[Lalaith]

Of course Tolkien knew the Nieblungerlied! That is like saying a professor of astronomy might not know about the moon landings...Good God, he was a professor of mediaeval studies, and this is one of the major works of mediaeval literature!
Wagner based his ring cycle of operas on the Nieblungerlied, a poem written in around the 13th century. This is the German version of the tale. An even earlier Norse (Scandinavian) version, which is rather different in many details, dates from around the 10th or 11th century.
And there is actually a 'ring' in the story, it is part of the dragon hoard of Fafnir and it is cursed.
Tolkien was immersed in all these poems, as part of his academic work. And the influence of Norse, Germanic, Anglo-Saxon and Finnish heroic and mythological literature on his work is very strong and noticable to anyone who is familiar with this literature.
It is much more immediately obvious than his Christian themes, in my opinion. That is in no way to imply that Tolkien's work is unChristian, or that it is derivative or plagiarising anything, incidently. Authors have always used many sources as inspiration.