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Photonics Technology Letters, IEEE

Issue 22 • Date Nov.15, 2009

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Displaying Results 1 - 25 of 32
  • [Front cover]

    Publication Year: 2009 , Page(s): C1
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    Freely Available from IEEE
  • IEEE Photonics Technology Letters publication information

    Publication Year: 2009 , Page(s): C2
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    Freely Available from IEEE
  • Table of contents

    Publication Year: 2009 , Page(s): 1651 - 1652
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  • Optical Fiber Cavity Ring Down Measurement of Refractive Index With a Microchannel Drilled by Femtosecond Laser

    Publication Year: 2009 , Page(s): 1653 - 1655
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (255 KB) |  | HTML iconHTML  

    A microchannel was inscribed in the fiber of a ring cavity which was constructed using two 0.1% : 99.9% couplers and a 10-m fiber loop. Cavity ring down spectroscopy was used to measure the refractive index (RI) of gels infused into the microchannel. The ring down time discloses a nonlinear increase with respect to RI of the gel and sensitivity up to 300 mus/RI unit and an index resolution of 1.4 times10-4 was obtained. View full abstract»

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  • Blue-Enhanced PIN Finger Photodiodes in a 0.35- \mu{\hbox {m}} SiGe BiCMOS Technology

    Publication Year: 2009 , Page(s): 1656 - 1658
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (162 KB) |  | HTML iconHTML  

    Finger photodiodes in PIN technology are introduced to enhance the responsivity for blue and ultraviolet light. A thick low doped epitaxial layer results in high responsivity and high bandwidth also for red and near-infrared light. Results of PIN finger photodiodes are compared to that of PIN photodiodes for 10- and 15-mum epitaxial intrinsic layer thickness. The cathode finger structure results in a high responsivity of 0.20 A/W (quantum efficiency 61%) for 410-nm light and a bandwidth of 1.25 GHz for 10- mum epi thickness at a reverse bias voltage of 3 V. The rise and fall times with an epitaxial layer thickness of 15 mum are below 1 ns for the wavelength range from 410 to 785 nm. View full abstract»

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  • GaN-Based LEDs With GaN \mu -Pillars Around Mesa, Patterned Substrate, and Reflector Under Pads

    Publication Year: 2009 , Page(s): 1659 - 1661
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (288 KB) |  | HTML iconHTML  

    Nitride-based light-emitting diodes (LEDs) with textured sidewall, GaN mu-pillars around mesa region, patterned sapphire substrate (PSS), and highly reflective Ag-Cr-Au electrode pads were fabricated using the conventional lithography method (labeled as experimental LEDs). When a 20-mA injection current was applied, forward voltages were 3.18 and 3.4 V for the conventional and experimental LEDs, respectively. The high 20-mA Vf of LEDs with Ag-Cr-Au electrode pads could be attributed to the fact that the specific contact resistance of n+-GaN-Ag-Cr-Au is slightly higher than that of the n+ -GaN-Cr-Au contact. It was found that we could achieve much stronger LED output power with textured sidewalls, GaN mu-pillars around mesa region, PSS, and highly reflective Ag-Cr-Au electrode pads. It was also found that we could enhance LED output power by more than 80% compared with the conventional LEDs. View full abstract»

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  • Reduction of MAI and Beat Noise in OCDMA Systems Using an SA-SOA-TPA-Based Receiver

    Publication Year: 2009 , Page(s): 1662 - 1664
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (383 KB) |  | HTML iconHTML  

    In this letter, we investigate the removal of multiple access interference and optical beat noise from a two-channel optical system that simulates the output from a time-spread optical code-division multiple access system operating at a data rate of 100 Mb/s. Both noise sources were removed using a saturable absorber semiconductor optical amplifier two-photon absorption receiver structure. Experimental results show error-free operation when all three devices are used together. View full abstract»

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  • Near-Stoichiometric Ti : LiNbO _{3} Strip Waveguides Fabricated by Standard Ti Diffusion and Post-VTE

    Publication Year: 2009 , Page(s): 1665 - 1667
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (209 KB) |  | HTML iconHTML  

    We report near-stoichiometric (NS) Ti : LiNbO3 waveguides fabricated by indiffusion of 4-, 5-, 6-, 7-mum-wide 120-nm-thick Ti-strips at 1060degC for 10 h into a congruent LiNbO3 (i.e., standard Ti diffusion procedure) and post-vapour-transport-equilibration (VTE) treatment at 1100degC for 5 h. These waveguides are NS and single-mode at 1.5 mum, and have a loss of 1.0/0.8 dB/cm for the TM/TE mode. In the width/depth direction of the waveguide, the mode field follows a Gauss/Hermite-Gauss profile, and the Ti profile follows a sum of two error functions/a Gauss function. The post-VTE resulted in increase of diffusion width/depth by 2.0/1.0 mum. A two-dimensional refractive index profile in the guiding layer is suggested. View full abstract»

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  • Reconfigurable Two-Arm Spiral Antenna Microwave Photonic Polarization Diversity Technique

    Publication Year: 2009 , Page(s): 1668 - 1670
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (343 KB) |  | HTML iconHTML  

    A microwave photonic configuration for multipattern control of a two-arm spiral antenna is presented. An elegant polarization diversity multiplexing scheme allows the two arms to be combined with dynamically reconfigurable amplitude and phase. Experimental demonstration of the bandwidth of the antenna and dynamic control of the radiation patterns is presented. View full abstract»

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  • Hybrid Interrogation System for Distributed Fiber Strain Sensors and Point Temperature Sensors Based on Pulse Correlation and FBGs

    Publication Year: 2009 , Page(s): 1671 - 1673
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (316 KB) |  | HTML iconHTML  

    A hybrid interrogation scheme for distributed strain sensors and point temperature sensors is proposed and its feasibility is demonstrated. It exploits the advantages of distributed sensors and point sensors simultaneously. The proposed interrogation scheme uses a wavelength tunable pulse source and wavelength-dependent reflectors for region selective sensing. Experimental results confirm its linear response and a resolution of 0.02% of the total dynamic range, which in our experiment is over 2000 microstrains for sensing regions of around a 0.5-m length. The stability of the measurements is over 99.8%. Finally, the high input power from the signal source and the limited losses from the reflectors allow the usage of a large number of sensors in a fiber. View full abstract»

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  • Thermal Stability of Poly-Si Phototransistors Incorporating Ge Quantum Dots for Near-Ultraviolet Light Detection and Amplification

    Publication Year: 2009 , Page(s): 1674 - 1676
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (467 KB) |  | HTML iconHTML  

    We investigated temperature-dependent ( 300 K - 120 K ) subthreshold characteristics and transient photoresponses of poly-Si phototransistors (PTs) incorporating germanium (Ge) quantum dots (QDs) in the gate oxide for near-ultraviolet light detection and amplification. Incorporating Ge QDs into the poly-Si PT structure improves the device thermal stability in the subthreshold characteristics and transient photoresponse, due to better light absorption efficiency and photovoltaic effect suppression. View full abstract»

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  • Nodal Architectures for Shared Mesh Restoration of IP and Wavelength Services

    Publication Year: 2009 , Page(s): 1677 - 1679
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (354 KB) |  | HTML iconHTML  

    Future networks are expected to support heterogeneous traffic, including both Internet Protocol (IP) and wavelength services. IP services are typically restored using IP-layer rerouting mechanisms, whereas wavelength services are restored in the optical layer. With architectures where IP services are mapped into Layer-2 or time-division-multiplexing (TDM) protocols at the network edge, a common restoration mechanism can be utilized for both IP and wavelength services. This letter examines various nodal architectures that can be utilized to support such a unified restoration paradigm. View full abstract»

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  • Comparison of 112-Gb/s PM-RZ-DQPSK and PM-RZ-D8PSK in Terms of OSNR Requirement and Transmission Impairments

    Publication Year: 2009 , Page(s): 1680 - 1682
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (425 KB) |  | HTML iconHTML  

    We have, for the first time, experimentally investigated 112-Gb/s polarization-multiplexed return-to-zero differential 8-ary phase-shift keying (PM-RZ-D8PSK) with differential detection in terms of optical signal-to-noise ratio requirement, group velocity dispersion (GVD), and differential group delay (DGD) tolerances, together with a direct comparison with PM-RZ differential quadrature phase-shift keying at equivalent bit rate. The results indicate higher tolerances with respect to GVD and DGD but lower receiver sensitivity in the case of PM-RZ-D8PSK. View full abstract»

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  • Polarization-Dependent Sidewall Light Diffraction of LEDs Surrounded by Nanorod Arrays

    Publication Year: 2009 , Page(s): 1683 - 1685
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (334 KB) |  | HTML iconHTML  

    The polarization behavior of the light-emitting diodes (LEDs) with nanorods surrounding the p-mesa is investigated. The nanorods were fabricated using a natural nanosphere lithography and are intended to diffract laterally propagated light. In the horizontal direction, s-polarized light is dominated since the injected carriers choose to fill up the lowest energy state in a direction parallel to the quantum-well layers. The p/s-polarized ratio starts to increase with the increase of radiated angles and eventually saturates. Since the Bragg diffraction of laterally propagated p-polarized mode by nanorods is more efficient than the s-polarized light, the p/s-ratio of the device with nanorods is higher than that without rods. The p/s-ratio of the LED with nanorods is 1.96 at 90deg, and is 1.52 when the integrating intensity between 0deg and 90deg is considered. View full abstract»

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  • Microwave Photonic Delay Line With Separate Tuning of the Optical Carrier

    Publication Year: 2009 , Page(s): 1686 - 1688
    Cited by:  Papers (18)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (287 KB) |  | HTML iconHTML  

    Significant performance improvement for photonic delay lines in microwave-photonics based on a new concept of separately tuning the optical carrier is proposed and analyzed. Optical microresonator delay lines using a balanced SCISSOR design with additional resonators to separately tune the carrier phase delay to provide a true-time-delay for the broadband microwave signal are presented. Significant improvements in broadband tunable delay and devices losses are predicted. View full abstract»

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  • PDL and DGD Reduction in Bragg Gratings Using Twisted Fibers for the Inscription

    Publication Year: 2009 , Page(s): 1689 - 1691
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (254 KB) |  | HTML iconHTML  

    We report the possibility to reduce the polarization-dependent loss (PDL) and the differential group delay (DGD) in fiber Bragg gratings (FBGs) by inducing polarization-mode coupling (PMC). To induce the PMC, the fiber is twisted before the inscription and then relaxed once the FBG is written. The theoretical concept as well as the simulation method used to study FBGs exhibiting PMC is detailed. The obtained results point out a significant decrease of the gratings' PDL and DGD values. In addition, experimental results, in good agreement with the theory, demonstrate the possibility to implement this method in practice. View full abstract»

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  • A Highly Accurate FDTD Model for Simulating Lorentz Dielectric Dispersion

    Publication Year: 2009 , Page(s): 1692 - 1694
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (225 KB) |  | HTML iconHTML  

    A highly accurate and numerically stable model of Lorentz dielectric dispersion for the finite-difference time-domain (FDTD) method is presented. The coefficients of the proposed model are optimally derived based on the Maclaurin series expansion (MSE) method and it is shown that the model is much better than the other four reported models in implementing the Lorentz dielectric dispersion with error of relative permittivity several orders lower. The model's stability and performance are also analyzed when it is incorporated into the practical second- and fourth-order accurate FDTD algorithms for an exemplified Lorentz medium. Interestingly, we find that all the mentioned models show nearly the same performance in the second-order algorithm due to its large intrinsic numerical dispersion and the superiority of the proposed MSE model begins to be manifested in the higher-order, say, fourth-order FDTD algorithms as implied by the governing numerical dispersion equations. View full abstract»

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  • Compensation for Second-Order Temperature Dependence in Athermal Arrayed-Waveguide Grating Realizing Wide Temperature Range Operation

    Publication Year: 2009 , Page(s): 1695 - 1697
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (114 KB) |  | HTML iconHTML  

    We propose a new compensation technique for the second-order temperature dependence in a silica-based arrayed-waveguide grating (AWG) multi/demultiplexer with a resin-filled groove that realizes a wide operating temperature range. We newly employ an additional interferometer in the input port and control the optical field perturbation by using a first-mode lightwave at the entrance to the first slab waveguide. We employ the design to fabricate a 32-channel 100-GHz-spacing athermal AWG that is as compact as a conventional AWG, and demonstrate a reduction in the passband wavelength variation from 70 to 22 pm over an extended - 40degC to 80degC temperature range. View full abstract»

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  • Diplexer With Integrated Filters and Photodetector in Ge–Si Using \Gamma -{X} and \Gamma -{M} Directions in a Grating Coupler

    Publication Year: 2009 , Page(s): 1698 - 1700
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (320 KB) |  | HTML iconHTML  

    We demonstrate a central-office-type diplexer in which the filter and photodetector are monolithically integrated on a silicon-on-insulator substrate. The photonic integrated circuit receives a 1577-nm signal from an external laser and sends it to the fiber link using a two-dimensional grating coupler. The same grating coupler receives a 1270-nm signal from the fiber link and sends it to a monolithically integrated germanium photodetector using a polarization-diversity scheme to achieve polarization independence. The grating coupler is novel in that both the Gamma-X and Gamma-M directions are employed. This allows the grating coupler to couple both the 1577- and 1270-nm wavelengths with a small fiber tilt angle and hence have low polarization-dependent loss. View full abstract»

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  • Tunable Optical Dispersion Compensator Consisting of Simple Optics With Arrayed Waveguide Grating and Flat Mirror

    Publication Year: 2009 , Page(s): 1701 - 1703
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (221 KB) |  | HTML iconHTML  

    We propose a tunable optical dispersion compensator (TODC) that uses an arrayed waveguide grating (AWG) and a flat mirror. The TODC employs simple and cost-effective optics, and its chromatic dispersion can be changed simply by translating the AWG. We obtained a 3-dB bandwidth of 39 GHz when the dispersion was tuned within 800 ps/nm, and a maximum dispersion of plusmn3000 ps/nm. View full abstract»

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  • 10-GHz 11.5-ps Pulse Generation From a Single-Mode Gain-Switched InGaAs VCSEL at 1.1 \mu m

    Publication Year: 2009 , Page(s): 1704 - 1706
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (143 KB) |  | HTML iconHTML  

    We have successfully generated a 10-GHz 11.5-ps pulse train at 1.1 mum by using a gain switching technique with a high-speed and single-mode vertical-cavity surface-emitting laser (VCSEL). The InGaAs-based VCSEL we used had a sidemode suppression ratio of more than 50 dB and a modulation bandwidth of 7.2 GHz. A nearly transform-limited Gaussian pulse was obtained after chirp compensation, and the repetition rate can be increased up to 16 GHz. We also demonstrated a 10-Gb/s return-to-zero data modulation for the generated 10-GHz pulse train. View full abstract»

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  • XPM Statistics in 100% Precompensated WDM Transmission for OOK and DPSK Formats

    Publication Year: 2009 , Page(s): 1707 - 1709
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (310 KB) |  | HTML iconHTML  

    We numerically study cross-phase modulation (XPM) statistics in 100% precompensated wavelength-division-multiplexing transmission with on-off keying (OOK) and differential phase-shift keying (DPSK) formats. XPM and its randomness are determined by nonlinear diffusion bandwidth and specific modulation format in the target channel. XPM degradation in DPSK channels shows much less stochastic than that in OOK channels. The small duty cycle also helps to reduce XPM randomness. View full abstract»

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  • Wavelength-Tunable Laser for Signal Remodulation in WDM Access Networks Using DPSK Downlink and OOK Uplink

    Publication Year: 2009 , Page(s): 1710 - 1712
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (457 KB) |  | HTML iconHTML  

    In this investigation, a simple wavelength-tunable laser based on a Fabry-Perot laser diode (FP-LD) and an erbium-doped fiber amplifier to serve as a downlink signal in a colorless wavelength-division-multiplexed passive optical network (PON) is proposed and experimentally demonstrated. The tuning range of the proposed laser is between 1529.48 and 1560.72 nm, and the output performance of proposed laser is discussed. Colorless operation is implemented by using an FP-LD and a reflective semiconductor optical amplifier in each optical network unit for uplink signal remodulation, respectively. In addition, error-free data signal remodulation using 10-Gb/s downlink differential phase-shift keying and 2.5-Gb/s uplink on-off keying is achieved in a 25-km reach PON. View full abstract»

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  • Accurate Characterization of Twist-Induced Optical Activity in Single-Mode Fibers by Means of Polarization-Sensitive Reflectometry

    Publication Year: 2009 , Page(s): 1713 - 1715
    Cited by:  Papers (6)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (139 KB) |  | HTML iconHTML  

    The stress-optic rotation coefficient g, describing the twist-induced optical activity in single-mode optical fibers, has been accurately measured by means of polarization-sensitive frequency domain reflectometry. Measurements have been performed on both spun and unspun fibers and the measured values of g vary between 0.14 and 0.15, with an uncertainty of less than 4%. View full abstract»

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  • Full-Duplex 60-GHz RoF System With Optical Local Oscillating Carrier Distribution Scheme Based on FWM Effect in SOA

    Publication Year: 2009 , Page(s): 1716 - 1718
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (343 KB) |  | HTML iconHTML  

    A full-duplex 60-GHz radio-over-fiber (RoF) system using novel optical local oscillating (LO) carrier distribution scheme to reduce the system cost and realize centralized management is proposed and experimentally demonstrated. In the proposed scheme, the optical LO carriers for producing remote electrical LO signals at the base stations (BSs) are generated together with the downlink RoF carriers at the central station (CS) via four-wave-mixing effect in semiconductor optical amplifier, and are then distributed to the BSs along with the downlink RoF signals. By down-converting the 60-GHz-band uplink signal with the remotely produced 60-GHz LO signal and reusing the optical LO carriers as the uplink optical source, only a cost-effective intermediate frequency modulator is required at each BS to transmit the uplink signal, which will dramatically reduce the whole system budget due to a large amount of BSs. Moreover, the operating frequency of each BS can be controlled remotely at the CS end to realize centralized management and convenient reconfiguration. Using the proposed scheme, 622-Mb/s signals for both directions are successfully transmitted over a 20-km single-mode fiber link and a 50-cm wireless channel with less than 0.1- and 0.2-dB power penalty for downlink and uplink, respectively. View full abstract»

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Aims & Scope

This letters journal addresses all aspects of the IEEE Photonics Society Constitutional Field of Interest with emphasis on photonic/lightwave components and applications, laser physics and systems and laser/electro-optics technology.

Full Aims & Scope

Meet Our Editors

Editor-in-Chief
Dr. Seb J. Savory
University College London