Recent years the application of free-space laser communication system is become more important.A
smart antenna system combines multiple antenna elements with a signalprocessing capability to
optimize its radiation and/or reception pattern automatically in response to the signal environment. In
this paper, we mainly study the Optical adaptive Antenna Array in the free-space laser communication.
Considering that shot noise is Poisson distribution and the envelope of background optical noise is Rayleigh distribution, the Gaussian Approximation method is firstly used to evaluate the performance of Satellites Laser Communications precisely. The Moment Generating Function expression of considering shot noise, background optical noise and hot noise is firstly derived. The system performance of On Off Key modulation of traditional method is compared with GA method in direct detection system. Results indicate that the performance of Satellites Laser Communications by GA is different from traditional method.
This paper proposes a method of using fiber Bragg grating as optical filter in laser inter-satellites
communication system. Effects of Doppler shift to SNR and band requirement of optical filter are researched in
this paper. Given the wavelength is 1550nm, strong fiber and Blackman windows function are used in designing
fiber grating to satisfy the need of the inter-satellites communication system. And the simulation and experiment
results show that fiber Bragg grating can be used as optical filter in optical signal communication system of
Antenna, which whether transmits or receives correct signal or not is our main care and our direction, is an
important part in any wireless communication systems. Because of the characteristics of laser different from
radio, the antenna system of point-to-point laser communication system must be designed strictly. In this paper,
we mainly study the optical system in the inter-satellites laser communication. We compare with three kinds of
optical antennas: refractor and reflector and Catadioptrics of the passive optical system; we also analyze the
effect of bandwidth to the WDM communication systems; we use the correlative software, simulate the curves
of the performance of the optical antennas. These analyses will be the base of the system of WDM laser
Recent years have seen an explosive increase in the application of inter-satellites laser communication system.
Considerations make phased arrays an attractive target for optical communication applications. This paper proposes a novel
telescope array for inter-satellites laser communication and investigates phased telescope arrays to be employed in receive
terminals of free-space laser inter-satellites communication links. Potential advantages over single monolithic telescopes
consist in non-mechanical adaptive fine pointing of the mainlobe and a reduction of terminal volume, mass and cost.
First, the basic function, the interfaces, and the performance parameters of one telescope are given. Next, the structure of a
receive telescope array are described, and then the performance parameters of this telescope array are discussed. The
different performances including antenna gain and pattern of optical antenna and telescope array in inter-satellites laser
communication system are given in this part. A quantitative assessment reveals that arrays using coaxial beam superposition
are best suited for optical data communications. Based on this finding, the main characteristics of superimposing telescope
arrays are calculated. And calculations prove that, in practical applications, telescope array has better performance than one
telescope used in laser inter-satellites communication, and even more, the influence of incoherent background radiation is
negligible. The analyses results show that smart antenna is better than optical antenna in this communication system.
In many important aspects of phased array design, we will consider 1) Frequency Synchronization and 2) Beam steering as
being of primary importance to the present analysis. Frequency synchronization is necessary for proper beam spatial
coherence, while beam steering is critical to how this cohered beam is pointed in a desired direction. We will address system
performance and implementation aspects of both issues in fiber optic control. Three basic architectures for beam steering
control via optics have been reported and proposed.
This paper proposes a method of wavelet analysis for de-noising at receiver system in WDM laser inter-satellites communication. Background noises such as galactic noise, sunlight and etc make the received power reduce. The noisy signal is decomposed using wavelets and wavelet packets; then is transformed into wavelet coefficients and the lower order coefficients are removed by applying a soft threshold. De-noised signal is obtained by reconstructing with the remaining coefficients. In this paper, we evaluate different wavelet analysis for de-noising at receiver system in inter-satellites laser communication. Simulation results indicate that if the wavelet de-noising method is used with different wavelet analyzing functions, it will improves the signal to noise ratio (SNR) about 2 dB when the signal frequency is 1.5 GHz.
Turbo codes are used to guarantee the performance in the power-limited radio-optical communication system, but the traditional parallel structure is difficult to overcome the 'error floor'. In this paper, a hybrid structure is studied, it is the combination of the parallel structure and the serial structure. Turbo codes with the
hybrid structure can improve the system performance validly, but the complication is the cost. Through the theoretic analyses and computer simulation, the hybrid structure is proved to be valid.
In the modern world of telecommunications, the concept of wireless global coverage is of the utmost importance. However, real global coverage can only be achieved by satellite systems. Satellites communication is the most important mean of the communication network. The traditional satellites communication and inter-satellites links are built by microwave. In recent years, laser links for inter-satellites communication are becoming more and more important. Laser communication systems operate in a frequency range above the regulated spectrum. Laser provides many advantages for using in point-to-point ISLs (inter-satellites links) such as for links between satellites and spacecraft in deep space. Such advantages include: high speed; high bandwidth; small antenna size; narrow field of view; and narrow antenna beam. These advantages combined with the advantages in fiber optic components (optical preamplifiers, multiplexers, detectors, etc) have made laser attractive for laser links. Now we can bring WDM (wavelength-division multiplexing) to emerging broadband satellite communication systems. By using the common antenna system and ATP (Aiming, Tracking and Pointing) system, the satellites will get more capacity. In the inter-satellites laser communication, the important performances of the systems such as BER and BL both have direct relation with the optical systems. The optical systems have the function of ATP. The optical antenna is the most important component of the optical system. So the optical antenna is an important key technology to the inter-satellites laser communication. In this paper, we mainly study the optical system in the inter-satellites laser communication. we compare with three kinds of optical antennas: refractor and reflector and Catadioptrics of the passive optical system; we also analyze the effect of bandwidth to the WDM communication systems; we use the correlative software, simulate the curves of the performance of the optical antennas. These analyses will be the base of the system of WDM laser inter-satellites communication.
Signal regeneration is one of the critical functions for the future long-haul transmission distances in all-optical networks. In this paper, the different realization approaches of all optical regenerators are also presented. The theory of FWM is discussed and the application of FWM in Dispersion-Shifted Fiber based optical 2R regenerator is introduced. A realization approach of Optical 3R Regeneration based on Four Wave Mixing will be proposed.
Optical MEMS (Micro-Electro-Mechanical Systems) is the integration of mechanical elements, sensors, actuators, and electronics on a common silicon substrate through microfabrication technology. And Optical MEMS has created a new fabrication paradigm for optical devices and systems. Using tools developed for the integrated-circuits industry, Optical MEMS brings unprecedented levels of miniaturization and integration to optical communication systems. Today, the capacity of optical communication networks is limited by the switches that are electronic in their core. Optical MEMS is transforming the telecommunications infrastructure by providing all-optical switches that enable high-capacity networks. Optical MEMS devices are driving the trend toward all-optical telecommunication networks. With the ability to directly manipulate an optical signal, MEMS have several applications that eliminate unnecessary optical-electrical-optical (O-E-O) conversions. In optical communication, electrical components such as inductors and tunable capacitors can be improved significantly compared to their integrated counterparts if they are made using optical MEMS technology. With the integration of such components, the performance of communication circuits will improve, while the total circuit area, power consumption and cost will be reduced. In addition, the mechanical switch, as developed by several research groups, is a key component with huge potential in various microwave circuits. Optical MEMS technology is currently used in low- or medium-volume applications. There are also some of the obstacles preventing its wider adoption. Such as a mechanism giving smaller organizations responsive and affordable access to optical MEMS fabrication. And the packaging of optical MEMS devices and systems needs to improve considerably from its current primitive state. Currently the designer of an optical MEMS device requires a high level of fabrication knowledge in order to create a successful design. This paper presents the technology of optical MEMS and the application of this technology in the optical communication.