FIO-D Series "Mini" Isolators are for applications that require minimum sized isolators. This small size is achieved through the use of BIG (bismuth-iron garnet) film as the magneto-optic material, and dichroic Very Low Power Polarizers. VLP Polarizers absorb the unwanted polarization vector and are therefore limited in laser power capability.
To achieve maximum isolation and transmission, these mini isolators are set to the exact laser wavelength of use. Once set, Mini Isolators cannot be adjusted.