Optical Communication 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

Receiving of remote sensed data's signals in urban space information reception centers is usually difficult, because of complex electromagnetic situation in cities and insufficient EMC. Traditional methods for digital reconstruction of images use smoothing and autoregressive forecasting. In this case anomalous spikes on the image are lost. Alternative method based on Kolmogorov-Wiener's filters and fractal properties of satellite images is

Present a collection of slides covering the following topics: ATM communications; integrated communication-navigation and surveillance; next generation concept; air-to-ground communication; air-to-air communication; cellular network;... more

- by Aloke Roy
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- Computer Science, Optical Communication, Cellular Network, asynchronous Transfer Mode

This paper addresses and implements a Direct Sequence Spread Spectrum (DSSS) transceiver for Visible Light Communication (VLC) systems based on FPGA. A transceiver was implemented including a transmitter capable of driving an array of light emitting diodes (LED) and a Pseudo-Noise (PN) matched decorrelator. The receiver architecture uses a discrete FIR correlator for data synchronization and acquisition. In this paper, a novel and simple PN code with a 10 bit sequence length is developed. This code ...

- by Jyoti Pal
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- FPGA, Optical Communication, Intelligent Transport System, Multidisciplinary
- by Armando Marques-Guedes
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- History, Cultural History, Sociology, Political Sociology
- by S. Tudisco
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- Physics, Photonics, Optical Communication, Quantum Cryptography

Advanced modulation formats can enable >40 Gb/s data rates in waveguide-based optical interconnects without the need for high-specification optoelectronic components. Record 56Gb/s PAM-4 data transmission is demonstrated over a 1 m-long... more

- by Deepa Venkitesh
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- Engineering, Applied Physics, Optical Communication, Fiber Laser

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.

- by M. Kilickaya
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- Optical Communication, Communication System, Fiber Bragg grating, Optical physics

Optical solitons propagating in media exhibiting saturable nonlinearity offer advantages over Kerr-medium solitons for transmission over large distances through optical fibers with loss. Soliton pulses in saturable media offer greater energy for a given peak power, and upper-branch solitons decrease in width with distance traveled. These properties result in pulses that remain distinct and detectable for greater distances than Kerr-medium solitons do with the same peak power.

- by Gregory Aicklen and +1
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- Applied Mathematics, Nonlinear Optics, Optical Communication, Optical physics

Rapid advancements of both microsystem technology and multi-agent systems have generated a new discipline, arising from the fusion of microrobotics technologies and of swarm intelligence theories. Microrobotics contributes with new capabilities in manipulating objects in the microscale and in developing miniaturized intelligent machines, while swarm intelligence supplies new algorithms allowing sets of simple robotic agents to solve complex tasks. A microrobotic swarm that is able to collectively achieve a cleaning task in an arena has been developed. This paper presents a novel platform for microrobotic swarms with the goal to apply swarm intelligence results to practical micromanipulation tasks and describes in details two main features of the platform: an optical communication strategy between the microrobotic agents, in order to share information and to coordinate swarm actions, and a micromanipulation technique -based on electrostatic phenomena -which can be performed by each microrobotic agent.

- by Nikolay Zheludev
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- Physics, Optics, Optical Communication, Magnetic field

A two-beam setup based on the totally reflecting prism coupler is shown to be a powerful means of characterizing light-induced refractive-index modifications in dielectric thin films. Rise and relaxation times and amplitudes of thin-film refractive-index variations can be measured. Some developments of the electromagnetic theory of prism coupling are presented for Gaussian incident beams. Measurements made on a single Ta 2 O 5 layer deposited on a silica glass are presented. Relaxation times of a few milliseconds reveal the thermal origin of the phenomena. The thermal nonlinear coefficient of this Ta 2 O 5 layer is nearly 10 Ϫ15 m 2 ͞W.

- by S. Tisserand
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- Mechanical Engineering, Optical Communication, Thin Film, Refractive Index

In this paper, we first measure fiber nonlinear Kerr coefficient of a two-mode fiber (TMF) by characterizing the four-wave mixing (FWM) components. Based on the measured nonlinear coefficient, we present an analysis of the link capacity for a two-mode fiber. It is shown that despite strong spatial overlapping of the three modes, the overall capacity approaches three times of that of a single-mode fiber.

- by Abdullah Al Amin
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- Optical Communication, Four Wave Mixing, Single Mode Fiber

Beam propagation method simulation shows that evanescently coupled waveguide/photodiodes can be optimized to have absorption lengths as short as butt-coupled photodiodes. Efficient focalization of optical power in the absorber is achievable by appropriate choice of layers geometry and refractive index. Two AlGaInAs-GaInAs structures have been designed for ultrawide-band operation at 60 and 100 GHz: these devices exhibit internal quantum efficiency as high as 94% and 75%, respectively, at 1.55-m wavelength. Such promising performances are suitable for the realization of high-speed high-efficiency integrated photoreceivers with applications to millimeter-wave optical fiber links.

- by S. Demiguel
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- Optical Communication, Optical Design, Millimeter Wave Antennas, Refractive Index

In this paper the performance analyses of incoherent time spread optical Code Division Multiple Access (CDMA) system with non-ideal optical hard-limiters is studied using the signal to interference ratio as the performance merit. Shortened Optical Orthogonal Codes achieved multiple accesses in investigated CDMA system. Shortened Optical Orthogonal Codes are generated by extended set technique. The performance improvement for cases of optical CDMA receiver without, with one and with two optical hard-limiters, respectively, is shown by simulation of CDMA encoder output and signal to interference ratio. The signal to interference ratio versus the number of active users for various weight code is reported.

A novel inband forward-error correction (FEC) method, devised for the electronic-mitigation of physical optical transmission impairments, is implemented and experimentally demonstrated. The proposed inband-FEC scheme, Free-Of-Charge Uniform Shield (FOCUS), is an inherently low-cost approach, applicable to standard synchronous digital hierarchy/synchronous optical network rates, allowing optically transparent signal propagation over longer distances. The performance/efficiency of the FOCUS method is evaluated in terms of tolerance against optical signal-to-noise ratio degradation and chromatic-dispersion, associated with the signal transmission over standard single-mode fiber. Bit-error-rate measurements and coding gain calculations at the standard STM-64 rate (9.953 Gb/s) reveal significant coding-gain improvement for all cases examined.

- by John Kikidis and +2
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- Optical Communication, Metropolitan Area Network, Optical physics, Forward Error Correction

In this paper, the content of two laboratory courses developed at the Department of Electronics of the Technological Educational Institute of Crete, Greece, focused on optoelectronics and optical communications, respectively, is presented. Both of these laboratory courses were developed with the philosophy of introducing a research-oriented approach. Emphasis is given on handson experimentation. In such a way, students get a better understanding of the various theoretical concepts (generation of light through single mode Continuous Wave lasers, transmission of optical power, etc.), and become able to analyze and solve problems associated with photonics components and their integration to optical systems. Coupling of experimentation and research is facilitated with a Marie Curie EU-funded grant for the establishment of a Centre of Excellence via the transfer of knowledge in the scientific area of optoelectronics and lasers. Our approach is presented by referring to specific laboratory exercises, such as the experimental study of a variable optical attenuator developed for research purposes, the development of an X-ray high power x-pinch optolectronic device, etc.).

- by Giorgos S Liodakis
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- Optical Communication, Course Development, X Rays, Experimental Study

| Near-Earth laser communication system designs typically use the near-symmetric power levels in duplex links as bright sources upon which to base active beam stabilization. In deep space, it may be difficult to provide a constant, highpower laser beacon as a stabilization reference. We describe here several means, aimed at different frequency ranges of control, for generating a combined pointing reference and for actively controlling beam position. Such a blended approach gives a highly flexible system for performing beam stabilization in deep space, where distances, conditions, and power levels can vary widely.

- by Jamie Burnside
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- Biomedical Engineering, Optical Communication, System Design, Communication System

This paper proposes a security architecture for optical code division multiple access networks based on lattice cryptography. Unlike existing approaches, which have mainly focused on optical components such as phase masks and delay lines, our cryptosystem encompasses a secure code construction process. In fact, given a set of optical orthogonal codewords, we associate a pair of bases (a public basis and a private basis) to every user and we show that the projection of a codeword on the public basis of the receiver and the addition of a random error enhances the confidentiality performance of the code. The proposed public key cryptosystem is based on lattice cryptography. The security of this scheme relies mainly on the complexity of the closest vector-problem in an integer lattice. We found that our technique performs better than the existing approaches in terms of robustness to cryptanalysis. We also study the security of our lattice cryptosystem with regard to the properties of the bases pairs and the error vectors.

Skew constacyclic codes are displaying vital role in the field of coding theory. This paper is mainly focused on skew-α constacyclic codes over R = Fq + uFq + vFq + uvFq, with u 2 = v 2 = 1, uv = vu, q = 3 m , and α is an unit of R fixed by the authomorphism θ. It is briey derived as well that the Gray map of skew cyclic code of length n over R is skew quasicyclic code of length 4n over Fq of index 4. Furthermore, the decomposition of a skew α constacyclic codes over R are also determined. A complete analysis about the relationship between skew α constacyclic code and its dual is also carried out.

The Sagnac all-optical fiber logic gate functions as a two-input AND gate, a two-input AND gate with one inverting input, or both. The fiber logic gate is pipelined and has a fixed latency. This latency has no effect on feed-forward combinatoric circuits. The latency can be used to time multiplex circuits or to time multiplex gates to emulate a circuit. Possible applications such as a bit-jitter-tolerant communications system, an asynchronous communications system, a bit-interleaved self-routing switching system, an exchange/bypass permutation unit, and a folded universal state machine are discussed.

- by Alan Huang
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- Mechanical Engineering, Optical Communication, Information Processing, Applied

Laser communications systems offer a significant advantage over traditional radio frequency systems due to the shorter wavelength of laser light. Data can be sent at higher rates for less power with proportionally smaller transmitters and receivers. A laser communications system has never been demonstrated in a moon to Earth link at MBps data rates This paper presents a model of a laser downlink from the moon, developed to rapidly explore various system architectures. Modeling and analysis shows that the target data rates of above 2 Mb/s are possible with 300mW of transmitter power using a 3.5 mm aperture, a 1.5 m receiver diameter and a minimum gimbal resolution (maximum step size) of 78 μrad. 19.89 Mb/s data rates are possible using a 1 cm transmit aperture but with a much stricter minimum gimbal resolution (maximum step size) of 27 μrad. 12

- by Edwin Portugal Gomez
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- Physics, Earth, Optical Communication, Aerospace

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

We propose using optical repeaters in optical freespace communication systems to increase the transmission-length stably. We demonstrate an 8 10-Gb/s terrestrial optical freespace transmission over 3.4 km using an optical repeater at the halfway. The optical repeater not only amplifies the signal channels but also prevents the accumulation of the detrimental scintillation noise during the propagation.

- by Jaeseung Lee
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- Optical Communication, Communication System, Optical physics, Optical fiber

We propose coherent detection with one sample/ symbol. Maximum-likelihood sequence estimation (MLSE) is used to compensate for intersymbol interference introduced by antialiasing filtering. The 100 000-ps/nm chromatic dispersion and... more

- by Dan Sadot and +1
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- Signal Processing, Optical Communication, Blind Equalization, Maximum Likelihood Estimation

— In this paper, we proposed an approach to automatically regulate the mood or brainwave of the paralyzed or sensory impaired or psychologically sick people. A MATLAB based algorithm has been developed to analyze the brain wave signals obtained from a real time EEG data acquisition system corresponding to different moods of the subject people. The program translated the brain wave signals into command to select and play suitable music tracks according to the state of the brain. These music or sound tracks, selected based on the choice of the target people, acted in turn as a feedback to continuously adjust the subject's mood as desired. Relaxation music, subcontinental soft patriotic, Rabindra Sangeet & motivational songs were used as example for relaxation, entertainment and warm-up respectively. Sample stored EEG data of different patients having different moods were used to verify the feasibility of the approach and the obtained results ensured its effectiveness.

We report simulation results of pulse width modulation (PWM)-based pulse position modulation (PPM) signal format for visible light communication systems. For simultaneous operation of data transmission and dimming control, PPM data format is added to PWM dimming control signal. To show dimming control, the PWM duty ratio is changed from 40 % to 80 % during PPM data transmission. The PWM frame rate is set to 1 kHz to avoid flickering in human eyes. The PPM data rate is set to 20 kb/s. The waveforms, eye diagrams and BER of this system are calculated. The simulation shows the BER of 1×10 -5 is achievable.

- by Zabih Ghassemlooy
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- Optical Communication, BER, Pulse Width Modulation

Light-emitting diode (LED) nonlinear differential gain (DG) and differential phase (DP) were measured, since they are important performance factors in video signal transmission. Typical, experimentally measured temperature dependence of DG and DP is also presented. A linearizing method for minimizing LED DG and DP distortions, using predistortion, is proposed and experimentally examined. With this technique, and with precise adjustment of the predistortion circuits, the DG of a typical LED was improved from 12.5 percent to less than 1 percent, and the DP from 2.8° to 1°. This corresponds to an improvement in second and third-order harmonic distortions of 19 dB and 21 dB, respectively. DG and DP were measured with respect to the 3.58-MHz color subcarrier frequency superimposed on the 15.75-kHz horizontal scanning sawtooth wave. The linearization stability with regard to temperature variation was lowered to be less than 1-percent DG and 1° DP in the temperature range from 15 to 45°C.

- by Koichi Asatani
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- Signal Processing, Optical Communication, Circuits, Temperature measurement
- by Ezequiel Ramos
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- Computer Science, Optical Communication

This paper studies the performance analysis of wavelength-division multiplexed optical communication
systems (WDM). First, flat-gain erbium doped fiber amplifiers (EDFAs) are seriously needed to obtain
proper and equal amplification of all channels. Such amplifiers can be designed by intrinsically modifying
the host material or extrinsically using proper filters. In this research, we benefit from both the intrinsic
and extrinsic methods to achieve sharp flat EDFA output gain using cascaded fiber Bragg gratings (FBGs).
Second, the performance of our technique has been evaluated through calculating the bit error rate (BER)
and signal-to-noise ratio (SNR) of a WDM system embedded with the reported EDFA flattening system.
The parametric simulations of the FWHM of FBGs, SNR, optical power and the transmission distance have
shown a noticeable improved performance. Sending data via an optical WDM system will be proven from
comprehensive simulations to achieve high quality signal transmission spectrums, increased transmission
distances and low power consumption. By extension, the reported design using cascaded FBGs
can also be generalized to equalize the gain of any arbitrary profile.

- by Amr Mahros
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- Optical Communication

This paper describes the achievements in optical intersatellite communication based on technology developments that started in Europe (European Space Agency) more than 30 years ago. In 2001, the world-first optical intersatellite communication link was established (between the SPOT-4 and Advanced Relay and TEchnology MIssion Satellite (ARTEMIS) satellites), proving that optical communication technologies can be reliably mastered in space. In 2006, the Japanese Space Agency (JAXA)

- by Zoran Sodnik
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- Quantum Physics, Optical Communication, Technology development, Optical physics

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.

Adam Smoliński, Optoelektronika Światłowodowa, WKiŁ, Warszawa 1985 (dedykacja autora)

- by Ryszard Romaniuk
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- Optical Engineering, Optics, Optical Fiber Communications, Fiber Optics

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.

In this paper, we discuss the realization of an optical microphone array using fiber Bragg gratings as sensing elements. The wavelength shift induced by acoustic waves perturbing the sensing Bragg grating is transduced into an intensity modulation. The interrogation unit is based on a fixed-wavelength laser source and - as receiver - a photodetector with proper amplification; the system has been implemented using devices for standard optical communications, achieving a low-cost interrogator. One of the advantages of the proposed approach is that no voltage-to-strain calibration is required for tracking dynamic shifts. The optical sensor is complemented by signal processing tools, including a data-dependent frequency estimator and adaptive filters, in order to improve the frequency-domain analysis and mitigate the effects of disturbances. Feasibility and performances of the optical system have been tested measuring the output of a loudspeaker. With this configuration, the sensor is capable of correctly detecting sounds up to 3 kHz, with a frequency response that exhibits a top sensitivity within the range 200-500 Hz; single-frequency input sounds inducing an axial strain higher than ~10nɛ are correctly detected. The repeatability range is ~0.1%. The sensor has also been applied for the detection of pulsed stimuli generated from a metronome.

- by Daniele Tosi
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- Signal Processing, Optical Communication, Optical Sensor, Fiber Bragg grating

Underwater connectors using inductive power transfer provide increased reliability and number of mate/de-mate cycles because no electrical contacts are physically utilized. While the general concept is not new, this paper presents a connector that uses resonant coupling to improve the power transfer efficiency. An additional feature of the connector is the use of optical windows for data transfer. The connector is designed for sensor interconnection, but is scalable to other applications.

We experimentally demonstrate the feasibility of the bandwidth tuning of a liquid-crystal based bandpass Lyot filter. This bandwidth tuning is achieved by applying a voltage to vary the birefringence of the liquid-crystal cells whose optical path difference takes predefined discrete values. We show that for a 2-stage liquid-crystal Lyot filter and at λ i = 1.543 μm, the measured 3-dB bandwidth varies from 17nm to 60 nm when the applied voltage increases from 0V to 5.24V. The shape of the transmission response remains unchanged during the bandwidth tuning process.

- by Rachid Hamdi and +2
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- Optical Communication, Optical fiber, Liquid Crystal, Band Pass Filter

In this thesis a Fully-Photonic DRoF (FP-DRoF) system is proposed for deploying of future super-broadband access networks. Digital Radio over Fibre (DRoF) is more independent of the fibre network impairments and the length of fibre than the ARoF link. In order for fully optical deployment of the signal conversion techniques in the FP-DRoF architecture, two key components an Analogue-to-Digital Converter (ADC) and a Digital-to-Analogue Converter (DAC)) for data conversion are designed and their performance are investigated whereas the physical functionality is evaluated. 2.7.3. Design Criteria and Conclusion 50 2.8. References 51 vii | P a g e Chapter 3: Digital Radio over Fibre Technology 55 3.1.

- by Seyed Reza Abdollahi
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- Optical Communication

Özetçe -Bu bildiride, Zemax 13 yazılımı aracılıgı ile görünür ışık haberleşmesi (visible light communication, VLC) kanalları karakterize edilecektir. Yaklaşımımızda, ölçülerini tanımlayacagımız iç mekân ortamı üçboyutlu olarak Zemax 'da oluşturulmakta ve LED tabanlı ışık kaynakları uygun noktalara yerleştirilmektedir. Sözkonusu yazılımım ışın izleme (ray tracing) araçları kullanılarak, alıcı tarafa dogrudan ve dolaylı yollardan (yansımalar) ulaşan sinyallerin gücü ve gecikme süreleri hesaplanmaktadır. Daha sonra bu bilgiler Matlab 'a aktarılarak uygun normalleştirmeler aracılıgı ile bu iç mekan propagasyon ortamına karşılık gelen kanal dürtü cevabı elde edilmektedir. Bu yöntem izlenerek, degişik ebatlardaki odalarda farklı alıcı/verici yerleşimleri varsayımları altında kanal dürtü cevapları elde edilmiş ve gecikme yayılımı, DC kazancı vb kanal parametreleri hesaplanmıştır.

- by Mohamed Abdallah
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- Optical Communication, Ray Tracing, Detectors, GNSS receivers

This paper analyses the possibility of exploiting a small spacecrafts constellation around Mars to ensure a complete and continuous coverage of the planet, for the purpose of supporting future human and robotic operations and taking advantage of optical transmission techniques. The study foresees such a communications mission to be implemented at least after 2020 and a high data-rate requirement is imposed for the return of huge scientific data from massive robotic exploration or to allow video transmissions from a possible human outpost.In addition, the set-up of a communication constellation around Mars would give the opportunity of exploiting this multi-platform infrastructure to perform network science, that would largely increase our knowledge of the planet.The paper covers all technical aspects of a feasibility study performed for the primary communications mission. Results are presented for the system trade-offs, including communication architecture, constellation configuration and transfer strategy, and the mission analysis optimization, performed through the application of a multi-objective genetic algorithm to two models of increasing difficulty for the low-thrust trajectory definition.The resulting communication architecture is quite complex and includes six 530 kg spacecrafts on two different orbital planes, plus one redundant unit per plane, that ensure complete coverage of the planet’s surface; communications between the satellites and Earth are achieved through optical links, that allow lower mass and power consumption with respect to traditional radio-frequency technology, while inter-satellite links and spacecrafts-to-Mars connections are ensured by radio transmissions. The resulting data-rates for Earth–Mars uplink and downlink, satellite-to-satellite and satellite-to-surface are respectively 13.7 Mbps, 10.2 Mbps, 4.8 Mbps and 4.3 Mbps, in worst-case.Two electric propulsion modules are foreseen, to be placed on a C3∼0 escape orbit with two Zenith Sea Launch rockets in March 2021 and carrying four satellites each. After the entrance in Mars sphere of influence, the single spacecrafts separate and spiral-down with Hall effect thrusters until they reach the final operational orbits in April 2025, at 17,030 km of altitude and 37 deg of inclination. The preliminary design includes 105 kg and 577 W of mass and power margin for each satellite, that can be allocated for scientific payloads.The main challenges of the proposed design are represented by the optical technology development and the connected strict pointing constraints satisfaction, as well as by the Martian constellation operations management.This mission study has therefore shown the possibility of deploying an effective communication infrastructure in Mars orbit employing a small amount of the resources needed for the human exploration programme, additionally providing the chance of performing important scientific research either from orbit or with a network of small rovers carried on-board and deployed on the surface.

The group velocity dispersion (GVD) imposes severe limit on information carrying capacity of optical communication systems. By choosing appropriate pulse shape highly stable light pulses known as solitons are generated when effect of GVD is balanced by self-phase modulation (SPM). The application of solitons in communication systems opens the way to ultrahigh-speed information superhighways. Transmission speed of order of Tbit/s can be achieved if optical amplifiers are combined with WDM in soliton based communication systems.

- by Akbar Ghaffarpour Rahbar
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- Optical Communication

Circuit and system of the Auto Gain Control (AGC) is a very important to be used in Visible Light Communication (VLC) transceiver receives the range of receivers and overcoming the near-far effect of the signal link. This paper discusses circuit design of AGC by using IC LM13700, a Trans-conductance amplifier. This IC is available in the electronic market and very low-cost. AGC is able to offer limited VLC mobility (movable) access at a certain distance and angle. We have performed an AGC circuit test that implemented in the optical link, the result shows (AVOL vs frequency) that AGC is effective to amplify the weak signal of VLC system (can be changed distance orientation up to 45 cm and angle of the receiver against The LED up to> 45 degrees.

- by Wendimu Fanta
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- Science, Optical Communication, Multidisciplinary, Magnetic Resonance

Abstact-Light Fidelity (Li-Fi) refers to the 5G Visible Light Communication systems using light-emitting diodes as a medium for high-speed communication in a similar manner as Wi-Fi. [5] As now a days where internet has become a major demand, people are in a search for Wi-Fi hotspots for their activities. Li-Fi is a better alternative to Wi-Fi in wireless communication as it is [1] bidirectional, high speed and fully networked wireless communications similar to Wi-Fi. It is a subset of visible light communication(VLC) and can be a complement to RF communication , or a replacement in contexts of data broadcasting. This paper proposes a survey on Li-Fi Technology. Li-Fi has more capacity in terms of bandwidth in visible region therefore it does not interfere in other communications which uses radio frequency range, without taking its frequency bands. It has thousand times greater speed than Wi-Fi.Such technology has brought not only greener but safer and cheaper future of communication.

- by Sachin Verma
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- Optical Fiber Communications, Wireless Communications, Optical Communication, Wi-Fi