Free Space Optics Technology

Introduction to Free Space Optics

CableFree FSO - Free Space Optics
CableFree 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 doesn’t require expensive fibre-optic cable and removes need for securing spectrum licenses for radio frequency (RF) solutions. FSO technology requires light. The use of light is a simple concept similar to optical transmissions using fiber-optic cables; the only difference is the medium. Light travels through air faster than it does through glass, so it is fair to classify FSO technology as optical communications at the speed of light.

History of Free Space Optics

Optical communications, in various forms, have been used for thousands of years. The Ancient Greeks used a coded alphabetic system of signalling with torches developed by Cleoxenus, Democleitus and Polybius. In the modern era, semaphores and wireless solar telegraphs called heliographs were developed, using coded signals to communicate with their recipients. In 1880 Alexander Graham Bell and his assistant Charles Sumner Tainter created the Photophone, at Bell’s newly established Volta Laboratory in Washington, DC. Bell considered it his most important invention. The device allowed for the transmission of sound on a beam of light. On June 3, 1880, Bell conducted the world’s first wireless telephone transmission between two buildings, some 213 meters (700 feet) apart.  Its first practical use came in military communication systems many decades later, first for optical telegraphy. German colonial troops used Heliograph telegraphy transmitters during the 1904/05 Herero Genocide in German South-West Africa (today’s Namibia) as did British, French, US or Ottoman signals.

During the trench warfare of World War I when wire communications were often cut, German signals used three types of optical Morse transmitters called Blinkgerät, the intermediate type for distances of up to 4 km (2.5 miles) at daylight and of up to 8 km (5 miles) at night, using red filters for undetected communications. Optical telephone communications were tested at the end of the war, but not introduced at troop level. In addition, special blinkgeräts were used for communication with airplanes, balloons, and tanks, with varying success. A major technological step was to replace the Morse code by modulating optical waves in speech transmission. Carl Zeiss Jena developed the Lichtsprechgerät 80/80 (literal translation: optical speaking device) that the German army used in their World War II anti-aircraft defense units, or in bunkers at the Atlantic Wall.

The invention of lasers in the 1960s revolutionized free space optics. Military organizations were particularly interested and boosted their development. However the technology lost market momentum when the installation of optical fiber networks for civilian uses was at its peak.

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

CableFree Free Space Optics at London 2012 OlympicsThe concept behind FSO technology is very simple. It’s based on connectivity between FSO-based optical wireless units, each consisting of an optical transceiver with a transmitter and a receiver to provide full-duplex (bi-directional) capability. Each optical wireless unit uses an optical source, plus a lens or telescope that transmits light through the atmosphere to another lens receiving the information. At this point, the receiving lens or telescope connects to a high-sensitivity receiver via optical fibre. This Free Space Optics technology approach has a number of advantages: Requires no RF spectrum licensing. Is easily upgradeable, and its open interfaces support equipment from a variety of vendors, which helps enterprises and service providers protect their investment in embedded telecommunications infrastructures. Requires no security software upgrades. Is immune to radio frequency interference or saturation. FSO Can be deployed behind windows, eliminating the need for costly rooftop rights.

Choosing Free Space Optics or Radio Frequency Wireless

CableFree FSO links in Cairo, EgyptOptical 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, in the future, 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 realize the vision of an all-optical network.

Free Space Technology in Communication Networks

CableFree FSO used in CCTV NetworksFree-space optics technology (FSO) has several applications in communications networks, where a connectivity gap exists between two or more points. FSO technology delivers cost-effective optical wireless connectivity and a faster return on investment (ROI) for Enterprises and Mobile Carriers. With the ever-increasing demand for greater bandwidth by Enterprise and Mobile Carrier subscribers comes a critical need for FSO-based products for a balance of throughput, distance and availability. During the last few years, customer deployments of FSO-based products have grown. Here are some of the primary network uses:

CableFree FSO NetworkEnterprise

Because of the scalability and flexibility of FSO technology, optical wireless products can be deployed in many enterprise applications including building-to-building connectivity, disaster recovery, network redundancy and temporary connectivity for applications such as data, voice and data, video services, medical imaging, CAD and engineering services, and fixed-line carrier bypass.

Mobile Carrier Backhaul

FSO - Free Space Optics InstallationFree Space Optics is valuable tool in Mobile Carrier Backhaul: FSO technology and optical wireless products can be deployed to provide traditional PDH 16xE1/T1, STM-1 and STM-4, and Modern IP Gigabit Ethernet backhaul connectivity and Greenfield mobile networks.

Front-Haul: Mobile Carrier Base Station “Hoteling”

Free Space Optics CPRI Front-Haul for 4G NetworksFSO-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 by up to 2km from the Base station with a 1.22Gbps CPRI “native” link between them.

Low Latency Networks

CableFree Free Space OpticsFree Space Optics is an inherently Low Latency Technology, with effectively no delay between packets being transmitted and received at the other end, except the Line of Sight propagation delay.  The Speed of Light through the air is approximately 40% higher than through fibre optics, giving customers an immediate 40% reduction in latency compared to fibre optics.  In addition, fibre optic installations are almost never in a straight line, with realities of building layout, street ducts and requirement to use existing telecom infrastructure, the fibre run can be 100% longer than the direct Line of Sight path between two end points.  Hence FSO is popular in Low Latency Applications such as High Frequency Trading and other uses.

Low Latency Wireless Networks for High Frequency Trading

Low Latency Wireless Networks for High Frequency Trading

CableFree Low Latency speed-of-light-wall-street-high-frequency-trading
Microwave Millimeter Wave and FSO used in Low Latency High Frequency Trading (HFT)

The need for speed:  Best Practices for Building Ultra-Low Latency Microwave Networks.

To achieve the lowest end-to-end Ultra Low Latency with the highest possible reliability and network stability not only requires a wireless transmission platform that supports cutting edge low latency performance, but also must be combined with the experience and expertise necessary to design, deploy, support and operate a Millimeter wave, Free Space Optics or Microwave transmission network.

In High Frequency Trading (HFT) applications where computers can make millions of decisions in fractions of a second, receiving data even a single millisecond sooner can equate to a distinct advantage and generate significant profits.  This is called Low Latency or Ultra Low Latency networking.

Reducing Latency is critical - MW, MMW, FSO
Reducing Latency is critical – MW, MMW, FSO

According to Information Week Magazine¹: “A one (1) millisecond advantage in trading applications can be worth $100 million a year to a major brokerage firm”. Currently electronic trading makes between 60% and 70% of daily volume of the New York Stock Exchange. Tabb Group, a research firm, estimated that High-frequency traders generated about $21 billion in 2008.

Financial Trading centres with HF Traders can be in locations separated by long distances for example Chicago and New York. Data communications between these locations is commonly over leased circuits on fibre optic networks. But if the data was carried over Microwave radio links between the same two locations it would arrive several milliseconds earlier. Why?

Millimeter Wave, MMW and Microwave are the best for Ultra Low Latency

Faster Propagation

Millimeter Wave, Microwave and Free Space Optics can ensure Lowest Latency
Millimeter Wave, Microwave and Free Space Optics can massively reduce network latency

Optical, Millimeter Wave and Microwave signals travel through the air about 40% faster than light through optical fiber. Latency in a data communications circuit, or the time difference between sending a request for data and receiving the reply, will consequently be longer over a fibre optic circuit than a microwave circuit of the exact same length.

Latency is largely a function of the speed of light, which is 299,792,458 meters/second in vacuum. Microwave signals travel through the air at approximately the same speed as light through a vacuum and will have a latency of approximately 5.4 microseconds for every mile of path length. Light travel in optical fibre has latency of 8.01 microseconds for every mile of cable, due to the refraction in the fibre. When data has to travel over 1400 miles from Chicago to New York and back again the latency difference due to the communications medium alone is more than 3.5 milliseconds.
Straighter Routes Microwave networks have shorter routes, reducing the total network distance and consequently further improving latency. Microwave links can overcome topographical obstacles such as rivers, mountains and highways while optical networks in many cases have to go around them or follow existing roads or bridges. In general, signals over fibre networks have to travel farther and thus take longer to get to their destination.

Total latency in any network includes additional latency due to data queuing delay, processing delay through gateways, network design, equipment configuration and extra distances due to circuitous routes.
Overall, CableFree Millimeter wave (MMW), Free Space Optics (FSO) and Microwave networks offer a better solution for Ultra Low Latency applications such as HFT in comparison to fiber optic equipment because of a combination of an advantage in transmission medium and simple geometry—shortest distance between two points is a straight line.