Laser source for emitting at least one multispectral light radiation (RLM) having a plurality of spectral lines separated by a determined spectral interval, the laser source comprising: - a bank (B) of tunable lasers, a spectral line of the multispectral light radiation (RLM) corresponding to a frequency, referred to as the "emission frequency", of the light radiation emitted by a tunable laser (La, Lb, Lc) of the bank (B); - means for adjusting the emission frequencies of the tunable lasers; - an optical filter (MR; MO+MR) having a plurality of resonant frequencies, two successive resonant frequencies being separated by the determined spectral interval, the optical filter (MR; MO+MR) being arranged optically downstream of the bank (B) of tunable lasers, the optical filter (MR; MO+MR) being provided with a device for adjusting (H) the plurality of resonant frequencies; - a photodetector (PD) arranged optically downstream of the optical filter (MR) in order to establish a signal (V) representative of the multispectral light radiation transmitted through the filter (MR; MO+MR); - a modulator (M) associated with means for adjusting the emission frequencies of the tunable lasers, the modulator (M) being designed to generate a modulation signal (Vd; Vda, Vdb, Vdc) and to modulate the emission frequency of the light radiation emitted by at least one tunable laser (La, Lb, Lc) of the bank (B); - a locking device (R) connected to the means for adjusting the emission frequency of the tunable lasers and connected to the device for adjusting (H) the plurality of resonant frequencies, the locking device (R) being designed to process the signal representative of the multispectral radiation (V) and to lock the emission frequencies of the tunable lasers to the resonant frequencies of the filter (MR; MO+MR). - a bank (B) of tunable lasers, a spectral line of the multispectral light radiation (RLM) corresponding to a frequency, referred to as the "emission frequency", of the light radiation emitted by a tunable laser (La, Lb, Lc) of the bank (B); - means for adjusting the emission frequencies of the tunable lasers; - an optical filter (MR; MO+MR) having a plurality of resonant frequencies, two successive resonant frequencies being separated by the determined spectral interval, the optical filter (MR; MO+MR) being arranged optically downstream of the bank (B) of tunable lasers, the optical filter (MR; MO+MR) being provided with a device for adjusting (H) the plurality of resonant frequencies; - a photodetector (PD) arranged optically downstream of the optical filter (MR) in order to establish a signal (V) representative of the multispectral light radiation transmitted through the filter (MR; MO+MR); - a modulator (M) associated with means for adjusting the emission frequencies of the tunable lasers, the modulator (M) being designed to generate a modulation signal (Vd; Vda, Vdb, Vdc) and to modulate the emission frequency of the light radiation emitted by at least one tunable laser (La, Lb, Lc) of the bank (B); - a locking device (R) connected to the means for adjusting the emission frequency of the tunable lasers and connected to the device for adjusting (H) the plurality of resonant frequencies, the locking device (R) being designed to process the signal representative of the multispectral radiation (V) and to lock the emission frequencies of the tunable lasers to the resonant frequencies of the filter (MR; MO+MR). <EOS>