Optical sensor

An optical sensor, comprising:

• at least one light source which emits excitation light in the direction of at least a first sensor layer;
• a first sensor layer embodied to contact a medium, wherein the first sensor layer emits emission light as a function of incident excitation light and a concentration of a measured variable of the medium;
• at least one receiver which receives the emission light and converts the emission light into a received signal, wherein a measured value for the measured variable can be generated from the emission light;
• a first light guide which conducts excitation light from the at least one light source onto a first region of the first sensor layer and conducts emission light from the first region of the first sensor layer to the at least one receiver;
• and
• a second light guide which is independent of the first light guide and conducts excitation light from the at least one light source onto a second region of the first sensor layer and conducts emission light from the second region of the first sensor layer to the at least one receiver.