Fiber-Optic Rotation Sensors and Related Technologies: Proceedings of the ... - Google Books

https://books.google.de/books?id=Ouv0CAAAQBAJ&pg=PA393#v=onepage&q=%22W%20m2%20Hz%22&f=false

Currently there is considerable interest in the application of optical meth ods for the measurement of absolute rotation. Active approaches, so-called ring laser gyros, have been under serious development for at least 15 years. More recently, passive…