Free-space optics indispensable as Taiwan's satellite development gains a military dimension

Misha Lu, DIGITIMES Asia, Taipei 0

Credit: SpaceX

With photonic integrated circuits, above all silicon photonics, seeing a wave of industry hype owing to their vast potential in the datacom and telecom applications, relevant suppliers in Taiwan's semiconductor and electronics manufacturing sector have been gearing up for the opportunities, particularly as international photonics players increasingly seek to tap into Taiwanese chip manufacturing prowess.

However, the satellite application of free-space optics - the wireless transmission of data via a modulated optical beam directed through free space - has to date received relatively little attention from Taiwanese photonics suppliers amid the AI datacom hype, even as Taiwanese manufacturers generally look to the satcom industry as one of the future engines of growth. FSO is now widely regarded as a viable alternative to radio waves that have been the dominant means of satellite-to-satellite and satellite-to-ground communications, particularly given the many advantages FSO brings, including higher data rate, narrower beam width, resistance to electromagnetic interference, and the current unregulated optical spectrum.

As pointed out by the Belgium-based semiconductor R&D institute Imec, the compactness and low power consumption of integrated photonics offer a path to deploy free-space optical transceivers in space. By eliminating moving parts, integrated photonics also offers a level of robustness against the vibrations caused by space launch.

On December 14, Amazon announced that its low-Earth-orbit (LEO) satellite internet program, Project Kuiper, has successfully tested its laser-based inter-satellite links between its two prototypes, KuiperSat-1 and KuiperSat-2. As indicated by Amazon, the onboard optical communication payloads between the two satellites 1,000 km apart maintained a two-way 100 Gbps link for one hour. The experiment is set to pave the way for Project Kuiper's ambition to include laser links on every satellite in its constellation to form a mesh network in space.

Back in January 2021 SpaceX's Starlink already launched ten satellites equipped with laser crosslinks to bypass the need to build ground stations to cover the polar region. Starting in 2023, SpaceX began to launch its next-gen "V2 Mini" satellites equipped with laser-based communication capabilities. The company indicates that it has deployed 8,000 such lasers in the constellation, across 5,000 satellites, capable of transferring up to 100 Gbps on each link.

The strategic significance of FSO, especially in terms of military application, is reflected in the respective efforts of the Defence Advanced Research Projects Agency (DARPA) and the Defence Innovation Unit (DIU) to cultivate the US military's space-based optical communications capabilities.

For instance, DARPA and CACI International, a company engaged in photonics design services and free-space optics, cooperated in 2022 to evaluate the pointing, acquisition, and tracking algorithms crucial to enabling high-speed optical communication between satellites. The collaboration is part of DARPA's Blackjack program dedicated to demonstrating the military utility of incorporating commercial LEO technologies to achieve previously unavailable economies of scale, short design cycles, and frequent technology updates.

A standardization race underway

Silicon Valley-based Defence Innovation Unit, an organization under the US Department of Defense created in 2015 to accelerate military deployment of commercial and dual-use technologies, also included free-space optics in the second phase of its Hybrid Space Architecture (HSA) program first launched in 2021. The DIU believes the HSA to be a critical enabler of the Pentagon's new warfighting concept - Joint All-Domain Command and Control (JADC2) - that ultimately seeks to link military assets across space, air, land, sea, and cyber domains, and fuse their intelligence, surveillance, and reconnaissance data into a common operational picture.

In contrast to new space commercial space systems that use modern information architectures based on open standards, the DIU notes that legacy government space communications systems are reliant on proprietary data architectures that are neither scalable nor interoperable with commercial counterparts. In this context, a hybrid space architecture capable of integrating government space systems with emergent commercial space sensors and communication abilities becomes crucial - especially the capability to integrate with allied and friendly foreign systems. The program sees free space optics as a crucial area of focus alongside high-performance edge computing, data fusion, and space-based sensing.

Though FSO is of great strategic importance and gaining traction worldwide, and the Taiwan Space Agency (TASA) is working on the development of optical communication systems and components, the ground segment still dominates Taiwan's space industry: Taiwanese space sector saw US$7.2 billion worth of output in 2022, but 98.7% of it was derived from ground equipment. As Infinio Capital, a Los Angeles-based venture capital familiar with the Taiwanese space supply chain, pointed out, Taiwan should gain a leading position in laser-based space optical communication before the technology goes mainstream, especially when the country can already supply some of the key components.

Indeed, considering that the Taiwanese government has begun to recognize the military implications of the space domain, and has started to build a satellite-based communications network for emergency and wartime applications, in addition to the fact that the race to standardize FSO technology is now underway, further attention should be paid to laser-based space optical communication. As shown by the aforementioned Hybrid Space Architecture program, interoperability with allied space systems should be in mind - an ultimate direction that also guides US-Taiwan defense industry cooperation. It might also open a path for the Taiwanese supply chain that long eagers to have a further presence in the global aerospace and defense market.

Not to mention the growing potential of satellite-to-ground optical communication, another emergent application currently being explored by the US and China: a projection by Research & Markets shows that the global space-based laser communication market will reach US$10.72 billion by 2033, while the global satellite optical ground market is projected to reach US$113.3 billion in 2028.

Meanwhile, the Taiwanese government in December listed 22 core technologies with national security implications, eight of them for space applications. Though the list included the technologies for satellite control, x-band image download, image compression electronic unit, CMOS image sensing, active phased array antenna, passive reflector antenna, radar image processing, and the design, manufacturing, and integration of optical payload, it is not clear to what degree is FSO involved in the optical payload.