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Lightwave Technology, Journal of

Issue 7 • Date Jul 1989

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Displaying Results 1 - 16 of 16
  • Crosstalk and its power penalty in multichannel transmission due to gain saturation in a semiconductor laser amplifier

    Publication Year: 1989 , Page(s): 1118 - 1124
    Cited by:  Papers (16)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (576 KB)  

    A theoretical study of channel crosstalk due to gain saturation in a laser amplifier in multichannel transmission is discussed. When the amplifier is gain-saturated, the gain of any channel is influenced by the light intensity of the other channels, which causes channel crosstalk in intensity-modulated multiplexing transmission. On-off-keying modulation systems with more than two channels are discussed. Considering the probability distribution, the power penalty due to crosstalk is presented for practical system design. Calculated examples reveal that the power penalty is dependent on both the level of gain saturation and the number of multiplexed channels View full abstract»

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  • Optical fiber up-tapers with index perturbations-performance analysis

    Publication Year: 1989 , Page(s): 1055 - 1062
    Cited by:  Papers (2)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (616 KB)  

    The performance of step index up-tapers subjected to certain index perturbations in investigated by computer simulation. Concentric symmetric and asymmetric index profile perturbations as well as localized spherical, called regions bubbles, having a different index are studied. It is found that some low-valued perturbations of small scale size (less than a wavelength) do not alter the optical fiber performance. However, the amount of beam expansion in the up-taper may be ultimately limited by such perturbations. Excessive magnification in the presence of perturbations can cause a distortion of the quasi-Gaussian shape and symmetry of the pure step-index fundamental mode as well as increase the excess loss and degrade the lateral and axial displacement tolerance improvements of the up-tapers. For example, an index variation of Δn≈10-5 in conjunction with a perturbation scale size of 40 μm can be detrimental. Bubble-type perturbations could also cause similar problems. A single 12.8-μm-diameter bubble with a relative index of -0.02, embedded in a 128-μm-diameter step index core with relative index of 0.5%, produced a 0.3-dB excess loss View full abstract»

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  • Measurement of mode partition characteristics of laser diodes modulated by M-sequences

    Publication Year: 1989 , Page(s): 1125 - 1129
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    A method which permits the determination of k-values of laser diodes modulated by M-sequences is described. With this method, the mode partition characteristics of laser diodes in actual operating conditions can be measured. Measurements at frequencies which are lower by two orders of magnitude compared with conventional methods are possible View full abstract»

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  • Spectral analysis of optical mixing measurements

    Publication Year: 1989 , Page(s): 1083 - 1096
    Cited by:  Papers (33)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1156 KB)  

    A general rigorous theory of optical heterodyne and homodyne measurements is presented. The power spectrum of the photocurrent resulting from two uncorrelated optical beams mixing on a photodetector is derived. In particular, a rigorous analysis is presented for the delayed self-homodyne method which is used to characterize laser source linewidth by a Mach-Zehnder interferometer with a delay exceeding the source coherence length. Existing treatments are generalized to address non-Lorentzian laser sources of arbitrary lineshape. The analysis is further generalized to cover the case of modulated nonstationary sources. An example of the application of this theory is given. It is shown how the theory may be used to interpret an experimental result obtained using the gated delayed self-homodyne technique for characterizing the frequency chirp of laser sources under modulation View full abstract»

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  • Overlap integral factors in integrated optic modulators and switches

    Publication Year: 1989 , Page(s): 1063 - 1070
    Cited by:  Papers (25)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (544 KB)  

    Coplanar strip and complementary coplanar strip electrodes are often used in integrated optical switches and modulators using the optical directional coupler. The field analysis of these electrodes is performed to determine the optimum overlap integral between the optical field and the modulating electromagnetic field. The optimal placement of the electrodes with respect to the optical channel waveguides is presented as a function of electrode width and spacing View full abstract»

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  • Modeling of Ti:LiNbO3 waveguide devices. II. S-shaped channel waveguide bends

    Publication Year: 1989 , Page(s): 1016 - 1022
    Cited by:  Papers (18)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (528 KB)  

    For pt.I see ibid., vol.7, no.3, p.533-9, 1989. Directly from design and fabrication parameters, the performances of S-shaped channel waveguide bends are calculated by using the same formalism described in Part I. The calculated insertion losses of S-shaped waveguide bends are in agreement with all experimental data found in the literature. Different S-curves for short-length low-loss waveguide bend design were also studied. Results show that the widely used sine-generated S-curve does not provide lower insertion loss than other S-curves View full abstract»

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  • Saturation and depletion effect of Raman scattering in optical fibers

    Publication Year: 1989 , Page(s): 1109 - 1117
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (584 KB)  

    The analytical solution of nonlinear power coupled equations involving three waves is given. The study reveals that the Raman gain saturation effect caused by the generation of the second Stokes has to be taken into consideration in light amplification by stimulated Raman scattering, though it can be ignored in spontaneous stimulated Raman scattering. It is also shown that it is advantageous to feed the fiber with a small low-order Stokes signal in amplifying the higher-order Stokes signal for easing the requirement of high pump power and long fiber length. A model to calculate higher-order Stokes radiation in low-loss optical fibers is presented View full abstract»

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  • Optical switch matrix with simplified N×N tree structure

    Publication Year: 1989 , Page(s): 1023 - 1028
    Cited by:  Papers (19)  |  Patents (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (488 KB)  

    Optical switch matrices with compact size and excellent crosstalk characteristics are discussed. Novel architectures for optical switch matrices are obtained by condensing the structure of N× N tree structure. 4×4 switches fabricated on LiNbO3 substrates are discussed View full abstract»

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  • Low-loss single-mode GaAs/AlGaAs miniature optical waveguides with straight and bending structures

    Publication Year: 1989 , Page(s): 1044 - 1054
    Cited by:  Papers (14)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (988 KB)  

    Low-loss single-mode GaAs/AlGaAs miniature optical waveguides fabricated for use in monolithically integrated optical circuits are discussed. The propagation characteristics of these waveguides with straight and S-bending structures have been investigated at wavelengths of 1.30 and 1.55 μm. The lowest propagation losses are estimated to be 0.58 dB/cm and 0.69 dB/cm at wavelengths of 1.30 and 1.55 μm, respectively. The total loss of an S-bending waveguide with a curvature radius of 2 mm and with a lateral displacement of 200 μm was 0.61 dB and 0.46 dB at wavelengths of 1.30 and 1.55 μm. The fabricated single-mode strip-loaded waveguides proved to be suitable for application of the semiconductor waveguide into monolithically integrated optical circuits View full abstract»

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  • Effect of temperature variations on optical waveguiding in GaAs multiple quantum wells

    Publication Year: 1989 , Page(s): 1130 - 1135
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (444 KB)  

    Photoluminescence and grating coupling techniques have been used to investigate the effect of temperature variations, about room temperature, on the optical waveguiding properties of GaAs/AlGaAs multiple-quantum-well structures. The modal properties are found to exhibit a large temperature dependence near the excitonic resonance and an equally strong dependence on detuning. From the simultaneous measurement of changes in refractive index and absorption over a 20 K temperature range, it is concluded that temperature variations should be kept to within several kelvin in quantum-well devices, if substantial detuning and dielectric shifts are to be avoided View full abstract»

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  • Zirconium fluoride glass fiber radiometer for low temperature measurements

    Publication Year: 1989 , Page(s): 1097 - 1100
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (252 KB)  

    Infrared signal transmission through zirconium fluoride glass fibers is used for noncontact temperature measurement. A radiometer was developed for temperature measurement between 30°C and 150°C. The dependence of the radiometer signal on the black-body temperature is presented. Experimental and theoretical results are compared View full abstract»

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  • Analysis of a 1060-nm Nd:SiO2 superfluorescent fiber laser

    Publication Year: 1989 , Page(s): 1009 - 1015
    Cited by:  Papers (13)  |  Patents (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (628 KB)  

    This CW source is made of a single-mode Nd-doped silica fiber end-pumped near 830 nm by a dye laser, with a thin high reflector placed against its input end for enhanced conversion. At the maximum output power of 13 mW, obtained with a pump power of 75 mW, the emission linewidth is still as broad as 16 nm, and the pump-to-signal conversion efficiency approaches the quantum limit of 78%. A simple model of superfluorescence in fibers, which relates the source emission characteristics to the fiber single-pass gain, is also presented. The single-pass gain, measured to be 0.27 dB/mW, was used to fit the model to the data. A good agreement is found for the nonlinear output versus input power curves of the sources, but it appears that the emission linewidth does not narrow with increasing pump power as fast as expected. Based on these results and an existing model of gain in single-mode fibers, it is suggested that simple improvements in the fiber design may reduce the pump requirement of this source and make laser-diode pumping possible View full abstract»

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  • Limits to normal incidence electroabsorption modulation in GaAs/(GaAl)As multiple quantum well diodes

    Publication Year: 1989 , Page(s): 1101 - 1108
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (676 KB)  

    The achievable electroabsorption modulation in GaAs/(GaAl)As normal-incidence multiple-quantum-well (MQW) diodes with 50-Å and 100-Å well widths is assessed. It is suggested that modulation performance should be characterized by the transmission change (T hi-Tlo) when the device is used in a simple source-modulator-detector communication link, whereas in more complex applications in which optical signals are merged, the contrast is more appropriate. For either transmission change or contrast there is an optimum number of wells which varies with design voltage, and this is used to calculate achievable modulation in the bias-absorbing mode for 100-Å and 50-Å well widths. The effects of improved smoothness at the interfaces and lower background dopings are investigated. It is found that a transmission change of 40% at 5 V is typical and does not improve significantly with better growth, while the achievable contrast depends strongly on the background doping. The results are compared with those of real modulators View full abstract»

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  • Lightwave systems with optical amplifiers

    Publication Year: 1989 , Page(s): 1071 - 1082
    Cited by:  Papers (303)  |  Patents (21)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (880 KB)  

    Fiber-optic communication systems using semiconductor laser amplifiers are investigated theoretically and experimentally. The noise and bit-error-rate characteristics of lightwave systems with optical amplifiers are calculated and the dependence of system performance on amplifier characteristics such as optical bandwidth, noise figure, gain, etc., is shown. Experimental results for both a 4-Gb/s optical preamplifier as well as coherent and direct detection systems with four inline amplifiers are presented View full abstract»

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  • New endless polarization control method using three fiber squeezers

    Publication Year: 1989 , Page(s): 1033 - 1043
    Cited by:  Papers (6)  |  Patents (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (724 KB)  

    In a polarization control system using two fiber squeezers of limited range, the reset causes momentary signal loss. To prevent this loss, an extra squeezer is required and a special controlling algorithm must be developed. A theoretical approach to the problem is presented resulting in such an algorithm. The presence of angular misalignment between the fiber squeezers is also discussed View full abstract»

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  • Electric-discharge sensor utilizing fluorescent optical fiber

    Publication Year: 1989 , Page(s): 1029 - 1032
    Cited by:  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (356 KB)  

    A fluorescent optical fiber made of Na2O-CaO-5SiO2 glass doped with Sm3+ which absorbs light and then emits a longer-wavelength light is discussed. The sensor can capture light from a light source even though its aperture is not directed toward the source. This property is useful for detecting light from an unfixed light source, such as in cases of electric discharge. An electric-discharge sensor utilizing this fiber has been constructed and successfully applied to the detection of electric discharges in a test device similar to a section of a gas-insulated substation (GIS) 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.

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Meet Our Editors

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