Formation of Bragg gratings in optical fibers by a transverse holographic method

Abstract

Bragg gratings have been produced in germanosilicate optical fibers by exposing the core, through the side of the cladding, to a coherent UV two-beam interference pattern with a wavelength selected to lie in the oxygen-vacancy defect band of germania, near 244 nm. Fractional index perturbations of approximately 3 x 10(-5) have been written in a 4.4-mm length of the core with a 5-min exposure. The Bragg filters formed by this new technique had reflectivities of 50-55% and spectral widths, at half-maximum, of 42 GHz.

Ultraviolet-light-induced processes in germanium-doped silica

“…Hydrogen loading may catalyze some of these excitations to decay in a different way, leading to the formation of D 2 defects. This is described by 2 . Excitation of the D 2 defect at 242 nm ͑5.12 eV͒ brings it well above the band gap which leads to its elimination.…”

“…Since the discovery of light-induced refractive index changes in silica glass materials 1 and the invention of the side-writing method, 2 UV writing of gratings in optical fibers has become an important technological field of great commercial importance for telecommunications and optical sensors. However, fundamental understanding of the UVinduced processes in glass materials has lagged far behind the technological development.…”

Optical Fiber Sensor Based on Second-Order Superstructure Fiber Bragg Grating

“…Since the first fabrication of a fiber grating by transverse holographic technology in 1989, (1) the fiber grating has been developed for various applications such as telecommunications and fiber sensor systems. (2)(3)(4) Optical fiber sensors are currently attracting significant interest for civil engineering applications and biosensors.…”

Femtosecond pulse written fiber gratings: a new avenue to integrated fiber technology

“…The contrast of the refractive index modulation is typically Δn ≈ 10 −4 [7]. Although Hill already envisioned the potential of FBGs, production became practicable only 10 years later, by inscribing the FBG via side illumination by a UV-laser [8]. The insatiable demand for fiber-integrated filters by the telecommunication industry led to a variety of inscription techniques based on this concept [9][10][11][12][13].…”