Free-space optical communication (FSO) is a technology that transmits data through light traveling in free space, such as air, vacuum, or outer space, without using physical cables. Instead of relying on fiber optics, FSO systems use lasers to send information between two points in a wireless optical link.
FAQ - Aerospace and Defense
Optical communications
Free-space optical (FSO) communications enable high-speed, laser-based data transmission through the atmosphere or space across multiple link types:
✓ Satellite-to-satellite links: between LEO, MEO, or GEO satellites, in the same orbit or across different orbital planes.
✓ Satellite-to-ground links: between LEO, MEO, or GEO satellites and Optical Ground Stations (OGS), in both uplink and downlink directions.
✓ Ground-to-ground links: between two terrestrial distant sites with a line-of-sight.
✓ HAPS and UAV configurations: connecting high-altitude platforms or drones with ground or space segments.
The main performance differences between optical and radio frequency (RF) communications stem from their operating frequencies. Optical systems, which use light, offer a much wider bandwidth, enabling data rates up to 100 times faster and significantly lower latency than RF links. They also provide enhanced security and stealth, thanks to the high directionality of the optical beam and are completely immune to electromagnetic interference. However, RF communications remain more robust in adverse weather conditions and not affected by atmospheric turbulence, while being able to operate without a direct line of sight.
Atmospheric turbulence refers to random fluctuations in air temperature and density that cause variations in the refractive index of the atmosphere. For optical communications, this results in beam wandering, scintillation, and signal fading, which degrade the quality and stability of the optical link for space-to-ground links.
Several advanced techniques are used to mitigate atmospheric turbulence effects and maintain stable, high-quality optical communications:
✓ Multi-Plane Light Conversion (MPLC by Cailabs) by reshaping optical modes to make the beam more resilient to turbulence, improving coupling efficiency and signal stability.
✓ Adaptive optics: by correcting in real-time the wavefront distortions using mechanical deformable mirrors.
✓ Spatial diversity: by deploying multiple transmitters, receivers, or apertures to average out signal fluctuations and minimize fading effects.
Standards
Standards in optical communications ensure interoperability, reliability, and performance consistency across systems developed by different manufacturers or used in different environments. They define the protocols, wavelengths, modulation formats, and interface specifications that allow equipment to work together seamlessly. By following recognized standards, the optical communication industry guarantees compatibility, scalability, and safety, while accelerating technology adoption and reducing deployment costs.
Several international standards govern optical communications, depending on the application domain and environment:
✓ SDA (Space Development Agency): defines optical inter-satellite link (OISL) standards to ensure interoperability among spacecraft from different manufacturers and operators within large constellations.
✓ CCSDS (Consultative Committee for Space Data Systems): establishes standards for space-to-ground and inter-satellite optical communications, covering modulation formats, coding schemes, synchronization, and link protocols used by space agencies worldwide.
✓ ESTOL (European Space Optical Link): specifies European requirements for optical terminal interfaces and performance, promoting compatibility across governmental and commercial space missions.
The SDA develops a unified Optical Communication Terminal (OCT) standard to ensure interoperability between different satellite manufacturers and operators.
It follows a “spiral development” approach, with new capabilities added through iterative tranches released approximately every two years:
✓ Tranche 0 (T0): first demonstration phase, validating basic interoperability of optical inter-satellite links (OISL) using the OISL Standard v2.x.
✓ Tranche 1 (T1): deployment of the OCT Standard v3.x–4.0.0, expanding to space-to-space (S2S), space-to-ground (S2G), and other link types.
TILBA®
TILBA® builds on three core building-block technologies, TILBA®-ATMO, TILBA®-IBC, and TILBA®-CBC, all derived from Cailabs’ proprietary Multi-Plane Light Conversion (MPLC) technology.
✓ TILBA®-ATMO provides Rx turbulence mitigation without adaptive optics, using a fully passive and non-mechanical approach.
✓ TILBA®-IBC leverages Incoherent Beam Combining for Tx turbulence mitigation, enhancing transmission robustness under turbulent atmospheric conditions.
✓ TILBA®-CBC leverages Coherent Beam Combining to enhance transmission performance by phase-aligning multiple laser beams into a single, powerful and coherent output.
A bidirectional optical communication allows simultaneous two-way data exchange between two terminals. For example, it uses separate optical channels for uplink (ground-to-space) and downlink (space-to-ground) transmissions. This enables real-time communication, synchronization, and continuous data flow.
TILBA®-OGS
TILBA®-OGS is a turnkey optical ground station developed by Cailabs, enabling bidirectional satellite-to-ground optical communication at 10+ Gbps. It integrates key building blocks derived from Cailabs’ patented MPLC (Multi-Plane Light Conversion) technology. TILBA®-OGS includes building blocks, TILBA®-ATMO and TILBA®-IBC to mitigate atmospheric turbulence on Rx and Tx side.
An Optical Ground Station integrates advanced optical, electronic, and control subsystems that enable precise and reliable laser communication operations:
✓ Pointing, Acquisition & Tracking (PAT): ensures accurate alignment with moving satellites for stable optical links.
✓ Beacon and laser uplink: provides reference and transmission signals for satellite tracking and communication.
✓ Weather and turbulence monitoring: continuously analyzes atmospheric conditions to optimize link performance.
✓ Turbulence mitigation modules: TILBA®-ATMO (Rx) and TILBA®-IBC (Tx) compensate for atmospheric distortion using MPLC-based passive beam shaping.
✓ Data Communication (COM): manages optical signal modulation, demodulation, and high-speed data exchange.
✓ Monitor & Control Management (MCM): supervises system health, telemetry, and network coordination.
✓ Infrastructure: includes the dome, power, and environmental systems ensuring stable and secure operation.
An optical ground station can handle all types of data transmitted between space and ground segments, depending on the mission and network configuration. This includes scientific and Earth observation data, high-throughput communication traffic, command and telemetry signals, or secure and encrypted governmental and defense information. In essence, any form of digital data that can be modulated onto an optical carrier can transit through an optical ground station.
TILBA®-OGS systems are designed for interoperability with SDA and CCSDS standards and will be upgraded to ESTOL standard.
TILBA®-OGS systems can be adapted and upgraded to interoperability with QKD secure communication technology.
TILBA®-LOS
TILBA®-LOS is a ground-to-ground solution developed by Cailabs, enabling bidirectional optical communication at 10 Gbps beyond 10 km range. It leverages our expertise in turbulence mitigation, enabling us to manage atmospheric turbulence during transmission significantly enhancing the stability and resilience of the optical link.
TILBA®-LOS enables secure and stealthy ultra-directional laser communications that are undetectable by traditional RF sensors and immune to jamming.
TILBA®-LOS can operate in relay configuration, allowing data to be transmitted from one terminal to another seamlessly. This architecture enables a fully meshed optical network, where each node can receive, amplify, and retransmit the optical signal to extend range and coverage.
Glossary
An Optical Ground Station (OGS) is a turnkey ground-based facility equipped with telescopes and laser-communication hardware, designed to establish high-speed optical links with satellites (e.g., LEO, MEO, GEO)
Line-of-Sight (LOS) systems enable direct point-to-point laser communication between two optical terminals. LOS systems are most commonly used for ground-to-ground optical links, where line-of-sight obstructions and alignment constraints are typically more critical than in satellite-to-ground links.
Multi‑Plane Light Conversion (MPLC) technology is a patented passive and low loss optical system that converts and shapes laser light by passing it through a series of transverse phase‐profiles spaced at specific propagation distances.
Free-Space Optical Communication (FSOC) refers to a telecommunication technology that uses a light beam, typically a laser, to transmit data through free space, without requiring optical fiber. The optical link can be established ground-to-ground, ground-to-space, or space-to-space.
Space Development Agency (SDA) is a U.S. Department of Defense Agency focused on rapidly deploying resilient satellite constellations and optical links for national security.
The Consultative Committee for Space Data Systems (CCSDS) is an international standards body that develops technical norms to ensure interoperability between space agencies worldwide.
ESA Specification for Terabit/sec Optical Links (ESTOL) is a specification developed by the European Space Agency (ESA), in collaboration with industry and academic partners, that defines the physical-layer and data-link-layer requirements for bidirectional high-data-rate optical links between satellites and between space and ground.
Quantum Key Distribution (QKD) is a secure communication technology that uses the principles of quantum mechanics to generate and exchange encryption keys between two parties. By transmitting individual photons carrying quantum information, QKD ensures that any interception attempt disturbs the signal and is immediately detectable.