Optical Intersatellite Communication Links Research Articles

Acquisition performance analysis for intersatellite optical communications with vibration influence**Project supported by the Program of Excellent Team in Harbin Institute of Technology, China.

A stable and accurate pointing, acquisition system is an important part of initially building intersatellite optical communication links. Satellite platform vibration can cause the system instability and reduce the system precision in building and maintenance of a satellite optical communication system. In this paper, vibration influence is consciously discussed by acquisition time for intersatellite optical communications. Analytical expression of acquisition possibility is derived, taking the scan parameters and platform vibration into account, and vibration influence on the multi-scan acquisition time is also presented. The theoretical result calculated by the proposed analytical expression is approximate to the result by the Monte Carlo simulation.

Vibration Influence on Hit Probability During Beaconless Spatial Acquisition

Starting November 2007 and continuing through the present, Tesat-Spacecom has been conducting successfully optical intersatellite communication links utilizing laser communication payloads built by Tesat-Spacecom under DLR funding. A total of four communication payloads are in space at the time of writing. Also optical space-to-ground communication links have been successfully conducted using a compatible ground terminal built by Tesat-Spacecom and the ESA Optical Ground Station on Tenerife. All terminals are using a beaconless spatial acquisition algorithm which was developed by Tesat-Spacecom for intersatellite communication links. We present an analytical investigation on the influence of vibrations deferring the laser beam search pattern on the receiving probability of the counter terminal. A Gaussian distribution of the vibrations is assumed. Results are presented here and compared to computer simulations to verify the analytical results. The influence of link margin and slave terminal position in the scan field on hit probability is addressed.

Source-induced fading of a multiple-input–single-output optical satellite communication system described by beta functions

In this study, the authors investigate the outage behaviour of optical inter-satellite communication links. The main issues addressed in the present work are: (i) source-induced fading, (ii) transmitter diversity and (iii) maximal ratio combining (MRC). They show that the fading follows the ‘reciprocal Pareto distribution’. Then they derive a set of closed-form outage probabilities in terms of the ‘beta function’ and the ‘incomplete beta function’. Numerical examples reveal that there is a threshold that determines the superiority of multiple-input–single-output (MISO) MRC. Influence of wavelengths is also observed.

Hybrid network based on optical intersatellite communication links and WDM technology

AbstractThe use of optical wavelengths for intersatellite link can lead the whole system at high data rates performing, low interference, low power requirement and small antenna size. Systems based on Wavelength Division Multiplexing (WDM) technology preserve data signal from interchannel interference. Proposed system is composed of one fixed node, a HAP, High Altitude Platform, in a quasi‐stationary position at an altitude of 30 km from the Earth surface, and a mobile node on a LEO orbit which communicates by an optical link with HAP and other LEO microsatellites. The choice of microsatellites number guarantees a good area target coverage and a continuous data transfer from slave nodes to master, with the consequent increase in communication capacity. The HAP motion makes it possible to configure an ad‐hoc network for the monitoring of natural and man‐made disasters, or every emergency application on rural environment. The main constraint affecting the system performance is concerned with signal degradation, due to antenna misalignment as well as the Doppler effect suffered by the signal because of relative motion between satellite. The subsystem configuration is based on semiconductor laser, transmitting at ITU grid frequencies, and an EDFA preamplifier at receiver end. Copyright © 2008 John Wiley & Sons, Ltd.

Homodyne BPSK-based optical intersatellite communication links to be tested

Homodyne BPSK-based optical intersatellite communication links to be tested

High-power Nd-doped fiber amplifier for coherent intersatellite links

Intersatellite optical communication links require laser beams of at least 1 W of power modulated at gigahertz frequencies. They can be delivered by a master oscillator power amplifier system which consists of a stable single-frequency Nd:YAG laser, a high-speed phase modulator, and an optical amplifier. To allow coherent detection, the polarization state must be stable and controllable at the amplifier output and the phase noise must be kept low. We report here the design and the experimental results of a diode laser-pumped double clad Nd-doped fiber amplifier with polarization control, 30-dB gain, and about 1.3 W of output power.

Fading statistics for intersatellite optical communication

The narrow beam widths associated with intersatellite optical communication links make such links susceptible to signal fading because of pointing jitter. Such fading can be aggravated by stationary offsets in pointing. We calculated the fade rates for the case of two spaceborne telescopes having Gaussian beam profiles, a pointing offset, and pointing jitter that can be described by Gaussian statistics. An integral solution is derived for the general case of a nonsymmetrical system, with and without pointing bias, and closed-form solutions are presented for the case of a symmetrical system (identical platforms and optics). These results show that, for a system with 3-dB margin, the rms pointing jitter must be held to less than 7% of the full beam width to keep the fade rate below once per year.

Multigigabit Transmission Characteristics in the Optical Transmitter and Receiver for Optical Intersatellite Links at 1.06.MU.m.

We examine 2.5Gbit/s and 5Gbit/s transmission characteristics of Nd-doped fiber amplifier (NDFA) at 1.064m as a booster amplifier and a pre-amplifier in the intersatellite optical communication links. It is found that the combination of the booster amplifier (100mW output) and the pre-amplifier (3dB noise figure) employing the NDFAs can establish giga-bit optical links between low-earth-orbit satellites with several thousands kilo-meters. Features of the NDFA such as high power conversion efficiency (52%) and low noise and high gain amplification characteristics, spatial-distortion-free beam output, polarization independence and vibration-free will allow it to replace the solid-state laser amplifier in free-space applications.

Impact of random pointing and tracking errors on the design of coherent and incoherent optical intersatellite communication links

Given the RMS transmitter pointing error and the desired probability of bit error (PBE), it can be shown that an optimal transmitter antenna gain exists which minimizes the required transmitter power. Given the RMS local oscillator tracking error, an optimum receiver antenna gain can be found which optimizes the receiver performance. The impact of pointing and tracking errors on the design of direct-detection pulse-position modulation (PPM) and heterodyne noncoherent frequency-shift keying (NCFSK) systems is then analyzed in terms of constraints on the antenna size and the power penalty incurred. It is shown that in the limit of large spatial tracking errors, the advantage in receiver sensitivity for the heterodyne system is quickly offset by the smaller antenna gain and the higher power penalty due to tracking errors. In contrast, for systems with small spatial tracking errors, the heterodyne system is superior because of the higher receiver sensitivity.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>