Laser communications offer a viable alternative to RF communications for inter-satellite links and other applications where high-performance links are a necessity. The high data rate, small antenna size, narrow beam divergence, and narrow field of view are characteristics of laser communications that offer a number of potential advantages for system design.
Lasers have been considered for space communications since their realization in 1960. Specific advancements were needed in component performance and system engineering particularly for space-qualified hardware. Advances in system architecture, data formatting, and component technology over the past three decades have made laser communications in space not only viable but also an attractive approach to inter-satellite link applications.
Lasers have been considered for space communications since their realization in 1960. Specific advancements were needed in component performance and system engineering particularly for space-qualified hardware. Advances in system architecture, data formatting, and component technology over the past three decades have made laser communications in space not only viable but also an attractive approach to inter-satellite link applications.
Laser communication systems offer many advantages over radio frequency (RF) systems. Most of the differences between laser communication and RF arise from the very large difference in the wavelengths. RF wavelengths are thousands of times longer than those at optical frequencies are. This high ratio of wavelengths leads to some interesting differences in the two systems. First, the beam-width attainable with the laser communication system is narrower than that of the RF system by the same ratio at the same antenna diameters (the telescope of the laser communication system is frequently referred to as an antenna). For a given transmitter power level, the laser beam is brighter at the receiver by the square of this ratio due to the very narrow beam that exits the transmitting telescope. Taking advantage of this brighter beam or higher gain permits the laser communication designer to come up with a system that has a much smaller antenna than the RF system and further, needs to transmit much less power than the RF system for the same receiver power. However, since it is much harder to point, acquisition of the other satellite terminal is more difficult. Some advantages of laser communications over RF are smaller antenna size, lower weight, lower power, and minimal integration impact on the satellite. Laser communication is capable of much higher data rates than RF.
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