AOLTB - Optical RF Distribution Flight Demonstrator

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The main objective of the project is to design and fabricate an EQM-level payload in-orbit demonstrator of Photonic Technology for On-board Reference and LO distribution by optical links. Full EQM-level functional and environmental qualification has been performed Two optical links operating at 10 MHz and 10 GHz, including 10 meters fibre and a power splitter, have been integrated in the HISPASAT Amazonas 5 satellite, successfully launched and tested in orbit in 2018.


The main key issues of the activity are the use of non-qualified components and a new technology to perform the LO distribution as well as a first in-orbit demonstration of this technology.


New concepts of satellite payloads require a high number of feeds, or even phased array systems, for multi-beam applications with an associated high quantity of converters. For these applications the frequency distribution unit networks could become a critical issue. A high number of feeds and converters make analogue optical links a promising signal distribution candidate compared to traditional RF systems in terms of properties 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 have to 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

The payload for the IoD, called AOLTB, accommodates two complete optical RF links.

  • Analog optical link for reference signal distribution and transportation up to 2,5 GHz, but designed specifically for the demonstrator at 10MHz.
  • Analog optical links for reference signal distribution and transportation up to 30 GHz, but designed specifically for the demonstrator at 10GHz.

The AOLTB provides information regarding power and phase deviation of the optical RF links, levels of power consumption and radiation performances during the mission.


System Architecture

The IOD consist on a piggyback demonstrator of Photonic Technology for On-board Reference, LO and RF distribution by using the low and high frequency links described above. The IOD will have the following characteristics:

  • In-Orbit test of the optical links, including a fiber of 10 meters and a power splitter.
  • Phase drift of 10 MHz reference by measuring the Allan deviation introduced by the optical link
  • Power stability of both optical links (low and high frequency) tested at 10 MHz and 10 GHz.
  • Health monitoring, measuring multiple parameters of the links (current(s) consumption, temperature, bias references…) and its environment.

In order to evaluate the behaviour of the optical links in real space environment, the system encompasses the following additional parts:

  • Power Supply Unit (PSU): The PSU extracts the voltages from the main power bus and generates secondary voltages needed in the different subsystems of the equipment.
  • Power Distribution Unit (PDU) is the unit responsible for current sensing and limiting
  • Interface Control Unit (ICU) is in charge of the communication between test Bed and satellite processor. by using the 1553 protocol
  • Optical Control Units (OCU) control the optical links and monitors the status


The Project has been successfully concluded, and the piggyback demonstrator is operating properly in HISPASAT AMAZONAS 5, flying since 11/09/2017. The experience gained and flight heritage is being leveraged in current payload developments using photonics technology.

Current status

After completing the components evaluation campaign, the EQM has been developed and functionally and environmentally tested. The AOLTB was integrated in the payload completing the integration tests and was successfully launched as piggyback payload of HISPASAT AMAZONAS 5. The 1 year in orbit data has been analysed and the AOLTB is continued to be monitored in orbit.

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