Steam turbine and method of measuring the vibration of a moving blade in a flow passage of a steam turbine

The invention generally relates to a steam turbine having a flow passage in which a moving blade is arranged. More preferably, it relates to one including a measuring system for measuring a vibration of the moving blade. The invention also generally relates to a method of measuring the vibration of a moving blade in a flow passage of a steam turbine. The invention relates to a steam turbine () comprising an optical measuring system () for measuring a moving blade vibration. A transmitter () produces a light beam () which strikes the moving blades () and is reflected by these into a receiver (). By providing that the transmitter () is separated from the receiver (), the invention achieves a measuring angle that actually reduces the scattered light effect of the steam enough to enable reliable optical measurements of the blades vibration. The invention also relates to a method for measuring the vibration of a moving blade () in a flow channel () of a steam turbine ().