.

Mitigation involves maintaining minimum bend radii during installation, using bend-insensitive fiber designs that better confine light under bending, and avoiding tight coils or routing around sharp corners. Proper protection and slack management reduce stress-induced macrobends in cabling assemblies.

Applications and relevance: Macrobends are a key consideration in telecommunications fiber networks and data center cabling, affecting link budgets and reliability. Standards and manufacturers provide bend-radius recommendations and test methods to quantify macrobend loss.