Disclosed herein is an optical fiber including a core doped with first metal ions; and a cladding formed so as to surround the core and doped with second metal ions selected so that the absorption coefficient in a transition wavelength band of first transition of the first metal ions is greater than the absorption coefficient in a transition wavelength band of second transition of the first metal ions. The amplification of light due to the first transition is suppressed, and at least the amplification or oscillation of light due to the second transition is effected. Also disclosed are an optical amplification/oscillation device, a laser light generating device, and a laser display unit, and a color laser display unit each employing the optical fiber.