Process and device for making gratings in optical fibres

A process of making gratings in an optical fibre having a core surrounded by cladding, the process comprising inducing local periodic variations in the refractive index of the said core by exposure to radiation having corresponding periodic intensity variations, wherein the said variations of the refractive index are induced by exposing the said core to a plurality of radiations which strike the core in respective different directions distributed angularly in an essentially uniform way, the plurality of radiations being obtained from a single radiation source, sending a first radiation of the plurality of radiations directly towards the fibre while sending the other radiations towards the fibre while sending the other radiations towards the fibre after being subjected to reflection, providing, for the generation of each of the said other radiations, a respective reflective surface capable of being struck by the said first radiation, redirecting the said first radiation towards the said core as a result of reflection, the said respective reflective, surface lying in a plane forming an angle (α) of 60° to the direction of propagation of the said first radiation.

A process of making gratings in an optical fibre having a core surrounded by cladding, the process comprising inducing local periodic variations of refractive index in the core by exposing the core to radiation having corresponding periodic intensity variations sufficient to form the refractive index, the variations of the refractive index being induced by exposing the core to radiation which strikes the core from different plural directions with substantially the same intensity, the radiation from the different plural directions emanating from a single radiation source, the radiation at one of said directions being incident directly on the fiber from the single source, without reflection, and radiation from the single source at the other directions being incident on the core after being reflected, the reflected radiation being reflected from two reflecting surfaces upon which the fiber abuts while the gratings are being formed.

A process of making gratings in an optical fiber having a core surrounded by a cladding, the process comprising inducing local periodic variations of refractive index in the core by exposing the core to radiation having corresponding periodic intensity variations sufficient to form the refractive index, the variations of the refractive index being induced by exposing the core to radiation which strikes the core from different plural directions with substantially the same intensity, the radiation at one of said directions being incident directly on the fiber from a source, without reflection, and radiation at the other directions being incident on the core after being reflected.

A process of making gratings in an optical fiber having a core surrounded by a cladding, the process comprising inducing local periodic variations of refractive index in the core by exposing the core to radiation having corresponding periodic intensity variations sufficient to form the refractive index, the variations of the refractive index being induced by exposing the core to radiation which strikes the core from different plural directions with substantially the same intensity, the radiation from the different plural directions emanating from a single radiation source, the radiation at one of said directions being incident directly on the fiber from the single source, without reflection, and radiation from the single source at the other directions being incident on the core after being reflected, the reflecting surfaces being planar and tilted at opposite directions displaced by 60 degrees from the direction of the radiation that is directly incident on the fiber.