 fiber optics cable and free space optics (FSO). Like fiber optics cable, FSO uses lasers to transmit data, but instead of enclosing the data stream in a glass fiber, it is transmitted through the air. Hence, “Wireless Fiber” has become another term for FSO systems. FSO enables optical transmission speeds which are not possible using existing fixed wireless radio frequency (RF) technology and obviates the need to buy expensive spectrum.

 the photodiode detector produces an output electrical current which is a measure of the optical power impinging on the device. The photodiode detector is often termed a square law device since the device can also be modeled as squaring the amplitude of the incoming electromagnetic signal and integrating over time to find the intensity.

Free Space Optics Challenges FSO systems are not worry-free and the technology has its limitations that affect link performance. At a given desired data rate, FSO systems performance can be characterized by four main parameters:  Total transmitter power  Transmitting beamwidth  Receiver sensitivity  line of sight

 FSO transmissions are inherently hard to intercept. FSO systems use a very narrow beam spread (1-11 milli-radian) that cannot be easily intercepted

 FSO indicates a very low incremental cost with high bandwidth performance. In comparison to fiber cable which can cost the U.S.