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Showing papers on "Radiation mode published in 1982"


Patent
06 Dec 1982
TL;DR: In this paper, the core index depression characteristics such as radial location, width, depth and shape are selected to achieve the desired waveguide dispersion characteristics, without adverse effect on system loss.
Abstract: Disclosed is an optical waveguide fiber having a core surrounded by a layer of cladding material The core is characterized in that it includes a region of depressed refractive index The inner radius a i of this region is greater than zero, and the outer radius a o thereof is less than the core radius By appropriately selecting the core index depression characteristics such as radial location, width, depth and shape, a fiber having the desired waveguide dispersion characteristics can be designed Dispersion minimization over a wide wavelength range can be achieved, without adverse effect on system loss

128 citations


Journal ArticleDOI
TL;DR: Taking into account the contribution of radiation mode, the power conservation at the junction is clearly verified and the analogy between the behavior of the single-mode Y junction and that of a beam splitter is discussed.
Abstract: An explanation of the working mechanism of single-mode optical-waveguide Y junction is presented. Taking into account the contribution of radiation mode, the power conservation at the junction is clearly verified. Also, the analogy between the behavior of the single-mode Y junction and that of a beam splitter is discussed.

107 citations


Journal ArticleDOI
TL;DR: In this paper, a model to calculate the mode size and propagation constant of single-mode Ti:LiNbO 3 waveguides from controllable fabrication parameters and basic constants is presented.
Abstract: We have formulated a model to calculate the mode size and propagation constant of single-mode titanium-lithium niobate diffused strip waveguides directly from controllable fabrication parameters and basic constants. The model is compared to measurements of the lateral and vertical mode width of Ti:LiNbO 3 waveguides for a variety of diffusion conditions. We show that the model accurately predicts the geometrical mean mode size of the two-dimensional waveguide. The model provides a simplified method for estimating the mode size and propagation constant of the guide, and is useful in designing waveguide devices having low fiber/waveguide coupling and bending losses.

95 citations


Journal ArticleDOI
TL;DR: In this paper, the authors demonstrate wavelength averaging of the power in either mode, permitting a simple measurement of power transfer to the cross-polarized mode as a function of fiber length, and confirm experimentally the theory of random mode coupling between the polarization modes.
Abstract: Perturbations in highly birefringent single-mode fibers couple the two polarization modes and degrade the polarization-holding ability. With a broadband source we demonstrate wavelength averaging of the power in either mode, permitting a simple measurement of the power transfer to the cross-polarized mode as a function of fiber length. Using this technique, we confirm experimentally the theory of random mode coupling between the polarization modes.

93 citations


ReportDOI
TL;DR: In this article, the authors reported measurements on mode converters to transform the TE01 mode into HE11 for electron cyclotron heating (ECH) experiments, and the overall efficiency of conversion from TE01 to HE11 exceeds 91% over a measured range of 59.2 to 60.1 GHz.
Abstract: The HE11 mode in corrugated waveguide has a field distribution very close to that of an ideal gaussian mode. Its radiation pattern is symmetric about the waveguide axis and exhibits virtually no cross polarization. This work reports measurements on mode converters to transform the TE01 mode into HE11 for electron cyclotron heating (ECH) experiments. The first mode converter is a 28 degree bend in 1.094-inch I.D. circular waveguide which generates TM11 from TE01 with a measured efficiency of over 95% at 60 GHz. A second converter consists of a straight corrugated waveguide section of the same I.D. in which the corrugation depth increases gradually from zero to nominally a quarter wavelength. This section converts TM11 to HE11 with an efficiency of about 97%. The overall efficiency of conversion from TE01 to HE11 exceeds 91% over a measured range of 59.2 to 60.1 GHz.

89 citations


Journal ArticleDOI
TL;DR: In this paper, the authors achieved very high optical throughput for titanium diffused lithium niobate waveguides coupled between input and output singlemode fibers by determining appropriate diffusion parameters to obtain excellent dimensional match between the fiber and waveguide modes and simultaneously low propagation loss.
Abstract: We report detailed results on the achievement of very high optical throughput for titanium diffused lithium niobate waveguides coupled between input and output single-mode fibers. By determining appropriate diffusion parameters to obtain excellent dimensional match between the fiber and waveguide modes and simultaneously low propagation loss, we have achieved total measured fiber-waveguide-fiber insertion loss as low as 1 dB for a 1 cm long waveguide at \lambda = 1.32 \mu m. The relative contributions of coupling and propagation loss are determined. Very good correlation is found between the coupling loss and the match between the fiber and waveguide mode dimensions. Design data for diffusion parameters to obtain good mode match for arbitrary fiber dimension are presented.

82 citations


Journal ArticleDOI
P. Sansonetti1
TL;DR: In this article, a simple and accurate approximation of modal dispersion in single-mode optical fibres deduced from spectral behaviour of mode spot size is presented. But neither knowledge of index profile nor of maximum refractive index difference are required in this approximation.
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.

47 citations


Journal ArticleDOI
TL;DR: In this paper, a theoretical parameter study of a TE/sub 11/ to HE/sub 12/ mode converter with ring-loaded slots is presented, where the analysis, using modal field-matching techniques to determine the scatter matrix, allows the return loss to be computed accurately.
Abstract: A theoretical parameter study is given of a TE/sub 11/ to HE/sub 11/ mode converter consisting of a section of cylindrical corrugated waveguide with ring-loaded slots. The analysis, using modal field-matching techniques to determine the scatter matrix of the converter, allows the return loss to be computed accurately. For a wide range of waveguide sizes it is shown that a bandwidth ratio of 1.5 with a return loss better than 30 dB is possible. The low-frequency performance of the converter is limited by the deterioration in return loss, while at high frequencies the generation of a small amount of unwanted EH/sub 12/ mode is the restriction. If the effects of this mode can be neglected, operation over a wider bandwidth is possible, particularly for larger waveguide size.

46 citations


Journal ArticleDOI
TL;DR: In this paper, a rapidly converging numerical procedure for the direct evaluation of the propagation constant and its first and second derivatives in single mode optical fibers with arbitrary refractive index profiles is presented.
Abstract: We present here a rapidly converging numerical procedure for the direct evaluation of the propagation constant and its first and second derivatives in single mode optical fibers with arbitrary refractive index profiles. To illustrate the procedure we have also used it to evaluate the propagation constant and its derivatives in single mode optical fibers with power law profiles in the presence of a Gaussian axial index dip, and hence, studied the effect of a dip on the dispersion characteristics of the fibers.

45 citations


Journal ArticleDOI
TL;DR: In this article, the mode coupling parameters between the orthogonally polarized HE 11 modes are compared for various kinds of waveguide imperfections and ambient fluctuations in the 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.

42 citations


Journal ArticleDOI
TL;DR: In this paper, the optimum waveguide structure for linearly single polarization fibers, which satisfies the large modal birefringence and the zero polarization mode dispersion simultaneously, has been investigated.
Abstract: The optimum waveguide structure for linearly single polarization fibers, which satisfies the large modal birefringence and the zero polarization mode dispersion simultaneously, has been investigated. The basic waveguide structure is the single-mode optical fiber that has an elliptical core and stress-applying parts with a different expansion coefficient from that of the cladding. Waveguide parameters, such as index difference, core ellipticity, and cutoff wavelength, are first determined to obtain highly birefringent fibers with B = 1 \times 10^{-5} or B = 5 \times 10^{-5} . The structure of the stress-applying parts that provides zero polarization mode dispersion is then determined.

Journal ArticleDOI
TL;DR: In this paper, a spatial technique based on a visibility maximum position measurement in an interferometer was used to measure the wavelength dependence of the modal dispersion by varying optical source wavelength between 821 and 904 nm.
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.

Journal ArticleDOI
TL;DR: In this paper, a rapidly converging numerical procedure for the direct evaluation of the propagation constant and its first and second derivatives in single mode optical fibers with arbitrary refractive index profiles is presented.
Abstract: We present here a rapidly converging numerical procedure for the direct evaluation of the propagation constant and its first and second derivatives in single mode optical fibers with arbitrary refractive index profiles. To illustrate the procedure we have also used it to evaluate the propagation constant and its derivatives in single mode optical fibers with power law profiles in the presence of a Gaussian axial index dip, and hence, studied the effect of a dip on the dispersion characteristics of the fibers.

Journal ArticleDOI
TL;DR: In this paper, a semiconductor interferometric laser with built-in index guiding for lateral mode stability is reported, where interference is caused by internal reflection from a small notch in the waveguide channel.
Abstract: A semiconductor interferometric laser with built‐in index guiding for lateral mode stability is reported. Interference is caused by internal reflection from a small notch in the waveguide channel. Very stable single longitudinal mode and stable lateral mode were observed. The intereference also causes wavelength locking over the ranges of more than 7 °C within which the wavelength changes at a moderate rate of about 0.6 A/°C.

Journal ArticleDOI
TL;DR: In this article, the 3 × 2 branching waveguide coupler with three input ports and two output ports has been studied theoretically and analytic output power expressions have been obtained for the three-dimensional 3 × 3 coupler from which they were derived.
Abstract: Gyroscope couplers with three input ports and two output ports which can be implemented in a planar geometry are studied theoretically. Using a local normal mode description in the approximation of coupled mode theory, analytic output power expressions are obtained for the 3 × 2 branching waveguide coupler and the 3 × 2 directional waveguide coupler. When optimized, these devices behave identically to each other and to the three-dimensional 3 × 3 coupler [1] from which they are derived.

Journal ArticleDOI
TL;DR: In this article, the coupling efficiency of a waveguide-laser resonator was evaluated in terms of a onefold integral, which can be evaluated in a closed form for three practical cases of interest corresponding to plane-parallel, half-concentric, and semiconfocal geometries.
Abstract: Coupling losses in a waveguide-laser resonator are considered for an arbitrary waveguide mode. For a rectangular waveguide the coupling efficiency is shown to be expressed in terms of a onefold integral, which can be evaluated in a closed form for three practical cases of interest corresponding to plane-parallel, half-concentric, and semiconfocal geometries. The results are used to discuss the extent of mode discrimination as well as the choice of optimum parameters for a compact waveguide-resonator design. The case of a phase-conjugate mirror is also considered. When an effective finite mirror size is used, a phase-conjugate waveguide resonator is shown to be capable of transverse-mode discrimination while providing low coupling losses for the fundamental waveguide mode.

Patent
24 Mar 1982
TL;DR: In this article, the waveguide exciter horn is dimensioned so that at least two independent modes of a higher order or combinations thereof having the same polarization as the main mode can be excited in the waveguer horn in addition to the main modes.
Abstract: A microwave transmission system for multipath propagation operating according to the angle diversity principle and comprising a transmitting and receiving device including a reflector antenna and a waveguide exciter horn wherein a fundamental mode and modes of a higher order can propagate, a mode coupler following the exciter horn for separating the energy components of the main mode and the higher order modes, and receiving and combining devices for obtaining the best signal from the received energy components of the various modes. The exciter horn is dimensioned so that at least two independent modes of a higher order or combinations thereof having the same polarization as the main mode can be excited in the waveguide exciter horn in addition to the main mode. In order to enlarge the radiation gain of the antenna, the waveguide exciter horn is designed, in its basic structure as well as by means of additional structural elements, such as pairs of apertures, corrugated structures, steps and bends, such that the aperture angle (α) of the radiation lobe of the main mode is matched to the aperture angle (β) of the radiation lobes of the higher modes or vice versa in the plane of the electrical field as well as in the plane of the magnetic field. The mode coupler feeds more than two mutually independent received signals from the received energy components of the different modes separately to the receiving and combining devices, and includes a transmitting port which excites one mode whose preferred field direction is orthogonal to the preferred field direction of the received main mode.

Patent
25 Jan 1982
TL;DR: In this article, a dual frequency band, dual-mode feedhorn comprising three serially connected waveguide sections (20, 22, 24) and a separate discontinuity (21, 23) was proposed.
Abstract: The present invention relates to a dual frequency band, dual-mode feedhorn comprising three serially connected waveguide sections (20, 22, 24) and a separate discontinuity (21, 23) at each joint between waveguide sections. More particularly, the feedhorn comprises a first waveguide section (20) for supporting the TE11 mode in both frequency bands. A first discontinuity (21) symmetrically increases the first waveguide size for converting a portion of the TE11 mode in both frequency bands into the TM11 mode. The second waveguide section (22) connected to the first discontinuity comprises an aperture size for supporting the TE11 mode in both frequency bands but only the TM11 mode of the higher frequency band. A second discontinuity (23) symmetrically increases the size of the second waveguide for converting another portion of the TE11 mode in both frequency bands into the TM11 mode. A third waveguide section (24) coupled to the second discontinuity is capable of propagating both modes in both frequency bands with a length to cause the vector sums of each of the remaining TE11 and TM11 modes in each frequency band to be in phase at the exit port of the feedhorn.

Journal ArticleDOI
TL;DR: In this paper, the feasibility of applying the equivalent-step-index parameters to estimate the single-mode waveguide dispersion of various radially inhomogeneous profiles is studied.
Abstract: In the letter, the feasibility of applying the equivalent-step-index parameters to estimate the single-mode waveguide dispersion of various radially inhomogeneous profiles is studied. The results are compared to the actual values obtained by numerical techniques and the errors estimated. The equivalent-step approach seems to be accurate only for cases where the profiles do not deviate severely from the step-index profile.

Journal ArticleDOI
TL;DR: In this paper, a new type of extremely low-loss optical waveguide is proposed for the vacuum-ultra-violet (VUV) region (wavelength less than 300 nm).

Journal ArticleDOI
TL;DR: In this article, the authors achieved very high optical throughput for titanium diffused lithium niobate waveguides coupled between input and output single-mode fibers by determining appropriate diffusion parameters to obtain excellent dimensional match between the fiber and waveguide modes and simultaneously low propagation loss.
Abstract: We report detailed results on the achievement of very high optical throughput for titanium diffused lithium niobate waveguides coupled between input and output single-mode fibers. By determining appropriate diffusion parameters to obtain excellent dimensional match between the fiber and waveguide modes and simultaneously low propagation loss, we have achieved total measured fiber-waveguide-fiber insertion loss as low as 1 dB for a 1 cm long waveguide at Lambda = 1.32 µm. The relative contributions of coupling and propagation loss are determined. Very good correlation is found between the coupling loss and the match between the fiber and waveguide mode dimensions. Design data for diffusion parameters to obtain good mode match for arbitrary fiber dimension are presented.

Journal ArticleDOI
TL;DR: In this paper, a fabrication procedure for multimode deposited silica waveguide (DS guide) consisting of uniform and thick glass layer formation for core and cladding, and amorphous Si mask film for reactive sputter etching was developed.
Abstract: A fabrication procedure has been developed for multimode deposited silica waveguide (DS guide), consisting of uniform and thick glass layer formation for core and cladding, and amorphous Si mask film for reactive sputter etching. The embedded multimode DS guide with a square core cross section has a transmission loss of 1.3 dB/cm at 633 nm wavelength. Waveguide parameters, such as core dimension, refractive index, and index difference, are similar to those of a multi-mode silica fiber. A multimode optical branching circuit with eight output ports was demonstrated by the above fabrication procedure. Excess insertion loss was 2 dB.

Journal ArticleDOI
TL;DR: In this article, the effect of the change in refractive index across the fiber was quantified and it was shown that the waveguide dispersion of the fundamental mode by the fiber is virtually unaffected by the polarization properties of the fiber.
Abstract: In the weak-guidance approximation, the properties of fundamental modes of optical fibers depend on solutions of the scalar-wave equation and contain no polarization effects that are due to the fiber. In this paper, we derive polarization-dependent corrections for the clad power-law and infinite parabolic profiles to quantify the effect of the change in refractive index across the fiber. In particular, the waveguide dispersion of the fundamental mode by the fiber is found to be virtually unaffected by the polarization properties of the fiber.

DOI
01 Jun 1982
TL;DR: In this article, the average or effective waveguide parameter Ṽ, which incorporates Ω 0, emerges naturally and universal formulas are given in terms of ǫ, Ω 2 = Ω2/Ω 0 and Ω 4 = Φ4/ǫ 0.
Abstract: Single-mode optical fibres are characterised by the moments Ωm of their refractive-index profiles. An accurate description of light propagation along such fibres is obtained when the complete profile details are replaced by the reduced profile data in the form of Ω0, Ω2 and Ω4. The average or effective waveguide parameter Ṽ, which incorporates Ω0, emerges naturally and universal formulas are given in terms of Ṽ, Ω2 = Ω2/Ω0 and Ω4 = Ω4/Ω0. These formulas cover the fundamental-mode eigenvalue, group velocity and dispersion parameters, field spot size and fraction of power propagating within the core, and the cutoff parameter for the second waveguide mode. They are simple to apply and their good accuracy, which is demonstrated for a wide variety of examples, indicates that they are suitable for use in fibre design studies. The formulas also naturally lead to a qualitative description ofwaveguide behaviour: different fibres have similar properties when these are considered as functions of Ṽ, and a residual magnitude scaling can be attributed to profile shape which enters principally through Ω2.

Book ChapterDOI
01 Jan 1982
TL;DR: In this paper, the double Y waveguide was proposed to fulfill all the requirements for reciprocal operation of a fiber-optic rotation sensor with a single-mode dielectric branching waveguide.
Abstract: After a review and synthesis of the properties of the single-mode dielectric branching waveguide, we propose a particularly simple and attractive integrated-opties device, the “double Y”, which fulfils all the requirements for reciprocal operation of a fiber-optic rotation sensor.

Journal ArticleDOI
TL;DR: In this article, a model to calculate the mode size and propagation constant of single-mode Ti:LiNbO/sub 3/ waveguides is proposed. But the model is not suitable for the case of single waveguide devices with low fiber/waveguide coupling and bending losses.
Abstract: We have formulated a model to calculate the mode size and propagation constant of single-mode titanium-lithium niobate diffused strip waveguides directly from controllable fabrication parameters and basic constants. The model is compared to measurements of the lateral and vertical mode width of Ti:LiNbO/sub 3/ waveguides for a variety of diffusion conditions. We show that the model accurately predicts the geometrical mean mode size of the two-dimensional waveguide. The model provides a simplified method for estimating the mode size and propagation constant of the guide, and is useful in designing waveguide devices having low fiber/waveguide coupling and bending losses.

Journal ArticleDOI
TL;DR: In this article, the optimum waveguide structure for linearly single polarization fibers, which satisfies the large modal birefringence and the zero polarization mode dispersion simultaneously, has been investigated.
Abstract: The optimum waveguide structure for linearly single polarization fibers, which satisfies the large modal birefringence and the zero polarization mode dispersion simultaneously, has been investigated. The basic waveguide structure is the single-mode optical fiber that has an elliptical core and stress-applying parts with a different expansion coefficient from that of the cladding. Waveguide parameters, such as index difference, core ellipticity, and cutoff wavelength, are first determined to obtain highly birefringent fibers with B = 1 X 10/sup -5/ or B = 5 X 10/sup -5/. The structure of the stress-applying parts that provides zero polarization mode dispersion is then determined.

Book ChapterDOI
01 Jan 1982
TL;DR: In this paper, a technique is described for fabrication of etched single mode fiber optical waveguide couplers which preserve the polarization state to within 10-4, and the coupling ratio is tunable over a broad range during fabrication.
Abstract: A technique is described for fabrication of etched single mode fiber optical waveguide couplers which preserve the polarization state to within 10–4. The coupling ratio is tunable over a broad range (0–90%) during fabrication. Back-coupling is less than 10–3, insertion loss is less than 1.5 dB, and coupling ratio thermal coefficient is about 1% per degree C.

Journal ArticleDOI
TL;DR: In this paper, the authors reported the measurements of the twist induced circular birefringence in a single mode fiber by direct observation of the scattered light, and an analysis of the evolution of the polarization in a linearly bireringent twisted medium (applicable to weakly guiding single mode (fibers) is given using the coupled mode theory and Poincare sphere representation.

Journal ArticleDOI
TL;DR: In this article, it was shown that the model index profile required for a waveguide Luneburg lens can be obtained by varying the index of the thin film, without changing its thickness.