LOW-LOSS RARE-EARTH-DOPED SINGLE-MODE FIBER BY SOL-GEL METHOD

Using a sol-gel process for rare-earth ions doping, a minimum optical loss of less than 2 dB/km in the region of 1.15mum has been reproducib ly achieved in Er3+ doped Al2O3-SiO2 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 d epend critically on a process capable of providing a consistently crac k-free film.