The invention relates to a method for optical measuring systems, comprising a sensor element (6) connected to a measuring and control unit (10) via an optical connection (3), and being adapted for providing a signal defining a measurement of a physical parameter (p) influencing the sensor element (6), said method comprising generation of a measuring signal that is brought to come in towards the sensor element (6), and detection of the intensity of the measuring signal (B) in the measuring and control unit (10), after influencing the measuring signal in the sensor element (6). The invention is characterised by comprising partial reflection of the measuring signal at a point along the optical connection (3), at a predetermined distance from the sensor element (6), detection of the intensity of the signal (A), corresponding to said partially reflected measuring signal, and determination of a measurement of said parameter (p) based upon the intensity of the partially reflected signal (A) and the intensity of the measuring signal (B). The invention also relates to a device for carrying out said method. Through the invention, measurements with an optical pressure measuring system are allowed, which exhibit effective compensation for any existing sources of error.