We extend an earlier proposed matrix method for the analysis of cylindrically symmetric arbitrary refractive-index profile optical fibers to calculate the propagation constant and leakage/absorption loss of modes. This method involves only straightforward multiplications of 2 × 2 matrices and is highly attractive, since no complex plane iterations are performed even to obtain leakage or absorption losses. Thus the method is ideally suited for implementation on desktop computers. The applicability of the method has been shown through calculations of propagation constants and leakage loss of the LP01 mode in depressed inner clad fibers.

Simple numerical technique for the analysis of cylindrically symmetric refractive-index profile optical fibers

Single-mode optical fiber transmission technology in the 1.0-1.8-{\mu} m wavelength region is reviewed. Owing to low fiber loss in the spectral region and to wide-band single-mode fiber characteristics, longwavelength single-mode fiber transmission systems are capable of high data-rate transmission over tens of kilometers distance without intermediate repeaters. The advantages of the systems and progress in fibers, fiber splicing, and devices are reviewed in detail. Using low-loss fibers and recently developed semiconductor lasers, transmission performance is confirmed at 1.05, 1.1, and 1.5 \mu m wavelengths. At 1.3 {\mu} m, where fiber dispersion almost vanishes, gigabit-per-second pulse signals are successfully transmitted over 20 km without intersymbol interference. The maximum tested data rate is 1.6 Gbit/s, at which 13-km nonrepeatered transmission is confirmed. At 1.5 {\mu} m, where ultimate low-loss characteristics are expected in silica fibers, 100 Mbit/s transmission is successfully demonstrated over a 29-km repeater span. These high data-rate transmission capabilities over long fiber spans are attractive for future communications networks which may provide a variety of services at reduced system cost and with improved maintenance and installation convenience.

Single-mode systems and components for longer wavelengths (Invited Paper)

In this paper we present highly accurate and simple methods for the evaluation of splice loss in single-mode graded-index fibers. These are based on accurate approximations of the modal field of such fibers which we have recently developed. Splice losses for angular and transverse offsets have been expressed in analytical forms which are quite easy to evaluate. A comparison of our results with those obtained using the Gaussian approximation is also presented which shows that our method is much more accurate than the latter.

Splice-loss evaluation for single-mode graded-index fibers

http://ieeexplore.ieee.org/iel5/31/23488/01084595.pdf

Single-Mode Systems and Components for Longer Wavelengths

An efficient model for evaluating the splice losses between two identical arbitrarily graded-index single-mode fibers caused by transverse and angular misalignments is presented. The power transmission coefficients at the splice are expressed as a weighted sum of simple Laguerre-Gaussian functions, the weight factors being computed by solving a linear matrix eigenvalue problem. An outline of the theory is presented and applied to refractive-index profiles of practical interest. The results of the model are compared with the predictions of other exact or approximate models. >

An efficient model for splice loss evaluation in single-mode graded-index fibers

A method is presented for calculating offset and tilt losses for fiber splices with axially symmetric arbitrary-index profiles by approximating the profile with a staircase function. This method is applied to a large-core dual-mode fiber with zero intermodal dispersion as well as to single-mode fibers with step- and parabolic-index profiles. When a splice loss of 0.2 dB is permitted, the normalized offset misalignment is found to be D(N) = 0.635 for the dual-mode fiber at normalized frequency v = 4.605 and a power-law exponent alpha = 4.5. The D(N) value compares favorably with the values 0.560 and 0.614 for conventional step- and parabolic-index single-mode fibers, respectively. The dual-mode fiber is superior to the step- and parabolic-index fibers with respect to permissible splice offset tolerances.

Tatsuya Kimura

Papers

Splice loss evaluation for optical fibers with arbitrary-index profile.