POF Reflection Meter
The POF reflection reter is designed to read out the sensor head of a measuring system over distances of 100m and more via a single fiber optic POF cable. The POF reflection meter is preferably used where high voltage, EMC, explosion hazard or unavailable electrical power supply create adverse conditions for an electrical measuring system. Another application for the system is the integration of the very inexpensive sensor heads around a machine or a building with the option of activating the sensor head later on with suitable electronics as required.
The operating principle of the POF reflection meter is sketched on the right. The most important functional element is a 1×2 splitter with very high crosstalk attenuation.
A POF cable, which is prepared as well as possible at both end faces, is connected. At the POF cable far end face, a sensor head that generates a varying reflection depending on the measurand is attached.. The reflection variation can be caused by:
- a movable mirror on the end face of the POF cable,
- by a color change of a substance sensitive to chemical or other physical processes, or
- deformation of a flexible fiber optic cable serving as sensor head.
The software control in the electronic evaluation unit allows the compensation of the optical crosstalk in the system setup and the zero calibration to the attenuation of the currently used POF cable, so that the measurand can be isolated from the perturbation effects in the system. The POF reflection meter measures the quantitative reflection of the light coupled into the POF cable and reflected at the sensor head. If the correlation between measured variable and reflection factor is known, the measured variable can be determined.