An optical probe for measuring light signals includes a first optical fiber guiding incoming light, a lens focusing incoming light towards a sample and collecting altered light from the sample, a second optical fiber guiding altered light, a light logging device measuring intensity fluctuations in the incoming light, wherein the light logging device is positioned after the first optical fiber, whereby the light logging device receives a part of the incoming light from the first fiber. The optical probe is normally applied for measuring light signals in vivo, and finds its primary applications within the field of optical spectroscopic measurements, where the light signals measured by the probe are applied in combination with an apparatus wherein light signals are analyzed against its spectral components for instance in Raman, fluorescence, phosphorescence absorption, diffusion and transmission studies.