The light-emitting diode LED or injection laser diode ILD emits the light signal, which propagates along the optical medium, and at the other end, the PIN or APD photodiode is used as a detector to receive the signal. The modulation of the optical carrier is amplitude shift keying, also known as brightness modulation. A typical approach is to represent two binary numbers with the appearance and disappearance of light at a given frequency. Both the light-emitting diode LED and the injection laser diode ILD signal can be modulated in this way, and the PIN and ILD detectors respond directly to the luminance modulation.
Power amplification: The optical amplifier is placed before the optical transmitting end to increase the optical power of the incoming fiber. The optical power of the entire line system is improved. Online relay amplification: when the building group is large or the distance between buildings is long, it can play the role of relay amplification and improve the optical power.
Pre-amplification: Amplify the micro-signal after the photodetector at the receiving end to improve the receiving capacity.
Fiber optic communications technology applications have grown rapidly, and since the first commercial installation of fiber optic systems in 1977, telephone companies have used fiber optic links to replace older copper systems. Many telephone companies today use fiber optic throughout their systems for the backbone structure and for long distance connections between city telephone systems. Fiber-optic transmission providers have begun trials with fiber-copper hybrid lines. This hybrid line allows for the integration of fiber optic and coaxial cables between fields. These locations, called nodes, provide optical receivers that convert light pulses into electrical signals, which are then routed through coaxial cables to individual homes. . It is evident that fiber optic cables are steadily replacing copper wires as a suitable means of transmitting communication signals, which span great distances between local telephone systems and provide backbone connections for many network systems.
Optical fiber is a technology that uses glass as a waveguide to transmit information in the form of light from one end to the other. Compared with the transmission medium developed in the early days, today's low-loss glass fiber is almost unlimited in bandwidth and has unique advantages. The point-to-point fiber transmission system consists of three basic parts: the optical transmitter that generates the optical signal, and the optical signal that carries the optical signal. the optical cable and the optical receiver that receives the optical signal.