Optical communication principle
The communication principle is as follows.At the sending end, the transmitted information (such as voice) should be first converted into electrical signals, and then the electrical signals are modulated to the laser beam emitted by the laser (light source), so that the intensity of light varies with the amplitude (frequency) of electrical signals and through the principle of total reflection of light, the optical signal is transmitted in the optical fiber.Due to the loss and dispersion of the optical fiber, the optical signal will be attenuated and distorted after being transmitted over a distance. The attenuated signal is amplified at the optical repeater to repair the distorted waveform.At the receiving end, the detector receives the optical signal and converts it into an electrical signal, which is demodulated to restore the original information.
Optical fiber transmission advantages:
● Large communication capacity, long communication distance, high sensitivity, and no interference from noise
● Small size, light weight, long life, good quality and low price
● Insulation, high pressure resistance, high temperature, corrosion, strong adaptability
● High confidentiality
●Rich raw materials and low potential: The most basic raw material for making quartz fiber is silica, which is sand, and sand is abun.
Optical fiber communication is composed of a series of optical communication devices.dant in nature, so its price is lower.Optical devices are classified into active devices and passive devices.An optical active device is a key device in an optical communication system for converting an electrical signal into an optical signal or converting an optical signal into an electrical signal,and is the heart of an optical transmission system.Optical passive components are devices that require a certain amount of energy in optical communication systems but do not have photoelectric or electro-optic conversion. They are key nodes of optical transmission systems, including fiber optic connectors, wavelength division multiplexers, optical splitters, and optical switches. , optical circulators and optical isolators.
● Fiber optic patch cords (also known as fiber optic connectors) refer to the connector plugs on both ends of the cable for optical path active connection.The plug at one end is called pigtail.
● Wavelength division multiplexer (WDM) combines a series of optical signals with different wavelengths and transmits them along a single optical fiber. A communication technique in which optical signals of different wavelengths are separated by some means at the receiving end.
● Optical splitter (also known as splitter) is a fiber-optic tandem device with multiple inputs and multiple outputs.According to the principle of splitting, the optical splitter can be divided into two types: a molten taper type and a planar waveguide type (PLC type).
● Optical switch is an optical switching device, which is an optical device with one or more optional transmission ports. Its function is to physically switch or logically operate optical signals in optical transmission lines or integrated optical paths.
●The optical circulator is a multi-port optical device with non-reciprocal characteristics.
● When the optical signal is input from any port, it is output from the next port with a small loss in digital order. If the signal is input from port 1, it can only be output from port 2. Similarly, if the signal is input from port 2, it can only be output from port 3.
● An optical isolator is a passive optical device that allows only unidirectional light to pass through and prevents it from passing in the opposite direction. Its working principle is based on the non-reciprocity of Faraday rotation.