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Lightwave Technology, Journal of

Issue 22 • Date Nov.15, 2011

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  • [Front cover]

    Page(s): C1
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  • Journal of Lightwave Technology publication information

    Page(s): C2
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  • Table of contents

    Page(s): 3365 - 3366
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  • Bragg Gratings in All-Solid Bragg Photonic Crystal Fiber Written With Femtosecond Pulses

    Page(s): 3367 - 3371
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (484 KB) |  | HTML iconHTML  

    Bragg gratings were fabricated in all-solid Bragg photonic crystal fibers with 100 fs, 800 nm infrared radiations and a phase mask. Both multimode and single-mode grating resonances were achieved by accurately adjusting the focal position of the irradiation beam in the Bragg fiber. Thermal annealing investigations indicated that the gratings were induced by Type I-IR and Type II-IR refractive index change. Typical Bragg wavelength shifted with the change of temperature and strain, which were measured respectively. View full abstract»

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  • 4096-Ary OCDM/OCDMA System Using Multidimensional PSK Codes Generated by a Single Multiport En/Decoder

    Page(s): 3372 - 3380
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1033 KB) |  | HTML iconHTML  

    We experimentally demonstrate a record 4096 (=16 × 16 × 16)-ary optical code division multiplexing (OCDM) system at 2.5 Gbps using multidimensional phase shift keying (PSK) codes generated/processed by a single multiport optical encoder/decoder (E/D). To analyze the system performance, we evaluate the power margin and the data confidentiality. For application to access networks, we propose and numerically evaluate the performance of 10 Gbps, 4096-ary optical code division multiple access (OCDMA)-based passive optical network (PON). View full abstract»

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  • Tunable Multi-Tap Bandpass Microwave Photonic Filter Using a Windowed Fabry-Pérot Filter-Based Multi-Wavelength Tunable Laser

    Page(s): 3381 - 3386
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (468 KB) |  | HTML iconHTML  

    A center frequency-tunable multi-tap bandpass microwave photonic filter (MPF) is proposed and experimentally demonstrated. A specially designed multi-wavelength fiber ring laser, in which a windowed Fabry-Pérot (FP) filter is used as the wavelength selection and power control component, has been developed to serve as the optical source for the MPF. By adjusting the windowed FP filter, both the wavelength spacing and power profile of the multi-wavelength laser can be changed. The output of the optical source is phase modulated by a microwave signal. 25 km of single-mode fiber (SMF) is then used to act as a dispersive medium to introduce time delays between taps. Thus, a tunable bandpass response is obtained at the output of a high-speed photodetector (PD). In addition, the passband centered at DC is removed due to the use of phase modulation. The experimental results show that more than 45 wavelengths can be generated in the multi-wavelength ring laser. With the electronic tuning of the wavelength spacing, tuning of the passband center frequency of the MPF by 3 GHz is achieved. View full abstract»

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  • High-Speed, Solid State, Interferometric Interrogator and Multiplexer for Fiber Bragg Grating Sensors

    Page(s): 3387 - 3392
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (237 KB) |  | HTML iconHTML  

    We report on the design and prototyping of a robust high-speed interferometric multiplexer and interrogator for fiber Bragg grating sensors. The scheme is based on the combination of active WDM channel switching and passive, instantaneous interferometry, allowing the resolution of virgin interferometric interrogators to be retained at MHz multiplexing rates. In this article the system design and operation are described, and a prototype scheme is characterized for three sensors and a multiplexing rate of 4 kHz, demonstrating a noise floor of 10 nε/√Hz and no cross-sensitivity. It is proposed that the system will be applicable to demanding monitoring applications requiring high speed and high resolution measurements across the sensor array. View full abstract»

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  • Radiation Tolerant Optical Fibers: From Sample Testing to Large Series Production

    Page(s): 3393 - 3400
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (602 KB) |  | HTML iconHTML  

    The process of selecting, manufacturing, and installing a large quantity (2500 km) of commercially available radiation tolerant specialty fibers is described. Radiation tests of various types of fibers from different manufacturers provided sufficient understanding of the radiation effects to select the best performing fiber type. Systematic verification of a sample of each preform assured a constant quality of the series production and allowed assessing the impact of small variations in the manufacturing process on the radiation hardness and the optical transmission characteristics. The fiber cable installation technique based on microjetting and plastic cable ducts has been validated for areas with high levels of radiation. View full abstract»

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  • Multiheterodyne Characterization of Excess Phase Noise in Atmospheric Transfer of a Femtosecond-Laser Frequency Comb

    Page(s): 3401 - 3407
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (907 KB) |  | HTML iconHTML  

    We report an experimental investigation on remote transfer of a femtosecond-laser frequency comb through an open atmospheric link. Optical multiheterodyne is used to measure the excess phase noise and the frequency stability of the transferred comb. The dispersion of air is found to have a minimal impact on the multiheterodyne signal, and the effectiveness of the technique to characterize the behaviors of comb lines under the influence of turbulence is theoretically analyzed. Large phase modulation due to the index fluctuation of the air over a 60-m transmission link is found to cause a significant linewidth broadening. Under low-wind conditions, a fractional frequency stability in the order of 10-14 has been achieved over several minutes with a 1-s averaging time. A comparison of this work with previous tests based on continuous wave (CW) lasers indicates that pulsed lasers can work as well as CW lasers for remote transfer of optical frequency references through the atmosphere. View full abstract»

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  • Regenerator Placement Strategies for Translucent OBS Networks

    Page(s): 3408 - 3420
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2048 KB) |  | HTML iconHTML  

    Most research works in optical burst switching (OBS) networks do not take into account the impact of physical layer impairments (PLIs) either by considering fully transparent (i.e., with optical 3R regeneration) or opaque (i.e., with electrical 3R regeneration) networks. However, both solutions are not feasible due to the technological requirements of the former and the high cost of the latter. In this paper, we deal with a translucent OBS (TL-OBS) network architecture that aims at bridging the gap between the transparent and opaque solutions. In order to evaluate its performance, a formulation of the routing and regenerator placement and dimensioning problem (RRPD) is presented. Since such formulation results in a complex problem, we also propose two alternative strategies. In particular, we evaluate the tradeoff between optimality and execution times provided by these methods. Finally, we conduct a series of simulation experiments that prove that the TL-OBS network model proposed effectively deals with burst losses caused by the impact of PLIs and ensures that the overall network performance remains unaffected. View full abstract»

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  • Theoretical and Experimental Study of a Semiconductor Resonant Cavity Linear Interferometric Intensity Modulator

    Page(s): 3421 - 3427
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1540 KB) |  | HTML iconHTML  

    The phase response of an injection locked semiconductor laser that is used as the phase modulator in a resonant cavity linear interferometric intensity modulator is studied in detail. It is shown that, signal-to-intermodulation ratio of such a modulator is affected by the injection ratio, linewidth enhancement factor of the semiconductor laser, residual amplitude modulation, depth of phase modulation, and linearity of the resonant cavity response. Experimental measurements of the signal-to-intermodulation ratio of this modulator using a semiconductor Fabry-Pérot laser as the resonant cavity are in good agreement with the theoretically predicted values. View full abstract»

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  • Spatially Flat In-Phase Supermode in Multicore Hybrid Photonic Crystal Fiber

    Page(s): 3428 - 3432
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (646 KB) |  | HTML iconHTML  

    We propose a novel hybrid multicore photonic crystal fiber in which the air holes between the cores are replaced with high-index rods. Using coupled mode theory and finite element method, we demonstrate that a spatially flat in-phase supermode can be achieved at the resonant wavelengths without mode shaping. Such a design is more robust to perturbations. View full abstract»

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  • Joint Routing and Wavelength Allocation Subject to Absolute QoS Constraints in OBS Networks

    Page(s): 3433 - 3444
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1557 KB) |  | HTML iconHTML  

    From the network layer perspective, the problem of burst losses is one of the most challenging problems which restrain the development of optical burst switching (OBS) networks. Indeed, OBS is a buffer-less technology and the consequent lack of guarantees for data delivery may affect significantly the quality of service (QoS) perceived by end users. To overcome these obstacles, dedicated network mechanisms and design methods are required for QoS provisioning in the network. With this end in view, in this paper, we present a traffic engineering (TE) approach to support the end-to-end traffic delivery with absolute QoS guarantees, in terms of burst losses, in an OBS network. We focus on the establishment of explicit routing paths and minimum allocation of wavelength resources in network links under the requirement that certain absolute level of burst loss probability for a given set of traffic demands is guaranteed. In this paper, we call such an off-line problem the virtual topology (VT) design problem. Since the VT design problem is NP-complete, as an alternative to the mixed integer linear programming formulation, we develop a local search heuristic algorithm to solve it. Moreover, we focus on a dynamic OBS network scenario, where the offered traffic is subject to a change. In this context, we propose an on-line VT maintenance mechanism that is responsible for traffic admission control and adaptation of the VT to traffic changes. Eventually, proposed algorithms and mechanisms for the TE-driven end-to-end QoS approach are verified both numerically and by means of network simulations for a number of network scenarios. View full abstract»

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  • Arbitrary-Order Full-Vectorial Interface Conditions and Higher Order Finite-Difference Analysis of Optical Waveguides

    Page(s): 3445 - 3452
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    We derive generalized full-vectorial continuity relations of field derivatives across an abrupt curved interface. Using the Helmholtz wave equation, we can extend the interface conditions by two orders. Repeating the process, we obtain interface conditions of even and odd orders from the zeroth- and first-order interface conditions, respectively, which can be extended to arbitrary orders. The interface conditions combined with Taylor series expansion are applied in higher order full-vectorial finite-difference analysis of several waveguide structures. From effective index convergence analysis of optical fiber modes, the 6-, 15-, and 28-point schemes give second-, fourth-, and sixth-order convergence, respectively. The higher order formulation is also applied to guided mode analysis of photonic crystal fibers and terahertz pipe waveguides, where improved accuracy is obtained when using higher order scheme. Our proposed method allows coarser discretization, which can greatly reduce the computation time and memory. The ultimate accuracy can also be higher due to smaller accumulated roundoff error. View full abstract»

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  • Performance Enhancement of Vibration Sensing Employing Multiple Phase-Shifted Fiber Bragg Grating

    Page(s): 3453 - 3460
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1306 KB) |  | HTML iconHTML  

    Multiple phase-shifted fiber Bragg gratings (MPS-FBGs) are proposed for a novel intensity-type vibration sensing scheme with broadband source based interrogation. In this scheme, the collective and simultaneous operation of the subchannels of MPS-FBG multiplies the total acquired signal power change at a particular channel, considerably enhancing sensitivity. Compared to a standard FBG scheme, our experiment scheme attained significant sensitivity enhancement of nearly 20 dB using 17 phase-shifted FBG. These experimental results agree with the theoretical prediction based on cross-correlation relations. The sensitivity enhancement while retaining the system simplicity would be an attractive option for an economical coarse wavelength division multiplexed (CWDM) vibration sensing system based on a single broadband source. View full abstract»

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  • 1.06 \mu m Picosecond Pulsed, Normal Dispersion Pumping for Generating Efficient Broadband Infrared Supercontinuum in Meter-Length Single-Mode Tellurite Holey Fiber With High Raman Gain Coefficient

    Page(s): 3461 - 3469
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    We investigate efficient broadband infrared supercontinuum generation in meter-length single-mode small-core tellurite holey fiber. The fiber is pumped by 1.06 μm picosecond pulses in the normal dispersion region. The high Raman gain coefficient and the broad Raman gain bands of the tellurite glass are exploited to generate a cascade of Raman Stokes orders, which initiate in the highly normal dispersion region and quickly extend to longer wavelengths across the zero dispersion wavelength with increasing pump power. A broadband supercontinuum from 1.06 μm to beyond 1.70 μm is generated. The effects of the pump power and of the fiber length on the spectrum and on the power conversion efficiency from the pump to the supercontinuum are discussed. Power scaling indicates that using this viable normal dispersion pumping scheme, 9.5 W average output power of infrared supercontinuum and more than 60% conversion efficiency can be obtained from a 1 m long tellurite fiber with a large mode area of 500 μm2 . View full abstract»

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  • A Microwave Bandpass Differentiator Implemented Based on a Nonuniformly-Spaced Photonic Microwave Delay-Line Filter

    Page(s): 3470 - 3475
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    A microwave bandpass differentiator implemented based on a finite impulse response (FIR) photonic microwave delay-line filter with nonuniformly-spaced taps is proposed and experimentally demonstrated. To implement a microwave bandpass differentiator, the coefficients of the photonic microwave delay-line filter should have both positive and negative coefficients. In the proposed approach, the negative coefficients are equivalently achieved by introducing an additional time delay to each of the taps, leading to a π phase shift to the tap. Compared with a uniformly-spaced photonic microwave delay-line filter with true negative coefficients, the proposed differentiator features a greatly simplified implementation. A microwave bandpass differentiator based on a six-tap nonuniformly-spaced photonic microwave delay-line filter is designed, simulated, and experimentally demonstrated. The reconfigurability of the microwave bandpass differentiator is experimentally investigated. The employment of the differentiator to perform differentiation of a bandpass microwave signal is also experimentally demonstrated. View full abstract»

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  • An Exact Probability Density Function for Intensity-Based Output Noise Propagating Through a Fiber Optic Sensor Demodulation Process

    Page(s): 3476 - 3482
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    Fiber optic interferometry is a common architecture in many optical sensing strategies and typically requires a demodulation scheme for phase (signal) extraction. For sensing applications, signal-to-noise and other statistical metrics are of great importance in characterizing system performance. In the context of a specific demodulation algorithm employing three-channel inputs, we analytically compute a probability density function of the demodulator output noise, given an arbitrary distribution of input intensity noise and arbitrary noise correlation among the three channels. We compare the analytical formulations with previously validated simulation data from a fiber Bragg grating sensor system, and we find excellent agreement within the specific example of Gaussian input noise. View full abstract»

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  • The Dynamic Gain Modulation Performance of Adjustable Gain-Clamped Semiconductor Optical Amplifiers (AGC-SOA)

    Page(s): 3483 - 3489
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    The growth in demand for high bandwidth services has stimulated the deployment of Passive Optical Networks (PONs), directly to the home or to the kerb. In many cases, particularly extended reach PONs which may cover distances of 100 km or more [1], there is the need for low cost reach extension technologies. Semiconductor Optical Amplifiers (SOAs) have a key role in this context, particularly because upstream traffic is commonly carried at 1.3 μm. Upstream traffic in a PON (from the Optical Network Unit, ONU to the Optical Line Terminal, OLT) is normally Time Division Multiplexed (TDM) with a wide variation in path loss arising from differences in transmission distances and splitting losses. The bursty nature of this traffic combined with a wide dynamic range of signal strength ( -15 dBm to -28 dBm-the difference between a very close ONU with a small split ratio and a distant ONU with a high split ratio), places severe demands on the burst mode receiver at the OLT. Conventional fibre amplifiers cannot adjust their gain with packet to packet variations due to their response time. Similarly, conventional SOAs suffer loss of linearity if their bias current and hence gain is rapidly reduced. The paper reports on an adjustable gain-clamped semiconductor optical amplifier (AGC-SOA) designed to maximize the output saturated power while adjusting gain to regulate power differences between packets without loss of linearity. Theoretical modeling predicts that this device is able to modulate gain at nanosecond rates. The analysis is validated experimentally. View full abstract»

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    Page(s): 3490
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    Page(s): 3491
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    Page(s): 3492
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    Page(s): 3494
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  • Journal of Lightwave Technology information for authors

    Page(s): C3
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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