Optical fiber amplifier and optical amplifying method employing it

The invention claims a straight the high output and high light beam of laser small and high efficiency of laser device. The: aThe transmission stimulation lamp first wave guides groove (21) refraction rate =n1); Of generating laser core (23) refraction rate =n3) and transmitting stimulation lamp layer (24) refractive indexes) =n2 the second end of which guides groove (22); And comprises a first wave to guide groove and 21 second wave guides groove 22 triple conductor to guide groove (25) refractive indexes) =n4. Use of wherein the refractive indexes to the n1<n4<n2<n3 the optical amplifying optical fibre of second (20), a cover (standard) and (10b) is stimulate in semiconductor laser.