What is FSO?
Free space optic (FSO) communication is a line-of-sight technology that uses infrared (IR) light through the atmosphere to provide wireless connectivity between two points.
In comparison to radio frequency (RF) counterparts, the FSO link has a very high optical bandwidth available, allowing much higher data rates on the order of Gigabits per second (Gbps). Since FSO systems use very narrow laser beams, the resulting spatial confinement provides a high reuse factor and an inherent security. Furthermore, their deployment does not require license fees since they operate in the IR optical band which is unregulated worldwide.
How does FSO work?
Similar to fiber optic, FSO links use lasers for data transmission, but instead of enclosing the data stream in a fiber, it is transmitted through the atmosphere.
The transmitter side typically consists of a laser diode, a modulator, an optical amplifier, and beamforming optics. Data bits from the information source are first modulated. The modulated laser beam is then passed through the optical amplifier to boost the optical intensity. The light beam is collected and refocused by means of beam forming optics before being transmitted.
The receiver side consists of optical filters and a lens followed by a photodiode. The optical front-end collects and focuses the received beam onto the photodiode. The photodiode detects changes in the light intensity and recovers the data.
Applications of FSO
FSO systems can bridge multiple buildings in corporate and campus networks supporting ultra-high speeds without the cost of dedicated fiber optic connections.
Backhauling for small cells
Small cells are low power and short range base stations installed on lamp posts, street lights and other street furniture. These allow mobile operators to increase their capacity in urban areas and increase their coverage in white zones. FSO links with a small footprint can be efficiently deployed as a backhaul solution for small cells.
Redundant link and disaster recovery
Natural disasters, terrorist attacks, and emergency situations require flexible and innovative responses. Temporary FSO links can be readily deployed within hours in such disaster situations in which local infrastructure could be damaged or unreliable.
Equipped with effective pointing, acquisition and tracking algorithms, FSO technology can be used in ground-to-air and air-to-air links for airborne vehicles such as aircrafts, unmanned aerial vehicles (UAVs), high altitude platforms (HAPs), balloons etc.
Video surveillance and monitoring
Surveillance cameras are convenient and easy to deploy, but conventional wireless technologies fail to provide high throughput requirements to support them. FSO technology presents a powerful alternative to support high quality video transmission.
In broadcasting of live events such as sports and ceremonies or television reporting from remote areas and war zones, signals from the camera need to be sent to the broadcasting vehicle which is connected to a central office via satellite uplink. The required high-quality transmission between the camera and the vehicle can be provided by a FSO link.
Quantum cryptography systems are typically considered in conjunction with fiber optic infrastructure. FSO links provide a versatile alternative in cases where the fiber optic deployment is costly and/or infeasible.