A method for monitoring a laser system including a plurality of laser modules connected in series, there being connected in parallel to each laser module a bypass arrangement for bridging the corresponding laser module, includes determining a first laser power of the laser system with a plurality of laser modules operational; activating the bypass arrangement of at least one laser module so that at least one of the plurality of laser modules is bypassed; determining a second laser power of the laser system with the at least one of the plurality of laser modules bypassed; and monitoring the laser system based on a difference between the first and second laser power.