DAS has developed optical links for ground segment beyond 40GHz, with high performance, while the qualified optical links for space segment applications go up to few GHz.
There is a general trend towards large satellites with broadband repeaters (targeting 1 Tbit/s) and multiple beam active antennas. In this kind of scenarios the RF and reference signal distribution become critical due to the mass, complexity and EMC/EMI issues. In those cases photonic links bring relevant benefits compared to traditional RF distribution technology.
Microwave optical links are a promising frequency distribution system which improves traditional cable limitations such as:
- Mass and size saving for medium/high reference signal distribution requirements
- Cable management flexibility: For those applications where a high number of cables shall be routed from the satellite payload there will be a considerable cable bundle to be managed.
- Lower optical fiber transmission losses
- Better phase stability over temperature and when bent in comparison with coaxial cable
- Low electromagnetic emissions
Optical Link performance is specially challenging because added phase noise and amplitude stability is required over a very wide temperature range (-40ºC to +85ºC). Mass, dimensions and power consumption are also key parameters.