Bragg gratings in a few mode microstructured polymer optical fiber in less than 30 seconds

Abstract

We report the inscription of a Bragg grating in an undoped polymethylmethacrylate based microstructured fiber in a time record. The fiber has been irradiated with a 248 nm ultraviolet radiation, through the phase mask technique using low fluence and low repetition rate. The experimental conditions were chosen to modify the core refractive index of the fiber at the incubation regime and avoiding polymer ablation. The peak reflection of the Bragg grating was centered in the infrared region with 20 dB reflection and 0.16 nm bandwidth. These spectral properties are well attractive for sensors and communications applications.

Fast and stable gratings inscription in POFs made of different materials with pulsed 248 nm KrF laser

“…Several FBGs were inscribed in each POF. If the energy per pulse is too high for the POF material, an overheating will occur, which causes an ablative process on the fiber [35]. Since the grating inscriptions were made in different POFs, a detailed study was performed to achieve the optimal energy per pulse to avoid overheating by the cumulative heating on each fiber material.…”

“…Furthermore, shorter inscription times are important for the grating stability after inscription [34]. Nevertheless, the time taken for a POFBG inscription can be reduced by several orders of magnitude with the application of a 248 nm laser with low fluence and repetition rate through the phase mask technique [35]. It was also demonstrated that the inscription time can be lowered by performing a thermal treatment on the fiber preforms [33].…”

Fabrication and characterization of polycarbonate microstructured polymer optical fibers for high-temperature-resistant fiber Bragg grating strain sensors

“…Short inscription times are of importance for the stability of a grating. The writing time in PMMA mPOFs can be reduced by either doping the fiber core [8,44,45] or using a different laser [46]. The same should hold true also for PC.…”

Characterization of Polymer Fiber Bragg Grating With Ultrafast Laser Micromachining

“…The refractive index decrease in PMMA materials was photoinduced by deep UV irradiation at 248 nm whereas an incubation process was observed below the ablation threshold [18,19]. Very recently, Oliveira et al reported that FBGs can be inscribed in undoped PMMA-based mPOF using 248 nm UV laser within 30 seconds, in which the laser conditions of low fluences and low repetition rates were properly controlled to modify the refractive index of fiber core at the incubation regime hence avoiding polymer ablation [20]. On the other hand, with the rise of laser parameters above the reported PMMA ablation threshold, the ablative process could occur [19].…”