Effects of intermodulation distortion on the performance of a hybrid radio/fiber system employing a self-pulsating laser diode transmitter

A self-pulsating laser is used to generate a multicarrier (five radio frequency (RF) channels) microwave optical signal for use in a hybrid radio/fiber system. The self-pulsation is achieved by external light injection into the laser diode. By varying the RF channel spacing, we have been able to estimate the degradation in system performance due to intermodulation distortion (caused by the nonlinear dynamic response of the laser). The power penalty on the central RF channel is found to be 3.2 dB for operation at the RF band around the laser self-pulsation frequency of 18.5 GHz. We have also characterized the performance of the multicarrier hybrid radio/fiber system in the frequency band corresponding to the inherent relaxation frequency of the laser

g-Golomb Rulers

A set of positive integers A is called a g-Golomb ruler if the difference between two distinct elements of A is repeated at most g times. This definition is a generalization of the Golomb ruler (g = 1). In this paper we construct g-Golomb ruler from Golomb ruler and we prove two theorems about extremal functions associated with this sets. To cite this article: Y. Caicedo, C.A. Martos, C.A. Trujillo, g-Golomb, Rev. Integr. Temas Mat. 33 (2015), No. 2, 161–172.Se dice que un conjunto de enteros positivos A satisface la regla g-Golomb si la diferencia entre dos elementos distintos de A se repite a lo más g veces. Esta definición es una generalización de las reglas de Golomb (g = 1). En este artículo construimos reglas g-Golomb a partir de reglas Golomb y demostramos dos teoremas sobre las funciones extremas asociadas con estos conjuntos. Para citar este artículo: Y. Caicedo, C.A. Martos, C.A. Trujillo, g-Golomb, Rev. Integr. Temas Mat. 33 (2015), No. 2, 161–172. &nbsp

Application of advanced on-board processing concepts to future satellite communications systems

An initial definition of on-board processing requirements for an advanced satellite communications system to service domestic markets in the 1990's is presented. An exemplar system architecture with both RF on-board switching and demodulation/remodulation baseband processing was used to identify important issues related to system implementation, cost, and technology development

Study of repeater technology for advanced multifunctional communications satellites

Investigations are presented concerning design concepts and implementation approaches for the satellite communication repeater subsystems of advanced multifunctional satellites. In such systems the important concepts are the use of multiple antenna beams, repeater switching (routing), and efficient spectrum utilization through frequency reuse. An information base on these techniques was developed and tradeoff analyses were made of repeater design concepts, with the work design taken in a broad sense to include modulation beam coverage patterns. There were five major areas of study: requirements analysis and processing; study of interbeam interference in multibeam systems; characterization of multiple-beam switching repeaters; estimation of repeater weight and power for a number of alternatives; and tradeoff analyses based on these weight and power data

Customer premise service study for 30/20 GHz satellite system

Satellite systems in which the space segment operates in the 30/20 GHz frequency band are defined and compared as to their potential for providing various types of communications services to customer premises and the economic and technical feasibility of doing so. Technical tasks performed include: market postulation, definition of the ground segment, definition of the space segment, definition of the integrated satellite system, service costs for satellite systems, sensitivity analysis, and critical technology. Based on an analysis of market data, a sufficiently large market for services is projected so as to make the system economically viable. A large market, and hence a high capacity satellite system, is found to be necessary to minimize service costs, i.e., economy of scale is found to hold. The wide bandwidth expected to be available in the 30/20 GHz band, along with frequency reuse which further increases the effective system bandwidth, makes possible the high capacity system. Extensive ground networking is required in most systems to both connect users into the system and to interconnect Earth stations to provide spatial diversity. Earth station spatial diversity is found to be a cost effective means of compensating the large fading encountered in the 30/20 GHz operating band

Proceedings of the Second International Mobile Satellite Conference (IMSC 1990)

Presented here are the proceedings of the Second International Mobile Satellite Conference (IMSC), held June 17-20, 1990 in Ottawa, Canada. Topics covered include future mobile satellite communications concepts, aeronautical applications, modulation and coding, propagation and experimental systems, mobile terminal equipment, network architecture and control, regulatory and policy considerations, vehicle antennas, and speech compression

Cold atoms in a ring cavity

An ensemble of atoms coupled to a high finesse optical cavity is an ideal test bed for the study of the cooperative behaviour of atom-photon systems. Dicke showed that an ensemble of excited atoms coupled to a light field interacts with the light in a collective and coherent fashion leading to the emission of highly directional spontaneous emission whose intensity scales with the square of the number of atoms, a phenomenon known as superradiance. This thesis describes the build of an experiment to study cooperative atom-photon interactions in a ring cavity. Particular focus is given to the cavities used in the experiment. Firstly a transfer cavity used for transferring stability to off-resonant lasers in the experiment, this was developed with the capability of exploiting Gouy phase degeneracies to produce tightly spaced frequency discriminants to be used as lock points. Secondly the ring cavity for the experiment which is atypical in its design allowing for bidirectional probing of the cavity mode and dynamic manipulation of the intra-cavity optical lattice. An intra-cavity MOT was produced and collective strong coupling was observed in the cavity with an Neff=6400 atoms coupled to the cavity mode

All-optical interferometric switches for data regeneration in fiber optic networks

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.Includes bibliographical references.In the thirty years since the installation of the first fiber optic data link, data rates in installed fiber links have risen from a few Mb/s to tens of Gb/s. In the laboratory, data rates in a single optical fiber have already reached tens of Tb/s. These data rates greatly exceed electronic processing rates, so researchers have turned to all-optical signal processing to achieve many basic network tasks, like wavelength conversion, packet switching, and data regeneration. As data rates increase, the impairments caused by propagation through the glass of optical fiber become worse. Chromatic dispersion causes the temporal broadening of optical bits during propagation, leading to interference between neighboring bits. Nonlinear effects, like the nonlinear index of refraction and four-wave mixing, can cause interference between neighboring wavelength channels. The interaction of dispersion and nonlinearities can lead to variations in the timing of bits and the appearance of optical energy where there had been none. All these effects make 1-bits and 0-bits difficult to distinguish. Today, these distortions are overcome by electronic regenerators. Optical data streams are converted to electrical signals, processed electronically, converted back to an optical signal, and returned to the optical network. In this way, regenerators prevent the accumulation of noise and prevent noise from contributing to the production of more noise. The electronic solution is costly because of the extra hardware required for optical to electrical to optical conversions and performs poorly because of the losses incurred by those conversions. In this thesis, we investigate two regenerators that restore the data quality of ON/OFF keyed data without a conversion of the data to the electrical domain.(cont..) Both regenerators are based on all-optical switches that take two inputs: the data pulses from the network, and a locally generated clock-pulse train. The all-optical switches then modulate the data pattern onto the clock-pulse train, which becomes the new data stream. The first switch we consider, the WMFUNI, uses the nonlinear properties of fiber to produce the switching action. Using the WMFUNI regenerator, we demonstrate the propagation of 10 Gb/s data over 20,000 km of commercial optical fiber. We also demonstrate the WMFUNI's ability to operate on 40-Gb/s data. Unfortunately, fiber has only a weak nonlinearity, so the WMFUNI is large (~40 cmx40 cm). The second switch uses the much stronger nonlinearity of a semiconductor optical amplifier (SOA). SOA-based switches can be integrated onto chip-scale optics. The switch we test, the SOA-MZI, fits on a ~0.5 cmxl cm chip. Using the SOA-MZI regenerator, we demonstrate the propagation of 10 Gb/s data over 10,000 km of commercial optical fiber. We also show in simulation that the SOA-MZI's operation may be extended to 40 Gb/s.by Shelby Jay Savage.Ph.D