History and current status of thermal poling of silicate fibres

It is known that amorphous glass with macroscopic inversion symmetry does not possess second order non-linearity (SON). It was shown in silica based optical fibres that the inversion symmetry can be broken by thermal poling. The magnitude of the achievable SON depends on the poling conditions and the fibre materials used. To-date, this value is typically of 1 pm/V which can be compensated by fibre length to form practical active all-fibre devices. the authors discuss the history and current status of thermal poling in silicate fibres