An optical fiber heat exchanger includes an outer body and an inner body inserted into the outer body. The inner body includes a plurality of guide walls to guide a cooling liquid through the optical fiber heat exchanger to exchange heat from an optical fiber inserted in the optical fiber heat exchanger, a first set of parallel straight channels, extending along an inlet portion of the inner body, formed by a first subset of the plurality of guide walls, a set of U-shaped channels, extending through a transition section of the inner body, formed by a second subset of the plurality of guide walls, and a second set of parallel straight channels, extending along an outlet portion of the inner body, formed by a third subset of the plurality of guide walls.