Optical Communication System

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.

A major impairment in Free Space Optical (FSO) links is the turbulence induced fading which severely degrades the link performance. To mitigate turbulence induced fading and, therefore, to improve the error rate performance, error control coding schemes can be ...

IEEE JOURNAL ON SELECTED AREAS IN COMMUNICATIONS, VOL. 11, NO. 3, APRIL 1993 ... John R. Barry, Joseph M. Kahn, William J. Krause, Edward A. Lee, and David G. Messerschmitt ... Abstract-We present a recursive method for evaluating the impulse response of an ...

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

Active photonic antenna (APhA) designed for 2.4 GHz communication in downlink side is proposed. The APhA consists of photodiode, RF amplifier and band pass filter (BPF) in small package, integrated with RF antenna. The APhA design is simulated using optical communication simulation software at varied fiber length and free space loss (FSL). Performance improvement over passive photonic antenna (PPhA) in term of signal power, SNR, constellation diagram, and BER is achieved, especially at PPhA service boundary.

Photonic devices with low insertion loss are important in dense wavelength division multiplexing (DWDM) systems. Currently most of these devices, such as variable optical attenuators (VOA), switches, filters, and dispersion compensators, etc., involve bulk (or micro-optic) ...

Weight In Motion (WIM) adalah pengukuran berat dari suatu objek yang bergerak, teknologi Weight In Motion (WIM) yang memungkinkan berat suatu benda dapat diketahui secara cepat. Salah satu komponen penting dalam sistem WIM adalah sensor. Beberapa syarat yang harus dipenuhi pada suatu sensor WIM antara lain kecepatan respon dan akurasi. Sensor serat optik memiliki beberapa keuntungan diantaranya adalah tahan terhadap interferensi gelombang elektromagnetik, memiliki sensitivitas tinggi, dan tahan terhadap korosi serta tahan terhadap suhu tinggi. Skema diagram blok sistem ini adalah sebagai berikut. Sensor serat optik berdasarkan prinsip mikrobending terdiri dari serat optik dan bending modulator yang menyebabkan terjadinya rugi-rugi daya dan intensitas cahaya. Mikrobending pada serat optic mengakibatkan sebagian cahaya dalam serat optik akan keluar dan menyebabkan intensitasnya menurun. Penurunan intensitas cahaya ini dapat dideteksi dengan photodiode sehingga gaya tekan yang dialami oleh serat optik dapat dihitung dengan melihat penurunan respon tegangan keluaran photodiode. Gambar 3. Skematik Mikrobending Spesifikasi laser diode yang digunakan yaitu panjang gelombang 1310 nm, daya 2.5 mW. Sedangkan photodetector menggunakan InGaAs Photodiode. Pemilihan laser dengan panjang gelombang 1310 nm karena photodiode InGaAs memiliki sensitifitas dan responsivitas yaitu perbandingan antara sinyal keluaran atau respons instrumen terhadap perubahan masukan atau variabel yang diukur, paling tinggi pada rentang panjang gelombang 1300 – 1400 nm, selain itu laser juga merupakan sumber cahaya monokromaris sehingga panjang gelombang yang dipancarkan adalah tetap/satu panjang gelombang saja sehingga tidaj akan mengganggu sistem pengukuran karena perubahan panjang gelombang akan mengakibatka penurunan sensitifitas sensor.

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

Multiwavelength all-optical regeneration has the potential to substantially increase both the capacity and scalability of future optical networks. In this paper, we review recent promising developments in this area. First, we recall the basic principles of multichannel regeneration of high bit rate signals in optical communication systems before discussing the current technological approaches. We then describe in detail two fiber-based multichannel 2R regeneration techniques for return-to-zero-on-off keying based on 1) dispersion managed systems and 2) direction and polarization multiplexing. We present results illustrating the levels of performance so far achieved and discuss various practical issues and prospects for further performance enhancement.

Low-power, high-speed, accurate computation of centroid from a pre-defined window in the image plane is important for a number of space-based and commercial applications. These include object tracking in robotic systems (l), autonomous navigation, image compression (2), and document copyright protection (3), as well as space guidance and navigation systems (4), and deep-space optical communication systems that require accurate and

We present a methodology for the characterization of the main parameters of VCSELs for its use in direct modulation. Power response, chirp parameter alpha, linewidth, side-mode suppression ratio, relaxation oscillations peak frequency, damping rate and relative intensity noise (RIN) are obtained from measurements of the emitted optical spectrum in continuous wave (CW) operation by means of a high resolution (10 MHz) and high dynamic range (80 dB) optical spectrum analyzer. Many of the main static and dynamic parameters of VCSEL lasers can be obtained from the analysis of the optical spectrum when emitting in CW operation, but traditional spectrum analysis techniques do not achieve enough high resolution and dynamic range and high signal to noise ratio to perform it. Recent developments in high resolution optical spectrum analyzer (OSA) technology allow a deeper characterization of the main properties of VCSELs for its applications in optical communication systems by analyzing their CW emitted spectrum.

Planar Photonic Circuits can perform many useful functions in optical communications systems, such as wavelength division multilplexing (WDM), optical channel add/drop, fibre/waveguide coupling, and amplifier gain equalization. They perform these functions by the interaction of the device structure with the light inside them. There are very effective and proven numerical methods available for modelling this interaction, such as the Beam Propagation Method (BPM), the Finite Difference Time Domain (FDTD) method, and coupled mode theory (CMT). However, these methods work on a microscopic level (typically the smallest distance is about 0.1 microns), but photonic circuits, on the other hand, can occupy an entire wafer (scale: 10 cm). The analysis must span 5 or more orders of magnitude in the change in scale. The successful analysis needs to combine the basic microscopic techniques with an approach at a more abstract, or system, level. It is interesting that software designed for the analysis of optical communication systems can be applied to planar photonic circuits. This paper shows an example of a practical photonic circuit, a lattice filter, that cannot be analysed by BPM alone. It will be demonstrated that when used with a system level analysis, the whole device can be simulated.