Optical Communications Research Papers - Academia.edu (original) (raw)

In recent years, several New England projects have promoted professional development and curriculum design in optics and photonics. Funded in part by the Advanced Technological Education (ATE) program of the National Science Foundation (NSF), these projects have prepared middle and high school teachers, college faculty and career counselors from more than 100 New England institutions to introduce fiber optics, telecommunications and photonics technology education. Four of these projects will be discussed here: (1) The New England Board of Higher Education's (NEBHE) Fiber Optics Technology Education Project, (FOTEP) was designed to teach fiber optics theory and to provide laboratory experiences at the secondary and postsecondary levels. (2) Springfield Technical Community College's Northeast Center for Telecommunications Technologies (NCTT) is developing curricula and instructional materials in lightwave, networking and wireless telecommunications technologies. (3) The Harvard-Smithsonian Center for Astrophysics project ComTech developed a 12-week, hands-on curriculum and teaching strategies for middle and high school science and technology teachers in telecommunications and focused on optical communication (fiber optics). (4) NEBHE's project PHOTON is preparing middle, secondary and postsecondary instructors to introduce theory and laboratory experiences in photonics, including geometric and wave optics as well as principles of lasers and photonics applications.

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- Optics, Curriculum Design, Fiber Optics, Telecommunications
- by Le Binh
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- Distributed Computing, Biomedical Optics, Optical Communications, Communications Systems

We demonstrate the transfer of information encoded as orbital angular momentum (OAM) states of a light beam. The transmitter and receiver units are based on spatial light modulators, which prepare or measure a laser beam in one of eight pure OAM states. We show that the information encoded in this way is resistant to eavesdropping in the sense that any attempt to sample the beam away from its axis will be subject to an angular restriction and a lateral offset, both of which result in inherent uncertainty in the measurement. This gives an experimental insight into the effects of aperturing and misalignment of the beam on the OAM measurement and demonstrates the uncertainty relationship for OAM.

We investigate the orthogonality of orbital angular momentum (OAM) with other multiplexing domains and present a free-space data link that uniquely combines OAM-, polarization-, and wavelength-division multiplexing. Specifically, we demonstrate the multiplexing/demultiplexing of 1008 data channels carried on 12 OAM beams, 2 polarizations, and 42 wavelengths. Each channel is encoded with 100 Gbit∕s quadrature phase-shift keying data, providing an aggregate capacity of 100.8 Tbit∕s (12 × 2 × 42 × 100 Gbit∕s).

- by Moshe Tur
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- Quantum Physics, Optical Communications, Multiplexing, Optical physics

This paper discusses the key principles of Gigabit Passive Optical Network (GPON) which is based on Time Division Multiplexing Passive Optical Network (TDM PON) and Wavelength Division Multiplexing Passive Optical Network (WDM PON), which is considered to be next generation passive optical network. In the present day scenario, access to broadband is increasing at a rapid pace. Because of the advantages of fiber access in terms of capacity and cost, most of the countries have started deploying GPON access as an important part of national strategy. Though GPON is promising, it has few limitations. On the other hand WDM PON, a next generation network, is quite promising unlike GPON, it is easily scalable and interoperable with different vendors. This paper provides an overview of GPON, WDM PON and its key dissimilarities based on technicalities and cost.

We propose three types of narrowband optical filters based on a Fox-Smith resonator. We demonstrate that by choosing the appropriate combination of coating materials on each prism facet, one can design either a high reflectance or a high transmittance optical filter, suitable for low bit rate optical communication applications with International Telecommunication Union-Telecommunication Standardization Sector (ITU-T) standards. We also show the possibility of designing an optical filter having a desirable finite reflectance/transmittance ratio with simultaneous peaks at ITU-T standard wavelengths. Such filters could be suitable for wavelength tuning applications.

- by M. Moravvej-Farshi and +2
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- Mechanical Engineering, Optical Communication, Optical Communications, Applied Optics

Since the introduction of Ethernet technology in the 1980s, Ethernet has undergone major modifications and recent advances such as the support of 10 G interfaces, the resilient packet ring (RPR) standard, the Ethernet passive optical networks (EPONs), and so on have transformed Ethernet from a dominant local area network (LAN) networking technology to a key, flexible and cost-effective networking technology for metropolitan area networks (MANs). The purpose of this paper is to assess Ethernet maturity for deployment in MANs, based on different assessment criteria such as service provisioning and delivery (scalability issues related to the media access control (MAC) addresses and the supported number of virtual LAN identifiers), network protection and restoration as well as network and service management (provisioning of Ethernet services, fault identification, and monitoring). This assessment is based on a real-case scenario of deploying an advance metropolitan gigabit Ethernet network from a network service provider in Greece, Attica Telecom.

In this article, the large-signal, small-signal, and noise performance of the Cherry-Hooper amplifier with emitter-follower feedback are analyzed from a design perspective. A method for choosing the component values to obtain a low group delay distortion or Bessel transfer function is given. The design theory is illustrated with an implementation of the circuit in a 47-GHz SiGe process. The amplifier has 19.7-dB gain, 13.7-GHz bandwidth, and 10-ps group delay distortion. The amplifier core consumes 34 mW from a 3.3-V supply.

- by Luigi Raffo
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- Wireless Sensor Networks, VLSI, Low Frequency, Work Environment

The explosive growth in data communications has stimulated the development of optical systems for high channel capacity and high bandwidth. Today almost all voice & data traffic is routed through terrestrial and submarine optical fiber link. This paper emphasizes the basic requirements and designs an efficient approach which is certainly optimum considerations for optical fiber communication link and involves the following steps: creating the optical signal involving the use of a transmitter, relaying the signal along the fiber, ensuring that the signal does not become too distorted or weak, receiving the optical signal and converting it into an electrical signal. The experiment used semiconductor laser diode at the transmitting end and a photodiode at the receiving end. This project is relatively low cost and adaptable. An overview of the project is included with representative designs and information.

Institute of Brooklyn). MRI gained worldwide recognition in the 50s and 60s for its research in electromagnetic theory, antennas and radiation, network theory and microwave networks, microwave components, and devices. It was also known through its series of 24 topical symposia and the widely distributed hardbound MRI Symposium Proceedings. Rededicated as the Weber Research Institute (WRI) in 1986, the institute currently conducts research in such areas as electromagnetic propagation and antennas, ultrabroadband electromagnetics, pulse power, acoustics, gaseous electronics, plasma physics, solid-state materials, quantum electronics, electromagnetic launchers, and networks. Following MRI tradition, WRI has launched its own series of in-depth topical conferences with published proceedings. Previous conferences in this series were:

- by Henry L Bertoni
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- Nonlinear Optics, Photonics, Optical switching, Optical Waveguides

Silicon-based large-scale photonic integrated circuits are becoming important, due to the need for higher complexity and lower cost for optical transmitters, receivers and optical buffers. In this paper, passive technologies for large-scale photonic integrated circuits are described, including polarization handling, light non-reciprocity and loss reduction. The design rule for polarization beam splitters based on asymmetrical directional couplers is summarized and several novel designs for ultra-short polarization beam splitters are reviewed. A novel concept for realizing a polarization splitter-rotator is presented with a very simple fabrication process. Realization of silicon-based light non-reciprocity devices (e.g., optical isolator), which is very important for transmitters to avoid sensitivity to reflections, is also demonstrated with the help of magneto-optical material by the bonding technology. Low-loss waveguides are another important technology for large-scale photonic integrated circuits. Ultra-low loss optical waveguides are achieved by designing a Si 3 N 4 core with a very high aspect ratio. The loss is reduced further to ,0.1 dB m 21 with an improved fabrication process incorporating a high-quality thermal oxide upper cladding by means of wafer bonding. With the developed ultra-low loss Si 3 N 4 optical waveguides, some devices are also demonstrated, including ultra-high-Q ring resonators, low-loss arrayed-waveguide grating (de)multiplexers, and high-extinction-ratio polarizers.

- by John Bowers
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- Quantum Optics, Nonlinear Optics, Nanophotonics, Spectroscopy

The sustainable growth of high-bandwidth services and on-demand applications has introduced new challenges to next-generation networks in terms of capacity, configurability, and resiliency. Significant networking advancements need to be achieved with architectures and technologies that are scalable with respect to cost, size, and power requirements, while they should be capable of handling high traffic volumes and dynamically changing connection patterns. Transparent networking has the potential to meet those requirements and offer significant benefits in terms of performance and cost. We present the key enabling technologies, review the state-of-the-art achievements, and discuss the new opportunities that optical transparency has and will introduce.

- by Juerg Leuthold and +1
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- Optical Networking, Optical Communications

In this paper, we show the comparison of performances of three different digital signal processing (DSP) based directly detected 100 Gb/s transmission schemes namely optical orthogonal frequency division multiplexing (DDO-OFDM), optical single carrier frequency domain equalization (DDO-SCFDE), and optical DFT-spread OFDM (DDO-DFTS). Performances of these systems are characterized with different link parameters including laser linewidth, modulation formats, RF frequency, modulator drive power, and so on. Simulation results suggest that at optimum operating conditions, receivers' sensitivities of these systems may not exhibit any significant difference with respect to each other confirming their suitability for next-generation 100 Gb/s short reach optical links.

- by Masud Bakaul
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- Next Generation Networks, Modulation, Optical Communications, Sensitivity

Quad-Carrier Quadrature Phase Shift Keyed orthogonal frequency division multiplexing (QPSK-OFDM) signal transmission and reception is successfully demonstrated with blind equalization like a 25-ary quadrature amplitude modulation (25-QAM) signal with cascaded multimodulus algorithm (CMMA) equalization. The phase recovery can be realized with simple Viterbi algorithm and the frequency offset estimation (FOE) should be done with 25-QAM signal before 4-point fast Fourier transform (FFT). 48-Gbit/s Quad-Carrier QPSK-OFDM signal is successfully transmitted over 80-km SMF-28 without penalty.

In a passive optical network with a hybrid wavelength division multiplexing time division multiple-access scheme, implementing reconfigurable wavelength assignment is complex; hence the need to determine the conditions for which the capacity improvements justify requiring reconfigurability over adopting a more inexpensive fixed wavelength assignment. Fixed and reconfigurable approaches to wavelength assignment are modeled and evaluated under nonstationary traffic conditions. The performance improvement is obtained in terms of bit rate gain relative to the nominal bandwidth and depends on the number of wavelength channels as well as the magnitude of the load offered by the optical network units. In addition, frame delay and frame loss in relation to the bit rate performance are obtained for Pareto and exponentially distributed traffic. Simulations show that when introducing reconfigurability, typical peak bit rate gains with respect to the fixed case are 17%, and maxima of 175% are potentially possible when traffic demands are particularly uneven.

- by David Garcia-Roger
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- Fiber Optics, Traffic Simulation, Optical Communication, Access Networks
- by Yahsing Yuan
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- Antennas, Fiber Optics, Telecommunications, Media

Complementing wireless radio networks with free-space optics (FSO) achieves high data rates by modulating radio subcarriers over an optical carrier without expensive optical fiber cabling, enabling a pervasive platform for reaching underserved areas. In this paper, we review the main features of FSO for terrestrial and inter-satellite communications. Simulations of 1 Gbps data transmission through FSO links in both terrestrial and inter-satellite communications have been investigated to highlight potential atmospheric challenges in FSO.

International Journal on Information Theory (IJIT) will provide an excellent international forum for sharing knowledge and results in theory, methodology and applications of Information Theory. Authors are solicited to contribute to the journals by submitting articles that illustrate research results, projects, surveying works and industrial experiences that describe significant advances in the areas of Information Theory and applications.

We demonstrate a linearly field-modulated, direct-detected virtual SSB-OFDM (VSSB-OFDM) transmission with an RF tone placed at the edge of the signal band. By employing the iterative estimation and cancellation technique for the signal-signal beat interference (SSBI) at the receiver, our approach alleviates the need of the frequency gap, which is typically reserved for isolating the SSBI, and saves half the electrical bandwidth, thus being very spectrally efficient. We derive the theoretical model for the VSSB-OFDM system and detail the signal processing for the iterative approach conducted at the receiver. Possible limitations for this iterative approach are also given and discussed. We successfully transmit a 10 Gbps, 4-quadrature-amplitude-modulation (QAM) VSSB-OFDM signal through 340 km of uncompensated standard single mode fiber (SSMF) with almost no penalty. In addition, the simulated results show that the proposed scheme has an ~2 dB optical-signal-to-noise-ratio (OSNR) gain and has a better chromatic dispersion (CD) tolerance compared with the previous intensity-modulated SSB-OFDM system.

- by Bishara Shamee
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- Optics, Telecommunications, Computer Aided Design, Optical Communications

The performance of single photon pulsed polarization based BB84 and B92 platforms against individual attacks for free space quantum optical communication links between a ground station and a satellite in the low earth orbit was compared. The comparison was attained by evaluating the quantum bit error rate and secure communication bit rate on secure optical link loss and the sensitivity of different parameters. Precisely, realistic experimental parameters were used and the results obtained were compared with those of other works. Quantum bit error rates as low as 3.5% have been regularly obtained. Moreover, with repetition rate of 10MHz at the low earth orbit standard orbital altitude of 100km and at zenith angle of 60 degrees, secure communication bit rates of ~280kHz and ~70kHz were received for the BB84 and B92 respectively. The obtained results show that the BB84 protocol exhibits better performance than B92 in the distribution of the secure communication key over long distance. Overall, these results reveal that it is possible to obtain secure key exchange in the low earth orbit, an idea which can be extended to other long distance laser links such as geostationary orbit.

- by Fouad Abbou
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- Optical Communications

In this letter, we demonstrate coherent optical spectrum analysis with 70-dB dynamic range based on a swept-tuned optical local oscillator and a coherent receiver operating in the 1.5-m wavelength band. Measurement principles are... more

Light-emitting diodes (LEDs) have been deployed for various applications in our daily lives. Similarly, image sensors or cameras integrated into mobile phones have become common. Hence, visible light communication (VLC) using LED and mobile phone cameras is attractive and provides low-cost wireless communication. In this paper, we propose and demonstrate a VLC system using color-shift-keying (CSK) modulation and code-division multiple-access (CDMA) technology simultaneously for the first time; a mobile phone camera is used as the receiver (Rx). CSK is used to enhance the VLC system capacity and to mitigate the single color light interference, whereas CDMA allows multiple users to access the network. The system design and operation mechanism of the proposed CSK-CDMA VLC system are discussed. A proof-of-concept demonstration is performed, and error-free transmission is achieved for multiple-access users. A 3-dB transmission gain is also obtained in each user when compared with the traditional on-off keying (OOK) modulation.

- by Siddu Sid
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- Image Processing, Wireless Communications, Optical Communications

Free space optical link is a growing field in communication due to its advantage of wide bandwidth, high security and easy installation. A wavelength division multiplexing (WDM) access network using free space optical (FSO) communication in different weather conditions like haze and rain are discussed in this article and find out the possibility of communication link up to 180 km in clear weather with 2.5 Gbps data rate on the wavelength of 1550 nm and up to 54 km in haze condition using same data rate & wave length. Further the effect of using two different low pass filter (Gaussian and Bessel) at the receiver are discussed and conclude that Bessel filter is better on 2.5 Gbps data rate for WDM based FSO link.

- by Editor IJRET
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- Optics, Wireless Communications, Optical Communications

Hybrid wavelength-division multiplexed/timedivision multiplexed passive optical access networks (WDM/TDM-PONs) combine the advance features of both WDM and TDM PONs to provide a cost-effective access network solution. We demonstrate and analyze the transmission performances and power budget issues of a colorless hybrid WDM/TDM-PON scheme. A 10-Gb/s downstream differential phase shift keying (DPSK) and remodulated upstream on/off keying (OOK) data signals are transmitted over 25 km standard single mode fiber. Simulation results show error free transmission having adequate power margins in both downstream and upstream transmission, which prove the applicability of the proposed scheme to future passive optical access networks. The power budget confines both the PON splitting ratio and the distance between the Optical Line Terminal (OLT) and Optical Network Unit (ONU).

- by Yousaf Khan
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- Optical Communications

Optical filters are essential in a wide range of applications, including optical communications, electronics, lighting, optical sensors, and photography. This article presents recent work which indicates that optical filters can be created from specialized nanoparticle suspensions. Specifically, this article describes a theoretical optimization process for designing nanofluid-based filters for hybrid solar photovoltaic/thermal (PV/T) applications. This particular application is suitable because nanofluids can be utilized as both volumetric solar absorbers and as flowing heat transfer mediums. The nanofluid filters described in this work compare favorably with conventional optical filters for five PV cell alternatives: InGaP, CdTe, InGaAs, Si, and Ge. This study demonstrates that nanofluids make efficient, compact, and potentially low-cost, spectrally selective optical filters.

- by Gary Rosengarten
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- Quantum Optics, Nonlinear Optics, Nanophotonics, Spectroscopy

A photonic crystal fiber in square lattice architecture is numerically investigated and proposed for broadband dispersion compensation in optical transmission system. Simulation results reveal that it is possible to obtain an ultra-high negative dispersion of about −571.7 to −1889.7 (ps/nm.km) in the wavelength range of 1340 nm to 1640 nm. Experimentally it is demonstrated that the design fiber covers a high birefringence of order 4.74×10

- by Kawsar Ahmed
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- Optical Communications

High power pulsed lasers are commonly deployed in harsh environments, like space flight and military missions, for a variety of systems such as LIDAR, optical communications over long distances, or optical firing of explosives. Fiber coupling of the laser pulse from the laser to where it is needed can often save size, reduce weight, and lead to a more robust and reliable system. Typical fiber optic termination procedures are not sufficient for injection of these high power laser pulses without catastrophic damage to the fiber endface. In the current study, we will review the causes of fiber damage during high power injection and discuss methods used to avoid these issues to permit fiber use with high reliability in these applications. A brief review of the design considerations for high peak power laser pulse injection will be presented to familiarize the audience with all the areas that need to be considered during the design phase. The majority of this paper focuses on the proper fiber polishing methods for high power use with an emphasis on laser polishing of the fibers. Results from recently build fibers will be shown to demonstrate the techniques.

- by Melanie Ott and +1
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- Fiber Optics, LiDAR, Optical Communication, Optical Communications

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, a comprehensive integral equation formulation of plasmonic transmission lines is presented for the first time. Such lines are made up of a number of metallic strips with arbitrary shapes and dimensions immersed within a stack of planar dielectric or metallic layers. These lines support a number of propagating modes. Each mode has its own phase constant, attenuation constant, and field distribution. The presented integral equation formulation is solved using the Method of Moments (MoM). It provides all the propagation characteristics of the modes. The new formulation is applied to a number of plasmonic transmission lines, such as: single rectangular strip, horizontally coupled strips, vertically coupled strips, triangular strip, and circular strip. The numerical study is performed in the frequency (wavelength) range of 150-450 THz (0.66-2.0 μm). The results of the proposed technique are compared with those obtained using Lumerical mode solution, and CST. Very good agreement has been observed. The main advantage of the MoM is its intrinsic speed for this type of problem compared to general purpose solvers.

- by Mai Sallam
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- Plasmonics, Optical Communications, Computer Simulation, Surface Plasmons

Recently, coherent-detection (CoD) polarization multiplexed (PM) transmission has attracted considerable interest, specifically as a possible solution for next-generation systems transmitting 100 Gb/s per channel and beyond. In this context, enabled by progress in ultra-fast digital signal processing (DSP) electronics, both multilevel phase/amplitude modulated formats (such as QAM) and orthogonal-frequency-division multiplexed (OFDM) formats have been proposed. One specific feature of DSP-supported CoD is the possibility of dealing with fiber chromatic dispersion (CD) electronically, either by post-filtering (PM-QAM) or by appropriately introducing symbol-duration redundancy (PM-OFDM). In both cases, ultra-long-haul fully uncompensated links seem to be possible. In this paper we estimate the computational effort required by CD compensation, when using the PM-QAM or PM-OFDM formats. Such effort, when expressed as number of operations per received bit, was found to be logarithmic with respect to link length, bit rate and fiber dispersion, for both classes of systems. We also found that PM-OFDM may have some advantage over PM-QAM, depending mostly on the over-sampling needed by the two systems. Asymptotically, for large channel memory and small over-sampling, the two systems tend to require the same CD-compensation computational effort. We also showed that the effort required by the mitigation of polarization-related effects can in principle be made small as compared to that of CD over long uncompensated links.

We review our recent results on Ge-based nearinfrared photodetectors grown on silicon. We fabricated metal-semiconductor-metal photodetectors based on epitaxial pure-Ge grown on silicon by Chemical Vapor Deposition. Material characterization and device performances are illustrated and discussed. Exploiting a novel approach based on evaporation of polycrystalline-Ge on silicon, we also realized efficient near-infrared photodiodes with good speed and sensitivity. Finally, multiple-element devices were designed, fabricated, and tested, such as a voltage-tunable wavelengthselective photodetector based on a SiGe superlattice and a linear array of 16 photodetectors in poly-Ge on Si.

- by Gaetano Assanto
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- Evaporation, Near Infrared, Chemical Vapor Deposition, Optical Communications

Single-photon imaging in infrared will add a new valuable tool to night imaging cameras. Despite years of development, high-sensitivity SWIR cameras are still expensive and not ready for large-volume production. Germanium (Ge) is a promising semiconductor to convert SWIR radiation and it has seen extensive development in conjunction with highspeed optical communications.

- by Jurgen Michel
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- Radiation, Semiconductors, Optical Communication, Prototyping

In this paper a hybrid modulation scheme based on pulse position modulation (PPM) and binary phase shift keying subcarrier intensity modulation (BPSK-SIM) schemes for free-space optical communications is proposed. The analytical bit error rate (BER) performance is investigated in weak and saturated turbulence channels and results are verified with the simulation data. Results show that performance of PPM-BPSK-SIM is superior to BPSK-SIM in all turbulence regimes; however, it outperforms 2-PPM for the turbulence variance σ 2 1 > 0.2. PPM-BPSK-SIM offers a signal-to-noise ratio (SNR) gain of 50 dB in the saturation regime compared to BPSK at a BER of 10 −6 . The SNR gain in comparison to PPM improves as the strength of the turbulence level increases.

In pulsed fiber laser using Q-switching or mode locking techniques, the choice of the different components and the management of linear and non linear parameters of the cavity, play a paramount role in the generation of stable ultra short pulses with high peak powers and low widths. In this paper, we focus on the operating process of mode locked fiber lasers especially passively and hybrid type Eight Fiber Lasers (8FLs). By modeling the light propagation within the two cavities, we describe the whole operating process of ultra short pulses generation. The interaction between the mode locking mechanism and nonlinear effects in fiber laser is also illustrated. We demonstrate enhancing non linear effects do not lead necessarily to better results. It depends on the type of mode locking techniques used. The highest and narrowest output pulses are obtained for specific values of the non linear parameters and the mean dispersion of the cavity.

- by Rabah Attia
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- Optical Communications

Free space optical system is a hot topic, which has gaining more and more attention. But, when the signal transmitted in the channel, the performance could be severely degraded due to the atmosphere turbulent. The purpose of this paper is to find a most suitable modulation method for FSO system under FSO channel. The performance of power efficiencies, bandwidth efficiency, BER and SNR for the four modulation schemes have studied and compared in this paper include On-Off keying (OOK), Binary Phase Shift Keying (BPSK), Differential Phase Shift Keying (DPSK) and Quadrature Phase Shift Keying (QPSK) without atmospheric turbulence. Numerical experiments show that BPSK and QPSK schemes are better compared to other schemes in BER performance and power requirements. When take intensity scintillation under Gamma-Gamma turbulence channel into consideration and the average BER is derived with Meijer-G function, BER performances of BPSK and QPSK scheme approximate the same. Compared with BPSK, BER performance for QPSK is 3dB lower. From the simulation results, modulation for BPSK is robust resist turbulence. As a result, BPSK scheme is suitable for free-space optical communication system.

- by Kulwinder Singh
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- Free Space Optics, Optical Communications, Bit Error Rate, Optical physics

This paper presents a brief review of infrared communications systems, modulation techniques and in particular, a digital pulse modulation scheme known as digital pulse interval modulation (DPIM) for infrared (IR) communication systems employing intensity modulation with direct detection (IM/DD). DPIM code characteristics, power spectral density and error probability in terms of the packet error rate are discussed. Performance comparison is made with that of on}o! keying (OOK) and pulse position modulation (PPM). For comparison, relevant expressions for both OOK and PPM are also presented. Using a threshold-detector-based receiver, we show that DPIM outperforms both OOK and PPM in terms of power e$ciency and PPM in terms of bandwidth e$ciency, by taking advantage of its inherent variable symbol duration. However, using a maximum-a posteriori (MAP) detector it provides marginally inferior error rate performance compared with PPM.

In this paper, we theoretically analyze and demonstrate that spectral efficiency of a conventional direct detection based optical OFDM system (DDO-OFDM) can be improved significantly using frequency interleaving of adjacent DDO-OFDM channels where OFDM signal band of one channel occupies the spectral gap of other channel and vice versa. We show that, at optimum operating condition, the proposed technique can effectively improve the spectral efficiency of the conventional DDO-OFDM system as much as 50%. We also show that such a frequency interleaved DDO-OFDM system, with a bit rate of 48 Gb/s within 25 GHz bandwidth, achieves sufficient power budget after transmission over 25 km single mode fiber to be used in next-generation time-division-multiplexed passive optical networks (TDM-PON). Moreover, by applying 64-quadrature amplitude modulation (QAM), the system can be further scaled up to 96 Gb/s with a power budget sufficient for 1:16 split TDM-PON.

- by Masud Bakaul
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- Optical Communication, Modulation, OFDM, Optical Communications

At present, system design usually assumes the Kolmogorov model of refractive index fluctuation spectra in the atmosphere. However, experimental data indicates that in the atmospheric boundary layer and at higher altitudes the turbulence can be different from Kolmogorov's type. In optical communications, analytical models of mean irradiance and scintillation index have been developed for a traditional Kolmogorov spectrum and must be revised for non-Kolmogorov turbulence. The image quality (resolution, MTF, etc.) is essentially dependent on the properties of turbulent media. Turbulence MTF must be generalized to include non-Kolmogorov statistics. The change in fluctuation correlations of the refractive index can lead to a considerable change in both the MTF form and the resolution value. In this work, on the basis of measurements and model calculations, the influence of non-Kolmogorov turbulence on imaging and communications through the atmosphere is estimated for different scenarios of vertical and slant-path propagation. The atmospheric model of an arbitrary (non-Kolmogorov) spectrum is applied to estimate the statistical quantities associated with optical communication links (e.g., scintillation and fading statistics) and imaging system. Implications can be significant for optical communication, imaging through the atmosphere, and remote sensing.

- by Arkadi Zilberman
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- Remote Sensing, Turbulence, Atmospheric Modeling, Optical Communication

A novel scheme for all-optical label reading and packet routing is proposed. The architecture is comprised of all-optical logic XOR gates and all-optical flip-flops based on single Mach-Zehnder interferometers incorporating semiconductor optical amplifiers (SOA-MZIs). The simulation results show that a very small penalty (less than 0.45 dB) for 10 Gbit/s packet processing can be achieved. , "1x2 optical packet switch using all-optical header processing," Electron. Lett. 37, 774-775 (2001). 2.

The concurrent realization of multiple polarization-based link impairments such as polarization-mode dispersion, polarization-dependent loss, and differential-attenuation slope creates a nontrivial measurement and analysis problem. The difficulties concerning the robustness of raw data, of minimizing drift artifacts experienced during multiple wavelength measurements, and the analysis methods that lead to physical significant interpretations are addressed. Measurements of an in-service wavelength-division-multiplexed metro-area network are presented that explicitly illustrate the limitations when using industry-standard commercial test equipment.

We describe an optical time-division-multiplexed (OTDM)/WDM network architecture that integrates high-speed optical time-division multiplexing at speeds of 40 Gbit/s and higher with lower-bit-rate WDM channels. An ultrafast wavelength converter is used as a regenerative multifunction building block for OTDM multiplexing, WDM-to-OTDM and OTDM-to-WDM transmultiplexing, OTDM/WDM multicasting, OTDM all-optical label read-write, and all-optical time-channel add-drop multiplexing. Subsystem design and underlying component technologies are described in detail. New results and performance measurements are shown at 40 and at 80 Gbit/s. OTDM/WDM networks that bridge high-bit-rate channels in the core network to lowerbit-rate WDM channels in metro and access networks have been proposed . In this paper we focus on the architecture shown in . Multiple low-bit-rate WDM channels are optically multiplexed into a single high-bit-rate channel. The routing within the core is accomplished by either wavelength conversion of the entire high-speed stream or by optical time add-drop of subrate channels within the stream. In addition, the high-speed channels may be optically multicast from one-to-multiple wavelengths. At the egress of the core network the high-bit-rate channel is demultiplexed back to low-bit-rate WDM channels. The network elements and functions that we demonstrate are synchronous in nature, and we assume bit-level synchronization.

- by John Bowers
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- Optical Networking, Optical Communications, High Speed, Performance Measure

As multiple accessing technique that can be used to provide access to multiple users to transmit data to same channel simultaneously without any scheduling or delay in transmission, Optical Code Division Multiple Access (OCDMA) has been an alluring for the past few decades. All users share all bandwidth simultaneously and access the network asynchronously. To provide access to multiple users simultaneously, many coding techniques to increase possible users and improve performance has been analyzed for OCDMA systems. In this paper, many different proposed methods of coding are reviewed. Performance, cardinality and capacity of these codes are discussed. Significance of introducing dimensions in optical code is also be discussed.

We demonstrate a handheld on-chip biosensing technology that employs plasmonic microarrays coupled with a lens-free computational imaging system towards multiplexed and high-throughput screening of biomolecular interactions for point-of-care applications and resource-limited settings. This lightweight and field-portable biosensing device, weighing 60 g and 7.5 cm tall, utilizes a compact optoelectronic sensor array to record the diffraction patterns of plasmonic nanostructures under uniform illumination by a single-light emitting diode tuned to the plasmonic mode of the nanoapertures. Employing a sensitive plasmonic array design that is combined with lens-free computational imaging, we demonstrate label-free and quantitative detection of biomolecules with a protein layer thickness down to 3 nm. Integrating large-scale plasmonic microarrays, our on-chip imaging platform enables simultaneous detection of protein mono-and bilayers on the same platform over a wide range of biomolecule concentrations. In this handheld device, we also employ an iterative phase retrieval-based image reconstruction method, which offers the ability to digitally image a highly multiplexed array of sensors on the same plasmonic chip, making this approach especially suitable for high-throughput diagnostic applications in field settings.

- by Ahmet F. Coskun
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- Quantum Optics, Nonlinear Optics, Nanophotonics, Spectroscopy

We designed an optical add/drop multiplexer for orbital-angular-momentum (OAM)-multiplexed data links by taking advantage of the ring-shaped intensity profile of OAM beams. We demonstrated adding/dropping a single OAM beam from three multiplexed OAM beams using liquid-crystal-on-silicon-based diffraction optical elements. For multiplexed OAM beams carrying 100 Gbit∕s quadrature phase-shift-keying data, a power penalty of <2 dB is observed to achieve a bit-error rate of 2.0 × 10 −3 for each channel of the add/drop multiplexer.

- by Moshe Tur
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- Quantum Physics, Optical Communications, Multiplexing, Optical physics

This paper introduces a novel fiber-wireless (FiWi) network architecture, called SuperMAN, and investigates the optical-wireless integration of a resilient packet ring (RPR) and WiMAX networks. We propose a novel hierarchical integrated scheduling algorithm that significantly improves the throughputdelay performance and triple-play quality-of-service support for fixed and mobile users. By means of extensive simulations we show in a benchmark comparison that the proposed hierarchical scheduler clearly outperforms the widely deployed weighted fair queuing (WFQ) scheduler in terms of mean aggregate throughput and mean delay as well as robustness for voice, video, and data traffic under realistic wireless channel conditions. order to optimize QoS support and to avoid replicated networking functions. Since wired and wireless networks deploy separate QoS mechanisms and quadruple-play services require the two coexisting platforms to interoperate closely, research has recently begun to address the problem of integrating wired and wireless access networks. The resultant hybrid fiber-wireless (FiWi) broadband access networks aim at providing wired and wireless services over the same infrastructure simultaneously, thus potentially leading to major cost savings.

- by Francesco Paolucci
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- Optical Networking, Optical Communications, Optical, Optical Wireless