What is free space optical communications

What exactly is free space optical communications and why is it so fundamental to the new space economy? In short, it offers the benefits of massive data rates, high security, low latency and freedom from spectrum regulation. Putting technical detail aside, you can pack a lot more data into light than you can into radio waves.

Minimal divergence is another benefit. If you shine an optical link back to Earth from Neptune, the beam diameter is approximately the same size as Earth. But with a radio link, it’s 10,000 times the diameter of Earth, which means most of the signal energy is wasted.

The second big question to answer about FSOC is ‘why now?’. The sheer amount of hardware that is arriving in space is dramatically increasing which creates escalating levels of data that need to be shifted around. There are number of key drivers behind this, not least the reduced cost of rocket launches in the wake of progress made by SpaceX and its many competitors. Geopolitical tensions sparking a greater emphasis on defence and security is of course another influential factor.

FSOC enables a transformative approach to data transmission by leveraging light propagation through free space to deliver unprecedented levels of communication in the satcom market. It can transmit data over significantly higher speeds for increased capacity, while also avoiding the radio spectrum that are restricted to satellite operators with licenses that are purchased for a hefty fee.

FSOC for the satellite industry

FSOC is attracting interest in industrial automation and military communications, but it’s particularly promising for the satellite industry because it provides low-latency, high-bandwidth links not just between satellites, but through the atmosphere to the ground. This is vital for the meaningful and timely exploitation of the ever-increasing amounts of data being collected and communicated through space-based networks. 

Let me stress though, that applying FSOC is certainly not just a walk in the park. A key area of system development right now is in PAT (pointing, acquisition and tracking). Efforts are continuing to optimise transmitter and receiver alignment; to maintain it despite the relative movement and disturbances of satellite operations, and compensate for atmospheric turbulence and absorption.

With terminals hurtling through space, satellite-to-satellite communication gets very complicated. The current use of mechanical PAT systems requires specific components on satellite systems to compensate for the changes in rotational momentum such as reaction wheels, so future developments are being geared towards solid-state beam steering – essentially the ability to electronically control your emission of light and point the beam in any direction you want. Right now, that’s simply not possible in a small form factor and with the amount of power required.

To find solutions, teams here at CC are dipping into our expertise in stratospheric phased arrays and RF beamforming. Radio phased arrays and optical phased arrays work the same way in principle, so we are optimistic of making good progress.

Free space optics and SWaP constraints

Space operations face big challenges when it comes to the size, weight and power (SWaP) constraints of terminals. Heavier, bulkier terminals mean higher launch prices and less room for payloads. The miniaturisation of optical terminals will be expedited using a relevant technological development: Photonic – or optical – computing. Photonic computing offers a compelling case for adoption in satellite systems, especially through photonic integrated circuits (PICs).

When it comes to miniaturisation, PICs integrate a number of optical components such as lasers, modulators, and detectors onto a single chip. Right away, this slashes the physical size and weight of conventional solutions. And it is because photonic systems transmit data using light that less power is consumed than traditional electronic systems.

They also generate less heat, thus saving power that’s necessary for cooling. In terms of high-bandwidth and speed, PICs support terabit-per-second data rates to help hasten high-throughput satellite links. Fewer components are needed, further reducing SWaP.

Sophisticated AI for FSOC

I’m personally spending a good deal of time right now tackling another issue – the fact that what is transparent for radio isn’t so for optical and vice versa. Atmospheric conditions, like clouds or movement of air, are troublesome for optical communications. This means FSOC has problems to overcome during bad weather that could disrupt space to ground links.

We’re investigating a range of solutions, including hybrid RF-optical links, AI processing, or spatial diversity involving multi-location routing. The team is also creating a model to circumvent adverse weather while cutting down on unnecessary costs and assets for a more streamlined operation.

I’ve spent a fair bit of time explaining the challenges – but I also want to emphasise the commercial opportunities. FSOC can be the backbone to tomorrow’s orbital data economy, and it is the early adopters who will prevail. CC’s advice here is clear: in competitive and fast-moving ecosystem, you’re stronger working as a team. We believe strategic, mutually beneficial partnerships will become perhaps the most valuable assets as the market evolves rapidly.

The same goes for evolving standards. For ambitious players, it’s crucial to get a place on the future-defining stage through understanding, influence and innovation. Conversations are happening right now, offering the chance to guide the direction of travel for the industry in space.

Coordinating with international regulatory bodies, and indeed other partners who may have expertise or resources that you don’t, is the only way to create harmonised systems that can promote global interoperability.

Standardisation marks a change for the satellite industry where previously proprietary standards and technology choices have dominated. In this standards-led ecosystem, new ways will need to be found to differentiate and innovate within a standard framework. And in this new, crowded marketplace, the traditional go-it-alone strategy is far less viable than it once was.

Collaboration begins with initial conversations, so do please reach out to me you’d like to discuss any aspects of this topic in more detail. Free space optical communications are at an inflection point, and those who invest now will define the intelligent and sustainable orbital networks of the future.

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