Optical communication principle and advantages of optical fiber transmission

Introduction: Optical fiber communication consists of a series of optical communication devices. Optical devices are divided into active devices and passive devices.

Principle of optical communication

The principle of optical communication is as follows. At the transmitting end, the transmitted information (such as voice) is first converted into an electrical signal, and then the electrical signal is modulated onto the laser beam emitted by the laser (light source) so that the intensity of the light varies with the amplitude of the electrical signal ( The frequency changes and changes, and the optical signal is transmitted on the optical fiber through the principle of total reflection of light; due to the loss and dispersion of the optical fiber, the optical signal will be attenuated and distorted after being transmitted over a distance, and the attenuation is required at the optical repeater. The signal is amplified to repair the distorted waveform; at the receiving end, the detector receives the optical signal and converts it into an electrical signal, and after demodulation, restores 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 sources of raw materials Potentially low price: The most basic raw material for making quartz fiber is silica, which is sand, and sand is abundant in nature, so its price is lower.

Optical fiber communication is composed of a series of optical communication devices. Optical devices are divided 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 information but different wavelengths into one bundle and transmits them along a single fiber. At the receiving end, the optical signals of different wavelengths are used in some way. Separate communication technology.

● 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).

● An optical switch is an optical path switching device that is an optical device with one or more optional transmission ports that performs physical or logical operations on optical signals in an optical transmission line or integrated optical path.

● The optical circulator is a multi-port optical device with non-reciprocal characteristics. When an optical signal is input from any port, it is output in a numerical order from the next port with a small loss. When inputting a signal from the 1-port, the signal can only be output from the 2-port. Similarly, the signal input from the 2-port can only be from the 3-port. The output, and so on, is called a circulator.

• 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.