The invention relates to the technical field of optical fiber amplifiers, and particularly, relates to a multiband rare earth doped optical fiber amplifier, which comprises an optical fiber amplifierbody. A protection device is arranged outside the optical fiber amplifier body. The protection device comprises a lower protection housing and an upper protection housing. Two first semicircular grooves are formed in the positions, close to the front side, of the top wall of the lower protection housing and the bottom wall of the upper protection housing. The top wall of the lower protection housin...
