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Photonics Technology Letters, IEEE

Issue 22 • Date Nov.15, 2010

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

    Publication Year: 2010 , Page(s): C1
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    Freely Available from IEEE
  • IEEE Photonics Technology Letters publication information

    Publication Year: 2010 , Page(s): C2
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  • Table of contents

    Publication Year: 2010 , Page(s): 1627 - 1628
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  • Magnesium Fluoride Whispering Gallery Mode Disk-Resonators for Microwave Photonics Applications

    Publication Year: 2010 , Page(s): 1629 - 1631
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (280 KB) |  | HTML iconHTML  

    We have manufactured a high-Q whispering gallery mode resonator with magnesium fluoride for microwave photonics applications in the gigahertz frequency range. This crystal is scarcely used for resonator fabrication despite its numerous advantages, that are mainly high mechanical hardness, low sensitivity to water vapor pollution, and low sensitivity to photo- and thermo-refractive fluctuations at optimal temperatures. Using a customized machining procedure, we have successfully fabricated and characterized a 5-mm resonator with a surface rugosity of the order of 1 nm (from 3 to 12 atoms). Cavity ring-down measurements enabled us to determine that the resonator has a quality factor Q = 3.4 × 108 at 1550 nm. View full abstract»

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  • OSNR Monitoring for Higher Order Modulation Formats Using Asynchronous Amplitude Histogram

    Publication Year: 2010 , Page(s): 1632 - 1634
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (486 KB) |  | HTML iconHTML  

    We propose an asynchronous-amplitude-histogram-based optical signal-to-noise ratio monitoring technique for higher order modulation formats. Simulation results show that the proposed technique enables a wide monitoring range for 25-GSym/s nonreturn-to-zero/return-to-zero 16- and 64-quadrature amplitude modulation systems with high monitoring sensitivity. The tolerance of the monitoring technique to other signal impairments such as chromatic dispersion and polarization-mode dispersion is also investigated. The proposed technique can be used along transmission links with simple low-cost hardware and/or in digital signal processing (DSP)-based coherent receivers without additional hardware, thus enabling next-generation optical networks using higher order modulation formats to achieve transmission rates of 100 Gb/s per channel and beyond. View full abstract»

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  • Fabrication of Long-Period Gratings by Femtosecond Laser-Induced Filling of Air-Holes in Photonic Crystal Fibers

    Publication Year: 2010 , Page(s): 1635 - 1637
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (310 KB) |  | HTML iconHTML  

    A new method for fabricating long-period gratings (LPGs) in photonic crystal fibers (PCFs) is presented. A tightly focused femtosecond infrared laser beam scans across a PCF periodically, resulting in periodic filling of cladding air-holes through a micro-explosion and redeposition process and forming an LPG. Strong resonance of ~26 dB has been demonstrated with a grating length of <;5 mm. An annealed LPG demonstrated stable operation at 800°C for over 30 h. View full abstract»

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  • Embedded Optical Microfiber Coil Resonator With Enhanced High- Q

    Publication Year: 2010 , Page(s): 1638 - 1640
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (346 KB) |  | HTML iconHTML  

    We successfully fabricate a uniform cylindrical microfiber coil resonator by wrapping a very thin strand of microfiber on a support rod and embedding/packaging it with a low refractive index polymer. An improved Q-factor in excess of 220 000 and an extinction ratio of 11.5 dB are achieved due to nearly ideal coupling and phase matching between the adjacent turns. The Q-factor is the highest reported value to date for any microfiber-based resonators. View full abstract»

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  • SPM-Tolerant Pulse Shaping for 40- and 100-Gb/s Dual-Polarization QPSK Systems

    Publication Year: 2010 , Page(s): 1641 - 1643
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (363 KB) |  | HTML iconHTML  

    An intersymbol-interference-free pulse shape is specifically designed for self-phase-modulation (SPM) mitigation. It is experimentally shown to increase the SPM tolerance of a 40-Gb/s single-channel postcompensated dual-polarization quadrature phase-shift keying system by 1.5 dB. Numerical analyses at 40 and 100 Gb/s indicate that the specialized pulse shape can increase the maximum reach for G.652 fiber and G.655 fiber up to 1190 and 820 km, respectively. View full abstract»

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  • Single- and Dual-Wavelength Fiber Ring Laser Using Fiber Microdisk Resonator

    Publication Year: 2010 , Page(s): 1644 - 1646
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (254 KB) |  | HTML iconHTML  

    We demonstrate a fiber ring laser using a fiber-based microdisk resonator as the wavelength filter and a 2-mm-long tapered fiber as the coupling component. The fabrication process of the microdisk and tapered fiber is described. Depending on the optical coupling between the microdisk and the tapered optical fiber, either the fundamental or higher order transverse optical modes in the axial direction of the microdisk can be excited. When only the fundamental transverse mode of the microdisk is excited, the fiber laser operates at single wavelength and is polarization-insensitive. When the higher order transverse modes are excited, the fiber laser exhibits polarization sensitivity, and can operate in either single or dual-wavelength operation. A small spectral separation of 0.62 nm is achieved for dual-wavelength operation. View full abstract»

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  • 70-Gb/s Multicore Multimode Fiber Transmissions for Optical Data Links

    Publication Year: 2010 , Page(s): 1647 - 1649
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (436 KB) |  | HTML iconHTML  

    This letter describes a novel structure and crosstalk characteristics of a graded-index multicore fiber with seven cores arranged in a hexagonal array. A total of 70 Gb/s (7 × 10 Gb/s) is transmitted over a single 100-m seven-core multimode fiber (MMF) using tapered multicore fiber connectors and 850-nm vertical-cavity surface-emitting lasers, demonstrating high-speed multicore MMF transmissions for parallel optical data links. View full abstract»

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  • 100-GHz Wireless-Over-Fiber Links With Up to 16-Gb/s QPSK Modulation Using Optical Heterodyne Generation and Digital Coherent Detection

    Publication Year: 2010 , Page(s): 1650 - 1652
    Cited by:  Papers (10)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (392 KB) |  | HTML iconHTML  

    In this letter, a novel technique for direct conversion of an optical baseband quadrature phase-shift keying (QPSK) signal to a millimeter-wave wireless signal and subsequent signal demodulation is reported. Optical heterodyne mixing of the optical baseband QPSK signal with a free-running unmodulated laser for the wireless signal generation is employed. To correct for the phase and frequency offset originating from the heterodyne mixing of the two free-running lasers, wireless signal demodulation based on optical coherent detection in combination with baseband digital signal processing is implemented. As a proof of concept, 5-Gb/s amplitude-shift keying and up to a 16-Gb/s QPSK wireless signal in the band of 75-110 GHz was generated and successfully demodulated. All-photonic millimeter-wave wireless signal generation and digital coherent detection at baud-rate are employed without complex optical phase-locked loop. View full abstract»

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  • Enhancing the Brightness of GaN Light-Emitting Diodes by Manipulating the Illumination Direction in the Photoelectrochemical Process

    Publication Year: 2010 , Page(s): 1653 - 1655
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (232 KB) |  | HTML iconHTML  

    In this report, a cost-effective photoenhanced electrochemical (PEC) process was proposed to assist in forming a deep undercut sidewall and rough surface on a GaN light-emitting diode (LED). As a result, a 51% improvement in light extraction efficiency was obtained compared to a standard LED without the PEC process. Manipulating the direction of light illumination during the PEC process produced an undercut angle and rough surface on the sidewall of GaN LED, which enhanced light extraction by about 14% compared to a sample prepared using the conventional PEC process. A simulation based on a two-dimensional finite-difference time-domain method was established to investigate the light output intensity for LED samples by manipulating different illumination directions in the PEC processes. Simulation results indicated that photons have a higher probability of being emitted from the undercut sidewall and cone-like surface of the LED structure formed by the PEC process; this improved the light extraction efficiency of GaN LED. View full abstract»

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  • An All-Fiber 2- \mu m Wavelength-Tunable Mode-Locked Laser

    Publication Year: 2010 , Page(s): 1656 - 1658
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (319 KB) |  | HTML iconHTML  

    We report an all-fiber thulium-doped wavelength-tunable mode-locked laser operating near 2 μm . Reliable self-starting mode locking over a large tuning range (>50 nm) using a fiber-taper-based carbon nanotube saturable absorber is observed. Spectral tuning is achieved by stretching another fiber taper. To the best of our knowledge, this is the first demonstration of an all-fiber wavelength tunable mode-locked laser near 2 μm . View full abstract»

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  • 50-Wavelength Channel-by-Channel Tunable Optical Dispersion Compensator Using a Combination of AWG and Bulk Grating

    Publication Year: 2010 , Page(s): 1659 - 1661
    Cited by:  Papers (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (315 KB) |  | HTML iconHTML  

    We propose a novel optical configuration for a multichannel tunable optical dispersion compensator (TODC) with channel-by-channel operation across the entire L-band. The TODC consists of a cyclic frequency arrayed-waveguide grating whose free spectral range coincides with the channel spacing, a bulk grating, and a liquid crystal on silicon. We achieved channel-by-channel compensation over 50 channels with a maximum chromatic dispersion of ±800 ps/nm. View full abstract»

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  • Tunable Long Wavelength ( \sim 2.8 \mu m) GaInAsSb–GaSb Quantum-Well Binary Superimposed Grating Lasers

    Publication Year: 2010 , Page(s): 1662 - 1664
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (322 KB) |  | HTML iconHTML  

    GaInAsSb-GaSb quantum-well diode lasers emitting around 2.80 μm with a single device tuning range of 60 nm are presented. This was achieved by the implementation of binary superimposed metal gratings. The lasers work at room temperature in continuous-wave mode and show tunable single-mode emission with a sidemode suppression ratio of more than 30 dB. The optical output power of more than 1 mW makes them suitable for gas sensing. View full abstract»

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  • Optical Performance Monitoring Using Artificial Neural Network Trained With Asynchronous Amplitude Histograms

    Publication Year: 2010 , Page(s): 1665 - 1667
    Cited by:  Papers (4)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (413 KB) |  | HTML iconHTML  

    We propose an optical performance monitoring technique for simultaneous monitoring of optical signal-to-noise ratio (OSNR), chromatic dispersion (CD), and polarization-mode dispersion (PMD) using an artificial neural network trained with asynchronous amplitude histograms (AAHs). Simulations are conducted to demonstrate the technique for both 40-Gb/s return-to-zero differential quadrature phase-shift keying (RZ-DQPSK) and 40-Gb/s noneturn-to-zero 16 quadrature amplitude modulation (16-QAM) systems. The OSNR, CD, and PMD monitoring range and root-mean-square (rms) errors are 10-30 and 0.43 dB, 0-400 and 9.82 ps/nm, and 0-10 and 0.92 ps, respectively, for RZ-DQPSK systems. For 16-QAM system, the monitoring range and rms errors are 10-30 and 0.2 dB, 0-400 and 9.66 ps/nm, and 0-30 and 0.65 ps for OSNR, CD, and PMD, respectively. As the generation of AAH does not require any clock or timing recovery, the proposed technique can serve as a low-cost option to realize in-service multiparameter monitoring for the next-generation transparent optical networks. View full abstract»

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  • 1.3- \mu m Laterally Tapered Ridge Waveguide DFB Lasers With Second-Order Cr Surface Gratings

    Publication Year: 2010 , Page(s): 1668 - 1670
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (368 KB) |  | HTML iconHTML  

    We report the laterally tapered ridge waveguide InGaAsP-InGaAsP multiple quantum-well distributed-feedback (DFB) lasers with metal surface gratings, operating at λ ~1.3 μm, by holographic lithography. Single-tapered and double-tapered (bow-tie) ridge waveguide DFB structures with second-order Cr surface gratings are employed to enhance the coupling efficiency. The 600-μm-long laterally coupled DFB laser with a double-tapered ridge waveguide structure exhibits significantly improved single-mode operation without mode hopping, with a maximum sidemode suppression ratio of 42 dB and temperature-dependent wavelength shift up to d λ/dT ~0.071 nm/K. View full abstract»

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  • Novel FBG Decoder for Simultaneous Time Domain Coherent Optical Code Recognition and Chromatic Dispersion Compensation

    Publication Year: 2010 , Page(s): 1671 - 1673
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (284 KB) |  | HTML iconHTML  

    A novel fiber Bragg grating (FBG) decoder is proposed for simultaneous time domain coherent optical code recognition and chromatic dispersion compensation. We derive the target frequency response of such a device and use the discrete layer peeling method to synthesize it. This dispersion compensation FBG decoder guarantees the system performance and simplifies the network structure. We also discuss the tolerance of the proposed device to the phase shift error in the fabrication. View full abstract»

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  • Mode-Locking Using \chi ^{(2)} Waveguide Arrays

    Publication Year: 2010 , Page(s): 1674 - 1676
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (140 KB) |  | HTML iconHTML  

    It is demonstrated theoretically that the use of a χ(2) waveguide array in conjunction with a fiber laser cavity is capable of producing self-starting, robust, and stable mode-locking. The χ(2) waveguide array takes advantage of several key effects to enhance the mode-locking stability and effective saturable absorption, including the nonlinear mode-coupling in the waveguide array and the phase-sensitivity of the amplifier. Specifically, the mode-locked pulse phase is locked and stabilized by the pump field upon successive cavity round-trips. The combined advantages of these mode-locking conditions make the χ(2) waveguide-array-based mode-locked laser a technologically attractive photonic device warranting further experimental and theoretical invesgation. View full abstract»

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  • Biometric Mapping of Fingertip Eccrine Glands With Optical Coherence Tomography

    Publication Year: 2010 , Page(s): 1677 - 1679
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (793 KB) |  | HTML iconHTML  

    Biometric access control systems often employ fingerprint recognition based on the analysis of ridge patterns and minutiae. The inclusion of finer details, such as sweat pores, increases the accuracy of fingerprint identification. However, the distribution of sweat pores is difficult to extract from conventional fingerprint images, where image quality is susceptible to variations in fingertip surface conditions. Furthermore, a fingertip surface can be routinely counterfeited with a variety of techniques. We propose a more reliable biometric technology using spectral domain optical coherence tomography (SD-OCT) to image the subsurface of a fingertip. Experiments demonstrate high repeatability in clearly visualizing the distribution of sweat (eccrine) glands in live fingertips. Experiments on artificial fingertips confirm this is a spoof-proof approach. We believe these encouraging results demonstrate the value of SD-OCT as a robust fingerprint identification technology for biometric recognition. View full abstract»

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  • Fast Random Bit Generation in Optical Domain With Ultrawide Bandwidth Chaotic Laser

    Publication Year: 2010 , Page(s): 1680 - 1682
    Cited by:  Papers (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (362 KB) |  | HTML iconHTML  

    We propose a novel scheme of random bit generator which does signal processing in the optical domain. The output of an ultrawide bandwidth chaotic laser is sampled through an electrooptical modulator, then quantized by an all-optical flip-flop, and finally coded into random bit sequences. Simulation results show that 5-Gb/s random bits in the return-to-zero format and with a duty ratio of 1/2 can be generated, which can pass standard statistical tests for randomness after an exclusive-or operation. View full abstract»

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  • A Second-Order Feedforward Optical Power Control Scheme for Automotive VCSEL Drivers

    Publication Year: 2010 , Page(s): 1683 - 1685
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (262 KB) |  | HTML iconHTML  

    This letter presents a feedforward optical power control scheme for automotive 150-Mb/s vertical-cavity surface-emitting laser (VCSEL) transmitters. The bias current exhibits a second-order dependence upon temperature, while the modulation current is provided with a piecewise linear compensation of temperature variations. The resulting VCSEL modulation performance was analyzed in detail and experimentally validated. Over the harsh automotive temperature range from -40°C to 105°C, a high extinction ratio was maintained despite very tight tolerances on pulsewidth distortion (PWD); the variation of the emitted optical power was measured to be less than 1.2 dB, while maintaining an extinction ratio better than 12 dB and a PWD less than ±2%. View full abstract»

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  • Fiber In-Line Mach–Zehnder Interferometer Embedded in FBG for Simultaneous Refractive Index and Temperature Measurement

    Publication Year: 2010 , Page(s): 1686 - 1688
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (321 KB) |  | HTML iconHTML  

    An ultracompact optical fiber sensor based on a Mach-Zehnder interferometer (MZI) embedded in fiber Bragg grating (FBG) is proposed and experimentally demonstrated for simultaneous refractive index (RI) and temperature measurement. By use of the resonant wavelength of the FBG and the interference dip of the MZI, the RI and temperature of the surrounding medium can be unambiguously determined. The interesting properties of the sensor include good operation linearity, extremely high RI sensitivity up to ~ -9148 nm/RI unit in the RI range between 1.30 and 1.325, and precise sensing location, determined by the MZI cavity created. View full abstract»

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  • Carrier Lifetime and Electron Spin Relaxation Time in (110)-Oriented GaAs–AlGaAs Quantum-Well Micro-Posts

    Publication Year: 2010 , Page(s): 1689 - 1691
    Cited by:  Papers (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (372 KB) |  | HTML iconHTML  

    Carrier lifetime and electron spin relaxation time in (110)-oriented GaAs-AlGaAs quantum-well (QW) micro-posts are investigated by polarization- and time-resolved photoluminescence measurements. The long electron spin relaxation time in QWs on GaAs (110) is found to be preserved even when the sidewall boundaries with fast surface recombination are introduced and the carrier lifetime is drastically shortened. Rate equation analysis shows that spin-controlled vertical-cavity surface-emitting lasers with such (110)-QW micro-posts will exhibit faster switching of lasing circular polarizations than that we previously demonstrated. In particular, 20-GHz switching is expected with 0.5-μm posts. View full abstract»

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  • Generation and Detection of Ultra-Wideband Waveforms Using Stimulated Brillouin Scattering Amplified Spontaneous Emission

    Publication Year: 2010 , Page(s): 1692 - 1694
    Cited by:  Papers (5)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (322 KB) |  | HTML iconHTML  

    A scheme for the photonic generation and coherent detection of ultra-wideband radio-frequency (RF) noise is proposed and demonstrated. The technique relies on the amplified spontaneous emission of a broadened stimulated Brillouin scattering process in an optical fiber (SBS-ASE). The SBS-ASE noise is on-off modulated, and down-converted to the RF spectral range via heterodyne beating. The spectrum of the SBS-ASE is broadened beyond 1 GHz by tailored direct modulation of the pump wave. A data transmitter and a coherent receiver are demonstrated experimentally. Coherent detection of the noise waveform is based on the transmission of a delayed, unmodulated replica alongside the data (transmit reference). A performance analysis of the receiver statistics is provided. Q parameter values of 4.6 at data rates of 4 Mb/s are demonstrated. 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.

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Meet Our Editors

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