Silica Core Single-mode Fiber Research Articles

Thermally Stable Type II FBGs Written Through Polyimide Coatings of Silica-Based Optical Fiber

Type II-IR fiber Bragg gratings (FBGs) were written directly through the protective polyimide coatings of off-the-shelf pure silica core and standard telecom Ge-doped silica core single mode fibers using ultrafast IR radiation and the phase mask FBG writing method. Using a short focal length acylindrical lens and nonlinear photoluminescent imaging, type II grating structures could be created when Fourier transform limited pulses were chirped to 500 fs. The resulting gratings in the Ge-doped fibers were thermally stable up to 1000 °C and could be used directly as fabricated without annealing to stabilize the structure.

Numerical Approach to Modeling and Characterization of Refractive Index Changes for a Long-Period Fiber Grating Fabricated by Femtosecond Laser

A 3D finite element model constructed to predict the intensity-dependent refractive index profile induced by femtosecond laser radiation is presented. A fiber core irradiated by a pulsed laser is modeled as a cylinder subject to predefined boundary conditions using COMSOL5.2 Multiphysics commercial package. The numerically obtained refractive index change is used to numerically design and experimentally fabricate long-period fiber grating (LPFG) in pure silica core single-mode fiber employing identical laser conditions. To reduce the high computational requirements, the beam envelope method approach is utilized in the aforementioned numerical models. The number of periods, grating length, and grating period considered in this work are numerically quantified. The numerically obtained spectral growth of the modeled LPFG seems to be consistent with the transmission of the experimentally fabricated LPFG single mode fiber. The sensing capabilities of the modeled LPFG are tested by varying the refractive index of the surrounding medium. The numerically obtained spectrum corresponding to the varied refractive index shows good agreement with the experimental findings.

Characterization of refractive index change and fabrication of long period gratings in pure silica fiber by femtosecond laser radiation

Abstract Ultrafast laser induced refractive index (RI) change in the core of a standard telecommunication fiber is quantified using the spectral shift of an in-fiber Bragg grating (FBG) based Fabry–Perot cavity. Measured RI change is used to design and then fabricate long period grating (LPG) in pure silica core single mode fiber (SMF) employing identical laser irradiation conditions used in core index characterization. A core length of 100 µm within the 10 mm long cavity structure is scanned with ultrafast laser pulses, and the corresponding spectral shift is used to calculate index modification. The index change of 0.000449 found in characterization process is used to simulate the LPG in pure silica fiber. Identical index modulation written in pure silica fiber by femtosecond laser radiation provides a rejection band that is in good agreement with the simulation results. The fabricated LPG sensors are also characterized for ambient temperature and RI.

Long-term reliability of single-mode fibers when exposed to high-power laser light

The reliability of a pure silica-core single-mode fiber (SCF) and a germanium-doped fiber [dispersion-shifted fiber (DSF)] with long-term exposure to continuous-wave (CW) high-power laser light is reported. It was found that the optical loss in the 0.6-1.6-/spl mu/m region and the Raman spectra of SCF and DSF remained unchanged after 1900 h of exposure to an 8-W CW laser light and 2000 h of exposure to an 8.5-W CW laser light at 1.48-/spl mu/m, respectively. The nonbridging oxygen hole center (NBOHC) concentration generated in SCF by 1900 h of exposure is estimated to be below the detection limit of 2/spl times/10/sup 12/ cm/sup -3/. SCF and DSF can be expected to exhibit long-term (> 20 years) reliability when exposed to several watts of laser power in the S, C, and L bands in terms of optical degradation due to defect formation via multiphoton absorption.

Long-Term Reliability of Pure Silica Core Single-Mode Fiber When Exposed to High-Power Laser Light

The reliability of a pure silica core single-mode fiber with long-term exposure to continuous wave (CW) high-power laser light is reported. It is found that the optical loss in the 0.6-1.6-μm region and the Raman spectrum remain unchanged after 1900 h of exposure to 8-W CW laser light at 1.48 μm. The nonbridging oxygen hole center concentration generated by 1900 h of exposure is estimated to be below our detection limit of 2×10/sup 12/ cm/sup -3/.

Rayleigh scattering reduction method for silica-based optical fiber

The effect of the thermal treatment of silica-based glasses and glass fibers on their Rayleigh scattering is investigated experimentally. The Rayleigh scattering coefficients of bulk glasses are found to be increased 5-10% by heating them to 1800 /spl deg/C because the density fluctuation is in proportion to their fictive temperature. Based on these results, we propose a method for reducing the Rayleigh scattering losses of silica-based optical fibers by drawing them slowly at low temperatures. We used this method to obtain a GeO/sub 2/ doped silica core single-mode fiber with a minimum loss of 0.16 dB/km at 1.55 /spl mu/m. As a result, we confirmed that the reduction in the fictive temperature of silica-based glasses and glass fibers reduces their Rayleigh scattering.

Gamma-ray radiation hardened properties of pure silica core single-mode fiber and its data link system in radioactive environments

The radiation resistances of pure silica core single-mode optical fiber (Si-SMF) and its data link module at 1.30 mu m were investigated. It was found that the induced loss of fibers exposed to gamma -rays at a low dose rate was proportional to the 0.54 power of total dose from the result of a low dose rate irradiation test for 3 years, and the induced loss for 40 years aging at 1 R/h was estimated to be 1.8 dB/km. It was ascertained that transmission is achievable at a bit rate of 125 Mb/s even under high dose rate irradiation to a total dose of 10/sup 8/ R, which corresponds to the postulated maximum gamma -ray exposure in nuclear power plants.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Concentration effect on optical amplification characteristics of Er-doped silica single-mode fibers

Optical amplification characteristics for Er-doped silica core single-mode fiber amplifiers with different Er concentrations pumped by 1.48- mu m-wavelength laser diodes are studied. Optical gain drastically depends on Er concentration, even when the Er concentration is less than 1000 p.p.m. In the case of the 40-mW incident pump power, the maximum net gain for the fiber containing 77 p.p.m. Er is higher than that for the fiber containing 970 p.p.m. Er by 11.4 dB.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Gamma -ray and neutron irradiation characteristics of pure silica core single mode fiber and its lifetime estimation

The investigation of the induced loss for a single-mode (SM) optical fiber under gamma -ray irradiation and neutron irradiation is described. An estimation method for induced loss with loss dose rate and long-term gamma -ray irradiation is proposed. The induced loss of pure-silica-core SM fiber is estimated to be 50 times lower than that of germanium containing silica-core SM fiber after irradiation with 1 R/h for 25 years.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Characteristics of pure silica core single-mode fiber

Abstract Single-mode fibers with low attenuation and sufficient reliability are especially important for long-span optical transmission systems. Conventionally, GeO2 has been added to the fiber core region in order to make a refractive index difference between the core and cladding. However, the addition of GeO2 increases Rayleigh scattering loss [1], and deteriorates the chemical stability against hydrogen atmosphere and γ-ray irradiation to bring about an increase in attenuation. [2][3] Therefore, pure silica core single-mode fiber was considered to be an ideal type of fiber, and it was succeeded in being fabricated by utilizing fluorine containing SiO2 cladding.