Matched-cladding Fibers Research Articles

An analysis of W-shaped plastic optical fibers by WKB approximation

The graded-index plastic optical fiber, because of its relatively large bandwidth and core diameter, is the type of fiber that is used in a majority of the fiber optic systems in existence today. Especially the type of optical fiber known as the W-fiber has some desirable properties and unique characteristics not found in matched-cladding fibers. In this work, by Wentzel–Kramers–Brillouin (WKB) method, the total number of modes of the graded-index W-shaped plastic optical fiber is theoretically reviewed. The obtained formula for the total number of modes of W-shaped optical fibers arises from an approximation of the WKB integral, which preserves the general validity requirements of the method. Also, by assumption that all modes were excited uniformly, the computational analyses investigating near- and far-field power distribution in W-shaped plastic optical fibers was carried out.

Induction of the refractive index change in B-doped optical fibers through relaxation of the mechanical stress

The structural model for the residual stress has often been used to account for the photosensitivity in Ge-doped optical fibers, and we used this approach in this paper to analyze the effect of the mechanical stress on the refractive index change in B-doped optical fibers. In particular, we will discuss the mechanism of refractive index modulation in long period fiber gratings induced by CO 2 laser irradiation using B-doped depressed clad and matched clad fibers for the first time as far as the authors are aware. The analysis presented in this work will strengthen the structural model for description of the fiber grating formation.

Design of Matched Cladding Fiber with UV-Sensitive Cladding for Minimization of Cladding-Mode Losses in Fiber Bragg Gratings

The effect on the Bragg-grating-induced cladding-mode coupling of varying the extent of the photosensitive region in a step-index fiber is analyzed. We introduce a figure of merit for the suppression of cladding-mode loss and compare different matched cladding fiber designs. It is found to be advantageous to increase the extent of the photosensitive region. However, no significant improvement is obtained by extending the photosensitive region more than approximately 10 μm into the cladding. This result is not in agreement with a simple analysis that neglects UV absorption, which suggests that the radius of the photosensitive region should be close to twice as large.

Characterization of the bending sensitivity of fibers by the MAC-value

The macro- and micro-bending performance of matched-cladding fibers was investigated experimentally by the pin-array test and the wire mesh test, respectively. In accordance with theoretical considerations it was demonstrated that the bending properties of step-index fibers cannot be completely described by the mode field diameter (MFD). In contradiction to general experiences in special cases a reduction of the bending losses with increasing MFD can be observed. It was stated that the MAC-value as the ratio of the mode field diameter and the cut-off wavelength is the best measure for the characterization of the bending sensitivity of step-index fibers.

New Gaussian-based approximation for modelling non-linear effects in optical fibers

The use of Gaussian field approximations enables simple analytical models to be derived for non-linear fibers and doped-fiber lasers and amplifiers. A new Gaussian-based method is described that is as easy to use as the standard Gaussian approximations, yet provides an rms error in the confinement factor of only 1.1% for a wide range of matched-cladding fibers. Similar accuracy is obtained for depressed-cladding fibers. The new approximation is used to predict Raman gain in a typical experimental MCVD fiber and excellent agreement is obtained between theory and experimental measurements. >

Circularly symmetric modal interferometers: Equalization wavelength and equivalent step determination for matched-cladding fibers

Abstract An LP01-LP02 modal interferometer fabricated from a standard matched-cladding telecommunication fiber is studied in the visible wavelength range. Its spectral response in the vicinity of the LP01/LP02 equalization wavelength is used to characterize the fiber by the determination of an equivalent step index profile.

Curvature dependence of the effective cutoff wavelength in single-mode fibers

The curvature dependence of the effective cutoff wavelength is investigated for both matched-cladding and depressed-cladding fibers. Contrary to the depressed-cladding fiber, the cutoff wavelength of the matched-cladding fiber is strongly curvature dependent. A formula is developed for the bending loss of the first higher-order mode group in a depressed-cladding fiber. By taking into account the effect of the stress-induced changes in the refractive index on the loss the first higher-order mode group, the effective cutoff wavelength as a function of curvature is calculated. The theoretical results show good agreement with measured values, which verify the curvature insensitivity of the effective cutoff wavelength of depressed cladding fibers.

The design and fabrication of monomode optical fiber

The design of monomode fibers is discussed in the context of optimizing fiber loss and dispersion simultaneously, with reference to the materials choices and limitations to preform and fiber fabrication by the MCVD technique. Two classes of monomode structure-matched cladding and depressed cladding-are considered. Ultralow attenuation has been achieved reproducibily in both classes of fiber. The control of fiber geometry and dispersion is also discussed. Matched cladding fiber suitable for systems operating at both 1.3 and 1.55 μm has been studied and mean losses of 0.45 dB/km at 1.3 μm and 0.28 dB/km at 1.55 μm have been achieved for a total of 130 km. The behavior of depressed cladding fiber is compared with predictions from the theory of propagation in <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">W</tex> fibers. Depressed cladding fiber with stable guidance has been demonstrated with attenuation of 0.37 dB/km at 1.3 μm and 0.21 dB/km at 1.55 μm.

The Design and Fabrication of Monomode Optical Fiber

The design of monomode fibers is discussed in the context of optimizing fiber loss and dispersion simultaneously, with reference to the materials choices and limitations to preform and fiber fabrication by the MCVD technique. Two classes of monomode structure-matched cladding and depressed cladding-are considered. Ultralow attenuation has been achieved reproducibly in both classes of fiber. The control of fiber geometry and dispersion is also discussed. Matched cladding fiber suitable for systems operating at both 1.3 and 1.55 µm has been studied and mean losses of 0.45 dB/km at 1.3 µm and 0.28 dB/km at 1.55 µm have been achieved for a total of 130 km. The behavior of depressed cladding fiber is compared with predictions from the theory of propagation in W fibers. Depressed cladding fiber with stable guidance has been demonstrated with attenuation of 0.37 dB/km at 1.3 µm and 0.21 dB/km at 1.55 µm.