Low-loss rare earth doped single-mode fiber by sol-gel method

Abstract Using a sol-gel process for rare-earth ions doping, a minimum optical loss of less than 2 dB/km in the region of 1.15μm has been reproducibly achieved in Er 3+ doped Al 2 O 3 SiO 2 glass single-mode fibers. A wide range of rare earth doping concentrations was successfully introduced into fibers using this technique. In the sol-gel dipcoating to deposit a thick film, the key to achievement of low loss fiber was found to depend critically on a process capable of providing a consistently crack-free film.