Experimental and theoretical studies in novel Er3+ doped fibre amplifiers
This thesis reports the results of investigations into the performance and design of Er3+ doped fibre amplifiers leading to novel configurations for the exploitation of additional optical bandwidth and improved operational characteristics. The first high-gain, broad spectral bandwidth gain measurements in an Al2O3-P2O5-SiO2 host glass fibre are presented showing small signal gains in excess of 25dB over a 3dB bandwidth of 35nm. Quantum conversion efficiency measurements in a variety of fibre types are undertaken which include the first report of a power amplifier with an efficiency of over 85% and 140mW of output power at 1550nm. The first demonstration that an Er3+ doped fibre amplifier can be configured to provide high gain in a further 30nm of optical bandwidth centred at 1590nm is presented. The initial device, pumped at 1555nm, is superseded with a dual wavelength pumped implementation in which it is shown that as well as long wavelength gains, near quantum limited noise performance can be achieved. All-optical gain control in Er3+ doped fibre amplifiers is investigated and a 1480nm pumped, linear cavity device is demonstrated. The analysis of the design criteria for such amplifiers is extended and it is shown, theoretically and experimentally, that optimum noise performance is achieved by the use of an asymmetric cavity design with the control laser wavelength chosen to be in a high gain region of the amplification spectrum.