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LASER Communication .


1.INTRODUCTION


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 into inter
satellite page link applications.
Information transfer is driving the requirements to higher data rates, laser cross -link
technology explosions, global development activity, increased hardware, and design
maturity. Most important in space laser communications has been the development of a
reliable, high power, single mode laser diode as a directly modulable laser source. This
technology advance offers the space laser communication system designer the flexibility
to design very lightweight, high bandwidth, low-cost communication payloads for
satellites whose launch costs are a very strong function of launch weigh. This feature
substantially reduces blockage of fields of view of most desirable areas on satellites. The
smaller antennas with diameter typically less than 30 centimeters create less momentum
disturbance to any sensitive satellite sensors. Fewer on board consumables are required
over the long lifetime because there are fewer disturbances to the satellite compared with
heavier and larger RF systems. The narrow beam divergence affords interference free and
secure operation.