Hi mohammed,
In general, these sellmeier coefficients can be calculated for different reference wavelengths. In case of design stage, I can refer you to consider following paper, which shows the dependencies of refractive index on several (most common) dopants. Please, see attached:
http://webcache.googleusercontent.com/search?q=cache:Gc0oKWOlusUJ:www.researchgate.net/publictopics.PublicPostFileLoader.html%3Fid%3D548ee34dd5a3f232678b459c%26key%3D2137e766-49df-4802-9857-daabc6e41332+&cd=3&hl=en&ct=clnk&gl=us