FSO Technology – Yesterday And Today

The history of FSO technology or atmospheric optical communication began not in the 90’s or in the 70’s of the XX century, but many centuries earlier. This is the oldest technology of long-distance communication.


The first “systems” of communication were watching outposts, located around settlements on towers, sometimes simply on trees. When the enemy approached, a fire of alarm was lit. Having seen the fire, the fire of the sentries was lit at an intermediate post, and the enemy could not catch the inhabitants unawares.

Typical watching outpost

We heard the legend of three thousand years ago about how the lights bonfires lit on the mountain tops told Clytemnestra, wife of Agamemnon, the leader of the Greeks in the Trojan War, the news of the fall of Troy the same night. In the campaigns of Hannibal, the signal lights were no longer unusual, and even today, in our technical age, we cannot abandon them. Whichever type of transport a citizen chooses – he is dominated by the “signal lights” of a traffic light. Of course, today, to light such a “signal fire” is not a difficult matter, but are modern lighting devices that regulate the movement of metro and land traffic flows so far away from the lights that announced the fall of Troy?

Signal lights for car drivers are so familiar and unobtrusive devices that no one thought that they are an element of FSO technology. But if its information characteristics expand and add a device that provides a dump of information to passing cars or traffic lights, then without downloading expensive radio air, information on traffic jams, route, news, music, etc. can be obtained on board. For 10 seconds of parking at an intersection, you can download up to 100 MB of information. And the connection can also be in two ways.


In the 17th and 18th centuries, when science, technology, and industry developed noticeably, new trade routes and close political and economic relations among peoples established, an acute need for more sophisticated and quicker means of communication appeared.

A special fame among the first inventors of special signaling equipment was acquired by the English scientist Robert Hooke, who is often called the founder of optical telegraphy. His apparatus consisted of a wooden frame, one corner of which was lined with boards and served as a fence. Behind the fence were hidden objects of special shape, denoting various letters or phrases. When transmitting messages, each such object moved out into the empty corner of the frame and could be seen at another station. To read the signals, Hook proposed using the recently invented telescopes, which then became an integral part of all signaling devices.

Robert Hooke

A few years later, after the invention of Hooke, a similar device was proposed by the French physicist Amonton. However, his first experiments were unsuccessful, and in the future, despite all attempts to improve his invention, Amonton’s invention was not supported by influential persons. The same fate befell many other inventors, such as Kessler, Gotei, Lehcher, whose ideas were to some extent applied to signaling practice only many years later.

And only at the end of the XVIII century, as the conclusion of all the ideas expressed, the remarkable invention of Claude Chapp appeared. 

Claude Chappe

Chapp was engaged in physical research, which he was fond of since childhood. One thought particularly occupied his imagination – the creation of a machine for transmitting messages. Of all the signaling methods that were offered in the past, the most interesting was the system with two identical vessels, described by Polybius. Chapp decided that the very idea behind this system could be used to create a more perfect device. Instead of vessels, he proposed to install on the stations with the same travel clock, on the dial of which instead of the numbers would be marked 24 letters. The initial position of the arrows was determined in advance. According to the conventional sign, the clock was simultaneously used. At the same time, the receiving station was supposed to observe the manipulations at the transmitting station. The signal that appeared there meant that it was necessary to notice on the dial the letter against which the arrow was at the moment. It must be said that the public experiments that Chapp conducted with these devices in 1791 in the town of Parsay were a success. But, despite this, the inventor soon became disillusioned with his devices, making sure that they could not be used to transmit messages over a distance of more than 12 to 15 versts. Continuing to improve his device, Chapp developed a number of signal device designs, of which the most successful in 1792 he brought to Paris.

Claude Chappe’s telegraph 

In July 1793, an official review of the apparatus of Schapp was held. The tests lasted for three days and the instruments worked remarkably accurately and quickly. As a result, the French government decided to immediately build a Paris-Lille telegraph line, with the length of 60 miles. Construction was entrusted to Claude Chapp, who on this occasion was awarded the world’s first title of a telegraph engineer, and lasted about a year. In 1794, during the war of the French Republic against Austria, the line first demonstrated its capabilities: the news that Le-Kesne was again in the hands of the revolutionary troops reached the capital in an hour. The simplicity of the telegraph device, the speed and accuracy of its work prompted the Convention to decide on the construction of several telegraph lines in France and to connect the capital with all the border points. In 1798 the Paris-Strasbourg-Brest line was opened, in 1803 the Paris-Lille line was continued to Dunkert and Brussels. In 1803, by order of Napoleon, the Paris-Milan line was built, continued in 1810 to Venice. In the years 1809-1810. the telegraph connected Antwerp and Boulogne, Amsterdam and Brussels. In 1823, the Telegraph line Paris-Baiogne entered into force.

In 1795 the apparatus of the Chapp system were installed in Spain and Italy. Soon a similar telegraph, but a slightly modified design appeared in England and Sweden. The British government has taken care of the similar signaling lines and in its colonies establishment. In India, the first line of the optical telegraph, built in 1823, connected Calcutta with the fortress of Shunar. Approximately at the same time, a similar line began to operate in Egypt between Alexandria and Cairo, where it took 40 minutes to transfer the sign from one city to another through 19 intermediate stations. In Prussia, an optical telegraph was introduced only in 1832.

The entire Western European press wrote about the successful application of the device. Soon the news reached Russia. At the end of 1794, the capital newspaper “Petersburg Stories”, reporting on the course of military operations in France, simultaneously noted the success of a new invention that played a big role in the capture of the French fortress of Conde. This fact could not remain unnoticed for the Russian ruling circles. Even the Catherine II was interested in the possibilities of such a “long-distance machine”. She correctly assessed the whole value of the invention. Having demanded to himself the most skilful mechanic of the academic workshop, she ordered him to build exactly the same machine. This mechanic was Ivan Petrovich Kulibin, famous in the people for his ingenious and useful inventions. In the same year  Kulibin developed the mechanism of an optical telegraph, a signal transmission system and an original code. However, the tsarist government did not use his invention and only later, under the pressure of military and political events, began building an optical telegraph that linked St. Petersburg with Shlisselburg (1824), Kronstadt (1834), Tsarskoe Selo (1835) and Gatchina 1835). The longest in the world (1200 km) line of optical telegraph was opened in 1839 between St. Petersburg and Warsaw


The invention of electricity, telegraph, telephone and radio for 150 years threw the system of optical communication into the backyard of history. But the appearance of lasers has revived interest in optical communication. The works carried out in the 70’s became classics. Almost at the same time, fiber-optic communication was born. And when its triumphal rise was crowned with success, strangely enough, people remembered about atmospheric optical communication or FSO technology. And it is obvious. A person does not like to spend much, does not like to tie himself firmly to one place and to one decision. He needs comfort, mobility and a lot of information.