Abstract: Disclosed is a method for measuring the absorbance of light of a substance in a solution in a measuring cell, said method comprising the steps of: transmitting a first light beam from a light source towards a beam splitter; dividing the first light beam into a signal light ray and a reference light ray by the beam splitter; modulating the signal light ray; modulating the reference light ray; providing the measuring cell such that the signal light ray passes through the measuring cell; detecting a signal in a detector, which signal is the combined signal intensity of the signal light ray and the reference light ray detected by the detector; performing synchronous detection of the detected signal in order to reconstruct the intensities of the signal light ray and the reference light ray from the combined signal detected by the detector, said synchronous detection being based on the modulation performed to the signal light ray and the reference light ray.

Abstract: Disclosed is a method for measuring the absorbance of light of a substance in a solution in a measuring cell (23; 223?), said method comprising the steps of: transmitting (S1) a first light beam (27; 27?) from a light source (25; 25?) towards a beam splitter (29; 29?); dividing (S3) the first light beam (27; 27?) into a signal light ray (31; 31?) and a reference light ray (33; 33?) by the beam splitter (29; 29?); modulating (S5) the signal light ray (31; 31?); modulating the reference light ray (33; 33?); providing (S9) the measuring cell (23; 23?) such that the signal light ray (31; 31?) passes through the measuring cell; detecting (S11) a signal in a detector (39; 39?), which signal is the combined signal intensity of the signal light ray (31; 31?) and the reference light ray (33; 33?) detected by the detector (39; 39?); performing synchronous detection (S15) of the detected signal in order to reconstruct the intensities of the signal light ray (31; 31?) and the reference light ray (33; 33?) from the combin

Abstract: Disclosed is a method for measuring the absorbance of light of a substance in a solution in a measuring cell (23; 223?), said method comprising the steps of: transmitting (S1) a first light beam (27; 27?) from a light source (25; 25?) towards a beam splitter (29; 29?); dividing (S3) the first light beam (27; 27?) into a signal light ray (31; 31?) and a reference light ray (33; 33?) by the beam splitter (29; 29?); modulating (S5) the signal light ray (31; 31?); modulating the reference light ray (33; 33?); providing (S9) the measuring cell (23; 23?) such that the signal light ray (31; 31?) passes through the measuring cell; detecting (S11) a signal in a detectoR (39; 39?), which signal is the combined signal intensity of the signal light ray (31; 31?) and the reference light ray (33; 33?) detected by the detector (39; 39?); performing synchronous detection (S15) of the detected signal in order to reconstruct the intensities of the signal light ray (31; 31?) and the reference light ray (33; 33?) from the combin

Abstract: Disclosed is an optical fiber arrangement for inducing coupling among propagation modes of light, said arrangement comprising a multimode optical fiber (30) having an input end (32) for receiving light and an output end (31) for emitting light, with a coupling inducing section (33) extending from said input end to said output end, and a holder (80) on which the optical fiber is arranged, wherein said multimode optical fiber has a non-circular cross section. Disclosed also is a system for measuring the absorption or determining the concentration of a substance, said system comprising at least one optical fiber arrangement.

Abstract: Disclosed is an optical fiber arrangement for inducing coupling among propagation modes of light, said arrangement comprising a multimode optical fiber (30) having an input end (32) for receiving light and an output end (31) for emitting light, with a coupling inducing section (33) extending from said input end to said output end, and a holder (80) on which the optical fiber is arranged, wherein said multimode optical fiber has a non-circular cross section. Disclosed also is a system for measuring the absorption or determining the concentration of a substance, said system comprising at least one optical fiber arrangement.