Erbium Doped Optical Fibres — Fabrication Technology

Development of erbium doped optical preforms by two different techniques and subsequent drawing of these into fibres is described. The first technique involved deposition of porous silica-germanio soot layer by the modified chemical vapour deposition (MCVD) process followed by incorporation of erbium through the solution doping technique. Both forward and backward pass deposition techniques were investigated to determine their relative advantages/disadvantages. The second technique relied on coaling of inner surface of a silica lube with stable sols of erbium oxide coated silica nano-particles and subsequent processing through the MCVD process. The geometrical and optical characteristics of the fabricated preforms and fibres were extensively investigated in order to identify any specific problems and how to overcome/minimise these in order to optimise the process steps as well as the fabrication parameters. The performance of the fibres in terms of optical gain was measured under various pump and signal powers. Results of fabricated erbium doped fibres suitable for realising EDFAs with flat gain across the C-band (1530–1565 nm) are presented.