We have modified the texts of our fiber collimators and fiber couplers to better account for the fact that the AR coating does not necessarily define the wavelength range in which an optics can be used. When it comes to short wavelengths (UV) or longer wavelengths (IR), an optics internal or glass transmission plays a key role, as it can significantly reduce the amount of light passing through the optics. When it comes to doublet optics also the cement between the single lenses must be considered.
This is why we have introduced the working range, which considers cement and both glass transmission as well as AR coating. Please note that all optics are always AR coated for the complete working range. The optics used in our products are the same as before, we only want to describe them more accurately in our documents.
When it comes to glass transmission the threshold is 2% internal transmission loss, unless explicitly specified otherwise. Details about the AR coating (rest reflectivity over wavelength) can be found in the AR coating plot, details about the internal glass transmission (transmission over wavelength) in the transmission plot. Both plots can be found in the downloads section of the respective product webpage.
Since changing all description texts is a time-consuming process, we thank you for understanding during the transition.