Introduction to Free Space Optics

FSO is a line-of-sight wireless communication technology that uses invisible beams of light to provide high speed wireless connections that can send and receive voice, video, and data information. Today, FSO technology – pioneered and championed by CableFree’s optical wireless offerings – has enabled the development of a new category of outdoor wireless products that can transmit voice, data, and video at bandwidths up to 1.25 Gbps. Free Space Optics connectivity does not require costly fibre-optic cabling and removes the need for acquiring radio frequency (RF) spectrum licenses. FSO relies on light to transmit data- using the sae principles as fibre-optic communication, but through air instead of glass. Since light travels faster through air than fibre, FSO can be a form of optical communication operating at the speed of light.

History of Free Space Optics

Optical wireless communication dates back thousands of years. Ancient Greeks used torches for coded alphabetic signalling, similar to more modern semaphores and heliographs (wireless solar telegraphs) which employed coded signals to communicate. In 1880, Alexander Graham Bell pioneered FSO with his photophone, which transmitted voice via light beams. It achieved the first wireless telephone transmission over 213 meters between two buildings.

FSO found practical use in military communication decades later, beginning with optical telegraphy, such as heliograph transmitters used during the 1904 Herero and Namaqua genocide in German South-West Africa. In World War I, German forces used optical Morse transmitters for communication over 4 km in daylight and 8 km at night. By World War II, the German army used an optical speaking device in anti-aircraft units and Atlantic Wall bunkers. This replaced Morse code by modulating optical waves in speech transmission.

More recently, FSO has been used by the military and NASA for high-speed, non-radio communication between satellites, drones, and other vehicles.

The development of lasers in the 1960s revolutionised FSO, with military organisations driving advancements. However, FSO’s commercial growth slowed during the peak of optical fibre network deployment for civilian use.

FSO vendor CableFree has extensive experience in this area: CableFree developed some of the world’s first successful commercial FSO links, with world-first achievements including:

• World’s first commercial 622Mbps wireless link: 1997
• World’s first commercial Gigabit Ethernet 1.25Gbps wireless link: 1999

While fibre-optic communications gained worldwide acceptance in the telecommunications industry, FSO communications is still considered relatively new. CableFree Free Space Optical technology from Wireless Excellence enables bandwidth transmission capabilities that are similar to fibre optics, using similar optical transmitters and receivers and even enabling WDM-like technologies to operate through free space.

How Free Space Optics / Laser Communications Work

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

Choosing Free Space Optics or Radio Frequency Wireless

Optical wireless, using FSO technology, is an outdoor wireless product category that provides the speed of fibre, with the flexibility of wireless. It enables optical transmission at speeds of up to 1.25 Gbps and is capable of speeds of 10 Gbps using WDM. This is not possible with any fixed wireless or RF technology. Optical wireless also eliminates the need to buy expensive spectrum (it requires no FCC or municipal license approvals worldwide), which further distinguishes it from fixed wireless technologies. Moreover, FSO technology’s narrow beam transmission is typically two meters versus 20 meters and more for traditional, even newer radio-based technologies such as millimeter-wave radio. Optical wireless products’ similarities with conventional wired optical solutions enable the seamless integration of access networks with optical core networks and helps to realise the vision of an all-optical network.

Free Space Technology in Communication Networks

FSO technology is increasingly used in communication networks to bridge connectivity gaps with cost-effective, high-speed, and low-latency optical wireless links. It offers a fast return on investment (ROI), making it attractive for both enterprise and mobile carrier subscribers. With the ever-increasing demand for greater bandwidth, CableFree FSO products balance throughput, distance and availability, with many network uses, some of which are listed below:

Enterprise

FSO is ideal for building-to-building links, disaster recovery, network redundancy, and temporary connections, supporting services like voice, video, data, CAD, and medical imaging.

Mobile Carrier Backhaul

FSO supports both legacy (PDH, STM-1/4) and modern (IP Gigabit Ethernet) backhaul needs, especially in Greenfield mobile networks.

Front-Haul: Mobile Carrier Base Station “Hoteling”

FSO-based products can be used to expand Mobile Carrier Network footprints through base station “hoteling”, using CPRI interface. Free Space Optics with CPRI enables front haul networks where the remote radio heads can be separated up to 2 km from the base station with a 1.22 Gbps CPRI native link between them.

Low Latency Networks

FSO offers ultra-low latency due to light travelling faster through air than fibre and along its direct Line-of-Sight path. This makes it especially suitable for low latency applications like High Frequency Trading.

For More Information

For further information on Free Space Optics and the range of CableFree wireless networking products, please Contact Us