ThorlabsDeformable Mirror

The world is ready to see images at levels of detail never seen. Read more about the many places deformable mirror technology is used.

Carriers have used fixed microwave links for years to handle these situations. But radio microwave frequencies might not be enough as the world demands greater internet speeds.

As the industry has seen during the last several years, optical transmission systems are being miniaturized from big, expensive line cards to small, affordable pluggables the size of a large USB stick. These compact transceivers with highly integrated optics and electronics have shorter interconnections, fewer losses, and more elements per chip area. These features all led to reduced power consumption over the last decade. Even greater efficiency gains are made possible by an optical system-on-chip (SoC) that integrates all photonic functions on a single chip—including lasers and amplifiers.

MEMSdeformable mirror

Laser beams in FSO are so narrow and focused that these issues don’t exist. At 1 km, a typical laser beam only spreads out about 2 m, and at 5 km, only about 5 m. There are no side and back lobes to worry about and no near-zone reflections. The beam is so narrow that intercepting the transmission becomes an enormous challenge. An intruder would need to get within inches of a terminal or the line of sight, making it easier to be discovered. To complicate things further, the intruder’s terminal would also need to be very well aligned to pick up enough of a signal.

But there are cases in which fiber isn’t cost-effective to deploy. For example, a network carrier might need to quickly increase its access network capacity for a big festival, and there is no point in deploying extra fiber. In many remote areas, the customer base is so small, the deployment of fiber won’t produce a return on investment. These situations can be addressed via some kind of wireless access solution.

Wikipediamirror

This is where free-space optics (FSO) comes into play. With FSO, a high-power laser source converts data into laser pulses and sends them through a lens system and into the atmosphere. The laser travels to the other side of the link and goes through a receiver lens system. A high-sensitivity photodetector then converts these laser pulses back into electronic data that can be processed (see Fig. 1). So instead of using an optical fiber as a medium to transmit the laser pulses, FSO uses air as a medium. The laser typically operates at an infrared wavelength of 1550 nm, which is safer on the eye.

Mirror

Fortunately, FSO developers also use sophisticated digital-signal processing techniques (DSP) to compensate for these impairments. These DSP methods allow reliable, high-capacity, quick deployments even through thick clouds and fog. FSO links can now handle gigabit-per-second capacity over several kilometers, thanks to all these advances in technologies.

Simply changing over to higher carrier frequencies will limit the reach of microwave links. The radio spectrum is also quite crowded, and carriers might not have the available licensed spectrum to deploy this wireless link. And microwave point-to-point links produce plenty of heat while struggling to deliver capacity beyond a few gigabits per second.

Largedeformable mirror

As optical signals move deeper and deeper into access networks, achieving the ambitious performance goals of 5G architectures requires more optics than ever between small cell sites.

Adaptive optics

A collaboration between Aircision and TNO demonstrated in 2021, for example, their FSO systems could reliably transmit 10 Gbit/s over 2.5 km. “It’s an important milestone to show we can outperform millimeter E-band antennas and provide a realistic solution for the upcoming 5G system,” says Aircision’s scientific director John Reid.

While fiber-optic communications drove the push for smaller and more efficient optical transceivers, this progress also has a beneficial impact on FSO.

FSO systems can handle these alignment issues with fast steering mirror (FSM) technology. These mirrors are driven with electrical signals and are fast, compact, and accurate enough to compensate the disturbances in the beam trajectory. But even if the system can maintain its beam trajectory and shape, atmospheric turbulence can still degrade the message and cause interference in the data.

FSO has struggled to break through into practical applications despite these benefits because of certain technical challenges. Communications infrastructure, therefore, focused on more stable transmission alternatives such as optical fiber and RF signals. But research and innovation during the last few decades is removing these technical barriers.

Your desire to push the limits shouldn't be hampered by not having the latest information. Let us connect you with the right people who can help you choose the best deformable mirror for your system so you can focus on moving your discovery forward with adaptive optics.

Deformablelens

ALPAODeformable mirror

FSO is often referred to as a futuristic technology for space applications, but can also be used for ground-to-ground links in access networks. FSO can deliver a wireless-access solution for quick deployment and with more bandwidth capacity, security features, and less power consumption than traditional point-to-point microwave links. And since it does not use the RF spectrum, there is no need to secure spectrum licenses.

One understated benefit of FSO is, from a physics perspective, they’re arguably the most secure form of wireless communication available today.

FSO can deliver a wireless access solution to be deployed quickly and with more bandwidth capacity, security features, and less power consumption than traditional point-to-point microwave links. And since it does not use the RF spectrum, it is unnecessary to secure spectrum licenses. Affordable direct-detect and coherent transceivers based on SoCs can further improve the quality and affordability of FSO transmission.

One obstacle to achieving longer distances with FSO is the quality of the laser signal. Over time, FSO developers have found a solution to this issue in adaptive optics systems. These systems compensate for distortions in the beam by using an active optical element—such as a deformable mirror or liquid crystal—that dynamically changes its structure depending on the shape of the laser beam. Dutch startup Aircision uses this kind of technology in its FSO systems to increase their tolerance to atmospheric disruptions.

Extending fiber optics deeper into remote communities “is a critical economic driver, promoting competition, increasing connectivity for the rural and underserved, and supporting densification for wireless,” according to Deloitte, a financial and tech consulting firm.1