Formation of enhanced regenerated grating in few-mode fiber by CO2 laser pretreatment

作者：Nazal, Nurul Asha Mohd; Lim, Kok-Sing^*; Zaini, Muhammad Khairol Annuar; Yang, Hang-Zhou; Ahmad, Harith

来源：Applied Optics, 2017, 56(36): 9882-9887.

DOI：10.1364/AO.56.009882

• RESIDUAL-STRESS RELAXATION
• REFRACTIVE-INDEX CHANGE
• OPTICAL-FIBER
• BRAGG GRATINGS
• AXIAL CONTRACTION
• IRRADIATION
• FBGS

In this work, we experimentally investigated the effect of CO2 laser pretreatment on regenerated grating formulated in few-mode fibers (FMFs) (two-mode and four-mode step-index fibers). In the preparation, the pristine FMFs were first treated with direct CO2 laser annealing followed by a slow cooling procedure to minimize the frozen-in stresses and the thermal stresses in the fibers before the grating inscription. After the thermal regeneration process, the produced regenerated gratings (RGs) were then subject to a thermal durability test at 1050 degrees C for 10 h. In the comparison against the results from the RGs formulated in non-treated FMFs, the finding indicates that RGs in treated fibers have a better regeneration ratio and thermal resilience. It is believed that the thermal stress relaxation and structural rearrangement in the fiber glass are the major factors that lead to the lower grating recovery during the state of thermal regeneration process and higher degradation in the grating strength in a longer exposure period. The elimination and reduction of stresses in the fibers by the laser pretreatment in the earliest stage enables the grating to be formed in a more thermal stable condition, hence, RGs with prolonged lifespan can be produced.

• 出版日期2017-12-20
• 单位西北大学