What is Free-space laser communication?
Free-space laser communication is a wireless communication technology that sends data across the atmosphere using lasers. This technology has several advantages over traditional wireless communication methods, including higher data rates, increased security, and improved resistance to interference. While fibre optic cables function similarly in laser communications systems, the beam is sent over space. Laser communication systems do not require concealed wires or broadcast rights, although the line of sight between the transmitter and receiver is required. Since laser communications systems are low-cost, portable, and don’t need to be studied for radio interference, they can be deployed. This article will discuss the principles of free-space laser communication, its applications, and its potential as a viable alternative to traditional wireless communication technologies.
The basic principle behind free-space laser communication is the use of lasers to transmit information through the atmosphere. A laser beam is a highly focused, collimated beam of light that can send data over long distances. The information is encoded in the laser beam’s intensity, phase, or polarisation and then decoded at the receiver end using a detector and a suitable decoding algorithm.
One of the main advantages of free-space laser communication is its high data rate. The data rate of a free-space laser communication system is typically much higher than that of a traditional wireless communication system, such as a radio frequency (RF) system. This is because the bandwidth of a laser beam is much higher than that of an RF signal, allowing for the transmission of more data in a given amount of time. In addition, the narrow beam width of a laser beam allows for multiple laser beams to transmit data simultaneously, further increasing the overall data rate of the system.
Another advantage of free-space laser communication is its increased security. Because the laser beam is highly focused and collimated, it is less susceptible to interference from external sources. This makes it more difficult for an attacker to intercept or jam the laser beam, making it a more secure method of communication. In addition, the laser beam is highly directional, making it a good choice for communication in situations where confidentiality is a concern.
Free-space laser communication also has improved resistance to interference compared to traditional wireless communication technologies. This is because the laser beam is less affected by atmospheric conditions such as fog, rain, or snow, which can disrupt the transmission of an RF signal. In addition, the laser beam is less likely to be disrupted by other RF signals, making it a good choice for communication in environments with high RF interference.
There are several different applications for free-space laser communication. One of the most common applications is satellite communication, where free-space laser communication is used to transmit data between satellite and ground stations. This technology is beneficial for satellite communication because it allows for high data rates and low latency, which are essential factors in satellite communication.
Free-space laser communication is also used in terrestrial applications, such as transmitting data between buildings or between a building and an aircraft. In these applications, the laser beam is typically transmitted over a short distance, such as a few hundred meters or kilometres. This type of free-space laser communication is often used to send data in situations where it is not possible to use traditional wireless communication technologies, such as in environments with a high level of RF interference or in cases where it is not possible to install a wired communication system.
One of the critical challenges in developing free-space laser communication is the need to maintain the alignment of the laser beam over long distances. If the alignment of the laser beam is disrupted, the laser will also disturb the data transmission. To maintain the alignment of the laser beam, free-space laser communication systems often use beam steering technology, which allows the laser beam to be continuously adjusted to maintain its alignment.
Links commonly use O/E and E/O converters and operate in the 780–1600 nm wavelength range. Light is necessary for FSO, and light-emitting diodes (LEDs) or lasers can focus that light (light amplification by stimulated emission of radiation). The transmission medium is the only difference between optical transmissions using fibre-optic cables and lasers. Since light moves through the air more quickly than it moves through glass, FSO can be considered visual communications moving at the speed of light. Radio relay link line-of-sight (LOS) communication technologies are being replaced by FSO communication.
Despite these challenges, free-space laser communication has the potential to be a viable alternative to traditional wireless.
High data speeds in the Gbit/s levels can be delivered using FSO communications across the atmosphere for distances ranging from a few hundred meters to a few kilometres. The following is a list of FSO links:
- chip-to-chip communication
- indoor infrared (IR) or VLC,
- inter-building communication
- free-space laser communications, including airborne, space-borne, and deep space missions
Three stages make up FSL components:
- The transmitter propagates optical radiation through the atmosphere by Beer-law.
- Lambert’s free space transmission channel contains turbulent eddies such as clouds, rain, smoke, gases, temperature variations, fog, and aerosols.
- The receiver analyses the signal after it has been received.
The typical link length is between 300 m to 5 km, although depending on the speed and availability needed, lengthier links of 8–11 km may be deployed.
Figure 3: 03-1910.pdf (nasa.gov)
- Telecommunication and computer networking
- Point-to-point LOS links
- Temporary network installation for events or another purpose as disaster recovery
- For communications between spacecraft, including elements of satellite constellation
- Security applications
- Enterprise connectivity: FSO lines are a natural choice for connecting local area network segments housed in buildings divided by public streets or other right-of-way property because of how simple it is to install them.
- Last-mile access: Due to the expansion of communication systems following the development of
- metropolitan areas, more than 95% of buildings in today’s cities lack access to fibre optic infrastructure. A possible approach to connecting end users to service providers or other existing networks is FSO technology. Additionally, FSO offers high-speed connections up to Gbps, which is much faster than the alternatives.