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Showing papers on "Step-index profile published in 1987"


Patent
William A. Reed1
02 Apr 1987
TL;DR: In this article, a single mode optical fiber is disclosed and the refractive index profile of the fiber comprises a depressed index or trench region in the cladding region, which can be adjusted by suitable adjustment of the position, width and index of the trench region.
Abstract: A single mode optical fiber is disclosed. The refractive index profile of the fiber comprises a depressed-index or trench region in the cladding region. By suitable adjustment of the position, width and index of the trench region, one or more fiber characteristics can be improved, relative to a similar fiber that does not comprise an index trench.

125 citations


Patent
16 Jun 1987
TL;DR: In this article, an optical fiber device comprises a core and a cladding, the core being made of an optical material having a refractive index n₁, and the cladding being made by an anisotropic optical material with a similar index.
Abstract: An optical fiber device (31) comprises a core (35) and a cladding (33), the core (35) being made of an optical mate­ rial having a refractive index n₁, and the cladding being made of an optical material having a refractive index n₂, end (34) of the optical fiber from which light radiates form­ ing a plane that is inclined to the fiber axis by an angle ϑ, a light reflective layer being formed at least on the outer pe­ riphery of said radiating end, and the two refractive indices n₁ and n₂ satisfying the following relation (1): n₁-n₂≧ 0.01 (1).

37 citations


Journal ArticleDOI
TL;DR: In this article, an effective index method was developed for the calculation of geometrical birefringence, i.e., the difference in phase velocity between the two fundamental polarization modes in a weakly guiding step-index fiber, of which the core can be of rectangular, elliptical, rhomboid or any other shape belonging to the same class, with arbitrary aspect ratio.
Abstract: Based on a scalar wave equation including the geometrical effect, an effective-index method is developed for the calculation of geometrical birefringence, i.e., the difference in phase velocity between the two fundamental polarization modes, in a weakly guiding step-index fiber, of which the core can be of rectangular, elliptical, rhomboid or any other shape belonging to the same class, with arbitrary aspect ratio. Numerical results show that the method is very efficient and accurate in obtaining the birefringence and can also provide very useful information on the birefringenee-induced dispersion in the fiber.

25 citations


Patent
07 Dec 1987
TL;DR: This article adjusted the refractive index distribution of a lens to better approach an ideal by heating the lens in an environment in which no additional ions can diffuse into the body, causing further migration of ions within the body.
Abstract: The refractive index distribution in refractive index distribution lenses may be adjusted to better approach an ideal by heating the refractive index distribution lens. When the refractive index distribution lens was created by diffusion of refractive index changing ions into a body, further heating in an environment in which no additional ions can diffuse into the body causes further migration of ions within the body so that its refractive index distribution approaches an ideal.

24 citations


Patent
30 Nov 1987
TL;DR: In this paper, a gradient index filter with integral antireflection properties without degrading the inband performance of the filter is proposed, which is for placement between an incident medium and a substrate to reflect incident electromagnetic energy having wavelengths within a predetermined band of wavelengths.
Abstract: A gradient index filter can be fabricated with integral antireflection properties without degrading the inband performance of the filter. The filter is for placement between an incident medium and a substrate to reflect incident electromagnetic energy having wavelengths within a predetermined band of wavelengths and to transmit incident electromagnetic energy having wavelengths outside of the reflection band. The filter includes an antireflecting portion having a nominal refractive index profile selected to reflect a minimum amount of electromagnetic energy from a theoretical interface between a first medium having a first predetermined refractive index and a second medium having a second predetermined refractive index. A band rejecting portion has a periodic refractive index profile whose periodicity and amplitude are selected to reflect a maximum amount of electromagnetic energy within the relfection band. At least part of the nominal refractive index profile is modulated by the superposition thereon of at least part of the periodic refractive index profile. The entire periodic refractive index profile maybe superimposed on the monial refractive index profile, while the periodic refractive index profile may be a rugate profile. In addition, the nominal incident and substrate refractive index profiles may be quintic refractive index profiles.

21 citations


Journal ArticleDOI
TL;DR: In this article, the refractive index of optical fiber cladding has been measured to an accuracy of 1×10−4 using multiple-beam Fizeau fringes, and the interferometric method has been also used as a control on the process of cladding production.
Abstract: The refractive index of optical fiber cladding has been measured to an accuracy of 1×10−4 using multiple‐beam Fizeau fringes. The interferometric method has been also used as a control on the process of cladding production by examining the homogeneity of fiber cladding.

9 citations



Patent
16 Nov 1987
TL;DR: In this article, the authors proposed a method to make the reflectance of the whole transparent plate extremely small by a method wherein a light absorbing metal layer or alloy layer is assembled within an antireflection film.
Abstract: PURPOSE: To make the reflectance of the whole transparent plate extremely small by a method wherein a light-absorbing metal layer or alloy layer is assembled within an antireflection film. CONSTITUTION: The antireflection film concerned is produced by forming a first high refractive index dielectric layer 2, the refractive index of which is 2.00W2.40 and the optical film thickness of which is 0.10×λ 0 /4W0.05×l 0 /4, a first refractive index dielectric layer 3, the refractive index of which is 1.37W1.50 and the optical film thickness of which is 0.6×λ 0 /4W1.6×λ 0 /4, a second high refractive index of which is 2.00W2.40 and the optical film thickness of which is 0.04×λ 0 /4W0.5×λ 0 /4, a metal layer 5 such as of titanium or the like having the film thickness of 10W60Å and a second low refractive index dielectric layer 6, the refractive index of which is 1.37W1.50 and the optical film thickness of which is 0.9×λ 0 /4W1.3×λ 0 /4 in the order named from the surface of a transparent plate. Accordingly, not only the light incident to the transparent plate but also the reflected light at the back of the transparent plate are absorbed and damped by the metal layer or alloy layer, resulting in making the whole reflected light small. COPYRIGHT: (C)1989,JPO&Japio

8 citations


Patent
30 Jan 1987
TL;DR: In this article, a dye was added to the core of a plastic optical fiber formed by coating a plastic having excellent light perriousness with a plastic clad having the refractive index lower than the core.
Abstract: PURPOSE:To enable laser oscillation with high efficiency in a continuous wavelength from visible to near IR light a continuous wavelength region from visible to near IR light by incorporating a dye into the core of a plastic optical fiber formed by coating a plastic having excellent light perriousness with a plastic clad having the refractive index lower than the refractive index of the core. CONSTITUTION:The plastic core 11 consisting of a material having excellent light perriousness, for example, polymethyl methacrylate (PMMA) is added with the dye for oscillating a laser at an arbitrary wavelength and the diameter thereof is, for example, 3.5mum. The plastic clad 12 formed to coat the core 11 is of the material having the refractive index smaller than the refractive index (1.496) of PMMA which is the material of the cores 1, for example, a PMMA-PFMA (1%) copolymer obtd. by copolymerizing a small amt. of polyfluoroalkyl methacrylate (PMFA) with PMMA and has the refractive index (1.493) slightly smaller than the refractive index of PMMA. The laser oscillation with high efficiency in the continuous wavelength region from visible to near IR light is thereby enabled.

6 citations



Proceedings ArticleDOI
01 Jan 1987
TL;DR: Theoretical analysis has been made to see the possibility of realization of low-loss hollow core optical fiber made of a glass functioning as the cladding whose refractive index is lower than unity as mentioned in this paper.
Abstract: Theoretical analysis has been made to see the possibility of realization of low-loss hollow core optical fiber made of a glass functioning as the cladding whose refractive index is lower than unity. It is shown that such total reflection-type waveguide can be realized only when the refractive index of the cladding is near unity not far from unity and also the absorption loss is extremely small.


Patent
16 Jun 1987
TL;DR: In this paper, the authors proposed a method to control the effective refractive index of an optical waveguide variably by applying voltage to the side section of the optical guide and changing the refractive indices between the region of the inside of the guide and the regions of a side section thereof.
Abstract: PURPOSE: To control the effective refractive index of an optical waveguide variably by applying voltage to the side section of the optical waveguide and changing a refractive index between the region of the inside of the optical guide and the region of a side section thereof. CONSTITUTION: Since the refractive indices of a waveguide layer 3 and clad layers 2, 4 on both sides of the layer 3 differ, light beams are propagated along the waveguide layer 3, and the bands of sections on both sides of the waveguide layer are bent when voltage is applied between an electrode 6 and an electrode 7, and an effective band gap changes. Consequently, the absorption coefficient of the region alters, a refractive index varies, and refractive index difference is formed among the central section and the sections on both sides of the waveguide layer 3. That is, the change of refractive indices is generated on the waveguide layer 3 and the side sections of the clad layers 2, 4 by applying voltage to the electrodes 6, 7, and regions 8 in which the change of refractive indices is generated substantially coincide with regions in which bands are bent by applying voltage, thus variably controlling a position where refractive index difference is generated in an optical guide and the variation of the refractive index. COPYRIGHT: (C)1988,JPO&Japio

Patent
15 Sep 1987
TL;DR: In this paper, a collimator optical system for effecting elliptical-to-circular cross section is disclosed which comprises two lenses in a slab form whose refractive index distribution in one plane is such that the refractive indices decreases gradually from the center outward in the direction of their thickness.
Abstract: A collimator optical system for effecting elliptical-to-circular cross section is disclosed which comprises two lenses in a slab form whose refractive index distribution in one plane is such that the refractive index decreases gradually from the center outward in the direction of their thickness. The two lenses are spaced on the optical axis in such a way that the direction of refractive index distribution in one lens crossing the direction of refractive index distribution in the other lens at right angles.

Journal ArticleDOI
M. Toda1
TL;DR: In this article, the authors pointed out that the assumption that higher bandgap materials necessarily have lower refractive index is incorrect, and presented a series of examples in support of this statement.
Abstract: Double heterojunction (DH) lasers are composed of a lower energy bandgap active layer sandwiched between higher bandgap cladding layers, and the refractive index of the active layer has to be higher than that of the cladding layer. A number of published papers are based on the belief that higher bandgap materials necessarily have lower refractive indexes, so that the correct-bandgap DH structure automatically satisfies the requirement for the refractive index. This paper points out that this belief appears to be incorrect, and presents a series of examples in support of this statement.

Journal ArticleDOI
TL;DR: In this paper, a stress-applied fiber with inhomogeneous core has been investigated, and the fiber characteristics are evaluated by stress analysis and modal analysis, using the finite-element method useful for arbitrary refractive-index profile.
Abstract: To extend the freedom in the design of polarization-maintaining single-mode optical fiber, a stress-applied fiber with inhomogeneous core has been investigated. The refractive index in the core has an α-power profile, and the refractive index of the stress-applying parts is decreased by doping. The fiber characteristics are evaluated by stress analysis and modal analysis, using the finite-element method useful for arbitrary refractive-index profile. For modal analysis, a new scalar variational expression useful for the analysis of weakly guiding birefringent fibers is presented. Using this expression, the polarization-mode properties of the fiber are studied in detail. From this analysis, it is found that the absolutely single-polarization operation can be realized in stress-applied fibers by proper selection of refractive-index profile in the core.

Journal ArticleDOI
TL;DR: In this article, the contrast of the light intensity pattern at the exit face of thick refractive index gratings in LiNbO 3 originating from incoherent illumination is measured as a function of the intensity amplitude and the wavelength.

Patent
09 Feb 1987
TL;DR: In this article, the optical fiber base material is dipped in the refractive index matching liquid 18 with a refractive (n), and the laser luminous flux 15 is scanned at right angles to the center axis of the base material 11, and the time when the luminous flow 15 is cut off by the base materials 11 is measured electrically.
Abstract: PURPOSE: To measure the external diameter of a core, etc., with high accuracy even when an optical fiber base material and refractive index matching liquid has a difference in refractive index by multiplying the apparent core diameter of the optical fiber base material by a correction coefficient and determining the real core diameter. CONSTITUTION: The optical fiber base material 11 is dipped in the refractive index matching liquid 18 with a refractive index (n), laser luminous flux 15 is scanned at right angles to the center axis of the base material 11, and the time when the luminous flux 15 is cut off by the base material 11 is measured electrically. Then the center position of the base material 11 and the center position of the core are determined according to the obtained data and the observed distance between the center of the base material 11 and the center of the core is found from those data. Then, the external diameter and apparent core diameter are determined according to those data and the apparent core diameter is multiplied by the correction coefficient K=n/n 1 (n 1 : refractive index of the clad of the base material 11) to determine the real core diameter. Thus, simple calculation or correction like this is added to accurately evaluate the shape of the base material with high accuracy. COPYRIGHT: (C)1988,JPO&Japio

Journal ArticleDOI
TL;DR: In this paper, a trapezoidal index of refraction profile was used for low dispersion operation in the 1.55-μm band using Ge doped silica core and pure silica cladding, and it was found that certain trapezoid proportions give a fiber with a combination of less Ge doping, larger core diameter, faster decay of the field in the radial direction within the cladding.
Abstract: An analytical study is made of single-mode fibers with a trapezoidal index of refraction profile for low dispersion operation in the 1.55-μm band using Ge doped silica core and pure silica cladding. It is found that certain trapezoid proportions give a fiber with a combination of less Ge doping, larger core diameter, faster decay of the field in the radial direction within the cladding, and smaller rate of change of dispersion with wavelength than is simultaneously possible with either the step index or triangular profiles.

Journal ArticleDOI
TL;DR: In this article, a comparison of the measured and calculated chromatic dispersion was made using a rigorous electrodynamic formulation of the problem of a single-mode fiber waveguide and the model of an equivalent step refractive index profile.
Abstract: A comparison of the measured and calculated chromatic dispersion was made using a rigorous electrodynamic formulation of the problem of a single-mode fiber waveguide and the model of an equivalent step refractive index profile. An analysis is made of various methods of constructing the equivalent step profile from the refractive index profile of a blank of a waveguide and the spectral dependence of the size of the mode spot. It is shown that the parameter of the equivalent step profile is best obtained from the higher-order moments of the refractive index profile. It is suggested that the radius of the core of a single-mode fiber waveguide be determined from the condition of equality of the experimental and calculated cutoff wavelengths of the first higher-order mode.

Patent
19 Nov 1987
TL;DR: An optical wave guide having at least one waveguide portion, which is clad by a cladding portion, is referred to as an optical waveguide as mentioned in this paper, and there is a refractive index difference between the wave guide and the optical wave.
Abstract: An optical wave guide having at least one wave guide portion (1) which is clad by a cladding portion (2) between whose refractive index and that of the wave guide portion (1) there is a refractive index difference characterised in that the refractive index difference increases as the wavelength of the light propagated through the wave guide increases.

Journal ArticleDOI
TL;DR: In this article, the authors used power transfer matrices to track the evolution of power distribution in ray packets and measured the power transfer of two ray packets for a step index fiber.
Abstract: The phase space diagram for parabolic and step index fibers leads to a graphic representation of the bound, leaky, and refracted rays of ray theory. This concept is used to predict the attenuation of typical components of local area networks. The technique uses power transfer matrices to track the evolution of power distribution in ray packets. In particular, we predict and then measure the power transfer of two ray packets for a step index fiber. The comparison is encouraging.

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the statistical properties of an optical field with a speckle structure in multimode fiber waveguides and obtained asymptotic formulas for the spatial correlation function of the field.
Abstract: An investigation is made of the statistical properties of an optical field with a speckle structure in multimode fiber waveguides. Asymptotic formulas are obtained for the spatial correlation function of the field. This function is used to obtain expressions for the statistical average density of dislocations in the wavefront of the field distributed over a transverse cross section of a waveguide with an arbitrary refractive index profile. It is shown that the dislocation density is an oscillatory function of the transverse coordinate. A study is also reported of the dependence of the dislocation density on the refractive index profile and on the conditions of excitation of a waveguide.

Journal ArticleDOI
TL;DR: In this paper, a simple non-destructive spatial filtering method for determination of the refractive index profile of preforms is presented, which works without any moving parts and can directly display the deflection function.
Abstract: A simple nondestructive spatial filtering method for determination of the refractive-index profile of preforms is presented. The method works without any moving parts and can directly display the deflection function.

Journal ArticleDOI
A. Bastawros1
TL;DR: In this article, a conical horn made of a nonhomogeneous material whose refractive index varies only axially can be directly mounted on the entrance face of a step-index fiber.
Abstract: A conical horn made of a nonhomogeneous material whose refractive index varies only axially can be directly mounted on the entrance face of a step-index fiber. Appropriate choice of the refractive index profile as well as of the dimensions of the horn leads to a considerable reduction of the modal delay. Through such a design, the acceptance angle of the fiber can also be enlarged.

Patent
11 Mar 1987
TL;DR: An optical switch comprises a pair of glass prisms (10, 11) of refractive index n g and base angle θ one on either side of a liquid crystal interface (12) of positive dielectric anisotropy and having an extraordinary refraction index n o.
Abstract: An optical switch comprises a pair of glass prisms (10, 11) of refractive index n g and base angle θ one on either side of a liquid crystal interface (12) of positive dielectric anisotropy and having an extraordinary refraction index n o and an ordinary refraction index no. To reduce crosstalk the refractive index n g is so chosen that

Patent
07 Aug 1987
TL;DR: In this paper, an optical system for coupling an output light of a semiconductor laser element to the tip part of the optical fiber through a lens was proposed. But the optical system was not designed to suppress a noise, and to transmit a good optical output signal by providing an optical fiber which has welded thermally a transparent medium whose refractive index difference to the optical fibre is <=20%, to the point of view of the lens.
Abstract: PURPOSE:To suppress a noise, and to transmit a good optical output signal by providing an optical fiber which has welded thermally a transparent medium whose refractive index difference to the optical fiber is <=20%, to the tip part of the optical fiber, and an optical system for coupling an output light of a semiconductor laser element to the tip part of the optical fiber through a lens. CONSTITUTION:An output light from a semiconductor laser 1 is brought to optical coupling through a lens system 2 to a rod 6 consisting of a transparent medium which has a refractive index of the same degree as that of an optical fiber on the end face and whose diameter is the same as or above the diameter of the optical fiber, for instance, that which has welded thermally a quartz rod step index fiber to optical fibers 3, 4. In this case, even if the rod end face is vertical against an incident optical axis, a waist after a reflected light has transmitted the lens is in a more distant position than the semiconductor laser, and a semiconductor laser light emitting part, a beam size is large. Accordingly, a light energy density is also extremely low, and a variatio of a semiconductor laser output caused by a reflected return light from the optical fiber end in an optical coupling device, an increase of a noise, and deterioration of a modulated pulse waveform can be eliminated.