Core to Cladding Diameter Ratio (CCDR)
This parameter is simply the ratio of core and cladding diameters. In order to minimise the attenuation through the evanescent field, the CCDR must be carefully considered for the product in question. For example, in a multimode fiber, with an NA of 0.22, the cladding thickness is typically kept greater than 10 times the operational wavelength. For single-mode fibers, the evanescent field must also be considered, particularly when the fiber is to be coiled/bent. A general rule is to keep the cladding diameter greater than 8-10 times the mode field diameter of the fundamental mode.
Related Terms: Attenuation , Cladding, Core , Mode Field Diameter (MFD), Multimode, Numerical Aperture (NA), Single-Mode