The principle of optical fiber communication is: at the transmitting end, the transmitted information (such as voice) must first be converted into an electrical signal, and then modulated to the laser beam emitted by the laser, so that the intensity of the light changes with the amplitude (frequency) of the electrical signal. It is sent out through optical fiber; at the receiving end, the detector converts the optical signal into an electrical signal after receiving it, and then restores the original information after demodulation.
Optical fiber communication is the main transmission method of modern communication networks. It has a history of only ten or twenty years and has experienced three generations: short-wavelength multimode optical fiber, long-wavelength multimode optical fiber, and long-wavelength single-mode optical fiber.
The use of optical fiber communication is a major change in the history of communication. More than 20 countries including the United States, Japan, Britain, and France have announced that they will no longer build cable communication lines and are committed to the development of optical fiber communication. China's optical fiber communication has entered the practical stage.
The key parts of the optical communication network are equipped with optical transmission devices. This device plays many roles.
1. Signal conversion (send signal): Convert electrical signals into optical signals.
2. Signal multiplexing: converge multiple narrow signals into a wide signal.
3. Signal relay: long-distance transmission, relay signal midway.
4. Signal direction: change the transmission direction of the signal.
5. Signal demultiplexing: Decompose the multiplexed signal into the original single signal.
6. Signal conversion (received signal): Convert optical signals into electrical signals.
Optical communication equipment, including optical fiber, G.657 fiber for FTTx, G.656 fiber for broadband long-distance high-speed large-capacity fiber transmission, photonic crystal fiber, rare earth-doped fiber (including ytterbium-doped fiber, erbium-doped fiber, thulium-doped fiber, etc.), Laser energy transmission fiber, and new type of fiber with some special properties, including plastic fiber, polymer fiber, etc.
Optical fiber access equipment, passive optical network (PON), optical line terminal (OLT), optical network unit (ONU), wavelength division multiplexer, etc.
