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Kerr nonlinearity imposes a limit on the achievable transmission performance and capacity of optical fibre communication links. We show that the nonlinear distortions of a pair of phase-conjugated twin waves are essentially anticorrelated, so cancellation of signal-to-signal nonlinear interactions can be achieved by coherently superimposing the twin waves at the end of the transmission line. We demonstrate that by applying this approach to fibre communication, nonlinear distortions can be reduced by >8.5 dB. In dispersive nonlinear transmission, the nonlinearity cancellation additionally requires a dispersion-symmetry condition that can be satisfied by appropriately predispersing the signals. By using these techniques we succeed in transmitting a 400 Gb s−1 superchannel over 12,800 km of fibre. We further show a connection between the nonlinearity cancellation and a nonlinear noise squeezing effect. The concept of using phase-conjugated twin waves to suppress nonlinear interactions may prove beneficial in other physical systems governed by the nonlinear Schrödinger equation. [ABSTRACT FROM AUTHOR]

Writing a fiber Bragg grating (FBG) in an optical fiber coupler is a very effective way to implement an optical add/drop filter (OADF). In order to analyze the influences on the bandwidth at the drop port of the OADF using fiber grating-assisted mismatched coupler, a uniform FBG and a linearly chirped FBG were written on the coupler, and two different OADFs were fabricated. The fiber grating is written in a 2×2 mismatched coupler, which is fused and tapered with a standard single mode fiber (SMF) and a high germanium doped photosensitive fiber, by using a 248 nm ultraviolet laser. For the OADF using the uniform FBG, the 3 dB and 20 dB bandwidths are 0.1 nm and 0.3 nm, respectively; for the OADF using the linear chirped FBG, the 3 dB and 20 dB bandwidths are 0.8 nm and 2 nm, respectively. The experimental results meet the theoretical analysis well. The bandwidth at the drop port of the device can be adjusted by adjusting the chirped coefficient of the linearly chirped FBG. [ABSTRACT FROM AUTHOR]

We experimentally demonstrate a random fiber laser operating at 1,115 nm using a LD-pumped Yb-doped fiber laser as the pump source. We achieve about 270 mW lasing output in a 50 km standard communication optical fiber with slope efficiency more than 28 %. A new wavelength is provided for the application of random distributed feedback fiber lasers as light sources. [ABSTRACT FROM AUTHOR]

The paper focuses on the description of the problem of modeling equipment failures by means of non-homogeneous flows of extremal events with the help of max-generalized Cox processes. [ABSTRACT FROM AUTHOR]

In this study, a fiber-optic dosimeter (FOD) was developed to measure entrance surface dose (ESD) in diagnostic radiology. We measured the scintillating lights in order to obtain ESDs, which changed with the various exposure parameters of a digital radiography (DR) system, such as tube potential, current-time product, focus-surface distance (FSD), and field size, using the fabricated FOD system. From the experimental results, the output light signals of the FOD were similar to the ESDs of the conventional semiconductor dosimeter. In conclusion, we characterized the measured ESDs as functions of exposure parameters by using two different types of dosimeters and demonstrated that the proposed FOD using a plastic scintillating fiber and a plastic optical fiber (POF) makes it possible to measure ESDs in the energy range of diagnostic radiology. From the results of this study, it is anticipated that the FOD will be a useful dosimeter in low-energy photon applications including diagnostic radiology. [ABSTRACT FROM AUTHOR]

We developed a scintillating fiber-optic image sensor system (SFISS) using square plastic optical fibers (POFs), a scintillating film, a right-angle mirror, and a complementary metal-oxide semiconductor (CMOS) image camera for dosimetry in radiotherapeutic applications. In this study, the scintillating light images were obtained for measuring two-dimensional planar dose distributions of a 6MV photon beam in a solid-water phantom. We also measured the percentage depth doses (PDDs) of 6 and 15MV photon beams using the SFISS and compared them with those obtained using conventional dosimetry films. The proposed sensor has many advantages, such as real-time readout, high-resolution measurement, and lack of corrections for temperature, pressure, and humidity. From the results of this study, it is expected that a SFISS can be developed to accurately measure the dose distribution in a small beam field for stereotactic radiosurgery (SRS). [ABSTRACT FROM AUTHOR]

Recent advances in WDM technology enable an optical fiber to carry up to 200 wavelengths operating at 40 Gbps each. In such networks, service disruptions caused by network faults ( e.g., fiber cut, amplifier dysfunction) may lead to high data losses. Therefore, it is mandatory for a network operator to be able to detect and localize such faults in the lowest possible delays. Fault detection and localization in meshed WDM networks have been deeply investigated in the literature. Numerous schemes, both exact and approximate, have been proposed to achieve fast and accurate failure localization. In this paper, we propose an original Meta-heuristic for Monitoring Trail Assignment ( MeMoTA). We show through numerical results that MeMoTA provides monitoring solutions closer to optimal than existing heuristic approaches while ensuring an acceptable scalability. [ABSTRACT FROM AUTHOR]

This paper presents feasible experimental schemes to realize controlled teleportation protocols via photonic Faraday rotations in low-Q cavities. The schemes deal with controlled teleportation of superposition states and two-particle entanglement of atomic states. The information is encoded in lambda configured three-level atoms trapped inside coupled cavities by optical fibers. Also, we estimate the success probability and the current feasibility of the schemes. [ABSTRACT FROM AUTHOR]

The prospect of an all-fibre optical communications network in which light can be generated, modulated and detected within the fibre itself without the need for discrete optoelectronic devices is an appealing one. However, to become a reality, this approach requires the incorporation of optoelectronic materials and functionalities into silica fibres to create a new breed of semiconductor-fibre hybrid devices for performing various tasks. Here, we report the integration of precisely doped semiconductor materials and high-quality rectifying semiconductor junctions into microstructured optical fibres, enabling high-speed, in-fibre functionalities such as photodetection at telecommunications wavelengths. These semiconductor-fibre hybrid devices exhibit a bandwidth of up to 3 GHz and seamless coupling to standard single-mode optical fibres. [ABSTRACT FROM AUTHOR]

Nowadays mobile robots become loaded with information. The application conditions need installation of various sensors, machine vision systems, and detection and navigation facilities. It goes without saying the requirements to a robot-operator transmission channel, its reliability, and capacity ramps up. The paper reviews the authors' experience in designing data transmission channels for mobile robots as exemplified by wire and wireless channels. Circuit design features, selection of hardware components, and the issues of unification and integration are discussed. [ABSTRACT FROM AUTHOR]

We consider the influence of the polarization mode dispersion, which is stipulated by the presence of random inhomogeneities in single-mode fiber lightguides, on the propagation of ultrashort optical pulses in the fiber communication lines with very weak linear birefringence. Evolution of the envelope of ultrashort optical pulses and their spectra as functions of the length of a single-mode fiber lightguide with very weak linear birefringence and random inhomogeneities are obtained by the method of mathematical simulation. An increase in the pulse duration is shown to be proportional to the square root of the length of a single-mode fiber lightguide. The numerical-simulation results are compared with the results of experimental measurements of the polarization mode dispersion. [ABSTRACT FROM AUTHOR]

The three thermal rate equations were built newly up at both ends and at the junction of a p- n diode, in order to derive analytically the temperature difference Δ T (between a junction and both ends) and the internal cooling efficiency η defined newly for a homojunction diode. The maxima Δ T and η of a diode were derived analytically as a function of V within the short-length approximation and calculated numerically as a function of V or V, where V is a voltage across the junction and V is a built-in voltage at the junction. As a result, Δ T increases abruptly with an increase of V below V=0.050 V or of V below V=0.10 V, while above their values, it increases slowly with an increase of V or V to saturate a certain value. For example, Δ T was estimated as 14.6 K for HgCdTe diode with V=0.36 V. η has a local maximum of 63% at V≈0.01 V or at V≈0.03 V, while above their respective values, it decreases abruptly with an increase of V or V and falls to 4.4% at V=0.80 V which is equivalent to that of a diode emitting a laser for fiber optical communication. However, the greater enhancements in Δ T and η of a diode are required to apply the internal cooling system to a laser-emitting diode which needs the exact control of temperature. These results should be useful for the application of the internal cooling system to the double heterojunction diode used in the optical communication. [ABSTRACT FROM AUTHOR]

We propose a scheme of entanglement transfer through two independent arrays of cavities coupled by optical fibers when each of the cavities contains a single two-level atom. We study the entanglement dynamics of the transferred states and find the explicit expression for the density matrix and concurrence. It is shown that the amount of the transferred entanglement has a direct connection with the target states and the lengths of the arrays of cavities. Moreover, the influence of the initial states and the length of the arrays of cavities on the phenomenon of entanglement sudden death is also investigated. [ABSTRACT FROM AUTHOR]

We investigate the dynamics of entanglement by means of concurrence for the case of two atoms which are trapped in spatially separated cavities connected by an optical fiber. It is shown that the phenomenon of sudden birth of entanglement occurs under some certain conditions. Moreover, it is found that the entanglement between two atoms can be controlled and manipulated by changing cavity-fiber coupling strength and the amplitude of the atom. [ABSTRACT FROM AUTHOR]

The results of a prompt determination of the Universal Time corrections in the e-VLBI mode on the Quasar VLBI network in 2009-2011 are presented. For this purpose, the hardware-software tools for observational data transfer from the Svetloe, Zelenchukskaya, and Badary Observatories to the Correlation Processing Center (St. Petersburg) over fiber-optic communication lines in a mode close to real time using the specialized Tsunami protocol have been developed. The rms error in the UTC-UT1 corrections with respect to the combined IERS series is 60 µs. [ABSTRACT FROM AUTHOR]

This paper reports an optical preamplifier intended for low-cost fiber-optic receivers. The preamplifier is based on a resistive shunt-feedback topology, is power-optimized and employs two different frequency compensation techniques, phantom zeros and shunt-peaking. The circuit is designed in a 1.8 V 0.18 μm CMOS technology. Experimental results report a transresistance of 58 dBΩ and a bandwidth of 1.5 GHz, respectively. Eye diagrams obtained at 2.5 Gb/s show a total jitter of 18 ps and a bit error rate (BER) of 10 when the input current amplitude (I) is equal to or higher than 8.5 μA. Higher bit rates up to 3 Gb/s also have been tested achieving a BER of 10 when I ≥9.5 μA. The power consumption and die active area are 23.7 mW and 0.017 mm, respectively. [ABSTRACT FROM AUTHOR]

Wireless Mesh Networks (WMN) have attracted increasing attention from the research community as a high-performance and low-cost solution to last-mile broadband Internet access. On the other side, Optical Burst Switching (OBS) is a promising access technology that uses optical fiber with burst switching paradigm. In this paper, we propose a novel Metropolitan Area Network (MAN) architecture, called Optical Burst Wireless Mesh Architecture (OBWMA) which integrates WMN at the user access side and OBS at the core of the MAN. OBWMA aims to combine advantages of both WMNs and OBS networks, such as large coverage at low cost and bandwidth availability. We specify the details of the interconnection and the internetworking of WMNs and the OBS network in OBWMA. Moreover, we develop an analytical model to compute the end-to-end delay in OBWMA in order to support flow requests with delay constraints. Furthermore, we propose a Control Bridge (CB) that ensures Quality of Service (QoS) mapping at the border between the WMN and the OBS parts. Also, we propose a burst assembly scheme, called Adaptive Hybrid Burst Assembly scheme (AHBA). Simulation results using ns-2 demonstrate the feasibility of OBWMA and the validity of our analytical model. [ABSTRACT FROM AUTHOR]

This study applies a novel fabrication process that combines anisotropic wet etching of silicon-on-insulator (SOI) wafers with electroforming to manufacture precision stampers. Micron-sized features, such as trapezoidal grooves and truncated pyramidal prisms, can be fabricated and distributed accurately. Because feature geometry and distribution can be accurately realized using the proposed scheme, design optimization of light guide plates (LGPs) becomes realistic. By observing the illumination characteristics of light emitting diode (LED) edge-lit LGPs, the distribution pattern of the LGP is transformed into a parameter design with seven anchor spacing and the spacing modulation amplitude of the micro features adjacent to LEDs. The proposed fuzzy optimization scheme manipulates distribution parameters to obtain an LGP design with high illumination uniformity. The design of a 3.5-inch LED edge-lit LGP is used as an illustrative example. The optical software program TracePro is applied to simulate luminance performance of BLM. The optimization converges rapidly and provides the optimum design with an average brightness of 2,266 (nit) and uniformity of 90% without use of diffusive sheets. Thus work demonstrates the feasibility and effectiveness of the proposed scheme. [ABSTRACT FROM AUTHOR]

We have theoretically and experimentally studied optical emission from the side faces of mesa structures for vertical-cavity surface-emitting lasers (VCSELs). The results of spatially resolved spectral measurements show that a new type of lasing modes is found in VCSELs with circular mesa structures, which corresponds to the π mode propagation along the mesa diameter with reflection from the sloped walls and the bottom Bragg mirror. [ABSTRACT FROM AUTHOR]

An all-optical 2R regeneration based on self-induced polarization rotation in a single semiconductor optical amplifier is presented. A theoretical model is built up to simulate the system performance. Experiment evidence is also provided. An extinction ratio improvement of 8.3 dB is obtained at a bit-rate of 10 Gbit/s. In the BER measurements, 6 dB improvement of the power penalty is achieved, clearly demonstrating the feasibility of the proposed scheme. Our approach has a simple structure, and allows photonic integration. [ABSTRACT FROM AUTHOR]

High frequency modeling of quantum-well (QW) laser diodes for optoelectronic integrated circuit (OEIC) design is discussed in this paper. Modeling of the intrinsic device and the extrinsic components is discussed by accounting for important physical effects at both dc and high frequency. The concepts of equivalent circuits representing both intrinsic and extrinsic components in a QW laser diode are analyzed to obtain a physics-based high frequency model. The model is based on the physical rate equations, and is versatile in that it permits both small- and large-signal simulations to be performed. Several procedures of the high frequency model parameter extraction are also discussed. Emphasis here is placed on validating the model via a comparison of simulated results with measured data of the small-signal modulation response, obtained over a wide range of optical output powers. [ABSTRACT FROM AUTHOR]

Abstract  We are building a long-range FM/cw nonscanning imaging lidar breadboard. This lidar system achieves ranging based on a frequency modulation/continuous wave (FM/cw) technique, implemented by an amplitude modulated mid-IR diode laser transmitter with a linear frequency modulation (LFM) of the subcarrier. Firstly, various schemes of light beam modulation are analyzed. Secondly, we put forward a laser modulation scheme whose core was formed by a 1.55 μm electro-absorption modulated laser diode (EML) and an erbium-doped optical fiber amplifier (EDFA), then a corresponding experimental system architecture and components for light beam modulation and detection are established. Finally, a corresponding experiment of laser beam modulation is completed for the first time. In our experiment, the EML amplitude is modulated by a 200 MHz to 800 MHz LFM signal, whose amplitude value is 2.05 V. The average output power of the modulated laser obtained in the experiment is 10 W, peak power is 16.4 W, and the average modulation depth is 78%. The results of tests predict that this laser modulation scheme is likely to improve the imaging range of the FM/cw lidar. [ABSTRACT FROM AUTHOR]

Choice of modulation format plays a critical role in the design and performance of fiber optic communication systems. We discuss the basic physics of electro-optic phase and amplitude modulation and derive model transfer functions for ideal and non-ideal Mach-Zehnder modulators. We describe the generation and characteristics of the standard nonreturn-to-zero (NRZ) modulation format, as well as advanced formats such as return-to-zero (RZ), carrier-suppressed RZ (CSRZ), duobinary, modified duobinary, differential phase-shift keyed (DPSK), and return-to-zero DPSK (RZ-DPSK). Finally, we discuss the relative merits of these formats with respect to a variety of system impairments. [ABSTRACT FROM AUTHOR]

Fiber Bragg Gratings (FBGs) attract great attention due to their present and prospective applications in fiber-optical communication systems and modern opto-electronics. FBGs are components having a wide range of applications in the fields of communication, lasers and sensors. This study is a theoretical study in the field of FBG. Our aim is, by using coupled-mode theory and changing-of-index variation function, to model the FBG and to elucidate the appropriate parameters of FBG. Diffraction spectra of a FBG and its first and second degrees were obtained. Maximum reflection of FBGs versus saturation coefficient was also examined. [ABSTRACT FROM AUTHOR]

Abstract  A simple rate-equation model of double pass (DP), remotely-pumped Erbium-doped fiber amplifier (R-EDFA) is developed based on the Giles-and-Desurvire (1991) model of a single pass (SP) EDFA. The mathematical equations to calculate stimulated absorption-and-emission rate between levels 1 and 2 of SP EDFA are modified by integrating the reflected backward-propagating signal of the DP R-EDFA. Besides the signal amplification, dispersion compensation by the chirped-fiber Bragg-grating (CFBG) inside the DP R-EDFA is also taken into account. The reflection losses of a signal by the CFBG are included in the backward-propagating signal of the DP R-EDFA. Considering a high gain and low noise figure (NF) by very low remote pump power as a main design objective, the design process of an optimized DP R-EDFA for a long haul optical-fiber-communication system (OFCS) is demonstrated. Robustness and stability of the DP R-EDFA rate-equation model developed are shown by analyzing the numerical results and output shapes using various design parameters of the DP R-EDFA. Finally, the DP R-EDFA rate-equation model developed is validated with the help of experimental results. [ABSTRACT FROM AUTHOR]

We propose a simple and efficient approach to the design of 3-wavelength backward-pumped Raman amplifiers with increased gain flatness over a wide spectral band. Three different methods dealing with the optimization of one or two different simple parameters are studied. Various examples are provided for illustration, and the dependence of both amplifier gain and gain flatness with pump power is shown. Gain flatness in the spectral range of 1,520–1,595 nm of about 1 dB for a 7.5 dB gain and of 1.8 dB for a 13.5 dB gain is demonstrated using only three pumps with wavelengths within the 1,420–1,480 nm interval. [ABSTRACT FROM AUTHOR]

The article presents a study which demonstrates wavelength tuning of double-cavity micromachined filter with electrical and thermal actuations. The study aimed to realize widely tunable filters for use in optical communication sytems. Such concept is important for tunable vertical cavity surface emitting lasers. Researchers also presented the theoretical and measured temperature dependence of fabricated micromachined filter.

The interaction of a five-level atomic system involving electromagnetically induced transparency with four light fields is investigated. Two different light-atom configurations are considered, and their efficiency in generating large nonlinear cross-phase shifts compared. The dispersive properties of those schemes are analyzed in detail, and the conditions leading to group velocity matching for two of the light fields are identified. An analytical treatment based on amplitude equations is used in order to obtain approximate solutions for the susceptibilities, which are shown to fit well with the numerical solution of the full Bloch equations in a large parameter region. [ABSTRACT FROM AUTHOR]

We report the generation of self-similar highly stable femtosecond pulses from an ytterbium-doped double-clad fiber laser. Positively chirped parabolic pulses with 6.4-ps duration and more than 3.2-nJ energy are obtained. These pulses are extra-cavity compressed to 140 fs. Radio-frequency noise measurements show that this regime of emission ensures low-noise operation with less than 0.05% amplitude fluctuations. [ABSTRACT FROM AUTHOR]

A loss-coupled 1550 nm distributed feedback (DFB) laser diode with automatically buried absorptive InAsP layer for the application to radio-over-fiber network was experimentally investigated where the automatically buried layer in the epitaxial growth reduced the process steps in loss-coupled DFB laser fabrication. It showed linearity in electro-optical conversion characteristics with reduced third order intermodulation distortion of -70 dBc which is comparable to the previous results of DFB lasers as the optical power increases to 5 mW under two-tone test at 1.8 GHz bands. [ABSTRACT FROM AUTHOR]

In the past years, telecommunications networks have seen an important evolution with the advances in optical technologies and the explosive growth of the Internet. Several optical systems allow a very large transport capacity, and data traffic has dramatically increased. Telecommunications networks are now moving towards a model of high-speed routers interconnected by intelligent optical core networks. Moreover, there is a general consensus that the control plan of the optical networks should utilize IP-based protocols for dynamic provisioning and restoration of lightpaths. The interaction of the IP routers with the optical core networks permits to achieve end-to-end connections, and the lightpaths of the optical networks define the topology of the IP network. This new infrastructure has to be sufficiently survivable, so that network services can be restored in the event of a catastrophic failure. In this paper we consider a multilayer survivable network design problem that may be of practical interest for IP-over-optical neworks. We give an integer programming formulation for this problem and discuss the associated polytope. We describe some valid inequalities and study when these are facet defining. We discuss separation algorithms for these inequalities and introduce some reduction operations. We develop a Branch-and-Cut algorithm based on these results and present extensive computational results. [ABSTRACT FROM AUTHOR]

This paper introduces the use of a fiber-optic communication system for interrogation and transmission of data from fiber Bragg grating (FBG) sensors. Signal coding and dispersion compensation methods, usually used in communication systems, are used to improve the sensing system’s performance. Moreover, communication system parameters are used to assess the improvement in the FBG sensing performance. This is done through the determination of the profiles of Q-factor and eye diagrams. The sensors considered in the simulations are strain sensors subjected to a wide range of strains. The results obtained show a clear improvement of the sensing system with symmetrical compensation. The proposed method is suitable for applications where fiber-optic links are available near both the sensing location and information-collection and-processing unit, even if these two are hundreds of kilometers apart. A good example of where such a system can be applied is the oil industry. The rigs are usually very far from headquarters, but both might be close to a fiber node. [ABSTRACT FROM AUTHOR]

The paper presents techno-economic results for fixed access networks which have been achieved within the IST MUSE (Multi Service Access Everywhere; ) integrated project in the first phase. The article summarises the results from studies of two major use cases, Network Migration Cases and the Native Ethernet approach. The results are based on a common framework. A specific attention is paid to the first mile deployment scenarios including Fibre to the Cabinet (FTTCab) and Point-to-Point optical networks (PtP). It has been observed that the migration from a best effort access network to a Quality of Service (QoS) enabled multi-service architecture based on Ethernet or IP forwarding is favourable in comparison with an ATM-based evolution scenario. Service enabling new network functionalities like Quality of Service (QoS), multicast and Internet (IP) based auto-configurations are moving closer to subscribers. This leads to an increased intelligence in access networks and related potential Capital Expenditures (CAPEX) savings of about 25% in aggregation networks. [ABSTRACT FROM AUTHOR]

Structure optimisation of the GaAs-based GaInNAsSb/GaNAs quantum-well (QW) vertical-cavity surface-emitting diode lasers (VCSELs) has been carried out using the comprehensive three-dimensional self-consistent physical model of their room-temperature (RT) continuous-wave (CW) threshold operation. The model has been applied to investigate a possibility to use these devices as carrier-wave lasing sources in the third-generation optical-fibre communication. In this simulation, all physical (optical, electrical, thermal and gain) phenomena crucial for a laser operation including all important interactions between them are taken into consideration. As expected, the 1.5λ-cavity VCSEL has been found to demonstrate the lowest RT CW threshold. However, for many VCSEL applications, the analogous VCSEL equipped with a longer 3λ-cavity should be recommended because it exhibits only slightly higher threshold but manifest much better mode selectivity – the desired single-fundamental-mode operation has been preserved in these devices up to at least 380 K. The Auger recombination has been found to be decidedly the main reason of the threshold current increase at higher temperatures. A proper initial red detuning of the resonator wavelength with respect to the gain spectrum may drastically decrease CW lasing thresholds, especially at higher temperatures. [ABSTRACT FROM AUTHOR]

We present a multi-population rate equation model for the analysis of the static and dynamic characteristics of a quantum dot (QD) semiconductor laser. The model is applied to the extraction of the differential gain and linewidth enhancement factor of the QD laser simulating the same kind of experiments usually done in the laboratory. Coherently with the experimental results, we show the difference between the values of the differential parameters extracted in below and above threshold characterizations. We demonstrate that such discrepancy is due the complex dynamics of the carriers in those energy states, whose carrier concentration is not clamped by the stimulated emission process above threshold. [ABSTRACT FROM AUTHOR]

Quantum dot (QD) lasers exhibit many interesting and useful properties such as low threshold current, temperature insensitivity or chirpless behavior. In order to reach the standards of long-haul optical transmissions, 1.55 μm InAs QD lasers on InP substrate have been developed. Based on time resolved photoluminescence (PL) measurements, carrier dynamics behavior is at first investigated. Electroluminescence (EL) results are then shown at room temperature exhibiting a laser emission centered at 1.61 μm associated to a threshold current density as low as 820 A/cm2 for a six InAs QD stacked layers. Finally, a rate equation model based on the reservoir theory is used to model both time-resolved photoluminescence (TRPL) and electroluminescence results. It is shown that carrier dynamic calculations are in a good agreement with measurements since the saturation effect occurring at high injected power is clearly predicted. [ABSTRACT FROM AUTHOR]

Physical aspects of an operation of the GaAs-based InGaAs/GaAs quantum-well (QW) VCSELs with the intentionally detuned optical cavities have been considered in the present paper using the comprehensive three-dimensional self-consistent optical–electrical–thermal-gain simulation. In GaAs-based structures, very good DBR resonator mirrors and a very efficient methods to confine radially both the current spreading and the electromagnetic field with the aid of oxide apertures may be applied. It has been found using the above simulation that even currently available immature technology enables manufacturing the above devices emitting radiation of wavelengths over 1.20 μm. In particular, while the room-temperature 1.30-μm lasing emission is still beyond possibilities of the InGaAs/GaAs QW VCSELs, these structures may offer analogous 1.25-μm emission, especially for the high-power and/or high-temperature operation. [ABSTRACT FROM AUTHOR]

Unique dispersion characteristics and enhanced nonlinearity make the small-core photonic crystal fiber (PCF) an ideal candidate for nonlinear optical devices to telecommunication applications. Some technical reasons behind great research interest of highly nonlinear PCFs in optical communication components are reviewed. Nonlinear effects in highly nonlinear PCFs and their research progress are presented. Several typical applications including WDM sources, optical amplification, optical switching, wavelength conversion, optical regeneration and all-optical demultiplexing etc are introduced, together with state-of-the art performances. Some new possible applications and future prospects are discussed. [ABSTRACT FROM AUTHOR]

We investigate the transmission performance of N × 40 Gbps carrier-suppressed return-to-zero (CS-RZ) and duobinary CS-RZ (DCS-RZ) modulated wavelength division multiplexed (WDM) signals over the standard single-mode fiber (SSMF) based on non-ideal Mach-Zehnder (MZ) modulators through numerical simulations. In addition to that, the impact on receiver margin related to the residual chirp due to an asymmetry ratio of modulators as well as the effect of the applied chirp of modulators has been studied. As the asymmetry ratio of modulators is increased, dispersion penalties are increased asymmetrically at around the zero dispersion wavelength for the CS-RZ format. The DCS-RZ modulation format has a symmetric behavior due to different characteristics of the residual chirp of modulators. The receiver margin for the DCS-RZ modulation format is larger than the CS-RZ modulation format above the asymmetry ratio of 0.82 of modulators (extinction ratio of 20 dB) with the optimal ΔλDCF. By controlling the negative/positive applied chirp of the first/second modulator, dispersion penalties can be reduced for both the CS-RZ and DCS-RZ formats. In the DCS-RZ format compared to the CS-RZ format, the effect of the applied chirp of the first modulator is more dominant than that of the second modulator. The simulation results show that the receiver margin is limited by the asymmetry ratio of modulators as well as a deviated wavelength from the zero dispersion wavelength of dispersion compensating fibers (DCF) in order to be fully post-compensated. Dispersion penalties can be reduced with appropriate chirp parameters of two non-ideal modulators. [ABSTRACT FROM AUTHOR]

A three-stage compensator used for Polarization mode dispersion (PMD) and Chromatic dispersion (CD) compensation is proposed. The compensator is capable of compensating the two components of second-order PMD when no CD exists. Two operating points of compensating second-order PMD have been proposed. Two-stage and three-stage compensators are compared by the outage probability. When CD is introduced, the compensator should retain a quantity of second-order PM D to compensate CD. The outage probability when PM D and CD coexist has been calculated. The results show that a tradeoff must he made in order to compensate CD and PM D at the same time. [ABSTRACT FROM AUTHOR]

Experiment was conducted to study Gaussian pulse transmission over ultra-high PMD fiber. Gaussian pulse is broken into a series of deformed pulses when it transmits over ultra-high PMD fiber. It is indicated that the walk-off deformed pulses were caused by ultra-high PMD. Transmitted experiment has been done using fiber with PMD coefficient 237.95ps/km1/2. The result of the experiment is consistent with the simulated one. [ABSTRACT FROM AUTHOR]

We present a fast tabu search method for the design of access tree networks. We connect a population of users to a set of switches using a variety of SONET channels on fiber optics links and ADM equipment at the nodes. We specifically take into account the economies of scale provided by the transmission systems and the transmission hierarchy of SONET systems. We describe in detail the parameters used for defining neighborhoods, penalty parameters, data structure and indicate how this can lead to substantial improvements of the overall computational time while providing costs lower than those of a more straightforward method. Results are provided for a set of random cases as well as for a real network. [ABSTRACT FROM AUTHOR]

The article focuses on concerns on the imminent capacity crunch in optical communications networks, which was discussed at the Communication Networks Beyond the Capacity Crunch meeting at The Royal Society held in London, England from May 11 20 12, 2015 and at a satellite meeting at Chicheley Hall in Buckinghamshire, England from May 13 to 14, 2015. Topics discussed include the Shannon limit of optical fiber capacity and efforts to increase the capacity of fiber optic communication systems.

The mechanism of femtosecond optical pulse generation in a self-starting Er3+-doped fiber ring soliton laser and experimental research results are discussed. Using the nonlinear polarization rotation effect of the fiber for sat-urable absorbers (and then self-amplitude modulation) which acts as the mode locking mechanism in an Er3+-doped fiber ring cavity laser, stable self-starting mode locking pulses have been generated. The shortest output pulse is 269 fs, with the central wavelength of 1,531 pm at the repetition rate of 21.37 MHz. The average output powen of the two terminators of the laser are 0.25 mW and 0.08 mW respectively. The threshold pump power which sustains the mode locking is 15 mW. Under high pump power, the laser works in a high order harmonic mode locking state. The mode locking pulse durations vs different cavity lengths are also studied. [ABSTRACT FROM AUTHOR]

This paper describes a method for fast engineering evaluation of the transmission characteristics of single-mode optical fibers. A versatile microcomputer program is presented which can be utilized to analyze mode field characteristics of single-mode fibers with arbitrary refractive index profiles. Our computation shows that the mathematical algorithm and the corresponding programs developed in this paper are relatively simple and accurate enough for the engineering design of single-mode fibers for optical communication systems. [ABSTRACT FROM AUTHOR]

An introduction is presented in which the editor discusses various reports within the issue on topics including Passive Optical Networks, multi-domain translucent wavelength switched optical networks, and optical networks control and management.

A new method of data transmission in DWDM systems along existing long-distance fiber-optic communication lines is proposed. The existing method, e.g., uses 32 wavelengths in the NRZ code with an average power of 16 conventional units (16 units and 16 zeros on the average) and transmission of 32 bits/cycle. In the new method, one of 124 wavelengths with a duration of one cycle each (at any time instant, no more than 16 obligatory different wavelengths) and capacity of 4 bits with an average power of 15 conventional units and rate of 64 bits/cycle is transmitted at every instant of a 1/16 cycle. The cross modulation and double Rayleigh scattering are significantly decreased owing to uniform distribution of power over time at different wavelengths. The time redundancy (forward error correction (FEC)) is about 7% and allows one to achieve a coding enhancement of about 6 dB by detecting and removing deletions and errors simultaneously. [ABSTRACT FROM AUTHOR]

The author reflects on the source of optical fields called surface plasmon amplification by stimulated emission of radiation (SPASER). He notes that spaser is useful to explain how it is possible to beat the diffraction limit and focus electromagnetic waves to spot smaller than wavelength. According to him, the ability of a nanostructured material to support and concentrate such fields is due to the existence of optical modes that are set on dimensions smaller than the optical wavelength.

In this work, we perform the numerical investigation of the performance of the small optical reservoir computing (RC) systems with four neurons using the commercial software for optical fiber communication system. The small optical RC system consists of the components of the optical fiber communication. The nonlinear function which is required in RC is provided by the erbium-doped optical fiber amplifiers (EDFA). We demonstrate that the EDFA should be operated in the saturated or non-linear regime to obtain a better performance of the small optical RC system. The performance of the small optical RC systems for different topological neuron structures is investigated. The results show that the interconnection between the neurons could offer a better performance than the systems without interconnection between the neurons. Moreover, the input signals with different noise levels are launched into the systems. The results show that the small optical RC system can classify the noisy input optical waveforms even when the signal-to-noise ratio is as low as − 2.55 dB. [ABSTRACT FROM AUTHOR]

For combining different single photon channels into a single path, we use an effective and reliable technique which is known as quantum multiple access. We take advantage of an add-drop multiplexer capable of pushing and withdrawing a single photon into an optical fiber cable which carries quantum bits from multiusers. In addition to this, spreading spreads the channel noise at receiver side and use of filters stop the overlapping of adjacent channels, which helps in reducing the noise level and improved signal-to-noise ratio. In this way, we obtain enhanced performance of code division multiple access-based QKD links with a single photon without necessity of amplifiers and modulators. [ABSTRACT FROM AUTHOR]