Method for the fibre-optical, spectrally coded transmission of the value of a variable physical measured quantity

摘要

In simple fibre-optical pickups, in which the measured quantity to be detected modulates the power of a first light flux and in which a second light flux is transmitted as reference power for approximate compensation of the fibre losses, a high independence of the transmission of the measured value from the characteristics of the fibre and their fluctuations is achieved by arranging that the measured quantity modulates the power ratio of the two light fluxes, and that the latter are then transmitted, together with mutually interleaved comb spectra consisting of many lines, over this fibre from the measurement sensor to the evaluation device. Because the two light fluxes thereby have the same mean optical frequencies, and thus also suffer the same losses, it is possible to use fibre plugs and fibres of different length, without influencing the display of measured values. The required filtering of the light fluxes in the measurement sensor and in the evaluation unit can be undertaken with different interference filters, in which the light fluxes are advantageously also interleaved spatially or in their polarisations. Modulation is possible by means of movable masks of polarisers, or else by means of elasto-optical members.