Optical Fiber Communication Research Papers (original) (raw)

An applications-oriented review of optical parametric amplifiers in fiber communications is presented. The emphasis is on parametric amplifiers in general and single pumped parametric amplifiers in particular. While a theoretical framework based on highly efficient four-photon mixing is provided, the focus is on the intriguing applications enabled by the parametric gain, such as all-optical signal sampling, time-demultiplexing, pulse generation, and wavelength conversion. As these amplifiers offer high gain and low noise at arbitrary wavelengths with proper fiber design and pump wavelength allocation, they are also candidate enablers to increase overall wavelength-division-multiplexing system capacities similar to the more well-known Raman amplifiers. Similarities and distinctions between Raman and parametric amplifiers will also be addressed. Since the first fiber-based parametric amplifier experiments providing net continuous-wave gain in the for the optical fiber communication applications interesting 1.5-m region were only conducted about two years ago, there is reason to believe that substantial progress may be made in the future, perhaps involving "holey fibers" to further enhance the nonlinearity and thus the gain. This together with the emergence of practical and inexpensive high-power pump lasers may in many cases prove fiber-based parametric amplifiers to be a desired implementation in optical communication systems.

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- Quantum Physics, Optical Communication System, Optical physics, Wavelength Conversion

We present simulation results for 192 Gb/s (16 ×12) OTDM transmission with different time delays over standard fiber G.652. The optical 192 Gb/s to 12 Gb/s demultiplexing (OTDM) is used and the results compared with 160 Gb/s to 10 Gb/s OTDM demultiplexing. The observations show the feasibility of an error free 192 Gb/s OTDM transmission with a minimum time delay of 1 ps which yields BER as low as 3.38E-89 while the minimum BER obtained at 1 ps time delay for 160 Gb/s OTDM is 1.21E-244, which is practically error free.

- by yugnanda malhotra
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- Optical Switch, Adaptive Optics, Time Delay, Bit Error Rate

We present experimental and modeling results for InP-based avalanche photodiodes designed for single photon counting in the wavelength range of 0.95-1.65 μm. We describe performance trade-offs and underlying mechanisms governing key... more

- by Mark Itzler
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- Optical Fiber Communication

A combination of orthogonal frequency-division multiplexing (OFDM) and compatible single-sideband modulation (CompSSB) using a standard direct-detection scheme is suggested to overcome chromatic dispersion without explicit compensation. Since the proposed type of SSB modulation does not require a spectral gap between optical carrier and subcarriers, it is highly spectrally efficient and the complexity in the analogue part is reduced compared to known direct-detection schemes for OFDM.

An InP-based high-speed optical modulator is presented. The Schottky-i-n waveguide structure on InP-based material was used to reduce the switching voltage V and the excess loss, while maintaining high-modulation efficiencies. To minimize residual amplitude modulation and to improve power handling capability, the bulk electrooptic effect in InGaAlAs was utilized for phase shifting. As a result, a simple structure InAlAs-InGaAlAs Mach-Zehnder optical modulator with traveling-wave electrodes was fabricated and characterized. This device achieved a switching voltage V of 3.6 V, extinction ratio (>23 dB) and high-speed operation at 1.55-m wavelength.

- by ROSE REYES
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- Semiconductor Devices, Optical physics, High Speed, Optical Modulator

Optical fiber communication is not as secure as generally perceived. There are a number of known methods of extracting or injecting information into a fiber link, while avoiding detection. Few incidents have been reported as a successfully tapped fiber is difficult to detect. In this paper we highlight a number of known fiber tapping methods. We report simulation of optical characteristics of a fiber being tapped by 'bend' method and proof of concept with physical experiment. We also presented visualized scenarios in which a resourceful eavesdropper can compromise security of a fiber link with existing technologies. Some measures to prevent fiber tapping or to nullify the significance of information tapped from fiber were also discussed.

- by Habib Fathallah
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- Engineering, Optical fiber, Optical Fiber Communication, Layer

This paper presents an efficient method for the design of complex fiber Bragg gratings. The method relies on the synthesis of the impulse response of the grating by means of a differential layer-peeling algorithm. The algorithm developed takes into account all the multiple reflections inside the grating, giving an exact solution to the inverse scattering problem. Its low algorithmic complexity enables the synthesis of long fiber gratings. The method is illustrated by designing several filters with interest for optical fiber communication systems: dispersionless bandpass filters and second-and third-order dispersion compensators.

- by Miguel A Muriel
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- Design, Inverse Problems, Inverse Scattering, Fiber Bragg grating

We use for what we believe is the first time narrowband end-reflectors to reduce losses through short-wavelength amplified stimulated emission (ASE) in silica-based erbium-doped fiber amplifiers operating at wavelengths above 1570 nm. The end-reflectors feed a small fraction of the ASE, up to a few tenths of a milliwatt, back into the amplifying fiber. The reflected ASE compresses the short-wavelength gain and thus reduces the ASElosses, from, e.g., 50 mW for a launched pump power of 110 mW at 980 nm without end-reflector to 10 mW with an optimized endreflector. We investigate possible improvements of gain (around 5 dB) and output power (up to 17 mW), and the influence of the amount and wavelength of the feedback.

- by Kim Gain
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- Silica, Erbium Doped Fiber Amplifier, Optical physics, Optical Fiber Communication

In this paper we have studied the asymmetric versus symmetric planar waveguide in terms of their usefulness in optical fiber communication systems. We have explored the thin waveguide versus thick waveguide first. Later on usefulness of asymmetric versus symmetric waveguide is carried out to target for WDM optical network application. All kinds of optical network components are fabricated on Si substrate with the point of view of their application. Here asymmetric planar structure may be more useful compared to symmetric waveguide in terms of their non-uniform power confinement properties. However, the symmetric waveguide structure may be more useful for their high power confinement properties. It is well known that the thin symmetric waveguide supports at least one mode. However the thick waveguide may support many even as well as odd modes. We study the power confinement properties for symmetric as well as asymmetric waveguide structure. We conclude that higher order modes show the nonlinear power variations. Mode field profile for various cases is discussed as well. Comparative study between asymmetric versus symmetric waveguide has a lot of significance in optical network area. It has been shown through analysis that in asymmetric waveguide, the power flows more through film region in the case of fundamental mode. Power confinement properties for asymmetric waveguide versus symmetric waveguide have been studied.

- by sanjeev raghuwanshi
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- Comparative Study, Optical Waveguide, Optical network, High Power

The intensive investment in optical microelectromechanical systems (MEMS) in the last decade has led to many successful components that satisfy the requirements of lightwave communication networks. In this paper, we review the current state of the art of MEMS devices and subsystems for lightwave communication applications. Depending on the design, these components can either be broadband (wavelength independent) or wavelength selective. Broadband devices include optical switches, crossconnects, optical attenuators, and data modulators, while wavelength-selective components encompass wavelength add/drop multiplexers, wavelength-selective switches and crossconnects, spectral equalizers, dispersion compensators, spectrometers, and tunable lasers. Integration of MEMS and planar lightwave circuits, microresonators, and photonic crystals could lead to further reduction in size and cost.

- by Yougui Wu and +1
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- Optical Switch, Photonic Crystal, Mechanical systems, Optical Signal Processing

We demonstrate photonic circuits monolithically integrated on an InP-based platform for use in coherent communication links. We describe a technology platform that allows for the integration of numerous circuit elements. We show examples of an integrated transmitter which offers an on-chip wavelengthdivision-multiplexing source with a flat gain profile across a 2 THz band and a new device design to provide a flatted gain over a 5 THz band. We show coherent receivers incorporating an integrated widely tunable local oscillator as well as an optical PLL. Finally, we demonstrate a tunable optical bandpass filter for use in analog coherent radio frequency links with a measured spurious-free dynamic range of 86.3 dB-Hz 2/3 as well as an improved design to exceed 117 dB-Hz 2/3 .

- by Pietro Binetti
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- Integrated Optics, IEEE, Optical Waveguide, Radio Frequency

Optical signal processing techniques employ a wide range of devices and various nonlinearities to achieve multiple network functionalities. The choice of nonlinearity can also impact the relative efficiency, both in terms of energy and material consumption, of the signal processing function being implemented. Techniques for some of the important functionalities, wavelength multicasting, wavelength-division multiplexing to time-division multiplexing, add-drop multiplexing, and wavelength exchange are compared in terms of the used optical spectrum, number of pumps required, and optical energy consumed. These include varieties of four-wave mixing, cross-phase modulation, Kerr-effectbased polarization rotation in optical fibers, and three-wave mixing in lithium niobate waveguides (WGs). Future possibilities of greener optical signal processing using on-chip WG technologies are discussed within the scope of recent developments in the dispersion tailored, highly nonlinear WGs.

- by Scott Nuccio
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- Quantum Physics, Nonlinear Optics, Optical Waveguides, Optical Waveguide

We demonstrate photonic circuits monolithically integrated on an InP-based platform for use in coherent communication links. We describe a technology platform that allows for the integration of numerous circuit elements. We show examples of an integrated transmitter which offers an on-chip wavelength-division-multiplexing source with a flat gain profile across a 2 THz band and a new device design to provide a flatted gain over a 5 THz band. We show coherent receivers incorporating an integrated widely tunable local oscillator as well as an optical PLL. Finally, we demonstrate a tunable optical bandpass filter for use in analog coherent radio frequency links with a measured spurious-free dynamic range of 86.3 dB-Hz2/3 as well as an improved design to exceed 117 dB-Hz2/3.

- by Mingzhi Lu
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- Integrated Optics, IEEE, Optical Waveguide, Radio Frequency

We review the research progress concerning some fundamental issues related to polarization-mode dispersion (PMD) in high-speed fiber-optic transmission systems. We pay particular attention to issues such as the PMD-induced pulse broadening, PMD measurement and emulation, as well as PMD compensation. An electrical equalization technique based on a transversal filter and an optical technique based on a nonlinear chirped fiber Bragg gratings for PMD compensation will be discussed.

- by Paulo André
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- Fiber Bragg grating, Optical Communication System, Optical physics, High Speed

This paper presents a simple and efficient design process of a remotely pumped optimized Erbium doped fiber amplifier (R-EDFA) for repeaterless long haul optical fiber communication system (OFCS) by the numerical analysis of EDFA rate equation model. The length of Erbium doped fiber (EDF) is optimized using very low remote pump power. The effect of pump power, signal power, signal wavelength and amplified spontaneous emission (ASE) on the gain and noise figure (NF) of R-EDFA is described in details using the numerical simulation of the EDFA rate equation model. Using these findings as well as considering high gain and low NF of R-EDFA as main design objectives, the designers are able to carry out the design of an optimized R-EDFA for long haul OFCS by following the proposed design process.

The performance of filtered analog photonic links, useful in signal processing applications, is analyzed along with techniques for compensation of distortion. We analyze the attributes of various link configurations and compare the performance of filtered coherent-detection links with intensity-modulated-direct-detection links. Experimental results on the dynamic range and the compensation of nonlinearities using predistortion compensation are presented for a filtered coherent link. We demonstrate suppression of third-order nonlinearity by 20 dB. In addition to supporting signal processing operations such as filtering and arbitrary intermediate frequency downconversion, at the same detected power, we find filtered coherent links to have up to 9 dB noise figure advantage over unfiltered direct-detection links, dependent on the limits of the operating optical power in the link.

- by Anjali Agarwal
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- Signal Processing, Radio Frequency, Microwave Photonics, Optical physics

Photorefractive materials, including traditional electro-optic photorefractive crystals as well as photopolymers and photosensitive glasses, have demonstrated their potential in information systems. In this paper, we describe several applications of various photorefractive materials in information storage, processing, and communication systems. Specifically, we briefly review the applications of the traditional electro-optic photorefractive crystals in optical information processing and volume holographic data storage, then discuss our recent works on the applications of photopolymers, holographic polymer dispersed liquid crystals, and photosensitive glasses in photonic devices for optical fiber communications.

- by Claire Gu
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- Materials Engineering, Communication System, Data storage, Optical physics

We propose and demonstrate two configurations for optical millimeter-wave (mm-wave) generation and transmission of 3-Gb/s downstream data based on a gain-switched laser (GSL). The first configuration generates an optical comb spectrum from a GSL that can be appropriately filtered to generate two optical sidebands with 60-GHz separation. These sidebands are modulated with baseband data by using an external intensity modulator and then transmitted via optical fiber to the remote antenna unit (RAU). The second configuration produces a modulated optical frequency comb by driving the laser with both RF local oscillator and data streams coupled together and then followed by the same optical filters to generate two modulated optical sidebands. At the RAU, these two sidebands are heterodyned using a photodetector to generate the electrical modulated mm-wave signal. We investigate the distribution of these two methods over 3-km fiber with 2-m wireless link and demonstrate the system simplicity and cost efficiency for mm-wave over fiber systems. Both configurations are simulated to verify our obtained results and show system performance at higher bit rates.

- by Liam Barry
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- Radio over fiber, Millimeter Wave Antennas, Switching, Antenna

Future metropolitan and access networks are expected to comprise heterogeneous optical and broadband wireless technologies. The growing demand of users for transparent, ubiquitous access to diverse communication services poses several challenges. We envision a future metro-access architecture that comprises Optical Burst Switching networks that feed Ethernet Passive Optical Networks (PON) or upcoming Wavelength-Division Multiplexing PON, which in turn feed IEEE 802.16 and IEEE 802.11 nodes. Nodes in the wireless realm may communicate in a multihop fashion, forming mesh networks. To maintain cost and resource efficiency, we propose the introduction of Quality of Service (QoS) proxies at the border between different link technologies. These entities handle QoS requirements and aid to the support of mobility. The architecture requires no modification of the Medium Access Control mechanisms of the different technologies. Index Terms-Optical fiber communication, mobile communication, metropolitan area networks.

- by Sebastia Sallent and +4
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- Mobile Communication, Wireless Technology, Quality of Service, Metropolitan Area Network

Simulation and experimental measurements are presented for 60 GHz transmission systems based on upconversion. We demonstrate that chirp in modulated semiconductor lasers combined with upconversion allows to realize a simple system resistant to chromatic dispersion without the need for customized filter. The comparison between two 60 GHz modulation schemes highlights the possibility to reduce power fading, due to chromatic dispersion, to a value as low as optical fiber attenuation.

- by Julien Poette and +1
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- Radio over fiber, Millimeter Wave Antennas, Organic Semiconductor Laser, Microwave Photonics

To provide higher capacity networks, 40-Gb/s transmission systems are under active development and their cost is on the way to be competitive with the one of 4 10 Gb/s. However, their lower tolerance to linear and nonlinear fiber impairments remains a major drawback for field deployment. To address the issue of linear impairments, coherent detection of multilevel formats with polarization division multiplexing appears as a promising solution by reducing the symbol rate to 10 Gbaud. Indeed, such coherent based systems have already demonstrated an improved tolerance to optical noise and an interesting capability to compensate for large amount of chromatic dispersion. In this paper, the tolerances to narrow optical filtering, chromatic dispersion, and polarization mode dispersion are investigated with coherent detection of 10-Gbaud quadrature phase shift keying (QPSK) with and without polarization division multiplexing. Moreover, the efficient mitigation of these linear impairments by digital processing in a coherent receiver is demonstrated in an ultralong haul transmission (4080 km) of 40-Gb/s QPSK polarization multiplexed data.

- by bigo bigo
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- Optics, Medical Imaging, Signal Processing, Fiber Optics

Large-scale photonic integrated circuits (LS PICs) have been extensively deployed throughout the fiber optic communication network. This paper discusses the properties of the LS PICs, the interaction between them, and what is necessary to... more

A hybrid WDM and SAC/Optical CDMA System is proposed to enhance the data network security and to exploit the capacity of an optical system. Code pulses of SAC/Optical CDMA are overlaid onto a multichannel WDM system. Modified Quadratic Congruence (MQC) code is as the signature address code for SAC/Optical CDMA. In general, OCDMA improves service availability for data of a network. With the use of WDM channels in a hybrid scheme, an eavesdropper faces another challenge for intercepting and decoding the coded signal. The interference that is the main factor limits the performance of the proposed system. So that, the notch filters and APD photo detectors instead of PIN photo detectors are used in order to improve the SAC/OCDMA performance. A simulation is presented as a demonstration of the concept.

- by Mark Kuznetsov
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- Ultraviolet, Power Consumption, Quantum Wells, VECSEL

We experimentally demonstrate several high-speed wavelength division multiplexing (WDM) to time division multiplexing (TDM) conversion schemes by using different nonlinearities in highly nonlinear fiber (HNLF). 40-160-Gb/s WDM-to-TDM conversion using cross-phase modulation (XPM) and 160-320-Gb/s conversion based on supercontinuum generation are shown. Furthermore, we investigate a different kind of HNLF, and demonstrate 40-80-Gb/s WDM-to-TDM conversion using XPM in a 0.8-m bismuth oxide HNLF (Bi-HNLF). Less than 3-dB power penalty is obtained for each case.

- by Scott Nuccio
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- Quantum Physics, Optical physics, High Speed, Wavelength Division Multiplexing

Summary form only given. We propose an architecture for a wavelength interchanging cross-connect (WIXC) that performs space cross-connection as well as wavelength interchange. The architecture uses difference frequency generation (DFG) λ-converters, which offer a number of unique properties not available in conventional wavelength converters. Besides a strictly transparent conversion process, these properties include simultaneous conversion of multiple wavelengths and a "mirror image" mapping function for the converted wavelengths. Despite the significant potential of DFG wavelength converters, there has been no cross-connect architecture to exploit their unique properties.

A coherent receiver module is presented, comprising two optical 90 hybrids monolithically integrated with eight waveguide p-i-n photodiodes in balanced configuration and two dual-channel linear transimpedance amplifiers. Its performance is demonstrated by transmitting up to 160 Gb/s dual-polarization quadrature phase-shift keying signals over 610 km standard single-mode fiber.

- by Stefano Bottacchi
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- Optics, Medical Imaging, Fiber Optics, Telecommunications

Four-Wave-Mixing (FWM) is one of the major degrading factors in Wavelength Division Multiplexing (WDM) optical fiber communication systems and networks along with other fiber non-linearties. As a result it is important to investigate the impact of FWM on the design and performance of WDM optical communication systems. This paper simulates that the FWM power reduced by increasing channel spacing of transmitted signals, dispersion and core effective area of fiber. Further, we propose a fuzzy based approach to calculate the FWM power by varying the channel spacing, dispersion, and core effective area of fiber. The Fuzzy logic helps in dealing with uncertain and complex systems difficult to model mathematically.

- by Ajay K Sharma
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- Information Systems, Fuzzy Logic, Optical Communication, Complex System

We investigate the interaction between Kerr nonlinearity and polarization mode dispersion (PMD) in homogeneous multi-channel polarization division multiplexing coherent phase shift keying transmissions. Assuming linear distortions can be fully equalized by the coherent receiver, we concentrate the investigation on the residual nonlinear penalty. We introduce a novel simulation procedure to discriminate intra-channel PMD, i.e., PMD within the channel, from inter-channel PMD, i.e., PMD among different channels, showing their relative impact on system performance in the nonlinear regime. A simple yet effective description of intra-channel PMD is proposed, which helps identify the PMD realizations giving the best/worst performance in the nonlinear regime. We show that on average PMD improves the performance of dispersion-managed links by reducing both nonlinear interactions among signals and nonlinear phase noise, while it has no effect in non-dispersion managed links.

In this paper investigation has been done on two different photodiodes PIN and APD for use as a receiver in free space fiber optical link. Eye Diagrams have been used to evaluate value of Q- factor in each and every case. Gaussian pulse modulation format has been used in this analysis work. It is clear from the findings of this analysis that value of Q-factor is maximum when APD has been used as the receiving photodiode at 1550nm wavelength and minimum when PIN diode has been used as receiving photodiode at 1550nm wavelength.

In this paper, we present measurement scheme for determining the optical fiber non-linear coefficient γ, using externally modulated continuous wave laser source. The measurement technique is based on four-wave mixing. The measurement source which uses one laser and one optical erbium-doped fiber amplifier only is described precisely. The proposed simple measurement scheme is polarization independent, enables high sensitivity and accuracy,

High-speed metamorphic double heterojunction photodiodes were fabricated on GaAs substrates for long-wavelength optical fiber communications. The high quality linearly graded quaternary InGaAlAs metamorphic buffer layer made possible the growth of excellent InGaAs-InGaAlAs-InAlAs heterostructures on GaAs substrates. The use of a novel double heterostructure employing an InGaAlAs optical impedance matching layer, a chirped InGaAs-InAlAs superlattice graded bandgap layer (SL-GBL), and a large bandgap I-InAlAs drift region enabled photodiodes to achieve a low dark current of 500 pA, a responsivity of 0.6 A/W, and a 3 dB bandwidth of 38 GHz at 5 V reverse bias for 1.55 m light. The effect of accumulated charges at the InGaAs-InAlAs heterointerface was examined through a comparison of the dark currents of InGaAs-InAlAs and InGaAs-InP abrupt single heterojunction photodiodes to photodiodes with chirped InGaAs-InAlAs SL-GBLs. The charge accumulation effects observed in abrupt heterojunction devices were suppressed by including a chirped InGaAs-InAlAs SL-GBL between the InGaAs absorption layer and InAlAs drift layer. The effect of passivation techniques was evaluated by comparing dark currents of unpassivated photodiodes and photodiodes passivated with either polyimide or SiN . The enhancement of photodiode bandwidth through the inclusion of a transparent large bandgap I-InAlAs drift region was verified by comparing the bandwidths of the P-i-I-N photodiodes that have I-InAlAs between i-InGaAs photoabsorption layer and + InAlAs cathode to conventional P-i-N photodiodes without a drift region. Index Terms-Drift region, GaAs, InGaAs, InP, metamorphic, P-i-I-N, P-i-N, photodiodes, superlattice graded bandgap layer.

- by Gabriel Cueva
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- Impedance Matching, Optical physics, High Speed, Optical Fiber Communication

Multimode interference in optical waveguides has interesting self-imaging properties, which have extensively been investigated and utilized in many integrated optical devices. Although these investigations started with most interest in step-index integrated waveguides, they have later included graded-index waveguides, where the dependence of the interference images on the refractive index grading of the waveguides was observed and utilized in the design and optimization of devices. Later on, multimode interference has also been explored in optical fibers in order to realize fiber devices, including sensors. A basic structure of these devices has been the Single mode - Multimode - Single mode (SMS) fiber section concatenation, where multimode interference in the multimode section leads to the formation of a self-image of the single mode fiber excitation onto the output single mode fiber core. This paper reports on the investigation of the self-imaging properties of these optical fiber structures and their possible use as sensors. Self-imaging in symmetrically excited multimode optical fibers is analytically studied, revealing the effect of refractive index grading on the characteristics of SMS fiber devices. The theoretical results are verified by numerical simulations using the beam propagation method. The experimental investigation of an SMS structure proposed as a bending sensor is then described and a discussion of the results obtained and possible application of the device is presented.

- by Ahmed Hisham Morshed
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- Numerical Simulation, Optical fiber sensor, Optical Waveguide, Interference

During the past years, monolithic integration in InP has been the driving force for the realization of integrated photonic routing systems. The advent of silicon as a basis for costeffective integration and its potential blend with III-V material is now opening exciting opportunities for the development of new, high-performance switching and routing equipment. Following this rationale, BOOM-as a European research initiative-aims to develop compact, cost-effective, and power-efficient silicon photonic components to enable optical Tb/s routers for current and new generation broadband core networks. This "siliconization" of photonic routers is expected to enable ultrahigh bit rates as well as higher levels of integration and power efficiency. The BOOM "device portfolio" includes all-optical wavelength converters, ultradense wavedivision multiplexing (UDWDM) photodetectors, and high-speed transmitters; all based on silicon waveguide substrates. Here, we present the device concepts, the fabrication of photonic building blocks and the experiments carried out as the initial steps toward the realization of the first high-capacity silicon photonic router.

With the recent increase of the number of Fiber-tothe-Home deployments worldwide, and the corresponding huge investment in infrastructure, there is a need to devise a migration path that assures the full future usability and enhanced performance of the installed fiber plant, possibly using emerging opto-electronic technologies. With this aim, within the IST ePhoton/One Network of Excellence, different technological solutions have been extensively analyzed and discussed. In this paper, a brief summary on access applications is presented.

- by Gerald Franzl
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- Long Term Evolution, Optical Fiber Communication, Access Network

GaAs-based dilute nitride lasers are potential light sources for future optical fiber communication systems at the wavelength of 1.3 m. In this paper we discuss the results of studies of optimization of the growth conditions and active regions of the GaAs-based lasers. To this end, a series of samples were grown using the molecular beam epitaxy technique. The active regions consisted of quantum wells, strain-compensating layers, and strain-mediating layers. They were characterized by photoluminescence and double crystal X-ray diffraction methods. The optical properties were very much affected by a choice of growth conditions, details of the quantum wells, and postgrowth thermal treatment. Preliminary results on diode-pumped vertical-cavity surface emitting lasers, which launch light power of 3.5 mW coupled into a single-mode fiber, are also presented.

We demonstrate an optical recirculating loop as a tool for performance evaluation of cascades of effects or elements in an optical communication system. We describe the critical issues to operate the recirculating loop properly and we present experimental results on the cascading of a dispersive fiber link and an optical amplifier. Additionally, we conduct a numerical simulation of the recirculating loop experimental conditions. Simulation and experimental results are in good agreement.

- by Joao Rosolem
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- Technology, Signal Processing, Microfluidics, Performance Evaluation

This work describes a concept of a hierarchical radio-over-fiber (RoF) network architecture that provides both intra-and inter-network connectivity for end user wireline and wireless terminals with high-bandwidth, in-building access applications. An intelligent gateway router (IGR) is proposed as a unified platform to accommodate multi-gigabit, millimeter-wave services at 60-GHz band as well as being backward compatible with all current wireless access technologies such as WiFi and WiMAX. In addition, we further present an advanced multi-band optical carrier generation technique that can simultaneously deliver independent 60-GHz mm-wave, 2.4-GHz WiFi, and 5.8-GHz WiMAX signals efficiently carried over the same wavelength, and is suitable for the proposed IGR. Finally, we report, for the first time to our knowledge, a campus-wide field trial demonstration of RoF system transmitting uncompressed 270-Mbps standard definition (SD) and 1.485-Gbps high definition (HD) real-time video contents carried by 2.4-GHz radio and 60-GHz millimeter wave signals, respectively, between two on-campus research buildings distanced over 2.5-km standard single mode fiber (SMF-28) through the Georgia Institute of Technology's (GT) fiber network.

- by Dr Arshad Chowdhury
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- Optics, Medical Imaging, Fiber Optics, Telecommunications

The nonlinear optical response of semiconductor nanowires has potential application for frequency conversion in nanoscale optical circuitry. Here, second-and third-harmonic generation (SHG, THG) are imaged on single zinc oxide (ZnO) nanowires using near-field scanning optical microscopy (NSOM). The absolute magnitudes of the two independent (2) elements of a single wire are determined, and the nanowire SHG and THG emission patterns as a function of incident polarization are attributed to the hexagonal nanowire geometry and (2) tensor symmetry.

We propose and demonstrate a novel fiber-based all-optical regenerator, where the wavelength shift induced by cross-phase modulation is employed for level discrimination. Regeneration of a 10-Gb/s signal using the proposed scheme improves the -factor by 1.8 dB. The scheme is stable and robust against changes in environmental conditions. Index Terms-Optical fiber communication, optical Kerr effect, optical repeaters, optical signal processing.

A novel algorithm that seeks the 'shortest-widest' path and assigns lightpaths according to their Q-factor is developed that exhibits better blocking performance, improved load-balancing and optimum physical performance when... more

- by Alexandros Stavdas
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- Nonlinear Optics, Routing algorithm, Q factor, Load Balancing

We demonstrate bandwidth-limited 1000km transmission of 43Gb/s RZ-DPSK signals. System bandwidth was limited via a MEMS-based wavelength-selective switch operating at 50GHz channel spacing. The system demonstrates increased tolerance to... more

- by Uri Mahlab
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- Optical Fiber Communication

Electroabsorption modulators with traveling-wave electrodes have been designed and fabricated using MOCVD grown InGaAsP-InGaAsP quantum wells. A modulation bandwidth of 25 GHz is achieved for a 2-m-wide 300-m-long device. Driving voltage... more

- by John Bowers
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- Optical physics, Optical Modulator, Optical Fiber Communication, Quantum Well

The activity devoted to the deployment of a new free space optics (FSO) link set up in Rome (Italy) is illustrated together with a preliminary FSO channel modelling and coupled optical/meteorological measurements. The two-way optical link at 1550 nm is about 1 km long and has a transmission rate up 1.5 Gbps. Among dust, precipitation, turbulence, fog, and any flying objects affecting the capacity of the optical channel, a focus is placed on water particle effects (fog and rain). A semi-empirical model evaluation of these atmospheric effects is illustrated.

- by P. Nocito and +1
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- Atmospheric Modeling, Free Space Optics, High Speed, Optical Fiber Communication

We demonstrate a standalone (no global clock) receiver for two-dimensional wavelength-time optical code-division multiple-access. The receiver provides the following functions: quantization (to eliminate multiple access interference), clock and data recovery, return-to-zero to nonreturn-to-zero conversion (for optical code-division multiple-access compatibility with digital logic), framing (for byte synchronization), and forward-error correction (FEC) using a (255, 239) Reed-Solomon decoder. The receiver more than doubles the number of supported users at a bit-error rate 10 10 . The receiver supports an information rate of 156.25 Mb/s. We performed the measurements at a bit rate of 167.4 Mb/s and a chip rate of 1.339 Gb/s (eight chips per bit) to account for FEC overhead. Index Terms-Clock and data recovery (CDR), forward-error correction (FEC), optical code-division multiple-access (OCDMA), optical fiber communications, optical receiver, Reed-Solomon (RS) codes.