A water-cooled package of an optical fiber head comprising a delivery optical fiber (DOF), a front optical end cap (OEC), a rear OEC, a glass ferrule, and a housing operates for delivering the laser light from DOF to free space. The rear OEC is fusion-spiced with a section of DOF with a cladding exposed whereas the section of DOF is enclosed in a bore of the glass ferrule. When the glass ferrule is connected and sealed between the front OEC and the rear OEC, cooling water in the water-cooled package is prevented from immersing the section of DOF to maintain reliability of DOF. It is, therefore, not needed to bond the section of DOF in a bore of the front OEC to be waterproof, minimizing varying stress-induced speckle patterns and ultimately maintaining beam quality of the laser light exiting from DOF to free space.