The Advantest model Q7067 is an optical chirp analyzer.

Measurement principle: Using the conversion characteristics between optical frequency and intensit. in the built-in optical-fiber-type Mach-Zehnder interferometer, the instrument converts the dynamic chirp (optical frequency modulation) into a change in optical power FM. By controlling the discrimination point of the interferometer, FM is either added to or subtracted from the intensity IM of the optical input Signal.