The Technology Behind Optical Wireless

Free-space optics (FSO) is a line-of-sight laser-based technology that delivers high-speed, reliable connectivity without the need for fibre-optic cables or spectrum licenses. Capable of transmitting voice, data, and video at up to 2.5 Gbps over distances of up to 4 km, FSO offers a fast return on investment and is easy to deploy globally.

FSO works by sending data through invisible beams of light- similar to fibre optics but through air instead of glass. Since light travels faster in air, it enables optical communication at the speed of light. FSO technology requires light, which can be focused by using either Light Emitting Diodes (LEDs) or lasers (light amplification by stimulated emission of radiation). As a leader in optical wireless communications, CableFree has built a range of products around this technology, making FSO ideal for high-speed “last-mile” connections and campus links.

History of Free Space Optics

Originally developed by the military and NASA, FSO has been used for over 30 years to deliver high-speed communication links, particularly in remote locations. CableFree brings deep expertise to this field- its engineers were developing prototype FSO systems in the mid-1990s, before most others had even begun exploring the technology.

While fibre-optic communication is now widely adopted across the telecom industry, FSO remains a newer but highly promising alternative. It offers fibre-like bandwidth using similar optical transmitters and receivers, and can even support WDM-like (Wavelength Division Multiplexing) techniques to operate through free space.

How it Works

FSO technology uses simple, full-duplex (bi-directional) communication between optical transceivers that transmit and receive light through the atmosphere using lenses and telescopes. The signal is then passed from the receiving lens to a high-sensitivity receiver via optical fibre. FSO offers several key advantages:

• Requires no RF spectrum licensing
• Easily upgradeable
• Its open interfaces support equipment from a variety of vendors
• No additional security software upgrades required
• Immunity to radio frequency interference or saturation
• Ability to operate through windows- eliminating the cost of rooftop access

FSO: Optical or Wireless?

Speed of fibre – flexibility of wireless.

Optical wireless, based on FSO technology, combines the speed of fibre with the flexibility of wireless. It delivers data rates up to 2.5 Gbps, with potential for 10 Gbps using WDM. Unlike fixed wireless, optical wireless requires no spectrum licenses, reducing costs and regulatory barriers. Its narrow beam (typically 2 metres) offers greater precision than radio technologies like millimeter-wave. With its similarity to traditional fibre optics, optical wireless integrates easily with optical core networks, supporting the vision of a seamless all-optical network.

Market Perspective:

As demand for high-bandwidth connectivity continues to surge, the global “last mile” – the final stretch between the end-user and the network – has emerged as a critical bottleneck. While many buildings are near fibre infrastructure, fewer than 10% are actually connected due to high installation costs, licensing hurdles, and the disruption caused by trenching. Further, most of the recent trenching has been to improve the metro core (backbone), rather than the metro access and edge (the “last mile”).

This can provide a huge market opportunity, with several technologies competing to address it, including fibre optic, radio frequency, wire and copper-based technologies, and FSO.

• Fibre optic cable offers the most reliable optical communications, but high costs, long deployment times, and lack of flexibility make it impractical for many last-mile applications.
• Radio Frequency (RF) solutions offer longer-range distances than FSO, but require costly spectrum licenses, are prone to interference, and lack scalability to gigabit speeds.
• Copper-based technologies like DSL, cable modem, and T1s are widely available but can’t meet the growing demand for high-speed, scalable bandwidth, since the bandwidth is limited to 2-3 megabits.

FSO technology – the “last mile” connectivity answer

FSO delivers fibre-speed performance without the need for digging, spectrum licenses, or heavy infrastructure.

Key benefits of FSO technology include:

• Gigabit-speed bandwidth, with scalability for future needs

• Rapid deployment in hours, not weeks or months

• Lower costs – typically 80% less than fibre installation

• Portable and redeployable if customer needs change

• Interoperable with existing network equipment

• License-free and immune to RF congestion

There are three market segments poised for significant growth:

• Enterprise campus networks: Easily connect buildings with high-speed links across a campus or business park.

• Wireline access: Ideal for service providers seeking cost-effective alternatives to leased lines or fibre in high-growth regions.

• Mobile Wireless backhaul: Supports current and next-gen mobile networks with high-capacity, scalable connections.

Challenges

While FSO and fibre-optic technologies share similar capabilities, they face different challenges due to their transmission mediums. Fibre is vulnerable to physical damage (e.g. construction, animals, underwater threats), whereas FSO, being a line-of-sight optical technology, is affected by atmospheric conditions and physical obstructions. However, with proper network design and planning, these issues can be effectively mitigated.

Key Environmental Challenges & Solutions:

• Fog: The biggest challenge for FSO, as water droplets scatter and absorb light. Solution: Shorter link distances, redundancy, and careful site selection.

• Absorption: Caused by water molecules reducing signal strength. Solution: Adjusting power levels and using spatial diversity (multi-beam systems).

• Scattering: Occurs when particles in the air redirect light (Rayleigh, Mie, and non-selective types, depending on the wavelength of the scatterer). Solution: Beam design optimised for distance and environmental conditions.

• Physical obstructions: Birds, cranes, etc. may momentarily block the beam. Solution: Multi-beam systems ensure quick recovery and consistent uptime.

• Building sway & seismic activity: Misalignment due to structural movement. Solution: Divergent beams and auto-tracking technologies maintain alignment.

• Scintillation (refractive turbulence): Caused by heat or temperature variations in the air, leading to signal fluctuation. This causes two primary effects on optical beams:

  • Beam wander: Caused by large turbulent eddies.

  • Beam spreading: Beam broadening over distance.
    Solution: Wide-beam optics and design techniques to minimise signal instability.

Safety

FSO systems use low-power lasers and comply with strict international safety standards (for both eye exposure and electrical safety). CableFree’s FSO products meet all required laser safety classifications, ensuring safe and reliable operation.

For Further Information

For more information on Carrier Class FSO, please Contact Us