高锟获noble的论文原文 诺贝尔奖

where subscripts 1 and 2 refer to the fibre and the outer region, respectively. All the modes exhibit cutoffs except the H E M mode, which is the lowest-order hybrid mode. It can assume two orthogonal polarisations, and it propagates with an increasing percentage of energy outside the fibre as the dimensions of the structure decrease. Thus, when operating the waveguide in the HE X 1 mode, it is possible to achieve a single-mode operation by reducing the diameter of the fibre sufficiently. Under this condition, a significant proportion of the energy is carried outside the fibre. If the outside medium is of a lower loss than the inside dielectric medium, the attenuation of the waveguide is reduced. With these properties, H E n mode operation is of particular interest. The physical and electromagnetic aspects of the dielectric-fibre waveguide carrying the H E n mode for use at optical frequencies will now be studied in detail. Conclusions are drawn as to the feasibility and the expected
-h\
= y2 + k20s2 u( = h(a,i=\ and 2
Paper 5O33E was originally published in the Proceedings IEE, July 1966. It was first received 24th November 1965 and in revised form 15th February 1966. The authors were formerly with Standard Telecommunication Laboratories Ltd., Harlow, Essex. Prof. Kao is now with ITT and Dr. Hockham is with Plessey Company Ltd., 241 Station Road, Addlestone, Surrey, United Kingdom
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Dielectric-fibre waveguide
The dielectric fibre with a circular cross-section can support a family of HOm and EOm modes and a family of hybrid HE nm modes. Solving the Maxwell equations under the boundary conditions imposed by the physical structure, the characteristic equations are as follows: for HE nm modes n2/32
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IEE PROCEEDINGS, Vol. 133, Pt. J, No. 3, JUNE 1986
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performance of such a waveguide for long-distancecommunication application. 3 Material aspects
i.e. loss is proportional to X 4 . It is estimated that the loss is of the order of a few decibels per kilometre at 1 /an wavelength. 3.1.2 Absorption: Absorption bands in solids are usually broad, owing to the close packing of the molecules. They arise from the natural-vibration frequencies of the molecular and electronic systems. Near such frequencies, the energy of the external electromagnetic field couples energy into the vibration of the molecules and electrons. In the wavelength region between 100 and 1 /an, many longitudinal and rotational resonances of molecules are present in almost all substances, especially the long-chain polymers. Strong absorption takes place throughout most of the region. In the 0.3-0.1 /mi region, electronic-resonance absorption bands are present. In the intermediate region (i.e. 1-0.3 /an), resonance-absorption phenomena are relatively absent. This represents a region for the material to have low loss. In inorganic glasses, it is known that absorption can occur owing to the presence of impurity ions. It is known that, in high-quality optical glasses, the main contribution to absorption loss in the 1-3 /an region is due to the Fe + + and Fe + + + ions. The ferrous ion has an absorption band centred at about 1 /mi, while the ferric ion has one at about 0.4 /an. At band centre, the absorption due to 1 part per million of Fe + 2 in certain glass systems3 is estimated to result in an absorption coefficient of less than 20 dB/km. 3.1.3 Present state of low-loss material: The present known low-loss materials in the frequency range of interest are mainly in the visible part of the spectrum. This is because transparent materials in this frequency range have been in high demand. The best transparent materials known in the visible spectrum are high-quality optical glasses, fused quartz, polymethyl methachrylate and polystyrene. The best absorption coefficient for glass is reported as 0.05% per cm, which is equivalent to tan (5 = 1 x 10~8 at 1 /mi, giving a bulk loss of about 200 dB/km. The published data on polymethyl methachrylate give 0.2% per cm, equivalent to a bulk loss of about 600 dB/km at 0.7 /an wavelength. This is for a commercial-grade material which is known to suffer from high particle-scattering losses. Typical absorption/wavelength curves can be seen in Figs. 1, 2 and 3, showing the measurements made on glass,
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Introduction
A dielectric fibre with a refractive index higher than its surrounding region is a form of dielectric waveguide which represents a possible medium for the guided transmission of energy at optical frequencies. This form of structure guides the electromagnetic waves along the definable boundary between the regions of different refractive indexes. The associated electromagnetic field is carried partially inside the fibre and partially outside it. The external field is evanescent in the direction normal to the direction of propagation, and it decays approximately exponentially to zero at infinity. Such structures are often referred to as open waveguides, and the propagation is known as the surface-wave mode. The particular type of dielectric-fibre waveguide to be discussed is one with a circular cross-section.
List of principle symbols Jn = nth-order Bessel function of the first kind Kn = nth-order modified Bessel function of the second kind 271 — — , phase coefficient of the waveguide Xg }'n = first derivative of Jn K^, = first derivative of Kn hi = radial wavenumber or decay coefficient = relative permittivity ,k0 = free-space propagation coefficient a = radius of the fibre y = longitudinal propagation coefficient k = Boltzman's constant T = absolute temperature, K j5 c = isothermal compressibility X = wavelength n = refractive index Hj,0 = uth-order Hankel function of the ith type H'v = derivation of H u v = azimuthal propagation coefficient = i^ — jv2 L = modulation period Subscript n is an integer and subscript m refers to the mth root of L = 0 B
Dielectric-fibre surface waveguides for optical frequencies
K.C. Kao and G.A. Hockham
Indexing terms: Optical fibres, Waveguides Abstract: A dielectric fibre with a refractive index higher than its surrounding region is a form of dielectric waveguide which represents a possible medium for the guided transmission of energy at optical frequencies. The particular type of dielectric-fibre waveguide discussed is one with a circular cross-section. The choice of the mode of propagation for a fibre waveguide used for communication purposes is governed by consideration of loss characteristics and information capacity. Dielectric loss, bending loss and radiation loss are discussed, and mode stability, dispersion and power handling are examined with respect to information capacity. Physicalrealisation aspects are also discussed. Experimental investigations at both optical and microwave wavelengths are included.