Showing papers on "Mode scrambler published in 1982"

Modal dispersion in single-mode fibres: simple approximation issued from mode spot size spectral behaviour

Abstract: We report a simple and accurate approximation of modal dispersion in single-mode optical fibres deduced from spectral behaviour of mode spot size; neither knowledge of index profile nor of maximum refractive index difference are required in this approximation.

Mode coupling effects in stress-applied single polarization fibers

Abstract: Mode coupling effects caused by waveguide imperfections and ambient fluctuations in the stress-applied single polarization fibers have been investigated. Several origins of mode coupling, such as: 1) core deformations, 2) deformation of stress-applying parts, 3) micro-bending, and 4) temperature fluctuations, have been treated. The mode coupling parameters between the orthogonally polarized HE 11 modes are compared for various kinds of waveguide imperfections and ambient fluctuations. It was clarified that the deformation of the stress-applying parts is the dominant factor in the mode coupling effects in stress-applied single polarization fibers.

Polarization mode dispersion measurement in elliptical core single-mode fibers by a spatial technique

Abstract: Polarization mode dispersion in elliptical core single-mode fibers has been measured by a spatial technique based on a visibility maximum position measurement in an interferometer. Using the technique, wavelength dependence of the modal dispersion has been measured by varying optical source wavelength between 821 and 904 nm. As a result, contribution of geometrical and strain birefringences on the modal dispersion has been evaluated, and normalized frequency dependence of the modal dispersion has been clarified. Moreover, the dispersion compensation effect has been observed by interchanging the fast and slow modes of two fibers at a splice point. The experimental results reveal that the spatial technique is very useful for polarization mode dispersion measurement.

Prediction of modal dispersion in single-mode fibres from spectral behaviour of mode spot size

Abstract: We report a simple calculation allowing the prediction of the modal dispersion in single-mode optical fibres from the spectral behaviour of the mode spot size and the profile index.

Coupling and Multiplexing Between Single Mode Optical Fibers

Abstract: Perhaps more than in the field of single mode optical communications, single mode fiber applications in sensors will require a whole set of functions that should be performed directly on the optical wave sensing a physical quantity. These are usually expected to be achieved by having recourse to the possibilities offered by integrated optics. However there still are a number of problems associated with the insertion of, say, a lithium niobate chip in a fiber sensor system, such as the difficulty in achieving an easy and straightforward fiber-film connection, the losses of such a junction due to the geometrical mismatch between the two guiding structures and also the additional problem caused by the reflection of coherent light due to the electromagnetic mismatch.

Modal Mode Partition Noise in Optical Fiber Systems

Abstract: The letter deals with an additional source of noise in optical transmission systems. Optical fiber connectors in multimode fiber systems lead to a wavelength dependent attenuation of the transmitted light and hence give rise to mode partition noise if a multimode laser is used. We give theoretical estimations of the created excess noise which show, that an increase of 25 dB by this modal mode partition noise is possible. Introduction

Fiber mode scrambler

Abstract: PURPOSE:To make a mode scrambler small-sized and to reduce a speckle noise, by providing a core diameter expansion part on a multimode optical fiber. CONSTITUTION:When a core diameter expansion part, which has been formed in a convex part 10 which is almost symmetrical to a fiber axis or in an asymmetrical convex part 10', and which has a radius of curvature which is 2-3 times as large as a radius of a core 9, is provided on a part of a multimode optical fiber 8, a light beam of plural modes, which has been transmitted into the optical fiber and is capable of interference, is reflected and stirred by the curved surface of the core in this core diameter expansion part, and is dispersed to much more modes, and mode mixing is executed. This core diameter expansion part is formed by equally heating a prescribed area of the optical fiber 8 to a high temperature from the surrounding part by means of electric discharge heating, etc., and by putting force in the axial direction of the optical fiber to the heating area from both sides of the heating area.

Relation between transverse mode control and longitudinal mode behavior in the injection laser

Abstract: Stabilization and control of the operating field mode in injection lasers are very important problems for wider application of the devices. This paper gives a theoretical analysis of the relation between transverse mode control and longitudinal mode behavior in the injection lasers which have undoped active regions. The guided modes are classified into three types, normal guided mode, active guided mode, and leaky mode, owing to guiding mechanism. Cutoff conditions for all types of modes are mentioned. Gain saturation was analyzed on the basis of the density matrix equation. The so-called weakly (partially) inhomogeneous property of the gain saturation was taken into account. The single longitudinal mode operation is expected when the transverse higher modes are in cutoff condition, because the suppression effect among the resonant modes is promoted. The normal guided mode is the most suitable for the single longitudinal mode operation, because the field profile and diffraction loss are invariable with increasing injection current. The transverse mode control is the most important characteristic in obtaining the single longitudinal mode operation in the injection lasers.

Single Longitudinal Mode Modified CSP Injection Laser for Single-Mode Optical Fiber

Abstract: Stable single transverse and longitudinal mode cw operation has been demonstrated using a newly developed gaussian channel substrate (GCSP) laser structure. These devices operate in excess of 14mW and are predominately single longitudinal mode over their entire operating range. Highly reliable performance is also expected due to low threshold current (16mA) and very high differential quantum efficiency (52% for single face). Using a tapered polished fiber technique, coupling efficiencies as high as 35% using 3 μm core single mode fiber were attained for cw lasers in the 840nm range. These devices appear ideally suited for use as optical sources for fiber optic interferometric applications.

Holograms for laser diode: Single mode optical fiber coupling

Abstract: The low coupling efficiency of semiconductor laser emissions into a single mode optical fibers place a severe restriction on their use. Associated with these conventional optical coupling techniques are stringent alignment sensitivities. Using holographic elements, the coupling efficiency may be increased and the alignment sensitivity greatly reduced. Both conventional and computer methods used in the generation of the holographic couplers are described and diagrammed. The reconstruction geometries used are shown to be somewhat restrictive but substantially less rigid than their conventional optical counterparts. Single and double hologram techniques are examined concerning their respective ease of fabrication and relative merits.