A laser-based light source comprises a laser, an optical fiber, a conversion device, and a detector, the laser for emitting laser light with a laser peak emission wavelength, the optical fiber for guiding the laser light for being received at a first surface of the conversion device, the conversion device for converting at least a part of the laser light to converted light with a peak emission wavelength being longer than the laser peak emission wavelength, the optical fiber further for guiding a part of the converted light back in the direction of the laser and the detector for detecting at least a part of the back guided converted light. A vehicle headlight comprises such a laser-based light source, and a lighting system comprises such a vehicle headlight.