Abstract: An optical filter for an optical data transmission system, including a substrate; a first and a second reflective structure which are spaced apart from each other such that they form a Fabry-Perot cavity, and at least one optical waveguide formed on or in the substrate, via which light can be coupled into the Fabry-Perot cavity and/or out of the Fabry-Perot cavity. The Fabry-Perot cavity formed by the first and the second reflective structure at least partly is a free-beam cavity, and the waveguide is an integrated waveguide which is formed by one or more layers arranged on the substrate, and the first and the second reflective structure are at least partly arranged in a cutout of the substrate or adjoin the cutout.

Abstract: A laser arrangement includes a laser having a laser cavity, at least one cavity external to the laser, which reflects one part of the light emitted by the laser back into the laser cavity, and a voltage measuring device for measuring a voltage on an active section of the laser. By means of the measured voltage a detuning of the emission wavelength of the laser and/or a property of a material adjacent to the external cavity can be determined. The external cavity includes an optical waveguide coupled to the laser.

Abstract: An optical filter for an optical data transmission system, including a substrate; a first and a second reflective structure which are spaced apart from each other such that they form a Fabry-Perot cavity, and at least one optical waveguide formed on or in the substrate, via which light can be coupled into the Fabry-Perot cavity and/or out of the Fabry-Perot cavity. The Fabry-Perot cavity formed by the first and the second reflective structure at least partly is a free-beam cavity, and the waveguide is an integrated waveguide which is formed by one or more layers arranged on the substrate, and the first and the second reflective structure are at least partly arranged in a cutout of the substrate or adjoin the cutout.