A method of coupling a high-power optical signal between an optical fiber and a mating optical component, the optical signal ranging in wavelength from x to y, and having a first diameter while propagating in a mode field within the fiber, the method comprising: (a) converting the high-power optical signal between the first diameter in the fiber and a second diameter significantly greater than the first diameter using a GRIN lens fused to an end of the fiber, the GRIN lens having a diameter substantially the same as that of the optical fiber and a length l complying with the following equation: ¼x+½nx≦l≦¼y+½ny, wherein n=0, 1, 2, 3 . . . 100; (b) establishing physical contact between the GRIN lens and a coupling surface of the mating optical component; and (c) while the high-power optical signal is at the second diameter, optically coupling it between the lens and the mating optical component.