Optical transceivers for high-speed space communications: en route for the New Space
In space, the standard transmission solutions using RF technology are limited to a data-rate of hundreds Mbit/s, at best. The need for high-speed communications, reaching the range of hundreds of Gbit/s creates an opportunity that can be addressed by photonics-based solutions. The added advantages of photonics solutions in space are also reliability, even under harsh environment, scalability (modulations schemes, numbers of optical channels, …) as well as smaller payload that reduces satellite consumption.
iXblue is a designer and a manufacturer of space grade optical components. The company masters the manufacturing of TRL9 optical components, with a track-record of successful missions embarking its “flight proven” components, such as: optical LiNbO3 modulators, radiation hardened (rad-hard) fibers and their matching Fiber Bragg Gratings (FBGs), fiber sources, low noise optical amplifiers, Multiplexer/Demultiplexer and other micro-optics assembly for the receiver. Our expertise in the telecommunication domain, experience in assembling complex systems as well as our space background allow us to provide fully integrated optical transceivers for the space markets.
iXblue delivers TRL9 optical solution for the Space market
The idea of the new space satellites network is to provide higher throughput at affordable cost. The satellites constellation needs to build a mesh coverage of Earth to share/deliver data even in the most remote places, including above the oceans and poles. Laser based inter-satellite links deliver highspeed data across the globe with a high level of security end-to-end communication services. The LiNbO3 modulators offer a unique combination of performance that makes them prime candidates to satisfy the optical system specifications, and to meet the tough requirements of space operation. Today, many embarked space photonic systems use iXblue modulators as key component to achieve intensity or phase modulation.
iXblue involvement in space is already substantial: with hundreds of TRL9 LiNbO3 modulators, more than 1000 km space qualified fibers currently flying, and the Astrix gyroscopes recording more than 6 million hours in orbit. Our products are either used onto the Geostationary Equatorial Orbit (GEO), or onto the MEO and LEO satellites. The GEO imposes the more stringent operating conditions and has to operate during at least 20 years (average GEO satellites life expectancy), sustaining extreme temperature variations. The instruments and components are also exposed to strong vibrations and shocks during the spacecraft take-off and while flying through the atmosphere in the satellite deployment phase, the space vacuum and the dangerous solar radiations.
With a dedicated team for space products, iXblue has already supplied numerous key space players. These space stamped products were successfully qualified with the following ECSS and MIL standards. iXblue products for laser space communications, robust by design and based on proven technology, do fit many needs of the New Space market. The company also has the capacity to be cost effective in their integration in complete transceiver systems.
From devices to fully integrated optical transceivers: the FOLC project
iXblue is involved in several EU projects to prove the ability of its components to address the need of space communications. One of them is the Feeder Optical Links for Constellation (FOLC1) project, started in 2017. Funded by ESA, supported by the French CNES, and with Airbus Defence and Space as a partner, it aims at building the telecommunication devices for future satellites constellation. It includes the links between satellites in low Earth orbit (LEO <> LEO), the links between LEO satellites and a GEO satellite, and the links between LEO/GEO satellites and Earth. The complete telecommunications network has the goal to reach data transmission rates higher than 1 Tb/s.
The project involves iXblue for the development of embedded optical communication and ground ModBox terminals while Airbus is dealing with the electronics components. iXblue has thus developed the first generation of space grade transceivers for the shaping of the laser signal transmitted through space. The transceiver is based on one transmitter emitting the optical data-signal via external modulation, (before emission) and a receiver module (see detail synoptic of the optical communication chain above).
For the first part of the project (FOLC1), that lasted until 2019, iXblue built a Reference Transmitter and Receiver ModBox with 12 transmission (Tx) and reception (Rx) channels for an in-lab demonstration. This study was required to define the level of performance of the Tx and the Rx: the modulation schemes, sensitivity of the photo-receiver, optical power budget, etc.
The second part of the project, FOLC2 (Feeder Optical Link Communication Chain), started in 2020 is to produce a Demonstrator Model Transceiver: a ready to flight model transmitter and receiver for a data transmission rate of 20 Gbit/s – a first step toward higher data rates. It was delivered in 2022 and embarked on a geostationary telecom satellite in 2023, onboard the TELEO (TELecoms on all Earth Orbits) optical communications demonstrator. As a “hosted payload”, it will be tested in real space conditions for interconnections between the satellite and Earth.
The transceiver and its space qualified sub-components
The FOLC project led to the development of a generic solution of transceiver available to any iXblue customer, with a transmitter based on 1 to 6 emission channels and a receiver based on 1 to 8 reception channels. Parameters as the total weight of the device and its maximal power can be adapted according to the customer needs. iXblue can provide transceivers for constellations counting between two to thousands of satellites.
The transceiver’s Tx is composed of iXblue sub-components that have been fully space qualified. The Compact Optical Channel Emitter (OCE) is composed of a laser (commercial one) and proprietary LiNbO3 modulator and a RF amplifier designed by iXblue. Several OCEs can be multiplexed by a Mux. Transceiver’s Rx possesses a proprietary LNOA (Low Noise Optical Amplifier) and commercial grade high-speed photoreceivers.
An optical multiplexer/demultiplexer produced by iXblue for other markets is also expected to obtain a space qualification in a near future, enabling its integration to the whole transceiver system.
To the next generation of ultra-fast space telecommunications
Another demonstrator is already being manufactured for a LEO orbit satellite dedicated to Earth imaging and will allow the transfer of ultra-high-resolution images of our planet taken from the orbit.
iXblue transceivers with proven robustness and reliability will be qualified for this new project, and our teams are already anticipating the next generation of ultra-fast space telecommunications, beyond the terabits/s range.
To conclude, iXblue space-grade transceivers have several main advantages. First, two modulation downlink modes (OOK -On-Off Keying- and DPSK -Differential Phase-Shift Keying-) of 10 Gbit/s or 25 Gbit/s are available, for a maximum reachable data rate of 125 Gb/s (with adapted design). Second, an uplink analog modulation or 10 Gb/s digital modulation is available, for a maximum reachable data rate of 125 Gb/s (with adapted design). Finally, the transceiver design (size and weight) can be customized according to the customer needs, with same level of space qualification.
