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Lightwave Technology, Journal of

Issue 2 • Date Feb 1988

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Displaying Results 1 - 25 of 29
  • Correlation processing of fluctuating optical waves guided in an externally perturbed birefringent single-mode fiber by optical heterodyne interferometry

    Page(s): 191 - 196
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (344 KB)  

    A description is given of experimental studies on the correlation processes for the optical waves guided in a birefringent single-mode fiber exposed to random vibrations. A laser beam with orthogonally polarized two-frequency components is launched into the fiber in such a way that the polarization directions of the two-frequency components coincide with the birefringent axes of the fiber. On leaving the fiber, its orthogonal components, modulated at random in phase and amplitude, are superimposed with a reference laser beam with two-frequency components; two beat photocurrents are produced from the combination of different frequency components of the signal and reference laser beams. The beat photocurrents can yield the fluctuating phase and amplitude components of the guided optical waves, which are statistically processed by use of a signal analyzer. Autocorrelation and cross-correlation functions for the fluctuation components are given together with their corresponding power spectra. Characteristic features extracted from the measured results are explained View full abstract»

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  • About coupled-mode theories for dielectric waveguides

    Page(s): 294 - 303
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    A critical examination is made of recent works on coupled-mode theory for dielectric waveguides with strongly overlapping fields. It is shown that there is no best formulation. In each case, explicit or implicit approximations lead to errors that are difficult to estimate. An investigation is made of the accuracy of coupled-mode formulas, in the case of strong guidance, for TM waves along coupled slabs or for HE11 modes along circular rods. Contrary to a previous prediction, there is no breakdown of coupled-mode formulas when the guidance is increased. The coupled-mode equations are applied to the problem of nonparallel waveguides in optical directional couplers. Comparison between coupled-mode predictions and beam-propagation-method simulations shows that bending effects in converging and diverging sections affect the accuracy. An improved coupled-mode theory is proposed in order to take these effects into account View full abstract»

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  • Model for hydrogen aging in multimode fibers

    Page(s): 197 - 202
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    In order to explain the variation of initial aging rate on the square root of the hydrogen pressure observed in two other studies, a model based on the production of hydrogen atoms by some defect site in the glass is developed. The model is then successfully tested against the detailed temporal behavior that was reported for fibers containing high levels of phosphorus as well as those containing low levels View full abstract»

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  • Improved coupled-mode theory for reciprocal anisotropic waveguides

    Page(s): 304 - 311
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    An improved coupled-mode theory for a reciprocal anisotropic multiwaveguide system is derived. The general reciprocal anisotropic medium is described by a symmetric permittivity tensor that can have nonzero off-diagonal elements. The derivation is based on the generalized reciprocity relation. The coupled-mode equations are applicable to both lossy (gain) and lossless systems. For the special case of lossless systems, it is shown that the matrices in the coupled-mode equation are Hermitian, so that energy conservation is observed exactly. For the special case of a single anisotropic waveguide, the results also reduce to the previously derived solutions by D. Marcuse (1975). The improved coupled-mode theory in an anisotropic multiwaveguide system is illustrated with numerical examples View full abstract»

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  • Very small single-mode ten-fiber connector

    Page(s): 269 - 272
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    A small plastic molded single-mode ten-fiber connector has been developed for high-count optical subscriber cables. The connector ferrule alignment mechanism is designed with a sufficient factor of safety to allow rough handling during connection. The ferrules are precisely aligned by alignment pins and guide sleeve. The fabricated connector, which has a cross section of just 4 mm × 6 mm, exhibited an average loss of 0.4 dB and reconnection time of less than 0.5 min. Connection loss does not change after over 1000 reconnections View full abstract»

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  • Suppression of galloping oscillation for a self-supporting optical fiber cable

    Page(s): 186 - 190
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    Estimation formulas for wind force coefficients for self-supporting (SS) optical fiber cable are derived. Using these formulas, a procedure for evaluating the critical wind velocity that triggers galloping oscillation is provided. An SS cable with projections is designed to increase the critical wind velocity View full abstract»

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  • Consolidation-atmosphere influence on drawing-induced defects in pure silica optical fibers

    Page(s): 172 - 178
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    Drawing-induced paramagnetic defects (E'centers and oxygen-associated hole centers (OHCs)) and optical absorption bands at 630 nm and in the UV region are investigated for optical fibers. These fibers are drawn from pure silica glass preforms consolidated in atmospheres containing O2 and Cl2. UV absorption bands at 245 nm and 275 nm are clearly observed through deconvolution of the absorption spectra of optical fibers. The defects and absorption bands are influenced by the atmosphere in the consolidation process: (1) the OHCs and the absorption bands at 630 nm and 275 nm increase the intensity with increasing O2 content and with decreasing Cl 2 content; (2) the E' centers decrease under the same conditions; and (3) the absorption band at 245 nm is independent of the atmosphere View full abstract»

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  • Bidirectional optical fiber transmission systems using Raman amplification

    Page(s): 312 - 317
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    Bidirectional optical fiber transmission systems using Raman amplification are discussed. Analytical expressions for signals amplified by both forward and backward Raman scattering are presented. It is found that there exists an optimal pump power for the maximum unrepeated transmission length in a bidirectional system and that the maximum length is about 450 km, which is about the same as that of the unidirectional system View full abstract»

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  • Interlaboratory comparison of radiation-induced attenuation in optical fibers. I. Steady-state exposures

    Page(s): 165 - 171
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    A comparison of the losses induced at 0.85 μm in three all glass-pure silica core optical fibers by steady-state radiation exposures has been made among five laboratories. Both the growth of the attenuation during irradiation and the recovery following exposures of 3000 and 105 rads have been measured. Although a standard set of parameters was attempted by all laboratories, the slight divergences (0.45⩽σ⩽0.99 dB/km) observed in some data indicate sensitivity of the results to factors such as photobleaching, injection conditions, and sample coil diameter View full abstract»

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  • Bandwidth of a single-mode optical fiber in PSK coherent optical transmission systems

    Page(s): 322 - 328
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    The author examines propagation characteristics of PSK modulated signal light under the influence of the group velocity dispersion (GVD), the higher-order dispersion (HOD), and the nonlinear refractive index of a single-mode fiber. Emphasis has been placed on behavior at and near the zero-dispersion wavelength (ZDWL), where the HOD as well as the GVD would be important. It is found that propagation at the ZDWL is similar to that away from the ZDWL; the effect of the nonlinear refractive index can be comfortably ignored. The effect of HOD is found to induce self-amplitude modulation (SAM) at the ZDWL; the amplitude of PSK-modulated light becomes modulated as the light travels down the fiber. The SAM considered produces a power penalty in the PSK coherent fiber transmission, and determines the dispersion limit of such systems. As the operating wavelength moves away from the ZDWL, the effect of GVD becomes important relative to that of HOD. The significance of the results is examined View full abstract»

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  • Fiber-optic transmissions of microwave 8-phase-PSK and 16-ary quadrature-amplitude-modulated signals at the 1.3-μm wavelength region

    Page(s): 273 - 280
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    Transmissions of a 6-GHz 8-phase phase-shift-keyed (8φ-PSK) signal over a 12.5-km single-mode fiber with a 5-dB power margin and bit-error-rate (BER) of 10-10 and a 6-GHz 16-ary quadrature-amplitude-modulated (QAM) signal over the same distance with a 2-dB power margin and BER of 10-12 were demonstrated. The 8φ-PSK digital modem operated at 78Mb/s and the 16-QAM digital modem operated at 90 Mb/s. A high-speed multimode InGaAsP laser diode and a high-speed p-i-n diode were used in both fiber-optic transmission systems. Floor characteristics and power penalties observed in the BER performances of both systems were found to be caused by the intensity noise of the laser diode, particularly the reflection-induced intensity noise View full abstract»

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  • Loss stability assurance against hydrogen for submarine optical fiber cable

    Page(s): 203 - 209
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (472 KB)  

    Hydrogen generation resulting from electrochemical reactions between cable metals and condensed water or moisture permeated through the cable jacket was studied. It was found that hydrogen generation increases exponentially as time elapses and tends to saturation after about one month. Partial pressure distribution along the cable of hydrogen generated in the immersed range of a damaged cable was analyzed by means of the diffusion equation and the optical loss increase was estimated. It was shown that a water-blocking resin effectively prevents water penetration and hydrogen diffusion along the cable View full abstract»

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  • A review of the environmental factors affecting optical cable design

    Page(s): 179 - 185
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    The main environmental factors considered are fiber bending loss, hydrogen loss degradation, and stress corrosion. The major bending and stress corrosion mechanisms that affect fibers are first discussed. Then each of the environmental factors is examined with respect to its impact on optical cable design View full abstract»

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  • Propagation constant and waveguide dispersion of single-mode fibers measured from far-field

    Page(s): 318 - 321
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    Wavelength-dependent measurements of the far-field pattern can be evaluated to yield a mode-field radius. It was recently proposed to fit these data to a formula that contained all the parameters necessary to construct an empirical relation for the wavelength dependence of the propagation constant. The authors report on the feasibility of this technique, using actual measurement data. They discuss the calculation of the waveguide dispersion from the measured mode-field radius. In both cases the choice of the empirical fitting function proves to be of great importance View full abstract»

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  • A four-channel optical waveguide multi/demultiplexer for 5-GHz spaced optical FDM transmission

    Page(s): 339 - 345
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    A four-channel optical waveguide multi/demultiplexer for 5-GHz spaced optical FDM transmission is developed. The multi/demultiplexing principle is first presented, followed by the extinction ratio dependence on the power transfer ratio of the directional couplers, transmission loss of the waveguide, and birefringence of the waveguide. Experimental results are described for waveguides of high-silica glass fabricated on the silicon substrate by combination of flame hydrolysis and reactive ion etching. Their measured characteristics, such as frequency transmittance, loss, extinction ratio, and dependence of polarization and temperature are reported and evaluated View full abstract»

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  • Realization of ultrahigh coherence in semiconductor lasers by negative electrical feedback

    Page(s): 245 - 256
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    To be useful, an ultrahigh-coherence semiconductor laser source requires high frequency stability, narrow linewidth, the capability of frequency tracking to a master laser, and stable frequency tuning. Negative electrical feedback is proposed to meet these four requirements simultaneously. Although the degree of frequency fluctuation that can be reduced by negative electrical feedback is limited by the noise contained in the feedback signal, theoretical calculations show that the fluctuations can be lower than the quantum noise limit. Experimental results obtained recently by the author are reviewed View full abstract»

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  • Optical and mechanical properties of infrared fibers

    Page(s): 233 - 239
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    Optical and mechanical properties have been investigated for As 2S3 and As2Se3 glass fibers and a KRS-5 polycrystalline fiber. A bending effect was serious for a KRS-5 fiber but not for chalcogenide fibers. In an aging test, a KRS-5 fiber showed a deterioration of transmissivity due to adsorption of moisture as well as plastic deformation of the crystal. Optical loss spectra of chalcogenide fibers were observed to change characteristically due to environmental factors such as humidity, high temperature, and ultraviolet radiation. The potential usefulness of these fibers is discussed View full abstract»

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  • Long-term reliability of transmission loss in optical fiber cables

    Page(s): 210 - 217
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    Increased optical-fiber cable losses due to hydrogen are discussed. A mathematical model is developed to predict the growth of hydrogen concentration in the cable, which is determined by the evolution from organic cable materials and permeation through the cable sheath. This cable model, together with the measured parameters for the cable materials, explains the measured results. Design criteria for the allowable hydrogen evolution from cable materials and for the cable sheath structure are established on the basis of the model View full abstract»

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  • Radiation resistivity in silica optical fibers

    Page(s): 145 - 149
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    Hydrogen treatment of optical fiber waveguides with pure silica cores and boron, fluorine codoped silica claddings was found to effectively reduce the y-ray induced loss increases in visible wavelength region. Germanium-doped core fibers free from metal impurities had good resistance against y-rays. The induced losses were shown to be dependent on the dose rate, a similar behavior to that of pure silica core fibers. Metal impurities such as phosphorus or alkalis added to germanium doped silica core were found to change the glass structure significantly, producing the precursors of a defect center related to the y-ray-induced loss and increasing sensitivity to y-irradiation View full abstract»

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  • The absorption and fluorescence spectra of rare earth ions in silica-based monomode fiber

    Page(s): 287 - 293
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    Rare-earth ions have been systematically incorporated into the cores of silica-based optical fibers, and the absorption and fluorescence spectra have been measured. The results provide basic data for a wide range of possible future fiber-based devices. For specific telecommunications applications, ions that could be useful for sources in the 1.3-μm and 1.5-μm low-loss windows are identified. It is suggested that Er3+, Nd3+, and Tm3+ are the most promising ions for semiconductor pumping with GaAs-based laser diodes View full abstract»

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  • Cross power and crosstalk in waveguide couplers

    Page(s): 257 - 268
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    The operation of two-guide couplers is re-examined to include the effects of cross power. Two two-guide coupler structures that operate as on-off switches are analyzed using both the exact eigenmodes of a slab model of the coupler and a coupled-mode theory that takes cross-power effects into account. The two coupler configurations analyzed are with the output guide on the same side as the input guide and on the side of the coupled guide. For the proper choice of the length of the coupler in the first case, the waveguide detuning can be adjusted so that ideal switching behavior can be achieved. For the second case, full on-off switching is not possible. Excellent agreement is found between results of the coupled-mode theory and exact slab analyses View full abstract»

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  • Subthreshold flaws and their failure prediction in long-distance optical fiber cables

    Page(s): 226 - 232
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    A study of surface defects and static fatigue data is presented to support the view that subthreshold surface defects are responsible for failure in proof-tested optical fibers. For this type of defect, crack initiation, as opposed to crack growth, is the rate-limiting step. Classical crack propagation theory does not describe this process sufficiently well for lifetime production, but semiempirical techniques indicate that this popular treatment may be pessimistic. A more conventional reliability treatment, similar to that used for other system components, appears to offer the best available approach to the task of failure lifetime prediction in proof-tested fibers View full abstract»

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  • Observation of coherent Rayleigh noise in single-source bidirectional optical fiber systems

    Page(s): 346 - 352
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    The authors report noise in a directional optical fiber system that they believe arises from the interference of the signal light with the Rayleigh backscattered light. This noise, called coherent Rayleigh noise (CRN), is the dominant noise source in this system. The interference provides a mechanism for translation of laser phase fluctuations into receiver photocurrent fluctuations. A number of noise reduction schemes are proposed. The authors demonstrate that CRN can be reduced, but not eliminated, by providing a small drive current modulation signal to the source laser to broaden its linewidth. Systems using this single-source-bidirectional architecture must take this noise source into account View full abstract»

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  • An optical-feedback transimpedance receiver for high sensitivity and wide dynamic range at low bit rates

    Page(s): 329 - 338
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    A novel transimpedance optical receiver using optically coupled feedback rather than a conventional feedback resistor is described. The optically coupled feedback has a number of advantages, including: (1) elimination of feedback-resistor Johnson noise for higher sensitivity; (2) elimination of feedback capacitance for higher bandwidth; and (3) the capability of large feedback current with low output voltage for wide dynamic range. A theoretical analysis is presented, along with experimental results for a long-wavelength optical-feedback receiver at a bit rate of 1.5 Mb/s. The experimental receiver uses InGaAs p-i-n photodiodes and a silicon JFET preamplifier and obtains a maximum sensitivity of -63.8 dBm for an error rate of 1×10-7. When the receiver is optimized for high level signals, an optical dynamic range of 40 dB is attained with no preamplifier automatic gain control (AGC). The results of a transmission experiment over a length of 303 km of single-mode optical fiber at a wavelength of 1.55 μm are presented View full abstract»

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  • A local view of radiation effects in fiber optics

    Page(s): 155 - 164
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    The reasons for the difficulties that can arise in assessing the potential behaviour of fiber optics in real radiation environments in devising realistic test procedures are considered. Present knowledge of the radiation effects is reviewed by relating the author's own measurements to those of other workers. Some common features of behavior across fiber types are pointed out, and a possible empirical model for the response of undoped core fibers is presented View full abstract»

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Aims & Scope

The Journal of Lightwave Technology contains articles on current research, applications and methods used in lightwave technology and fiber optics.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Peter J. Winzer
Alcatel-Lucent Bell Labs