Silica-based Single-mode Fibers Research Articles

Analysis of Silica Based Single-Mode Fiber Doped with Germanium at Different Transmission Window

In this paper, a germanium doped silica-based single-mode fiber for high speed optical communication link has been proposed. It is found that the proposed fiber is suitable for three transmission widows an excellent result at the third transmission window. Here, attenuation loss, dispersion, mode field diameter, bending loss, and material loss of the proposed fiber has been analyzed. It is found that dispersion such as material dispersion and waveguide dispersion is very low at the third transmission window (1550 nm), which is used for high speed optical fiber communication link. In addition to this, at the third transmission window, micro bending loss is almost disappeared and macro bending loss is also very low (0.00101 dB/km). All these analysis has been done using FDTD technique.

Radiation-induced effects in a new class of optical waveguides: the air-guiding photonic crystal fibers

Transient radiation-induced effects in air-guiding photonic crystal fibers (Air-PCF) are investigated for the first time to our knowledge. We characterize the vulnerability of this kind of waveguide by measuring the time dependent changes of their radiation-induced attenuation (RIA) at 1.55 /spl mu/m. We compare their radiation response to those of two silica-based single-mode fibers with germanium-doped and pure-silica cores. An X-ray pulse induces globally the same effects in all waveguides: a strong and transient increase of RIA. For higher tested doses (10<D<100 Gy), Air-PCF exhibits an interesting saturation of RIA at /spl sim/0.1 dB/m. The possible mechanisms involved in this radiation response are discussed. In particular, we assume that the design of the photonic bandgap structure of the fiber, responsible for the light guidance in the air-core, could strongly affect the amplitude of RIA. The kinetics of RIA recovery depends predominantly on the point defects created at the air/silica interface and in the silica-based part of the microstructured cladding.

Single-mode mid-IR guidance in a hollow-core photonic crystal fiber

We report, for the first time, bandgap guidance above 3 mum in a silica based air-core photonic crystal fiber. The peak of the bandgap is at 3.14mum with a typical attenuation of ~ 2.6 dB m-1. By further optimization of the structure, modeling suggests that a loss below 1 dB m-1 should be achievable, greatly extending the useful operating range of silica-based single-mode fibers. Such fibers have many potential applications in the mid-IR, offering an alternative to fluoride, tellurite or chalcogenide glass based optical fibers for chemical and biological sensing applications.

Bending loss measurement using a fiber cavity ringdown scheme

A novel sensitive technique for the determination of losses in fiber cavities is presented. The method is based on the cavity ringdown scheme implemented in silica-based single-mode fibers. Bending losses of fiber cavities of different lengths have been measured showing all an oscillating behavior with respect to the curvature radius of the fiber as predicted by a theoretical model. The best minimum detectable absorbance per cavity pass achieved by this new method is 1.72×10−3dB within a 10m-long cavity. This limit suffices well for an accurate determination of optical bending losses even in bend-insensitive fibers. Furthermore, the comparison of the measured bending losses with a theoretical model allows the extraction of different fiber parameters. Good agreement has been found between the experimentally derived parameters and literature data.

Infrared Absorption of Silica Fibers

Based on precise measurements of the attenuation coefficient an extended formula was developed for the calculation of the infrared absorption of silica between 1.3 μm and 1.7 μm wavelength, using a silica-based single-mode fiber with undoped core and fluorine-doped cladding. Below 1.3 μm, the infrared absorption is negligible due to our analysis: < 0.001 dB/km. Above 1.3 μm, the infrared absorption increases slowly with increasing wavelength; however, the slope becomes much steeper around 1.5 μm. Therefore, this function can be approximated more precisely by two exponential functions instead of only one exponential function as assumed so far. The four coefficients have been determined. At 1.55 pm, we obtained an infrared absorption coefficient of α IR,λ = 0.014 dB/km, which is in the middle of the values (0.021 dB/km respectively 0.009 dB/km) determined in the past.

Fiber-optic cavity sensing of hydrogen diffusion.

A novel type of fiber-optic cavity sensor for hydrogen diffusion into and out of fibers is presented. The sensor is an implementation of a cavity ringdown scheme in a silica-based single-mode fiber that has been exposed to gaseous hydrogen at normal pressure. The measured ringdown times during the H2 diffusion show good agreement with a theoretical diffusion model. This model allows the determination of the diffusion coefficient of hydrogen in silica, resulting in D = (3.02 +/- 0.07) x 10(-15) m2/s at 30 degrees C.

Optical loss property of silica-based single-mode fibers

The optical loss property of silica fibers has been investigated theoretically and experimentally based on their Rayleigh scattering and absorption losses. The Rayleigh scattering loss for fibers has been estimated using Rayleigh scattering coefficients and power distribution in the fiber. The Rayleigh scattering coefficients are measured for preforms prepared for fiber fabrication and are discussed for GeO/sub 2/-doped and F-doped glasses. The relationship between the optical loss and fiber parameters is clarified. Moreover, the loss increase due to residual stress which occurs during the drawing process is simulated. The optical loss limitations for GeO/sub 2/-doped and pure silica core fibers are shown. >

Drawing-induced 1.53-μm wavelength optical loss in single-mode fibers drawn at high speeds

Optical loss at 1.53-μm wavelength is observed in silica-based single-mode fibers drawn at high speeds. This loss, which is induced by high-speed drawing, is attributed to silylidyne group absorption. It is found that silica glass fibers occasionally contain hydrogens associated with silicons in addition to hydroxyl groups.