METHOD FOR MANUFACTURING A FIBER PREFER AND OPTICAL FIBER HAVING POLARIZATION OR POLARIZATION OBTAINED BY FIBRAGGING THE PREFORM

摘要

The process of fabricating a fiber preform for maintaining optical fiber polarization, comprises fabricating a slotted preform by forming two grooves in a primary cylindrical preform of circular section having an axis XX', fabricating two constraint bars comprising a core (1) and an external envelope (4, 4'), and assembling the slotted preform and the constraint bars respectively in grooves and a cylindrical sleeve (5) surrounding the slotted preform. The primary preform comprises a core, and a sheath (2) disposed around the core. The process of fabricating a fiber preform for maintaining optical fiber polarization, comprises fabricating a slotted preform by forming two grooves in a primary cylindrical preform of circular section having an axis XX', fabricating two constraint bars comprising a core (1) and an external envelope (4, 4'), and assembling the slotted preform and the constraint bars respectively in grooves and a cylindrical sleeve (5) surrounding the slotted preform. The primary preform comprises a core, and a sheath (2) disposed around the core. The grooves extend parallely or symmetrically disposed according to the axis XX'. The core material of the bars has a thermal expansion coefficient different from the sheath of the primary preform. The dimensions and shape of the constraint bars are adjusted with respect to the dimensions and shape of the grooves. The machining of the grooves is carried out using a grindstone and a groove wheel with flat bottom so that the profile of grooves in the preform is square or rectangular in shape. The machining of the envelope is carried out using a surface grinder. The grooves have a length L 1, and the diameter of the core of the bars is lower than L 1. The slotted groove is cleaned using hydrofluoric acid, and the preform is then etched. The optical index of core of the constraint bar is equal to optical index of the sheath. Hollow capillaries are inserted between the sleeves to form a ring. An independent claim is included for an optical fiber to maintain polarization.