Abstract: An interferometer suitable for length measurements, comprising a laser light source, a beam splitter to divide light stemming from the laser light source into a measuring beam and a reference beam, and recombination means at which the reference beam being guided along a reference path and the measuring beam interfere. The measuring beam travels along a measuring path that leads over a movable measuring reflector and partly through a gaseous ambient medium. The interferometer further comprises photodetector means to analyze optical interference signals stemming from the recombination means. At least one static etalon of a known length is provided to determine or compensate for variable environmental conditions (variable refractive index) of the ambient medium. The etalon comprises two reflection surfaces and is illuminated by light stemming from the laser light source. The space lying inbetween these reflection surfaces is filled with the ambient medium.

Abstract: Device for stabilizing the wavelength in air of a laser diode for an Interferometer which measures length in waveguide technology. To stablize the wavelength in air, an interference phenomenon, according to Young, is produced and detected in an air chamber of constant and stable length with two point-shaped light waves of a coherent beam. The point-shaped light waves are formed by the ends of waveguides. The photo-detectors and the control device control the frequency of the laser diode so that the interference phenomenon, and therefore the wavelength in air, remain stable inside the reference chamber. The arrangement is simple and compact.

Abstract: The invention concerns a device for generating light, in particular light for use in length measurement using an interferometer. The frequency of the laser light emitted is controlled as a function of the wavelength in the surrounding gaseous medium (air) in such a way that the wavelength in the air remains constant. The light source in this device is a laser diode. Located external to the laser resonator is a device for feeding back to the resonator, at selected frequencies, light emitted by the laser diode.