By Topic

Lightwave Technology, Journal of

Issue 15 • Date Aug.1, 2009

Filter Results

Displaying Results 1 - 25 of 49
  • [Front cover]

    Page(s): C1
    Save to Project icon | Request Permissions | PDF file iconPDF (381 KB)  
    Freely Available from IEEE
  • Journal of Lightwave Technology publication information

    Page(s): C2
    Save to Project icon | Request Permissions | PDF file iconPDF (38 KB)  
    Freely Available from IEEE
  • Table of contents

    Page(s): 2931 - 2932
    Save to Project icon | Request Permissions | PDF file iconPDF (50 KB)  
    Freely Available from IEEE
  • Effects of Second-Order Coupling Coefficient Dispersion on Short-Pulse Propagation and Switching in an Active Two-Core Nonlinear Fiber Coupler

    Page(s): 2933 - 2940
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1188 KB) |  | HTML iconHTML  

    The propagation and switching of short pulses in an active two-core fiber nonlinear directional coupler have been investigated theoretically by using the split-step Fourier method. The analysis highlights the effects of the second-order coupling coefficient dispersion, the linear gain coefficient, and the finite-gain bandwidth on the switching and propagation of short pulses. The research indicates that the linear gain can sharpen the switching characteristic and reduce considerably the switching threshold power, as well as significantly increase the switching efficiency with the influences of the second-order coupling coefficient dispersion. However, both the second-order coupling coefficient dispersion and the finite-gain bandwidth degrade the switching characteristics. In addition, the finite-gain bandwidth of linear gain not only suppresses significantly the pulse compression and amplification caused by the linear gain coefficient, but also suppresses effectively the frequent pulse fluctuation on pulse propagation induced by the second-order coupling coefficient dispersion; consequently, as in the case of the passive fiber coupler, optical pulses tend to restore periodical coupling propagation in active two-core fiber coupler. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Reliable Networks Based on General Passive Routing Devices

    Page(s): 2941 - 2948
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (452 KB) |  | HTML iconHTML  

    Survivable passive network architectures based on interconnecting a small number of arrayed waveguide gratings (AWGs) have been described in prior work. Such networks are desirable for communication between a small number of users in environments that are susceptible to a high rate of failure and where providing power in the network core is difficult. In this paper, it is shown that these network designs can be improved if passive devices that have routing properties different from those of standard AWGs are considered. Devices with routing matrices represented by Latin squares and devices with more arbitrary routing patterns are considered here. This illustrates that developing the capability of manufacturing more general passive routing devices is a worthwhile goal. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Precision Threshold Current Measurement for Semiconductor Lasers Based on Relaxation Oscillation Frequency

    Page(s): 2949 - 2952
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (101 KB) |  | HTML iconHTML  

    The soft turn-on of semiconductor lasers leads to uncertainty in defining and measuring the laser threshold injection current, I th. Previously, practical calculation algorithms have been developed to achieve high-accuracy measurement of a clearly defined and reproducible quantity which is called I th. We demonstrate a new and higher accuracy measurement of I th using the dependency of the relaxation oscillation frequency on injection current, as compared to the existing standardized approaches. Further, if it is accepted that relaxation oscillations do not occur below laser threshold, this may be regarded as a more fundamentally based definition and measurement method to determine the laser threshold injection current in a semiconductor laser. The method may also be applicable to other types of lasers. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Performance Investigation of One-to-Six Wavelength Multicasting of ASK–DPSK Signal in a Highly Nonlinear Bismuth Oxide Fiber

    Page(s): 2953 - 2957
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (540 KB) |  | HTML iconHTML  

    We investigate the wavelength multicast performance of a 20 Gb/s (Gigabit per second) orthogonally modulated ASK-differential phase-shift keying (DPSK) signal. The multicast is achieved using four-wave mixing in a 32 cm highly nonlinear bismuth oxide fiber. Six multicast channels each operating at 20 Gb/s are obtained at a 200-GHz spacing, resulting in a 120 Gb/s throughput. Widely opened eye diagrams are obtained in the detection of both the ASK and DPSK components of the multicast channels. Bit error rate measurements have also been performed for both the amplitude and the phase of the signals. A power penalty of less than 3 dB is obtained in all the six multicast channels. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Reconfigurable Multifunctional Operation Using Optical Injection-Locked Vertical-Cavity Surface-Emitting Lasers

    Page(s): 2958 - 2963
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1269 KB) |  | HTML iconHTML  

    In this paper, we extend the system application of optical injection-locked (OIL) vertical-cavity surface-emitting lasers (VCSELs) to future optical networks by realizing multifunctional operation using a filter-assisted OIL-VCSEL scheme that can be reconfigured. By using a single chirp-adjustable injection-locked VCSEL (either single mode or multimode) followed by a tunable delay line interferometer, we experimentally demonstrate three functions, showing ultra-wide band (UWB) monocycle generation, nonreturn-to-zero (NRZ) to pseudoreturn-to-zero (PRZ) data format conversion, and NRZ-data clock recovery at 10 Gb/s. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optical Reflectivity of Asymmetric Dielectric–Metal–Dielectric Planar Structures

    Page(s): 2964 - 2969
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (399 KB) |  | HTML iconHTML  

    We report simulations and experimental results on the incidence-angle dependence of the optical reflectivity of asymmetric dielectric-metal-dielectric planar structures. Transfer-matrix method and 2-D finite-element analysis revealed the presence of multiple resonances that were attributed to the surface plasmon (SP) polariton mode at the metal-dielectric interfaces and guided-wave polariton modes within the asymmetric dielectric-metal-dielectric waveguide. The number of guided-wave polariton resonances scale with the thickness of the dielectric guiding layer while the SP resonance remained essentially unaltered. These findings were validated through reflectivity measurements on sapphire-metal-polymer structures. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Influence of Residual Facet Reflection on the Eye-Diagram Performance of High-Speed Electroabsorption Modulated Lasers

    Page(s): 2970 - 2976
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (757 KB) |  | HTML iconHTML  

    The influence of residual facet reflection on the small-signal modulation response and the large-signal eye-diagram performance of 40 Gb/s electroabsorption modulated lasers (EMLs) is studied. Measurement and simulation show that the eye-diagram performance is not only limited by the modulation bandwidth of the device, but also significantly degraded by the low frequency resonances in the frequency response due to residual facet reflection. Clear eye-opening has been demonstrated by optimizing the anti-reflection (AR) coating of the EA modulator facet. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Measurement of Er-Doped Fiber Nonlinearity Using Continuous-Wave Self-Phase Modulation Method

    Page(s): 2977 - 2982
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (197 KB) |  | HTML iconHTML  

    The intensity-dependent nonlinear coefficient n 2/A eff of a short Er-doped, amplifying fiber is determined using a method thoroughly studied for measurements of passive fibers. Measurement uncertainty of 3.0% is achieved using modified continuous-wave self-phase modulation method. In addition to metrological aspects, we also discuss limitations and conditions imposed by the Er-doped fiber as compared with the measurement of a pure silica core fiber. The used measurement method is advantageous as compared with other techniques due to its reliability and ease of implementation. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Multistage Modified Fiber Drawing Process and Related Diameter Measuring System

    Page(s): 2983 - 2988
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1033 KB) |  | HTML iconHTML  

    Recent progress on the drawing of micro and nanowires shows the length could only reach several millimeters because of the lack of material feeding mechanism. We report here a multistage modified fiber drawing process which allows a fiber preform to be drawn several times in the heating zone so that the desired diameter of microns and nanometers can be achieved more than 1 m long. Current results show that by this approach the micro/nano optical wires (MNOWs) could be drawn with the length up to 165 cm and the diameter down to 1.9 mum. A real-time diameter measuring system is also developed to monitor the diameter in situ and hence to optimize our fabrication process. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Mode Characteristics of the Strongly Anisotropic a -Axis Single-Crystal Fiber

    Page(s): 2989 - 2999
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (828 KB) |  | HTML iconHTML  

    The mode theory of the strongly anisotropic a axis step-index single-crystal fiber is studied in this paper. The electromagnetic field equations of the a axis step-index single-crystal fiber are solved under the strongly anisotropic condition, and the transverse electric field components are obtained. The dispersion equations far from cutoff, near cutoff, and in the guided mode region are discussed, respectively. Numerical results of the mth-order elementary modes are presented for the strongly anisotropic a axis step-index single-crystal fiber. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Efficient Computation of Longitudinal Lasing Modes in Arbitrary Active Cavities: The Bidirectional Time Evolution Method

    Page(s): 3000 - 3009
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (730 KB) |  | HTML iconHTML  

    In this paper, we develop the Bidirectional Time Evolution Method (BTEM) as an efficient technique to determine the frequencies of the longitudinal lasing modes in arbitrary 1-D active cavities. The BTEM is based on a mathematical property of linear Maxwell equations for active media at real frequencies: the backward Fourier transform of their frequency-domain solution provides nonphysical time-reversed fields when the threshold condition is fulfilled (i.e., the round-trip gains overcome the round-trip losses). Although such time-reversed fields are not physically feasible, they can be easily computed and their spectrum provides all the (real) frequencies at which the threshold condition is fulfilled. On the other hand, the phase condition is given by the peaks of the cavity transmittance modulus. Numerical examples of Fabry-Perot, distributed Bragg reflector, DFB, random, and metamaterial active cavities illustrate the capabilities of our method. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Limit of Effective Area for Single-Mode Operation in Step-Index Large Mode Area Laser Fibers

    Page(s): 3010 - 3016
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (298 KB) |  | HTML iconHTML  

    Step-index (SI) fiber designs are commonly used in achieving large mode area (LMA) and single-mode (SM) operation in fiber lasers. These fibers can either be intrinsically single-moded fibers or few-moded fibers, which can be forced into SM operation through bending. In this paper we evaluate the limitation of the effective area for SM operation by taking into account the effects of practical constraints such as fiber bending loss, laser performance, and fiber mechanical reliability on these LMA fiber designs. It is shown that the effective area of these fibers cannot be arbitrarily scaled up with the size of the fiber core. We also use the modeling result to provide estimated upper limits to the core diameters and corresponding effective areas for conventional SI fiber designs taking into account fiber parameters that are achievable nowadays. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • 64-Channel Optical Pulse Stacker

    Page(s): 3017 - 3020
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (550 KB) |  | HTML iconHTML  

    In this paper, we demonstrate an all-fiber pulse-shaping system that can generate shape-controllable pulses with a short rise time and high resolution by adjusting variable optical attenuators of the 64 fiber channels independently. A 6.4 ns arbitrarily shaped pulse with less than 0.1 dB shaping precision is obtained by stacking 150 ps chirped subpulse of 1053 nm. The linewidth of pulse is 1.2 nm and the dynamic range operating at 1 Hz rate is more than 40 dB. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Versatile Characterization of Specialty Fibers Using the Phase-Sensitive Optical Low-Coherence Reflectometry Technique

    Page(s): 3021 - 3033
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1920 KB) |  | HTML iconHTML  

    Emergence of new fibers families induces considerable requirements in terms of characterization and metrology (group delay, chromatic dispersion, birefringence, bending losses, etc.). The optical low-coherence reflectometry (OLCR) technique is demonstrated as a versatile method for the characterization of most types of optical fiber. A synthesis of multiple analysis concerning different families of specialty fibers including rare-earth-doped fibers, few-mode fibers, and microstructured fibers will be presented. OLCR allows measuring precisely the group velocity dispersion value for both polarization modes and birefringence. It is also possible to measure small refractive-index variations in a pumped Erbium-doped fiber. Unique dispersive properties of higher order modes fiber offer novel solutions for dispersion compensation or nonlinear effects management. OLCR can allow each LP mode characterization without the requirement for mode converters. A new method, called ldquotime-wavelength reflection mapping,rdquo based on the OLCR interferogram processing is applied to the determination of chromatic dispersion of each guided LP mode whatever their group index. Finally, different characterization results concerning photonics crystal fibers with guiding based on the conventional total internal reflection principle (high-index guiding) or photonic bandgap effect (low-index guiding) will be presented. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Enhanced Spurious-Free Dynamic Range Using Mixed Polarization in Optical Single Sideband Mach–Zehnder Modulator

    Page(s): 3034 - 3041
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1032 KB) |  | HTML iconHTML  

    We analyze in theory, simulation, and experiment the spurious-free dynamic range (SFDR) for a radio-over-fiber system using an optical single sideband (OSSB) Mach-Zehnder modulator (MZM) that is linearized using mixed polarization. The mixed polarization OSSB MZM makes use of a dual-electrode z-cut LiNbO3 MZM, where a linear polarizer is placed in front and in behind the optical modulator, respectively. It is found that intermodulation distortion can be suppressed significantly regardless of modulation index. Thus intermodulation induced power fading and crosstalk via fiber chromatic dispersion for a given RF carrier is reduced compared to using the conventional OSSB MZM. Improvements of ~ 13 dB in SDFR is predicted in theory, simulation, and demonstrated experimentally. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Blind Equalization and Carrier Phase Recovery in a 16-QAM Optical Coherent System

    Page(s): 3042 - 3049
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (764 KB) |  | HTML iconHTML  

    Blind equalization and carrier phase recovery in a simulated 14 Gbaud 16-QAM optical coherent system are investigated. Equalization techniques to compensate for linear transmission impairments are presented using the constant modulus algorithm (CMA), the recursive least-squares (RLS)-CMA, and the radius directed equalization (RDE). With 7 T/2-spaced taps, the RDE and the RLS-CMA can compensate up to 1000 ps/nm of CD in the 16-QAM coherent system with performances comparable to the decision-directed (DD) equalizer. We show that the RDE is a promising technique for blind equalization in a 16-QAM coherent system with lower complexity than the RLS-CMA. Blind carrier phase recovery is investigated in a decision-directed-mode. We show that the blind carrier phase recovery algorithm can recover the Square-16-QAM constellation for laser beat linewidths of DeltanuTs ~ 10-4 in a polarization-multiplexed (POLMUX) 16-QAM coherent system with the RDE algorithm giving better overall performance than the CMA when compensating for CD and differential group delay (DGD). Finally, the dynamical characteristics of the equalizers to track endless polarization rotations are discussed. With the adaptation parameters optimized, the equalizers can track angular rate of rotation ~ 105 rad/s. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Characteristics of Thermally Diffused Transit Areas of Single-Mode Telecommunication Fibers

    Page(s): 3050 - 3056
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (532 KB) |  | HTML iconHTML  

    The paper deals with diffusion processes of the core dopant during thermal connection (splicing in electric arc) of telecommunication fibers whose parameters vary considerably. A method for defining values of diffusion coefficients GeO2 in SiO2 in splicing temperature has been presented. Better consistence of the dopant Gaussian and diffusion distribution has been found the longer the diffusion time-that is, splicing time. Theoretical analysis of thermally diffused expanded core (TEC) transit area transmission properties was performed which revealed that it is possible to obtain splice loss of thermal connections (splice) of fibers with different parameters, such as of the type G.652 and G.655, below 0.08 dB, using classical connection in electric arc. Whereas, using connection methods that increase the length of TEC, for example, connection by means of gas micro-burners, zero attenuation of such a connection can be accomplished. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Enhancement of CW THz Wave Power Under Noncollinear Phase-Matching Conditions in Difference Frequency Generation

    Page(s): 3057 - 3061
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (218 KB) |  | HTML iconHTML  

    We investigated methods for improvement of continuous-wave (CW) terahertz (THz) output power by laser diode (LD) pumping in noncollinear phase-matched difference frequency generation (DFG). The effects of interaction length and beam spot size of input lasers (near-IR) in GaP crystals were studied. The THz wave power dependence on various sizes of GaP crystals was investigated and it was observed that an output power of 4 nW was obtained with a 20 mm long GaP crystal at 1.5 THz. Also, the THz wave absorption coefficient was dominant for longer GaP crystals at high frequencies (above 2.5 THz). The THz wave power dependence on beam spot size (1.2 mm-300 mum) of near-IR lasers at 1.62 THz was studied, and an improvement of THz wave power being seen with a 500 mum beam spot size, while the beam divergence effect was dominant for beam spot sizes below 500 mum. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Polarization- and Phase-Sensitive Low-Coherence Interferometry Setup for the Characterization of Integrated Optical Components

    Page(s): 3062 - 3074
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1177 KB) |  | HTML iconHTML  

    A novel phase-sensitive and polarization-sensitive scheme to implement an optical low-coherence interferometry (OLCI) system is presented. With respect to conventional phase-sensitive OLCI, in our system the interference fringes of the coherent light used to recover phase information are conveniently detected by the same photodetector acquiring the low-coherence signal. This strategy guarantees the intrinsic synchronization of the two signals at any acquisition speed, makes measurements more robust against long-term fluctuations in the experimental setup, and reduces the measurement time without affecting phase accuracy. The residual phase error after the phase recovery procedure is less than 0.01 rad, to the authors' knowledge one of the best results reported so far for OLCI measurements. Polarization sensitivity is achieved in the same setup by means of polarization selective retarders (PSRs) employed to couple light into and out of the device under test. This scheme enables to retrieve the time and frequency domain response of an optical device for both the polarization states from a single data acquisition. The presented technique is extremely versatile; it can be implemented by using either fiber or free space optics and applied to the characterization of generic optical devices. Its effectiveness is demonstrated by reporting the measurement of the amplitude and phase response of integrated optical devices based on ring resonators. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Traffic Engineering in the Wavelength Domain for Optical Burst-Switched Networks

    Page(s): 3075 - 3091
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (633 KB) |  | HTML iconHTML  

    This paper addresses the possibility of using traffic engineering in the wavelength domain as a way to improve the performance of optical burst-switched (OBS) networks. With that aim, we detail a heuristic traffic engineering strategy that determines the order by which the ingress nodes of the network should search for an available wavelength for burst transmission, in order to minimize the probability that data bursts going through overlapping paths reach a common fiber link using the same wavelength. By means of network simulation, it is shown that the proposed traffic engineering strategy outperforms the existing strategies in reducing burst loss in OBS networks. This trend holds for core nodes with different degrees of wavelength conversion, ranging from the absence of wavelength converters to the use of dedicated full-range wavelength converters. More specifically, it is shown that using only traffic engineering in the wavelength domain can dramatically reduce burst loss in networks without wavelength conversion or alternatively it can reduce the number of wavelength converters in networks based on shared wavelength conversion. The simulation results also show that by combining traffic engineering in the wavelength domain with the use of the inexpensive electronic buffers at the ingress nodes, the performance of OBS networks with dedicated full-range wavelength converters can be further improved at the expense of a slight increase in the burst transfer delay. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Optical Signal Processor Using Electro-Optic Polymer Waveguides

    Page(s): 3092 - 3106
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1687 KB) |  | HTML iconHTML  

    We have investigated an optical signal processor using electro-optic polymer waveguides operating at a wavelength of 1.55 mum. Due to recent developments, many useful optical devices have become available such as optical filters, modulators, switches, and multiplexers. It will be useful to have a single optical device, which is reconfigurable to implement all of these functions. We call such a device an ldquooptical signal processor,rdquo which will play a similar role to digital signal processors in electrical circuits. We realize such an optical device in a planar lightwave circuit. Since the planar lightwave circuits are based on the multiple interference of coherent light and can be integrated with significant complexity, they have been implemented for various purposes of optical processing such as optical filters. However, their guiding waveguides are mostly passive, and the only viable mechanism to reconfigure their functions is thermal effects, which is slow and cannot be used for high-speed applications such as optical modulators or optical packet switches. On the other hand, electro-optic polymer has a very high electro-optic coefficient and a good velocity match between electrical and optical signals, thus, permitting the creation of high-speed optical devices with high efficiency. Therefore, we have implemented a planar lightwave circuit using the electro-optic polymer waveguides. As a result, the structure is complex enough to generate arbitrary functions and fast enough to obtain high data rates. Using the optical signal processor, we investigate interesting applications including arbitrary waveform generators. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.
  • Large Scale, All-Fiber Optical Cross-Connect Switches for Automated Patch-Panels

    Page(s): 3107 - 3115
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1478 KB) |  | HTML iconHTML  

    Transparent, all-optical cross-connect switches provide non-blocking, one-to-one reconfigurable interconnections between any of N input fibers and any of N output fibers. Cross-connects based on all-fiber rather than free-space interconnections have the potential for low opto-mechanical complexity, miniaturization, high optical power handling and ideal optical performance. In this paper, we propose and analyze novel architectures for large-scale, all-fiber cross-connects based on the application of theory of Knots and Braids to fiber switching and compare them on the basis of scalability, modularity and reconfiguration time. A prototype 140 input by 140 output, automated all-fiber cross-connect is developed to demonstrate these concepts. View full abstract»

    Full text access may be available. Click article title to sign in or learn about subscription options.

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