Nonlinear Optical Fibres

Abstract

The dielectric optical waveguide has been in existence for nearly 40 years[1]. Early research was focused at fibre bundles for image transmission, but even after pioneering papers by Spitzer on the weakly guiding phenomenon[2] it was several years later that glass optical fibres were recognised for their transmission potential[3]. Since then, a revolution has occurred: silica based optical fibre waveguides with transmission loss at a wavelength of 1550nm of less than 0.2dB/km have been routinely manufactured and long distance optical fibre transmission at gigabit rate has had a profound impact on communications. Along with this major advance, it has become apparent that low loss optical fibres are an ideal candidate for the investigation of a host of linear and nonlinear phenomena at modest optical powers. These include Rayleigh, Mie and Raman scattering[4–6], optical Kerr effect[7] all optical fibre amplification and fibre lasers[8] using rare-earth dopants such as erbium and neodymium in the silica host, all optical switching[9], soliton transmission[10], as well as the discovery of new phenomena such as photosensitivity[11] and optical damage at low optical powers[12]. Nonlinear optics[13–14] has been known since the invention of the laser, however, low loss optical fibres have made it possible to observe almost all non-linear effects; surprisingly, even material symmetry forbidden phenomena such as efficient second-harmonic generation, associated with crystalline media[11].