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Lightwave Technology, Journal of

Issue 3 • Date Mar 1999

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Displaying Results 1 - 18 of 18
  • Alternating cascade of spectrally different erbium-doped fiber amplifiers for link-loss-insensitive long-haul WDM transmission

    Publication Year: 1999 , Page(s): 434 - 444
    Cited by:  Papers (1)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (232 KB)  

    This paper numerically investigates a cascade of erbium-doped fiber amplifiers (EDFAs) with different spectral characteristics in an alternating scheme. Thereby, in a transmission band with appropriate spectral properties (1544-1550 nm), the sensitivity of optically amplified long-haul WDM transmission links on the span loss between amplifiers can be reduced to that of single-channel systems. This may be as much as an order of magnitude better than in a traditional, nonalternating, WDM cascade. While passive bandpass filters are necessary to control the wavelength range, there is no need for any active gain equalization or feed-back control. The gain in the cascade can also to some extent automatically adjust to compensate for a spectral tilt of the loss. We show that the range of this automatic loss tilt compensation can be increased, up to three times its original value, by enhancing the difference of the net gain that signals at different wavelengths experience in EDFAs of different types View full abstract»

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  • Effects of self-phase modulation on sub-500 fs pulse transmission over dispersion compensated fiber links

    Publication Year: 1999 , Page(s): 452 - 461
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB)  

    The effects of nonlinearity on sub-500 fs pulse transmission over dispersion compensated fiber links using dispersion compensating fiber technique are investigated numerically and experimentally. The pulse broadening and recompression ratio of the 2.5-km transmission link is over 300. The postcompensated and precompensated links are compared when the input pulse energy ranges from 15 to 159 pJ. At high powers, self-phase modulation (SPM) degrades the pulse recompression process and provides an upper bound on the transmitted pulse energy. The SPM effect is stronger in the postcompensated link than in the precompensated link. A dramatic spectral narrowing effect was observed in the postcompensated link. Pulse energies up to tens of pJ, consistent with high quality communication, should be possible for a sub-500 fs pulse in such dispersion compensated links View full abstract»

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  • Integrated optical device with second-harmonic generator, electrooptic lens, and electrooptic scanner in LiTaO3

    Publication Year: 1999 , Page(s): 462 - 465
    Cited by:  Papers (16)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (100 KB)  

    This paper reports the first demonstration of an integrated optical device in z-cut LiTaO3 that contains the following three functional parts: a quasiphase-matched second-harmonic generation (SHG) grating, an electrooptic (EO) lens, and an electrooptic scanner. The SHG device consists of channel waveguides passing through periodic domain-inverted gratings. The frequency of the input infrared (IR) light at 864 nm was doubled into blue light at 432 nm. A stack of EO lenses was used to collimate the light from the channel waveguide. The measured beam size at the output facet for various applied voltages to the lenses agreed with simulation. After collimation, light passes through an EO scanner that controls the angle of the output beam. A scanning sensitivity of 17 mrad/kV was measured for the scanner, compared to the calculated value of 15 mrad/kV View full abstract»

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  • Blocking performance with crosstalk consideration of the photonic switching networks based on electrooptical directional couplers

    Publication Year: 1999 , Page(s): 381 - 387
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (208 KB)  

    Crosstalk is a fundamental task in electrooptical directional coupler-based photonic switching systems. A good design must balance the amount of hardware and the level of crosstalk. In this paper, we study the tradeoff between these two parameters in designing Banyan-type photonic switching systems based on electrooptical directional couplers. We develop a novel simulation technique that can significantly reduce the simulation time View full abstract»

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  • Coherent optical beam forming with passive millimeter-wave arrays

    Publication Year: 1999 , Page(s): 418 - 425
    Cited by:  Papers (14)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (368 KB)  

    Passive millimeter-wave imaging requires large apertures to achieve an angular resolution comparable to that of typical infrared imagers. Aperture synthesis offers a route to achieving high resolution without using a single large aperture, by interferometrically combining the signals from a number of smaller distributed apertures. In such a system the individual millimeter-wave signals must be transported to a common location with good phase fidelity and combined to form the image. This paper discusses a technique called coherent optical beam forming which performs optical transport of the up-converted millimeter-wave signal and direct image formation at the optical frequency. Proof of principle experiments are described that demonstrate coherent optical beam forming with a point source and a method of self-calibrating the array to remove phase errors View full abstract»

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  • The dispersion characteristics of oblique coordinate beam propagation algorithms

    Publication Year: 1999 , Page(s): 514 - 518
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (152 KB)  

    The use of an oblique coordinate system with the finite difference beam propagation method has previously been demonstrated to offer significant computational advantages over using rectangular coordinates for a wide range of practical optical structures. The effects of finite mesh resolution, step size, and order of the algorithm in terms of numerical dispersion and dissipation are here investigated and quantified for the first time View full abstract»

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  • Combined Franz-Keldysh and quantum-confined Stark effect waveguide modulator for analog signal transmission

    Publication Year: 1999 , Page(s): 497 - 502
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (144 KB)  

    A novel approach to the design of electroabsorption waveguide modulators for use in broadband, analog radio frequency (RF) links is presented. The approach utilizes a linear combination of two electroabsorption effects (the Franz-Keldysh effect and the quantum-confined Stark effect) to improve the spurious-free dynamic range of the waveguide modulator. Measured transfer curves verify simultaneous improvement in linearity and modulation efficiency for an exemplary combination structure. Residual absorption is modeled to determine the impact on modulation efficiency View full abstract»

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  • Tapered polymer single-mode waveguides for mode transformation

    Publication Year: 1999 , Page(s): 466 - 474
    Cited by:  Papers (16)  |  Patents (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (200 KB)  

    This paper presents a tapered polymer waveguide structure for coupling light between optical waveguides with differing geometries. Optical fibers, lasers, and other photonic integrated circuit components can be coupled with tapered waveguides. The polymer waveguide performs a mode transformation between different mode shapes and sizes. For example, the mode transformation can be from an elliptical laser diode mode to that of a circular optical fiber mode. The input and output of a tapered waveguide structure are analyzed, for the case of laser to fiber coupling, in order to determine the effect of misalignments on the coupling efficiency. Adiabaticity in waveguide propagation is discussed. The fabrication of our polymer waveguides is also described View full abstract»

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  • The design of triple rib waveguide couplers by the discrete spectral index method

    Publication Year: 1999 , Page(s): 475 - 482
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (340 KB)  

    The operations of three-guide couplers are usually controlled by the width and refractive index of the guides. However, when rib waveguides are used in three-guide couplers and power dividers, we propose to use the dimensions of the ribs as the governing parameters instead. Formulating a new transcendental equation using the discrete spectral index (DSI) method, triple rib waveguide couplers are accurately analyzed for the first time. The new accurate and fast analysis of triple rib waveguides shows that the propagation constants of the various modes are dominantly controlled by the height of the middle rib. A systematic and simple procedure is consequently introduced to design quasi-transverse electric (TE) polarized triple rib waveguide couplers, which ensures maximum power transfer from one outermost guide to the other outermost guide. For triple rib power dividers, the height of the middle rib is found to control the amount of power that can be transferred from the excited middle rib waveguide to the two outer rib waveguides. Maximum power division is achieved when the three ribs of the waveguide are identical View full abstract»

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  • A time optimal wavelength rerouting algorithm for dynamic traffic in WDM networks

    Publication Year: 1999 , Page(s): 406 - 417
    Cited by:  Papers (35)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (240 KB)  

    In this paper, we consider wavelength rerouting in wavelength routed wavelength division multiplexed (WDM) networks with circuit switching, wherein lightpaths between source-destination pairs are dynamically established and released in response to a random pattern of arriving connection requests and connection holding times. The wavelength continuity constraint imposed by WDM networks leads to poor blocking performance. Wavelength rerouting is a viable and cost effective mechanism that ran improve the blocking performance by rearranging certain existing lightpaths to accommodate a new request. Recently, a rerouting scheme called “parallel move-to-vacant wavelength retuning (MTV-WR)” with many attractive features such as shorter disruption period and simple switching control, and a polynomial time rerouting algorithm, for this scheme, to minimize the weighted number of rerouted lightpaths have been proposed. This paper presents a time optimal rerouting algorithm for wavelength-routed WDM networks with parallel MTV-WR rerouting scheme. The algorithm requires only O(N2W) time units to minimize the weighted number of existing lightpaths to be rerouted, where N is the number of nodes in the network and W is the number of wavelength channels available on a fiber link. Our algorithm is an improvement over the earlier algorithm proposed in that it requires O(N3W+N2W2) time units, which is not time optimal. The simulation results show that our algorithm improves the blocking performance considerably and only very few lightpaths are required to be rerouted per rerouting. It is also established through simulation that our algorithm is faster than the earlier rerouting algorithm by measuring the time required for processing connection requests for different networks View full abstract»

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  • Performance of WDM ring and bus networks in the presence of homodyne crosstalk

    Publication Year: 1999 , Page(s): 388 - 396
    Cited by:  Papers (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (244 KB)  

    This paper examines the effects of coherent and incoherent homodyne crosstalk in wavelength division multiplexed (WDM) ring and bus networks using reconfigurable optical add-drop multiplexers (OADM's). It is widely understood that incoherent homodyne crosstalk causes power penalties at the receivers in these networks. We show that coherent homodyne crosstalk causes a range of possible received powers, and that coherent and incoherent crosstalk together lead to a range of possible power penalties. A Monte Carlo simulation is used to examine the probability distribution of power penalties due to homodyne crosstalk under various conditions. We find that increasing the switch and multiplexer crosstalk within each OADM, and increasing the number of WDM channels, all produce increased probabilities of large power penalties. However, the number of nodes through which a signal is transmitted does not affect the power penalty distribution View full abstract»

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  • Passive optical fast frequency-hop CDMA communications system

    Publication Year: 1999 , Page(s): 397 - 405
    Cited by:  Papers (154)  |  Patents (16)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (280 KB)  

    This paper proposes an all-fiber fast optical frequency-hop code division multiple access (FFH-CDMA) for high-bandwidth communications. The system does not require an optical frequency synthesizer allowing high communication bit rates. Encoding and decoding are passively achieved by Bragg gratings, Multiple Bragg gratings replace a frequency synthesizer, achieving a hopping rate in tens of GHz. A main lobe sine apodization can be used in writing the gratings to enhance the system capacity and the spectrum efficiency. All network users can use the same tunable encoder/decoder design. The simultaneous utilization of the time and frequency domains offers notable flexibility in code selection. Simulations show that the encoder efficiently performs the FFH spread spectrum signal generation and that the receiver easily extracts the desired signal from a received signal for several multiple access interference scenarios. We measure the system performance in terms of bit error rate, as well as auto-to cross-correlation contrast. A transmission rate of 500 Mb/s per user is supported in a system with up to 30 simultaneous users at 10-9 bit error rate. We compare FFH-CDMA to several direct sequence-CDMA systems in terms of bit error rate versus the number of simultaneous users. We show that an optical FFH-CDMA system requires new design criteria for code families, as optical device technology differs significantly from that of radio frequency communications View full abstract»

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  • Cryogenic performance of double-fused 1.5-μm vertical cavity lasers

    Publication Year: 1999 , Page(s): 503 - 508
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (160 KB)  

    The low-temperature performance of vertical cavity lasers (VCL's) is of interest for high-speed data transmission from superconducting and cryogenic semiconductor circuits. Our double-fused 1.5 μm lasers employ a strain-compensated InGaAsP-InP multiquantum-well (MQW) active region that is sandwiched between two AlGaAs-GaAs distributed Bragg reflectors. Continuous wave (CW) lasing at ambient temperature as low as 7 K is measured on the same type of top-emitting devices that previously lased at a record-high temperature of 337 K. The optimum temperature is found at 180 K giving minimum threshold current, maximum modulation bandwidth of 5 GHz, and more than 3 GHz/mA1/2 modulation current efficiency. The optimum temperature agrees very well with the theoretical prediction. Further device optimization for cryogenic high-speed applications is discussed in detail View full abstract»

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  • Crosstalk characteristics of a 1.3-μm/1.5-μm wavelength demultiplexing photodetector using laser-assisted MOMBE growth

    Publication Year: 1999 , Page(s): 483 - 489
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (160 KB)  

    This paper demonstrates a monolithic 1.3-μm/1.5-μm wavelength demultiplexing photodetector fabricated using Ar ion laser-assisted metal organic molecular beam epitaxy (MOMBE) growth. Reduction of crosstalk to -24 dB is accomplished in both 1.3-μm and 1.5-μm wavelength regions. The dependence of the crosstalk on the coupling efficiency between the fiber and device and the polarization dependence of the responsivity is also discussed View full abstract»

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  • 1.58-μm band gain-flattened erbium-doped fiber amplifiers for WDM transmission systems

    Publication Year: 1999 , Page(s): 490 - 496
    Cited by:  Papers (46)  |  Patents (7)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (152 KB)  

    This paper describes the amplification characteristics of gain-flattened Er3+-doped fiber amplifiers (EDFAs) by using 0.98-μm and 1.48-μm band pumping for a 1.58-μm band WDM signal. Silica-based Er3+-doped fiber (S-EDF) and fluoride-based Er 3+-doped fiber (F-EDF) have gain-flattened wavelength ranges from 1570 to 1600 nm and from 1565 to 1600 nm, respectively, and exhibit uniform gain characteristics with gain excursions of 0.7 and 1.0 dB, and the figure of merit of the gain flatness (gain excursion/average signal gain) of 3 and 4.3%, respectively, for an eight-channel signal in the 1.58-μm band. We show that 1.48-μm band pumping has a better quantum conversion efficiency and gain coefficient, and that 0.98-μm band pumping is effective for improving the noise characteristics. We also show that the EDFAs consisting of two cascaded amplification units pumped in the 0.98-μm and 1.48-μm bands are effective in constructing low-noise and high-gain 1.58-μm band amplifiers View full abstract»

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  • Single-polarization operation of fiber distributed feedback (DFB) lasers by injection locking

    Publication Year: 1999 , Page(s): 509 - 513
    Cited by:  Papers (16)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (144 KB)  

    This paper investigated injection locking characteristics of a fiber distributed feedback (DFB) laser operating in dual polarizations, and found that it could operate in a single polarization by injection locking. The locking bandwidth was less than 10 MHz, much narrower than DFB laser diodes as a consequence of longer cavity length and resulting longer photon lifetime. As a more practical method to realize single-polarization operation of the fiber DFB laser, we proposed self-injection locking with a polarization-selective optical feedback composed of a mirror and a polarizer, and demonstrated a stable single-polarization operation View full abstract»

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  • Second-order moment analysis of dispersion-managed solitons

    Publication Year: 1999 , Page(s): 445 - 451
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (204 KB)  

    This paper shows how a second-order moment analysis can be used to derive explicit approximate expressions for the evolution of the root-mean-square (rms) width and chirp parameters of a dispersion-managed soliton within one period of the dispersion map. The energy enhancement factor can also be estimated with a good accuracy View full abstract»

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  • A performance analysis of optical overlapping PPM-CDMA communication systems

    Publication Year: 1999 , Page(s): 426 - 433
    Cited by:  Papers (27)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (292 KB)  

    Direct-detection optical code-division multiple-access (CDMA) systems employing overlapping pulse-position modulation (OPPM) schemes are proposed. Both upper and lower hounds on the bit error rate (BER) are derived taking into account the effect of both multiple-user interference and receiver shot noise. The photodiodes' dark currents are neglected since their effect is minor. The throughput limitation of this system is evaluated as well. Performance characteristics are then compared to optical CDMA systems employing traditional ON-OFF keying (OOK) and pulse-position modulation (PPM) schemes. It is shown that under fixed data rate and chip time, OPPM-CDMA system superperforms both traditional systems. Moreover, it is shown that the throughput limitation of OPPM-CDMA is almost 6.7 times greater than that of OOK-CDMA 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