A multipass fiber amplifier comprises a micro-optic-module polarization separating device including a first ASE blocking device, a micro-optic-module 90° polarization rotating reflector including a second ASE blocking device, a pump source for providing pump light; a micro-optic-module wavelength-division multiplexer (WDM) for combining the pump light and the laser beam; and a gain fiber having a first end and a second end for amplifying the laser beam using the pump light, where the first ASE blocking device is coupled to the first end of the gain fiber and the second ASE blocking device is coupled to the second end of the gain fiber.
