Showing papers on "Mode scrambler published in 1991"

Adiabatic reflection apparatus

Abstract: A wavelength selective structure is coupled to an adiabatic Y-coupler via a multimode section which supports both symmetric and antisymmetric modes. One single mode branch of the coupler converts guided light to a symmetric mode, whereas the other single mode branch converts guided light to an anti-symmetric mode. The structure, which includes a pair of single mode waveguide arms coupled to the common section and a reflection device (such as a grating or ROR) located in each arm, converts reflected light from a symmetric mode to an anti-symmetric mode and conversely. Applications described include a channel dropping filter and channel balancing apparatus for WDM systems, and a dispersion compensator for fiber optic systems.

Mode scrambler as an optical isolator for higher-coherence lasers in multi-mode fiber plants

Abstract: A fiber-optic communication system (10) employs a Fabry-Perot laser (14) that launches its output onto a single-mode pigtail (16) physically coupled to a mode scrambler (22), which is air coupled to a transmission medium consisting of multi-mode fiber-optic cable. Because the mode scrambler (22) divides the laser output power among many modes, the fraction of any reflected light that is coupled back into the cavity of the laser (14) can be made small enough to permit sufficient laser coherence for high-data-rate-transmission.

Accurate modal characterization of passive components based on selective excitation of optical fibers

Abstract: Modal performances of multimode optical passive components are measured by use of a selective excitation techique. Pure LPm1 modes up to LP15 1 mode are generated in a Ti: sapphire laser cavity and launched in the input fiber of the component under test. Azimuthal dependency of the LP11 mode excitation coefficient is used in an accurate centering technique of monomode and multimode splices or connectors.

Model of an axially strained weakly guiding optical fiber modal pattern

Abstract: Axial strain may be determined by monitoring the modal pattern variation of an optical fiber. In this paper we present the results of a numerical model that has been developed to calculate the modal pattern variation at the end of a weakly guiding optical fiber under axial strain. Whenever an optical fiber is under stress, the optical path length, the index of refraction and the propagation constants of each fiber mode change. In consequence, the modal phase term of the fields and the fiber output pattern are also modified. For multimode fibers, very complicated patterns result. The predicted patterns are presented, and an expression for the phase variation with strain is derived.

Mode detector for multimode monitors

Abstract: A mode detector of a multimode monitor comprising a band separation circuit for separating band of input vertical and horizontal frequencies to provide logic signals, a control signal generation circuit for providing mode control signals, and a mode control circuit for controlling each mode of the multimode monitor. According to the present invention, the vertical and horizontal sizes, the vertical and horizontal oscillating frequencies, the horizontal pin cushion and the like can be automatically controlled according to the mode of input frequencies by detecting the mode of the input frequencies in the control signal generation circuit and by providing the combined logic signals of the control signal generation circuit to the mode control circuit.

Quasi-optical mode converter for directly transforming the whispering-gallery mode into the TE01 mode

Abstract: A quasi-optical mode converter is proposed to be used in a whispering-gallery-mode (WGM) gyrotron tube for transforming its oscillation mode into the TE01 mode In this mode conversion scheme, the WGM radiated from a circular waveguide cut is reflected by an annular mirror having suitable local normal vectors and fed into a tapered coaxial waveguide cut The mode conversion efficiency is calculated to be 92% for a 120 GHz TE122; mode input wave radiated from a 32mm diameter waveguide cut Making use of the converter in the tube enables us to separate the spent electron beam from the output wave for enlarging the beam collector

Analysis of the mode noise in interference fiber channels used for the distribution of microwave signals

Abstract: The results are given of a statistical theory of the speckle generalized to interference channels used for the distribution of microwave signals using multimode fiber waveguides with step and graded refractive-index profiles. A method is described for estimating the mode noise level in the open and closed regimes with one longitudinal speckle. The influence of the degree of mode filtering, losses at microbends, and spectral properties of a laser source on the statistical properties and the mode noise level is demonstrated. Numerical estimates are obtained of the ratio of the powers of the signal and mode noise for interference channels with typical parameters of fiber waveguides and a qualitative description is given of the effect of the mode noise.

Wavelength and mode-adjustable source for modal characterization of optical fiber components: application to a new alignment method

Abstract: Modal performances of multimode optical passive components are measured by use of a selective excitation technique. Pure LPm 1 modes up to LP15 1 mode are generated in a Ti:Sapphire laser cavity and launched in the input fiber of the component under test. Power measurements and modal analysis are operated at the output. Azimuthal dependency of LP1 1 mode excitation coefficient is used in an accurate centering technique of monomode and multimode splices or connectors.© (1991) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.