Interference of modes in optical fibers

Abstract

Experimentally obtained spectral dependencies of an optical signal influenced by intermodal interference in a fiber under various conditions (for example, different lengths or different fibers) are presented. It is shown that the difference between the propagating constants of the first two modes can be obtained from the measured spectrum. The obtained results illustrate the usefulness of such investigation for determination of basic parameters of fibers, especially for investigating the homogeneity of a produced fiber. © 2000 Society of Photo-Optical Instrumentation Engineers. [S0091-3286(00)03005-1]

Theoretical Study of the Statistical Properties of Single- and Double-PassM-Mode Er3+-Ti:LiNbO3Straight Waveguide Amplifiers

“…Turek et al [9], while the dopant distribution, d.x; y/ (with a surface concentration of about 1 10 26 m 3 , a diffusion depth of 20 m, and width of 5.12 m (defined at 1/e), is approximated by an erfc but also by Gaussian or constant functions in depth (labeled 1, 2, and 3, respectively) and a Gaussian function in width. These different Er concentration profiles correspond to various diffusion conditions (non-complete or complete diffusion, or doping during the crystal growth).…”

Beyond backscattering: optical neuroimaging by BRAD

“…The total intensity of these intermodal components should, theoretically, be nil owing to the orthogonality of the fiber modes in an ideal optical fiber [ 17 ], and likewise, where C is a constant and δ jk denotes Kronecker’s delta. Facilitated for instance by slight fiber bends, intermodal interference has been observed, investigated and exploited in real-world fibers [ 27 – 29 ]. Still, the intermodal interference signals described in Eq.…”

Modelling of Output Statistics of Single and -Mode Straight and Curved :Ti:LiNb Waveguide Amplifiers

“…Moreover, the presence of the boundary conditions (4) at both the extremities of the device requires an iterative procedure of integration: (1) integrate from z = 0 to z = L the equations for P A particular care should be taken for the evaluation of Γ 2,m (z) because this quantity determines the incremental gain in (13) and depends on the actual value of the approximation for P ± km (z); this implies that, at each step of the forward and backward integration along z, we have to evaluate the integral Γ 2,m (z). Because of our choice of a Runge-Kutta formula (4th order, 4 stages) as the basic integration method, at each step we should evaluate four times (one for each stage) the overlap integral, within a large expense of computer time.…”

“…Often in the waveguides is excited not only the fundamental mode but also other high-order (M) modes, which influence the output gain, noise figure, and the statistical 4 Advances in OptoElectronics properties of the waveguide. The normalized field transversal intensity distribution can be written as [13] …”

“…The reason of this analysis is related to the fact that often in the waveguides is excited not only the fundamental mode but also other high-order (M) modes [11,13], which influence the output gain, noise figure, signal-to-noise ratio, and the statistical properties of the waveguide.…”