Embracing Light: The Satellite Industry’s Transition from RF to Optical

While Radio Frequency (RF) systems are commonly used for low-rate space communications, recent advancements in Free Space Optical (FSO) or Laser Communications (lasercom) have made it a compelling alternative to RF systems. Lasercom has gained traction in the field of communications, appearing in new Optical Ground Stations (OGS) and Optical Communications Terminals (OCTs), which come in the form of ground terminals and terminals installed on satellites, drones, maritime vessels, and aircraft. The Space Development Agency (SDA), a division of the U.S. Space Force, has played a pivotal role in this progress by opening contracts to build a mesh network of optical satellites in Low Earth Orbit (LEO) (the Proliferated Warfighter Space Architecture (PWSA)) and issuing a set of technical standards for optical terminal manufacturers. As a result, numerous OCT vendors, such as Mynaric, TESAT, Honeywell, Skyloom, CACI, and others, are taking the lead on developing lasercom technologies for land, air, maritime, and space applications. With mega constellations, such as Starlink, OneWeb, Kuiper, Lightspeed, and Guo Wang, promising to use Optical Inter-Satellite Links (OISLs) to enhance networking capabilities, the future of lasercom looks bright.

OCTs will have a strong market opportunity for OISLs (or satellite crosslinks), but may face difficulties gaining traction for ground applications. Lasercom uses optical wavelengths of electromagnetic radiation to transmit wireless communications. Due to the higher frequencies used in lasercom, the amount of bandwidth available for communicating is much larger compared to RF and can achieve higher data rates. As a result, the beam width is also narrower than RF and requires more precision and directionality, which requires lasercom terminals to be mechanically steered. Smaller wavelengths mean the transmitter diameters and beam divergence of lasercom systems can also be much smaller, which enables the Size, Weight, and Power (SWaP) of lasercom systems to be lower than similar performing RF systems, especially useful properties for the emerging SmallSat class. Lastly, lasercom has a low probability of interception, is difficult to jam, encounters very little interference because of the narrow beamwidth, and is on unregulated frequencies.

Despite these advantages, lasercom has challenges in Space-to-Earth applications. Chiefly, OCTs are susceptible to large amounts of attenuation due to moisture and signal orientation can impact the communications link. This attenuation is prohibitive to communications when there is cloud coverage and incentivizes operators to build optical ground stations and deploy ground terminals in areas with clear skies. The small divergence of lasercom systems also means that lasercom solutions require a high orientation accuracy, which adds complexity to the lasercom terminals via software and mechanical steering. In these ways, lasercom ground terminals may be able to coexist with RF solutions, such as a phased array, but have inherent limitations that will impact their widespread applicability. Despite this, these solutions would be very beneficial for use cases requiring more security and encryption, such as quantum communications and the defense industry, and where the terminals can be deployed in scenarios with high optical visibility, such as in the air and space.

The SDA requires laser terminals capable of achieving communication speeds of 2.5 Gigabits per Second (Gbps). However, manufacturers like Mynaric’s CONDOR Mk3 terminals will eventually offer variable data rates up to 10 Gbps (akin to SES’ highest performing enterprise-grade O3b mPOWER solutions). It's not just the SDA that is interested in optical communications. There are also Satellite Communication (SatCom) networks known as “mega constellations,” such as Starlink, Kuiper, OneWeb, Lightspeed, and Guo Wang, that are interested. These constellations, consisting of hundreds to thousands of satellites, plan to heavily use OISLs for efficient communication between satellites when ground stations are unavailable in certain regions. Currently, some of Starlink’s satellites already employ OISLs. As this emerging technology advances, it has the potential to coexist with and even replace RF technologies for SatCom in the future, driven by the proliferation of LEO OISL networks in orbit.

With the expansion of optical solutions and the imminent expansion of the OCT ecosystem, operators and policymakers should consider several factors to make the most of this new market. Below are a few considerations:

• Standardization: Work with stakeholders to develop industry standards for lasercom systems to ensure interoperability between different manufacturers and facilitate adoption.
• Cross-Link Compatibility: Ensure compatibility between different manufacturers and lasercom solutions like OISLs and even ground terminals, so they can be developed to expand the ecosystem. Publishing specifications and source code to the public domain could be one of the solutions to this.
• Ecosystem Development: Foster collaboration between space agencies, research institutions, and private companies to pool resources, share knowledge, and accelerate the development and adoption of lasercom technology.