Enhanced UV photosensitivity in boron codoped germanosilicate fibres

Effects of Ge concentration, boron co-doping, and hydrogenation on fiber Bragg grating characteristics

“…Although boron codoping used in conjunction with high-Ge concentration aims to reduce the numerical aperture of the fiber, it has a profound effect upon the photosensitivity as well as the FBG inscription dynamics. Suggestions as to the cause of the enhanced photosensitivity in boron co-doped fibers include photo-induced stress relaxation instigated by the breaking of the bonding defect responsible for the 240-nm peak [6] and increased number of Si-Ge oxygen deficiency centers prompted by the improved mixing of the glass components [9] due to the presence of boron. Additionally, a proposed model for the UV-induced reaction in GeO 2 -doped glass in the presence of H 2 [10] involves H 2 molecules reacting at normal Si-O-Ge sites, thus resulting in the formation of OH species and UV-bleachable GeO 2 deficiency centers, which are responsible for the enhanced photosensitivity.…”

“…Boron co-doping is normally used to lower the NA of the Ge-enriched fibers. Boron co-doped fiber has an excellent photosensitive response-much greater than a fiber with an equivalent germanium concentration [6]. Hydrogen loading is often used to generate or significantly enhance the photosensitivity of various types of optical fibers and high reflectivities have been reported with hydrogenated boron co-doped fibers.…”

A Review on Optical Fiber Long Period Grating, its applications in Optical Communication System

“…The refractive index change is associated with the formation of Gerelated glass defects. Fibers with high photosensitivity have been developed by co-doping the core with boron and germanium [28] and by hydrogen loading [29]. The hydrogen loading treatment is used in optical fiber to increase its photosensitivity.…”

Chirped fiber Bragg gratings for WDM chromatic dispersion compensation in multispan 10-Gb/s transmission

“…Briefly, the UV source used for fabrication is a frequency doubled argon laser operating at 244 nm [7], with 200 mW of CW power. Deuterated boron-germanium codoped fiber [8] is placed in near contact with the phase-mask and the UV beam scanned across it [9]. Cosine envelope apodization is achieved during the writing of the fiber grating by repetitively stretching the fiber symmetrically around the centre of the grating [10].…”