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Lightwave Technology, Journal of

Issue 2 • Date Feb 2001

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Displaying Results 1 - 18 of 18
  • Real-time location of multiple time-varying strain disturbances, acting over a 40-km fiber section, using a novel dual-Sagnac interferometer

    Publication Year: 2001 , Page(s): 205 - 213
    Cited by:  Papers (25)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (216 KB)  

    Updated results using a novel sensing architecture based on a Sagnac interferometer are presented and, for the first time, real-time separation and positioning of multiple disturbances has been realized. A 40-km long dual-Sagnac sensor was formed by spectral slicing of light from a single, broad-band erbium-doped-fiber super-luminescent source and wavelength division multiplexed (WDM) routing around the loop to form an inherently low loss system. Independent active phase biasing of each Sagnac was employed, allowing the use of a single optical detector. The effects of residual optical cross talk between the two Sagnacs has been accurately modeled, allowing resulting errors to be corrected. The new system has capability for narrow-band fast Fourier transform (FFT) analysis of detected disturbance signals, and hence their separation in the frequency domain. For audio-frequency excitation, an average positional resolution of 100 m over a 40-km length was achieved with a postdetection signal processing bandwidth of 8 Hz View full abstract»

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  • Multi-bit rate passive double star system using time-unit packet

    Publication Year: 2001 , Page(s): 150 - 158
    Cited by:  Papers (3)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (356 KB)  

    This paper proposes a new optical access network system; the multi-bit rate passive double star (multi-bit rate-PDS) system. The multi-bit rate-PDS system passes multi-bit rate data streams between the optical service unit (OSU) and the optical network unit (ONU) using the time-unit packet (TP). This simplifies the provision of user flexibility and provides very economical network services to users. We describe the architecture and frame structure of the multi-bit rate-PDS system, and elaborate the advantage of its user accommodation. Furthermore, we show how to decide the multiplexed bit rates in the multi-bit rate-PDS system and how to realize the receiver circuit for multi-bit rate data packet streams View full abstract»

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  • Analysis of reflectivity for a beveled corner mirror in semiconductor ring lasers

    Publication Year: 2001 , Page(s): 222 - 229
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (216 KB)  

    A semiconductor ring laser is expected to be used as a tiny ring laser gyro with low power consumption, which is suitable for mobile systems. However, its corner mirrors may be beveled due to its fabrication processes. Therefore, in this paper, reflectivities of beveled corner mirrors in the semiconductor ring laser are examined. In the analysis here, a guided fundamental mode is expanded into plane waves, and thus vertical confinement of the guided mode is completely incorporated. It is revealed that there is an optimum guiding layer thickness of approximately 0.3 μm to minimize mirror losses in the beveled mirrors. Also, facet reflectivities of equilateral n-polygon shaped ring lasers with beveled mirrors are studied, and it is found that a large n leads to a low threshold current View full abstract»

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  • Effects of crosstalk in demultiplexers for photonic analog-to-digital converters

    Publication Year: 2001 , Page(s): 230 - 236
    Cited by:  Papers (14)  |  Patents (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (132 KB)  

    Time interleaving of samples digitized by a parallel array of analog-to-digital (A/D) converters provides a means of increasing the sampling rate beyond that possible with a single A/D converter. For time-interleaved photonic A/D converters, optical demultiplexers can be used to advantage. Both time-division and wavelength-division demultiplexers must yield low crosstalk between the parallel output channels in order to yield accurate A/D conversion. An analysis predicts the level and form of the resulting errors. The analytical results compare well with experiment View full abstract»

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  • Redundancy strategies for a high splitting optically amplified passive optical network

    Publication Year: 2001 , Page(s): 137 - 149
    Cited by:  Papers (21)  |  Patents (26)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (784 KB)  

    High splitting, optically amplified, passive optical networks (SuperPONs) are investigated in terms of redundancy provision and protection mechanisms. Options for redundancy, including the important special case of dual homing, are detailed, and it is determined as to which of these options (duplication of the feeder and first distribution section, and N+1 protection of the optical amplifiers in the amplified splitter) would be required to be provided to all attached users to facilitate appropriate availability of the basic telephony service. The distributed amplified splitter dual homing solution is found to outperform the single amplified splitter solution in terms of its survivability. The protection mechanisms necessary to automatically switch to the redundant provision are discussed and it is seen that with the aid of suitable regular precautionary procedures protection switching can generally be provided rapidly (<50 ms). Finally, an availability, and cost versus availability, study confirms the aforementioned redundancy assessment for fiber-to-the-home (FTTH) implementations, but shows fiber-to-the-curb (FTTC) as needing additional redundancy View full abstract»

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  • Waveform distortion due to stimulated Raman scattering in wide-band WDM transmission systems

    Publication Year: 2001 , Page(s): 159 - 171
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (328 KB)  

    The influence of stimulated Raman scattering (SRS) taking into account the random modulation and the walk-off effect on wide-band wavelength division multiplexing (WDM) transmission systems are studied theoretically. First, it is shown that power depletion due to SRS can be separated into average power loss and waveform distortion. The waveform distortion is evaluated for various types of pulse shapes and fibers, and simple equations for evaluating the waveform distortion due to SRS are derived. These equations can be easily applied for designing wide-band WDM transmission systems from the viewpoint of the SRS waveform distortion. We also compare results obtained from our method with those from the split-step Fourier method, and confirm validity of our method. Our method should be useful in the design of wide-band WDM transmission systems, in which SRS is expected to be a serious limitation View full abstract»

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  • Failure mechanism of avalanche photodiodes in the presence of water vapor

    Publication Year: 2001 , Page(s): 252 - 265
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (236 KB)  

    Lower cost optoelectronic modules (transmitters and receivers) could be produced if components could operate reliably in a nonhermetic package. Experiments (operation in humid ambient as a function of temperature, relative humidity (RH), and voltage) were carried out on InP-based avalanche photodiodes (APDs). The objectives were to reveal any moisture-related failure modes, to understand the failure mechanisms, to determine the relevant acceleration factors, and to propose design or material modifications to prevent the failures. Leakage current vs. time was measured for nine cells of 20 devices each. All devices were examined by optical microscopy, and representative samples were studied by scanning electron microscopy. A failure mechanism related to corrosion of the passivating SiN and the underlying semiconductor was identified. Based on the voltage and RH dependence of the degradation rate, a model for the failure process was developed. The mechanism involves RH-dependent transport of charge across the surface of the SiN and Poole-Frenkel current flow through the SiN. This process eventually produces a short circuit View full abstract»

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  • Aberration theory of arrayed waveguide grating

    Publication Year: 2001 , Page(s): 279 - 284
    Cited by:  Papers (6)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (156 KB)  

    The general aberration theory of arrayed waveguide grating (AWG) is proposed in this paper. The derived conclusions can be applied to any symmetrical AWGs. With the aberration theory, the spectral response can be optimized. Some performances of an AWG, for example, crosstalk and channel number, are expected to be improved by reducing the aberrations. A common AWG with the Rowland geometry has low aberrations for the absence of the second-order aberration. To further reduce the aberrations, nonstandard AWGs are considered. The AWG based on three stigmatic points is proved to have a perfect performance View full abstract»

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  • Evaluation of fiber slippage and core-axis offset distribution in optical fiber mechanical splice

    Publication Year: 2001 , Page(s): 195 - 204
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (208 KB)  

    When fibers are clamped together between two fiber-holding substrates and butt-joined, variations in the fabrication accuracy of both fibers and substrates usually result in the fibers experiencing different clamping forces. If, for example, a couple of fibers are undersized or the substrate surface is deformed, the clamping force will be insufficient in places. In such cases, the fibers will leave only faint linear marks on the substrate surface and may slip when internal or external forces act on them. By using Hertz's theory, we converted the resistance force to fiber slippage into a line width curve for the onset of slippage. We spliced single fibers with known outer diameters to examine the influence of line width on slippage. We performed a fiber retention test, a temperature cycling test to determine any insertion loss change, and observed the linear marks with a microscope. No fiber slippage occurred when the width of the linear marks was outside the line width curve. Furthermore, we calculated the core-axis offset probability distribution when the optical fiber axes were aligned View full abstract»

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  • Magnetooptical waveguides with polarization-independent nonreciprocal phase shift

    Publication Year: 2001 , Page(s): 214 - 221
    Cited by:  Papers (11)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (212 KB)  

    Magnetooptical waveguides having nonreciprocal phase shift for both TE and TM modes can be prepared by properly adjusting the spatial variation of the Faraday rotation. Such waveguides are attractive to realize optical isolators. We investigate four concepts of magnetooptical waveguides which yield equal nonreciprocal phase shifts for the fundamental TE and TM modes. A polarization-independent Mach-Zehnder-type integrated optical isolator is presented. All the calculations are performed using material parameters typical for garnet films View full abstract»

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  • Digitally linearized wide-band photonic link

    Publication Year: 2001 , Page(s): 172 - 179
    Cited by:  Papers (8)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (128 KB)  

    A photonic analog-to-digital (A/D) link with third-order distortion suppression is proposed and demonstrated. Experimental results with single-and two-tone analog input signals and a one giga-sample per second (GSPS) photonic A/D system with 500-MHz instantaneous bandwidth are presented. The application of a simple time-domain linearization scheme results in distortion suppression approaching 30 dB and allows optical modulation depths over 80% View full abstract»

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  • On differential group-delay statistics for polarization-mode dispersion emulators

    Publication Year: 2001 , Page(s): 285 - 290
    Cited by:  Papers (19)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (120 KB)  

    We present a theoretical study on differential group-delay (DGD) statistics for common models of polarization-mode dispersion (PMD) emulators. Our study will show, for the first time to our knowledge, that the statistics for the length of the PMD vector will not necessarily behave as a system with three degrees of freedom when the number of sections in the PMD emulator is low. However, when the number of sections is large, i.e., 10 sections or more, the length of the PMD vector is well described with a system with three degrees of freedom View full abstract»

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  • Gain enhancement in cascaded fiber parametric amplifier with quasi-phase matching: theory and experiment

    Publication Year: 2001 , Page(s): 247 - 251
    Cited by:  Papers (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (108 KB)  

    We report a novel gain enhancement scheme for fiber-optic parametric amplifiers utilizing cascaded amplification and quasi-phase matching (QPM). The theory and method of QPM for four-wave mixing (FWM) are developed for the first time to our knowledge. In experimental implementations of the theory, we achieve >12 dB gain improvement in a three-stage dispersion-shifted (DS) fiber parametric amplifier. A 16-dB overall gain is obtained with 11 nm separation between zero-dispersion wavelength and pump wavelength. The experimental results show good agreement with theory and simulations. The influence of QPM on spectral characteristics of parametric gain is investigated with numerical simulations View full abstract»

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  • Trellis-coded asynchronous optical CDMA systems

    Publication Year: 2001 , Page(s): 180 - 185
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (128 KB)  

    Since optical code division multiple access (CDMA) is an interference-limited system, we propose a system employing trellis-coded scheme and double optical hardlimiters (TC-DHLs) to alleviate the adverse impact of multiple access interference. For asynchronous transmission, optical orthogonal code (OOC) is utilized as signature sequence. System performance is evaluated under the chip synchronous case among different users, and thermal noise, avalanche photodiode (APD) noise, and interference are taken into consideration. Numerical results show that our proposed scheme can further reduce the error floor up to several orders over systems that using only double optical hardlimiters View full abstract»

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  • Analysis of optical DEMUX characteristics based on four-wave mixing in semiconductor optical amplifiers

    Publication Year: 2001 , Page(s): 237 - 246
    Cited by:  Papers (9)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (204 KB)  

    We have analyzed the basic characteristics of all-optical demultiplexing (DEMUX) based on four-wave mixing (FWM) in semiconductor optical amplifiers (SOAs) by solving a modified nonlinear Schrodinger equation by the finite-difference beam propagation method. Amplified spontaneous emission noise was not included in our model. The optimum pump pulsewidth for obtaining the high ON-OFF ratio is 1~3 ps for 1 ps, 250 Gb/s probe pulses. The shorter limit of the pulsewidth is due to detuning between the pump and probe frequencies, which is determined by the gain bandwidth of the SOA. In order to achieve faster DEMUX operation, an SOA with broader gain bandwidth is required. We also simulated pattern effects in the FWM signal. Power fluctuation in the FWM signal can be reduced by using a strong energy pump pulse and/or weak energy probe pulse. The energy fluctuation of the FWM signal decreases to less than 1% for a 30-bit, 250-Gb/s input probe pulse train with a pulse energy of 0.01 pJ. This small fluctuation should not disturb DEMUX operation. We have also examined DEMUX from time multiplexed signals by repetitive pump pulses. Strong energy pump pulses decrease the FWM signal intensity. However, there is no pattern effect due to gain saturation because the pump pulses are injected continuously View full abstract»

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  • High-speed monolithic silicon photoreceivers on high resistivity and SOI substrates

    Publication Year: 2001 , Page(s): 272 - 278
    Cited by:  Papers (21)  |  Patents (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (196 KB)  

    We compare monolithic silicon optical receivers fabricated on high resistivity and silicon-on-insulator (SOI) substrates. Each receiver consisted of a lateral p-i-n photodiode and an NMOS transimpedance preamplifier. At a drain voltage (VDD) of 3.5 V, a photodiode voltage (VPD) of 30 V, and a wavelength of 850 nm, the high resistivity receiver exhibited sensitivities of -31.9 dBm at 622 Mb/s and -23.2 dBm at the maximum operating speed of 1.0 Gb/s. At VDD =5 V and VPD=20 V, the sensitivity of the SOI receiver was -26.1 dBm at 622 Mb/s, -20.2 dBm at 1.0 Gb/s and -12.2 dBm at the maximum speed of 2.0 Gb/s. Single supply operation at 5 V and 3 V was also demonstrated for the SOI receiver. Methods for extending the speed and improving the sensitivity characteristics in more advanced technologies with lower supply voltages are discussed View full abstract»

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  • Ultrashort optical pulse transmission characteristics of vertically coupled microring resonator add/drop filter

    Publication Year: 2001 , Page(s): 266 - 271
    Cited by:  Papers (5)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (132 KB)  

    The ultrashort optical pulse transmission characteristics of a vertically coupled microring resonator (VCMRR) filter were measured at 1.55 μm wavelength, and the transmission capacity per channel was evaluated. The pulsewidth at the output was measured to be 3.4 ps, when 1.2 ps input pulse with a sech pulse shape from a fiber laser was incident on the microring resonator filter with a fullwidth at half-maximum (FWHM) of 0.75 nm (94 GHz). From this result, the maximum transmission capacity of the filter was estimated to be approximately 50 Gb/s. The pulse broadening through the filter was theoretically analyzed, and it was confirmed that the pulse broadening evaluated from the bandwidth of the filter spectrum response were in good agreement with the measured results View full abstract»

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  • Perfect difference codes for synchronous fiber-optic CDMA communication systems

    Publication Year: 2001 , Page(s): 186 - 194
    Cited by:  Papers (30)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (212 KB)  

    In this paper, we introduce the perfect difference sets and propose a synchronous fiber-optic code-division multiple-access system (CDMA) using these sets to generate the signature codes. Two interesting properties of these codes are discussed: (1) any two different codes are cyclic-shifted with each other; and (2) the cross correlation between any two different codes is exactly one. Thus, we may treat these codes as quasi-orthogonal codes. Using the first property of these codes, we can simplify design of the transmitter. In the receiver, we can use the second property to effectively eliminate the multiple-user interference (MUI) without reducing the number of usable codes. Based on the proposed transmitter and receiver, the system performance is derived. The numerical examples reveal that the proposed system can provide reliable communication even under heavy load. We believe that the proposed system using perfect difference codes outperforms any other synchronous fiber-optic CDMA systems 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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Editor-in-Chief
Peter J. Winzer
Alcatel-Lucent Bell Labs