A system and method for monitoring a wavelength of light produced by a light source is disclosed. The system and method comprise a diffractor for diffracting the light. A first portion of the light is transmitted without diffraction and has a propagation direction. A second portion of the light has a predetermined wavelength and is diffracted through a predetermined angle from the propagation direction. The system also comprises a plurality of filters at the predetermined angle from the propagation direction from the diffractor. The filters transmit light of the predetermined wavelength. The system also comprises a plurality of photodiodes. Each photodiode provides a signal corresponding to an intensity of light and corresponds to a one of the plurality of filters. Each photodiode is placed behind a corresponding filter. According to the system and method disclosed, the system and method monitor the wavelength without significant interruption of the beam. The system and method are also compact, low in cost and require very little alignment. Consequently, overall system performance is increased.