Abstract: In a modular laser system, a plurality of laser modules are interchangeably mounted on a support rack with each laser module transmitting an output beam to a respective optical pump fiber, and the plurality of pump fibers are optically coupled to a laser rod for generating a combined output beam. A laser diode array is mounted within a sealed chamber of each module, and an output wave-guide of each module is coupled through a plurality of optical fibers to the diode array to receive the laser emissions. The other end of each output wave-guide has a first connector, and each pump fiber has a corresponding second connector permitting the output wave-guides to be interchangeably connected to the pump fibers. A control circuit of each laser module monitors the status of its laser diodes, the voltage and current supplied thereto, and the temperature conditions, and generates signals indicative of these parameters for detecting and replacing failed or defective laser modules.