Light Propagation Characteristics Research Articles

Bandwidth of a single-mode optical fiber in PSK coherent optical transmission systems

The author examines propagation characteristics of PSK modulated signal light under the influence of the group velocity dispersion (GVD), the higher-order dispersion (HOD), and the nonlinear refractive index of a single-mode fiber. Emphasis has been placed on behavior at and near the zero-dispersion wavelength (ZDWL), where the HOD as well as the GVD would be important. It is found that propagation at the ZDWL is similar to that away from the ZDWL; the effect of the nonlinear refractive index can be comfortably ignored. The effect of HOD is found to induce self-amplitude modulation (SAM) at the ZDWL; the amplitude of PSK-modulated light becomes modulated as the light travels down the fiber. The SAM considered produces a power penalty in the PSK coherent fiber transmission, and determines the dispersion limit of such systems. As the operating wavelength moves away from the ZDWL, the effect of GVD becomes important relative to that of HOD. The significance of the results is examined. >

Optical fiber sensors using the method of polarization-rotated reflection

The method of polarization-rotated reflection is applied to sensors with polarization-maintaining optical fibers. By the use of this scheme, stable measurement can be realized because the fluctuation of the light propagation characteristics in the fiber is canceled automatically without any additional active phase compensation techniques. Several kinds of sensors were designed for the measurement of different physical values. A magnetic field sensor and a temperature sensor were built and the performances were tested to confirm their basic features experimentally.

Organic Polymeric and Non‐Polymeric Materials with Large Optical Nonlinearities

AbstractNonlinear optical properties are a sensitive probe of the electronic and solid‐state structure of organic compounds and as a consequence find various applications in many areas of optoelectronics including optical communications, laser scanning and control functions, and integrated optics technology. Because of their strongly delocalized π electronic systems, polymeric and non‐polymeric aromatic compounds show highly nonlinear optical effects. Nowadays, polymer chemists are able to tailor specific materials properties for various applications. Some organic substances with π electronic systems exhibit the largest known nonlinear coefficients, often considerably larger than those of the more conventional inorganic dielectrics and semiconductors, and thus show promise for thin‐film fabrication, allowing the enormous function and cost advantages of integrated electronic circuitry. The electronic origins of nonlinear optical effects in organic π electronic systems are reviewed, with special emphasis being given to second‐order nonlinear optical effects. Methods for measuring nonlinear optical responses are outlined, and the critical relationships of the propagation characteristics of light to observed nonlinear optical effects and to solid‐state structure are discussed. Finally, the synthesis and characterization of organic crystals and polymer films with large second‐order optical nonlinearities are summarized.

Noncircular optical waveguides and modal choice

In this paper we investigate the propagation characteristics of light in noncircular dielectric optical waveguides based on the microwave model experiments. It is found that the attenuation of noncircular waveguides is smaller than that of circular guides and the attenuation of the odd modes is smaller than that of the even modes in noncircular dielectric waveguides. Hence it is advantageous to use noncircular optical fibers. Furthermore, it is advantageous to choose the polarization for single mode optical fiber so that a better propagation characteristic is obtained.

Relativistic Reduction of Astronomical Measurements and Reference Frames

AbstractWith the accuracy of modern observations the relativistic treatment of the basic astronomical reference frames only requires the consideration of comparatively simple types of metrics such as heliocentric Schwarzschild metric, geocentric Schwarzschild metric and metric of the Earth-Sun system. Dynamical (related to the motion of the bodies) and kinematical (related to the light propagation) characteristics of these metrics enable one to perform the accurate relativistic reduction of astronomical measurements. In this reduction, the choice of specific quasi-Galilean coordinates may remain arbitrary. This paper presents expressions for the main relativistic terms in coordinates of the principal planets and Moon using the PPN formalism parameters β, γ and coordinate parameter α. General formulae for the reduction of radar, radio-interferometric and astrometric observations of planets and for the interpretation of lunar laser ranging are given. For estimating the actual magnitude of relativistic effects, the ephemeris data should be expressed in terms of physically measurable quantities.

Propagation of truncated Gaussian beams in multimode fiber guides

The ability to predict the light propagation characteristics in various practical multimode guiding structures is very important in optical fiber communications and in optical image transfer. The usual mode-by-mode analysis is impractical when the guiding structure is capable of supporting hundreds or thousands of modes. In this study a numerical technique is described which is capable of providing useful data on the propagation characteristics of optical multimode guiding structures whose index of refraction variation may be quite arbitrary. As a specific example, the problem of infinite or truncated Gaussian beam propagation in a radially inhomogeneous fiber with parabolic index profile is solved. The numerical results for the infinite Gaussian beam case are compared with exact analytical data and they are in complete agreement.