Showing papers on "Equilibrium mode distribution published in 1981"
TL;DR: In this paper, a method to measure polarisation mode dispersion was described, in which the accuracy was more than 0.1 ps and the result was compared with the retardation obtained for a short length of the fibre.
Abstract: A new method to measure polarisation mode dispersion is described, in which the accuracy is more than 0.1 ps. 0.17 ps polarisation mode dispersion was obtained for about 1 km length of fibre. The result is compared with the retardation obtained for a short length of the fibre.
45 citations
TL;DR: In this paper, the cutoff characteristics of the first higher-order mode and phase coefficient, group velocity and power distribution characteristics of dominant modes are presented over a wide range of parameters and a two-layer step index elliptical fiber waveguide is presented as a special case.
Abstract: Single mode propagation in three-layer step index elliptical fiber waveguides is investigated theoretically. Previous analysis of the elliptical dielectric tube waveguide is extended to include cladded, W-type and tube-type fibers. Numerical results on cutoff characteristics of the first higher-order mode and phase coefficient, group velocity and power distribution characteristics of the dominant modes are presented over a wide range of parameters. A two-layer step index elliptical fiber waveguide is presented as a special case. High eccentricity single mode fibers have small modal beat lengths but have small core size and greater power distribution in the claddings. W-type fiber in the middle range of eccentricities is suggested for single mode single polarization applications.
17 citations
TL;DR: In this article, the normal mode theory for shallow water propagation is used to develop a method permitting the excitation of a single mode by means of a vertical array of sources, whose gain and polarity depend on the mode to be excited.
Abstract: The normal mode theory for shallow water propagation is used to develop a method permitting the excitation of a single mode by means of a vertical array of sources. The experiments were carried out in a laboratory tank, in a thin layer of water lying on a thick sand bed. Single mode excitation was performed by a vertical array of 15 piezoelectric transducers, whose gain and polarity depend on the mode to be excited. Single mode propagation between a source array and a receiving array is also examined. The receiving array can simultaneously resolve five modes. In these conditions crosstalk between mode and mode conversion can be studied.
13 citations
TL;DR: In this article, phase-matched sum-frequency light in optical fibres is investigated to determine the input power dependence and fiber length dependence, and the output power at 0.54 m increases in proportion to the square root of the input energy, increasing almost exponentially with increases in the fibre length from 4 m to 17 m and becoming nearly constant above 17 m.
Abstract: Characteristics of phase-matched sum-frequency light in optical fibres is investigated to determine the input power dependence and fibre length dependence. The output power at 0.54 ?m increases in proportion to the square root of the input power, increasing almost exponentially with increases in the fibre length from 4 m to 17 m and becoming nearly constant above 17 m.
5 citations
TL;DR: An experimental analysis of the dielectric waveguide laser modes has been carried out and it has been shown that the maximum power output is related to the EH 11 or TEM 00 mode oscillation as mentioned in this paper.
5 citations
TL;DR: Attenuation and near-and far-field measurements, which were made with different launch spot sizes and numerical apertures on sub-1.0-dB/km optical waveguides, have shown that an equilibrium mode distribution is not established in the 1.1-km length.
Abstract: Attenuation and near-and far-field measurements, which were made with different launch spot sizes and numerical apertures on sub-1.0-dB/km optical waveguides, have shown that an equilibrium mode distribution is not established in the 1.1-km length. It was experimentally found that the source launch conditions could be described by an effective mode volume (EMV) that was found to be correlated with the measured attenuation rate. By using an EMV transfer model, the insertion loss of a 3.3-km concatenated section was predicted within 0.21 dB of that measured for a variety of launch conditions.
4 citations
TL;DR: It is confirmed that frequency domain measurements make it simple to obtain mode conversion coefficients and mode dependent losses and that the dynamic equilibrium is attained after propagation over a few kilometers even in available step-index fibers.
Abstract: A simplified method for the measurement of mode conversion coefficients and mode dependent losses is proposed. The method utilizes sinusoidally modulated light instead of optical pulses and is applied to step-index multimode fibers. The results obtained by frequency domain measurement agree satisfactorily with those obtained by time domain measurement. It is confirmed that frequency domain measurements make it simple to obtain mode conversion coefficients and mode dependent losses. Experiments also show that mode dependent losses in the fibers are roughly independent of the mode order, and that the dynamic equilibrium is attained after propagation over a few kilometers even in available step-index fibers.
3 citations
TL;DR: In this paper, an easy-handle S-shaped mode-filter/mixer is investigated by far-field pattern and attenuation measurements, and it is proved that the S-Filter/Mixer is superior to the so called 70% excitation and is usable for estimating mode coupling and intrinsic fiber loss.
3 citations
TL;DR: In this paper, a generalized tensor permittivity applicable to a twisted elliptic-core fiber is derived and the polarization characteristics are analyzed by combining the even and odd modes of HE11 mode which is a fundamental mode in the single-mode optical fiber.
Abstract: Because of complexity in the refractivity distribution of the twisted optical fiber, the theoretical study on the polarization characteristics is difficult. Therefore an experimental investigation is made first. A simple model is proposed to explain generation of cross-polarization components in case of linearly polarized wave incidence. A generalized tensor permittivity applicable to a twisted elliptic-core fiber is derived. For the circular-core fiber, the off-diagonal elements of the tensor have the θ-z component ϵθz only. For the elliptic-core fiber, both the r-θ components ϵrθ and the r-z component ϵrz appear as the off-diagonal components. The polarization characteristics are analyzed by combining the even and odd modes of HE11 mode which is a fundamental mode in the single-mode optical fiber.
2 citations
25 Feb 1981
TL;DR: In this article, a method for producing microlenses on the ends of single-modeoptical fibers was devised for coupling light between single mode fibers and single mode planar waveguides, where a lens is formed by dipping the fiber end into negative photoresist while the fiber core carries Z 0.1 mW of HeNe laser light.
Abstract: Philip D. BearMcDonnell Douglas Astronautics Company -St. Louis, St. Louis, Missouri 63166AbstractA new method has been devised for producing microlenses on the ends of single -modeoptical fibers. A lens is formed by dipping the fiber end into negative photoresistwhile the fiber core carries Z0.1 mW of HeNe laser light. The photoresist lenses re-quire no developing or rinsing. The lenses are shown to transform the near -Gaussianbeam emitted by the fiber into another near -Gaussian beam with a reduced waist diameter.The size of the new waist can be selected by varying the number of times the fiber isdipped into the photoresist. The waist reduction is shown to increase coupling intosingle -mode optical waveguides.IntroductionWhen coupling light between single mode fibers and single mode planar waveguides, oneshould be cognizant of the variables upon which the process depends. The degree to whichthe phase and amplitude distributions are matched determines the efficiency of coupling.First, let us address the matching of the phase distributions of the light. A single modefiber emits a beam which begins diverging upon exiting the fiber so that the waist of thebeam, which exhibits a planar phase, is located at the fiber end. The phase of the lightin a single mode planar waveguide is also planar. Therefore, to achieve maximum couplingwith respect to phase matching, the fiber end should be butt -coupled to the edge of theplanar waveguide.In order to match the amplitude distributions there are two conditions to be considered.The first is that the coupling is affected by the relative displacement of the two modes.When the regions of maximum mode intensity for each mode lie on a common optic axis thecoupling is maximized with respect to this parameter. The second condition concerns therelative sizes of the two modes. The closer the mode in the fiber is to matching the modesize in the waveguide the better the coupling efficiency which is achievable.Fabrication of microlensesIt may be difficult, in general, to vary parameters such as the indices of refractionor wavelength in order to match the mode sizes. For example, the single -mode fiber used inthis laboratory has a waist diameter of 2 Wo
1 citations