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Lightwave Technology, Journal of

Issue 9 • Date Sept. 1990

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Displaying Results 1 - 25 of 26
  • Table of contents - Journal of Lightwave Technology

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    Freely Available from IEEE
  • Silicon bipolar integrated circuits for multigigabit-per-second lightwave communications

    Page(s): 1371 - 1378
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    Recent results on silicon bipolar ICs for lightwave communications in the multigigabits-per second (Gb/s) range are presented. These state-of-the-art results demonstrate the inherent speed difference between the different types of basic circuits. With the fastest ones (multiplexing and demultiplexing), bit rates above 10 Gb/s are achieved, even with production technologies. The technologies, as well as circuit and design principles to achieve such high operating speeds, are discussed, and some experimental examples are described in more detail. Moreover, the high-speed potential of present 1-μm silicon bipolar technologies is demonstrated by the simulation of carefully optimized communication ICs. With most of the basic circuits, bit rates above 10 Gb/s, and in some cases above 20 Gb/s, are achievable View full abstract»

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  • The effect of four-wave mixing in fibers on optical frequency-division multiplexed systems

    Page(s): 1402 - 1408
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    The limiting effects of four-wave mixing on optical frequency-division multiplexing (OFDM) systems are described. The optical nonlinearity in a single-mode fiber imposes a fundamental limitation on the capacity of optical frequency-division multiplexed systems. In particular, four-wave mixing (FWM) crosstalk may severely degrade the system performance when the fiber input powers are large and/or the channel spacing is too small. Theoretical and experimental results of the effects of FWM in OFDM systems are presented. The theoretical results demonstrate the dependence of FWM on various system parameters. An analysis of FWM in both undirectional and bidirectional transmission systems is included. The receiver sensitivity degradation from FWM crosstalk is measured in a 16-channel coherent system View full abstract»

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  • Correlation of the absence of the 630-nm band with the intensity of photobleaching of ionizing radiation-induced loss in undoped silica fibers at -55°C

    Page(s): 1284 - 1288
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    A correlation is reported between the intensity of the 630-nm drawing-induced band in undoped silica-core fibers and the abatement of photobleaching by 865-nm light of ionizing radiation-induced loss at 865 nm following gamma-ray exposure at -55°C. At -55°C, undoped silica-core fibers, both low- and high-OH containing, and polymer and glass clad, show intense, 865-nm photostimulated recovery of ionizing radiation-induced loss near 865 nm when the 630-nm drawing-induced band is weak or not present. This photobleaching behavior contributed significantly toward the low induced loss demonstrated by these fibers during exposure, and their faster recovery after exposure at low temperature View full abstract»

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  • High-speed optical modulator for application in instrumentation

    Page(s): 1363 - 1370
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    The design and characterization of the first integrated optic modulator for a commercial instrument application are described. Alternative forms of modulation, including direct laser current modulation and optical heterodyne techniques, are reviewed for the application, which requires modulation to 20 GHz. The advantages of an integrated optic modulator fabricated using titanium in-diffused lithium niobate are discussed. Performance tradeoffs between x-cut and z-cut LiNbO3 including bandwidth, modulation efficiency, bias point stability, and acoustic resonances are detailed. The x-cut device is found to give the best overall performance for this instrument application. Device reliability and testing, including temperature cycling, humidity, electrostatic discharge, mechanical shock, and vibration are described for complete packaged and pigtailed devices View full abstract»

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  • A novel flip-chip interconnection technique using solder bumps for high-speed photoreceivers

    Page(s): 1323 - 1327
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    A flip-chip interconnection technique using small solder bumps instead of conventional wire bonding for high-speed broadband photoreceivers is described. The technique achieves interconnection with low parasitic elements, no damage to devices, and easy assembly. A photoreceiver composed of a broadband p-i-n photodiode and a laser-speed GaAS metal-semiconductor field-effect transistor (MESFET) preamplifier connected using solder bumps that are about 26 μm in diameter, with a frequency response of over 22 GHz at 1.55 μm, is demonstrated. This confirms the effectiveness of the solder bump interconnection technique for future high-speed broadband optical modules View full abstract»

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  • Planar flexible fiber-optic acoustic sensors

    Page(s): 1298 - 1303
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    The acoustic sensitivity of optical fibers is considered analytically. High sensitivity is obtained with low bulk modulus, very thick polymeric coatings. The fiber coatings play an important role in determining the fiber acoustic sensitivity. The very thick coating limit is realized by embedding optical fibers in an appropriate elastomer (polyurethane). A planar flexible fiber-optic interferometric acoustic sensor is developed by wrapping optimized single-mode fibers in a planar spiral form, and then embedding the fiber in a thin polyurethane layer. The acoustic sensitivity of the sensor is found to be high, and frequency (0.2-2.5 kHz) and static pressure independent. The sensor is found to be compatible with water, and is compared favorably to that of a planar polyvinylidene fluoride sensor of similar geometry View full abstract»

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  • Noninvasive switchable acousto-optic taps for optical fiber

    Page(s): 1304 - 1312
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    Two novel tap designs are demonstrated based on phase-matched coupling from the fundamental mode of a fiber to a higher-order core-guided or cladding-guided mode through the acoustooptic effect. The acoustic waves are coupled to the fiber using a Hertzian (deformed surface-to-surface) contact with a grooved transducer substrate. The first tap consists of a two-mode fiber coupler in conjunction with a microbend tap. The coupler converts approximately 5% of the fundamental mode power to the second-order mode. At the microbend tap, the higher-order mode is preferentially radiated from the fiber. The second tap uses a similar mode-coupling mechanism to convert a fraction of the fundamental mode power into a cladding-guided mode in a single-mode fiber View full abstract»

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  • Fiber-optic sensors using high-resolution optical time domain instrumentation systems

    Page(s): 1273 - 1277
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    Applications of high-resolution optical time domain instrumentation systems for the sensing of strain and temperature using optical fibers are discussed. It is demonstrated that optical fiber segmentation using partially reflective splices allows measurement of localized fiber parameters. In particular, localized fiber strain is measured using specially designed in-line reflectors spaced less than 1 m apart. It is shown that the time domain response to temperature variations can be improved by using silicone fluid-filled fibers with thermooptic coefficients as high as -4.2×10-4/°C. The applications of fiber-optic reentrant loops to further improve on system-imposed measurement resolution are discussed. It is shown that recirculation of the probing optical pulse through the sensing fiber yields an effective increase in fiber interaction length View full abstract»

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  • Low-noise current optoelectronic integrated receiver with internal equalizer for gigabit-per-second long-wavelength optical communications

    Page(s): 1328 - 1333
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    An equalizer, which is essential in order to improve the sensitivity of receiver optoelectronic integrated circuits (OEICs) at a gigabit-per-second data rate, has been monolithically integrated on an InP substrate with a p-i-n photodiode and a high-impedance high-electron-mobility-transistor (HEMT) amplifier. The receiver operated up to 1.6 Gb/s and showed low noise current characteristics. The minimum noise current is less than 4 pA/√Hz. The sensitivity calculated from the noise current characteristics is -28.4 dBm for 1.6-Gb/s signals. The receiver chip, which was assembled on a ceramic mount, exhibited a sensitivity of -30.4 dBm at 1.2 Gb/s and 1.3-μm wavelength. The performance is as good as those of receiver OEICs with an external equalizer and sufficient for practical use in gigabit-per-second optical communication system View full abstract»

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  • Narrow-band directional couplers made of dissimilar single-mode fibers with different cladding refractive indexes

    Page(s): 1289 - 1291
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    A wavelength-selective directional coupler, consisting of two polished single-mode fibers with different cladding refractive indexed, has been fabricated. In contrast to symmetrical couplers, where the power transfer characteristic is a quasiperiodic function of the wavelength, couplers made of dissimilar fibers show a true bandpass-filter characteristic. They consist of two fibers with different core diameters and refractive-index profiles, having the same cladding refractive index. The parameters of the fibers must be chosen in such a way that if their propagation constants β1, β2 are plotted over the wavelength, the curves intersect at a cross-over wavelength λ0 equal to the center wavelength of the filter. The 3-dB bandwidth of the coupler's power transfer characteristic is 13.6 nm, the best value achieved up to now View full abstract»

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  • 16×16 optical-fiber crossbar switch operating at 0.85 μm

    Page(s): 1334 - 1342
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    An optical-fiber crossbar switch has been constructed using fully integrated GaAs optoelectronic receivers, custom monolithic GaAs laser drivers, and an electrical 32×32 silicon crossbar switch. 470 Mb/s operation has been achieved with a bit error rate of less than 10-12. The approach uses a monolithic GaAs optoelectronic integrated receiver to convert optical signals into electrical signals that are fed into an Si 32×32 electronic crossbar switch. The switch outputs are used to drive laser transmitters consisting of a custom monolithic GaAs IC laser driver and a 0.85 μm GaAs/AlGaAs laser. The system could be reconfigured in 1 μm, limited by the control logic, with the switch chip capable of reconfiguration in 35 ns. No errors are induced by reconfiguration View full abstract»

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  • An optical bit-rate flexible transmission system with 5-Tb/s-km capacity employing multiple in-line erbium-doped fiber amplifiers

    Page(s): 1387 - 1395
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    An optical bit-rate flexible transmission system using erbium-doped fiber amplifiers (EDFAs) is proposed, and the system design is discussed. An optical bit-rate flexible system using multiple in-line erbium-doped fiber amplifiers has produced a regenerative repeater spacing of 505 km at 10 Gb/s and 523 km at 5 Gb/s for direct-detection systems. This system proves that an optical bit-rate flexible system with a transmission capacity of 5.05 Tb/s-km can be feasibly constructed. System capacity is clarified both theoretically and experimentally. The power penalties involved are discussed. The related optical and electrical circuits proved operational above 10 Gb/s. The 523 km at 5 Gb/s and 505 km at 10 Gb/s transmission experiments successfully demonstrated that EDFAs effectively enhance a system's transmission capacity View full abstract»

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  • Extremely low threshold current operation in 1.5-μm MQW-DFB laser diodes with semi-insulating InP current blocking region

    Page(s): 1343 - 1349
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    Threshold current operation of 1.5 mA was achieved for 1.5-μm multiple-quantum-well distributed feedback (MQW-DFB) laser diodes (LDs) with semi-insulating current blocking layers entirely grown by metalorganic vapor phase epitaxy (MOVPE). Such low-threshold current is attained by reducing leakage current and mirror loss in the laser structure. The required bias current for achieving several gigahertz bandwidth is markedly reduced due to the enhanced differential gain and low threshold current. Due to the reduced lasing delay time in such low threshold LDs, up to 5-GHz zero-bias current modulation, with a clear eye opening, is successfully demonstrated View full abstract»

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  • Performance of directly modulated DFB lasers in 10-Gb/s ASK, FSK, and DPSK lightwave systems

    Page(s): 1379 - 1386
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    A comparison is presented of the performance of amplitude-shift-keying (ASK), frequency-shift keying (FSK), and differential-phase-shift-keying (DPSK) lightwave systems which operate at 10 Gb/s with directly modulated 1550-nm distributed feedback (DFB) laser transmitters and conventional 1310-nm dispersion-optimized fiber. Computer modeling techniques were used to accurately simulate the amplitude modulation response and the frequency modulation response of DBF lasers. The system performance is evaluated from simulated eye patterns for both direct and heterodyne detection. With the narrow-optical spectral widths of these signal formats, fiber chromatic dispersion limits up to 70 km were obtained for transmission at 1550-nm using conventional 1310-nm optimized fiber View full abstract»

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  • Efficient power coupling from a 980-nm, broad-area laser to a single-mode fiber using a wedge-shaped fiber endface

    Page(s): 1313 - 1318
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    A theoretical and experimental study of an efficient technique for coupling a broad-area laser to a single-mode fiber without the use of bulk optical components was carried out. The technique uses a wedge-shaped fiber endface to approximate a cylindrical lens action to correct for the phase mismatch between the curved laser beam wavefront and the planar fiber beam. A theoretical formula for the coupling efficiency in the absence of both angular and transverse misalignments is derived. By optimizing the wedge angle and the axial separation between the laser facet and the fiber endface, a maximum coupling efficiency of 47%, compared to 20% for the square endface, achieved, resulting in 15.2 mW of power in the single-mode fiber. The fabrication process consists of a simple polishing procedure requiring a wedge-shaped polishing tool and is highly reproducible View full abstract»

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  • Gain characteristics of ER3+ doped fiber with a quasi-confined structure

    Page(s): 1319 - 1322
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    The fiber-structure dependence of the gain characteristics of Er 3+ doped fibers pumped at 1.48 μm is analyzed. The optimum V value is derived theoretically and experimentally. For step-index fibers, the optimum V value is 1.6, which is smaller than that needed to minimize spot size. The fiber with a small V value enjoys a large Er3+ confinement effect. For laser diode pumping, an efficiency of 1.7 dB/mW is achieved at 1.536 μm. The bending characteristics are also described View full abstract»

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  • First measurement of strain distribution along field-installed optical fibers using Brillouin spectroscopy

    Page(s): 1269 - 1272
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    Strain distributions along optical fibers in a 1.3-km-long cable before and after installation are measured using Brillouin optical-fiber time domain analysis. The residual strains in the installed optical fibers were found to vary from zero to 0.07%, depending on the conduit configuration and installation procedure. Strain distribution measurements were carried out on a 24-fiber slotted-core type single-mode optical fiber cable for 1.55-μm-wavelength transmission, whose length, outer diameter, and weight were 1.3 km, 14 mm, and 0.18 kg/m, respectively. No clear relation between strain distributions and the fiber configuration in the test cable are found View full abstract»

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  • Broad-band high-silica optical waveguide star coupler with asymmetric directional couplers

    Page(s): 1292 - 1297
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    A broadband optical waveguide star coupler with asymmetric directional couplers is proposed. A coupling or splitting ratio of the coupler is flattened with respect to wavelength by choosing appropriate values for Δβ and complete power transfer length. The wavelength characteristics of uniform and alternating Δθb directional couplers are investigated, and their broadband operation is shown theoretically. To demonstrate the feasibility of the new proposal, 8×8 star couplers composed of such asymmetric directional couplers are fabricated by using high-silica waveguides on a silicon chip. A star coupler composed of asymmetric directional couplers exhibited 2-dB loss variation in the wavelength range of 1.3-1.55 μm, and this value was almost one fourth of that of a star coupler composed of symmetric directional couplers View full abstract»

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  • Fiber diameter measurements and their calibration

    Page(s): 1259 - 1268
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    Seeks to establish a high level of confidence in fiber cladding diameter measurement by the use of three methods: white light interferometry, mechanical contact, and image inverting microscopy. Calibration with transfer fibers is considered unattractive because of the difficulty of maintaining the calibrated cleaved end. The uncertainties involved in calibrating other methods are investigated, namely image shear, grey scale digitization, and refracted near field, using chromium on glass circular patterns or lines. Their use is found to give consistent results with uncertainties not exceeding ±0.15 μm. Experimental arrangements are discussed. There are some sources of measurement error, but these can be overcome so that measurements of fiber diameter with an uncertainty of less than ±0.15 μm look feasible using chromium on glass calibration standards View full abstract»

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  • Recent progress in high-power GaInAsP lasers

    Page(s): 1350 - 1356
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    The high-power characteristics (180 mW, CW) and reliability of 1.48-μm Fabry-Perot laser diodes are studied for V-grooved inner stripe lasers grown by liquid phase epitaxy on p-type substrate (VIPS lasers). Their potential as pumping sources of erbium-doped fiber amplifiers is reported, and their power saturation behavior at several wavelengths is discussed. Aging tests were conducted at high power levels of up to 75% CW maximum power (Pmax) at -40, 25, and 70°C. The ageing power reached more than 200 mW at -40°C; however, no significant degradation was observed at any temperature level. At 25°C the median lifetime is estimated to be 60000 h, and stable operation is observed at the highest aging level (to date) of 200 mW for up to 1600 h at -40°C View full abstract»

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  • A 1320-nm experimental optical phase-locked loop: performance investigation and PSK homodyne experiments at 140 Mb/s and 2 Gb/s

    Page(s): 1414 - 1425
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    An experimental balanced optical phase-locked loop was constructed using two 1320 nm diode-laser pumped miniature Nd:YAG lasers. With a natural frequency of 13.5 kHz and a damping factor of 0.6, the loop phase error is less than 13.° when the received signal power P s is -65 dBm. For signal powers Ps⩾-62 dBm, the phase error is 0.3°, and is virtually independent of the signal power. When the natural frequency is 74 kHz, the damping factor is 0.03, and the DC gain is 68 MHz, the loop exhibits a chaotic behavior: it maintains the frequency lock, but not the phase lock. Using a phase-locked loop, phase-shift keying homodyne transmission is demonstrated at 140 Mb/S and 2 single-moded fiber is -62.8 dBm, corresponding to 25 photons/b View full abstract»

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  • Optical amplifier noise figure in a coherent optical transmission system

    Page(s): 1409 - 1413
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    Two important aspects of optical amplifier noise figure as measured with a heterodyne detection receiver are investigated. First, differential mode gain will result in polarization-dependent degradation of the perceived amplifier noise figure, even when the noise figures for the TE and TM modes of the amplifier are the same. For a differential mode gain of 7.5 dB the noise figure degradation can be as large as 3 dB, and experimental data is reported in good agreement with theoretical predictions. Secondly, the first experimental demonstration of the use of image-rejection techniques to improve the sensitivity of a heterodyne receiver limited by beat noise between the local oscillator and amplified spontaneous emission is discussed View full abstract»

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  • 5-Gb/s performance of integrated light source consisting of λ/4-shifted DFB laser and EA modulator with SI InP BH structure

    Page(s): 1357 - 1362
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    The fabrication process and characteristics, including 5-Gb/s transmission, of an integrated light source consisting of a λ/4-shifted distributed feedback laser and an electroabsorption (EA) modulator are discussed. By introducing a semi-insulating (SI) InP on the butt-joint region, both the large electrical isolation resistance (>10 MΩ) between the laser and the modulator and a high optical coupling efficiency (>80%) between them are achieved. A typical threshold current was 50-70 mA, and single-mode operation at 1.576 μm was maintained up to 5.5-mW output power. The modulation voltage to swing between 90% transmission and 10% transmission was 6.2-12 V, depending on the modulator length in the range 1000-400 μm. The 3-dB bandwidth is 7.7 GHz and a linewidth enhancement factor (α) of 0.9 is estimated from the sideband-to-carrier ratio of the spectra View full abstract»

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  • A 100-channel optical FDM transmission/distribution at 622 Mb/s over 50 km

    Page(s): 1396 - 1401
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    A 100-channel optical frequency-division multiplexing (FDM) transmission/distribution experiment at 622 Mb/s is demonstrated for a fiber length of 50 km. The feasibility of a polarization-insensitive waveguide frequency selection switch for 10-GHz intervals and a frequency-shift-keying (FSK) direct-detection scheme employing a Mach-Zehnder filter is verified. The demodulation circuit employs a Mach-Zehnder filter and a balanced receiver, which utilizes optical power more efficiently than the Fabry-Perot filter. No receiver sensitivity degradation is observed due to interchannel crosstalk of the 128-channel tunable waveguide frequency selection switch (FS-SW) or fiber four-wave mixing for transmissions over a 50-km-long nondispersion-shifted (NDS) fiber and a 26-km-long dispersion-shifted (DS) fiber 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