Laser communication in space
Photonics systems, sub-systems and components are found in an increasing number of applications of many high technology industry segments.
This remark applies particularly to space-embarked systems, which rely on the versatility and reliability of photonic systems to realize many of the critical functions needed to insure their safe and durable operation.
iXblue has a continuous presence in space across its Astrix products range of 3-axis fiber-optic gyroscopes (FOG). A privileged partnership between iXblue and Airbus Defence & Space has allowed the emergence of a new class of fiber-optic gyroscope instruments. The Astrix Series already equips more than 25 satellites on all types of orbits (LEO, MEO, GEO, Lagrangian point…) while counting more than 2 million hours in operation without incident. iXblue has also developed a FOG-based Inertial Navigation System dedicated to launchers, used in Ariane 5 since 2020 and in Ariane 6.
Our experience with iXblue FOGs being deployed in space opened the way to supply space grade components, such as passive and doped fibers, as well as the electro optical phase and amplitude modulators.
The electro-optic Lithium Niobate (LiNbO3) have long standing proven record of use in many applications (for instance long-haul and radio over fiber communications) as well as Distributed Temperature Sensors (DTS) where the modulators operate in harsh environmental conditions), and have been comprehensively and successfully qualified (e.g. Telcordia). The LiNbO3 modulators offer indeed a unique combination of performance that makes them prime candidates, not only to satisfy the optical system specifications, but also to meet the tough requirements of space operation. Today, many embarked space photonic systems use light modulators as a key component to achieve intensity or phase modulation of various light sources at different operating wavelengths.
The telecommunication and inter-satellites telecommunications are ones of these space applications where iXblue Photonics is today well involved.
Laser Communication Terminal
The spatial activities of telecommunications for Earth observation programs high-definition images and videos currently in service necessitate the improvement of the retransmission back to Earth for high speed communications, as the classic solutions are no longer able to handle the increases in data volumes.
The solution to resolve this situation is based on the deployment of optic transmissions in space.
Optics and the modulation of light are therefore employed to assist with radiofrequency links, used heretofore in satellite transmissions.
Free-space optical communication has been implemented between satellites since the 90's using directly modulated high power laser diodes at 820 nm to 850 nm. The emergence of fiber lasers in the near infrared and the availability of LiNbO3 modulators in this band have made possible space optical links (LEO to GEO to Ground Stations) using more efficient modulation formats and offering improved data rates and BER.
The laser terminal is designed to be installed aboard a geostationary satellite (GEO). The point of this GEO relay is to constantly transmit the data collected from the emitter, located on low-orbiting satellites (LEO – Low Earth Orbit). Orbiting at a low altitude, these LEO satellites must wait to pass over a station located on the ground to transfer the data collected.
In some cases, they are required to wait several hours before being able to transfer data, which can be detrimental - hence the idea to install data relays in geostationary orbit. Once the LEO satellite is visible to the relay satellite, a high-speed optic communication is established for the transmission of data packets.
Then, at nearly 36 000 km from Earth, the relay satellites, permanently positioned above the relay antennas of an optical ground station (OGS), can proceed with the transfer of the collected data, aided by radiofrequency waves.
Fig. 1: iXblue products in space and inter-satellite communication
After 10 years of experience, iXblue Photonics was involved in more than 20 projects, for which we supply more than 200 modulators for different flying users worldwide, either for big players or space agencies, and for LEO or GEO satellites, or the ISS as well. We supply 850 nm, 1064 nm and 1550 nm amplitude modulator and phase modulator as Breadboard, Engineering, Qualification and Flight models (please refer to the Application Note Space grade modulators definitions).
Fig. 2: Example of Flight Model Modulator
The main modulators specifications and environmental operating conditions are given here below in the table. These values refer to the FM operating conditions, knowing that more stringent and higher values on the tests conditions are applied to the Qualified Models during the qualification phases.
|Operating wavelength 800 nm 1060nm 1550 nm|
|Modulator types Phase, Amplitude, IQ|
|Modulator bandwidth Low frequencies up to 40 GHz|
|Insertion loss / Phase modulators 3,5 dB 3 dB 2,5 dB|
|Insertion loss / Amplitude modulators 4,5 dB 3,5 dB 3,5 dB|
|Amplitude modulator Extinction ratio (ER) > 20 dB > 30 dB > 30 dB|
|Polarisation Extinction Ratio (PER) > 20 dB > 20 dB > 20 dB|
|Optical input signal up to 25 mW up to 300 mW up to 200 mW|
|Operating temperature (full performances) 0 °C to +70 °C|
|Non operating temperature -40 °C to +85 °C|
|Vibration 2,5 min/axis, 33,6 gRMS|
|Shock* Level up to 1 000 g, 0,2 - 10 kHz|
|Radiation Gamma ray 352 Krad (Si)
Proton 1011 p/cm² (60 Mev)
|Lifetime Up to 15 years GEO|
|Missions compatibility GEO. EOR. MEO and LEO|
*Some type of packages succesfully tested up to 2 000 g
|Mass 120 g|
|Package size 110 x 15 x 9.7 mm3 or customised design|
|Fibers jacket Ø 1 mm PEEK tube|
Fig. 3: Operating conditions compliance table
Space grade solutions: from components to transceivers and receivers modules
Last March 2021, for ICSO virtual conference, Dr Hervé Gouraud, Sales Manager for iXblue Photonics, introduced the TRL9 space grade products portfolio: key fiber and electro-optical modulator components as well as sub-modules for high-speed space communication. These ten minutes talk describes briefly the already existing solution for space communication, as well as new modulation and receiver solution under development.
In September 2019 in Noordwijk, in collaboration with ESA, the European Photonics Industry Consortium (EPIC) has organized a meeting on New Space. Key actors and manufacturers involved in the Space Activity were invited. Dr Jérôme Hauden, R&D Manager for iXblue Photonics in Besançon, shared iXblue products and background in space, and he introduced iXblue Photonics strategy and roadmap related to the photonic components being deployed for high-speed space communication.