A coupler assembly for a fiber laser is disclosed. The assembly includes a tubular housing having a sidewall with an interior surface, an exterior surface, a first end and a second end. An input collimator unit is also included and configured to be received within the first end of the sidewall of the tubular housing. An output collimator unit received within the second end of the sidewall of the tubular housing. Further included is a compression mechanism configured and arranged to concentrically align the input collimator unit and the output collimator unit about a common central axis. The assembly may further include an alignment mechanism configured and arranged to optically align the input collimator unit and the output collimator unit about a common optical axis. Optionally, a fluid coolant system may also be included.