A hermetically sealed pump module for use with fiber devices is disclosed. The method and apparatus disclosed enable a pump module to be constructed that has a high coupling tolerance and which is inexpensive and easy to manufacture. The pump module may comprise a transparent window through which a pump beam is coupled from a laser diode into the inner cladding of a double cladding fiber. The transparent window also may serve as a substrate for the inner cladding of the double cladding fiber. The laser diode is sealed within the pump module housing with a lid and the window, which is bonded to the lid. The housing may contain a heat sink, heat-spreading sub-mount and a Peltier cooler.