In addition to fast transmission, optical fiber transmission also has high sensitivity and is not disturbed by electromagnetic noise; small size, light weight, long life; insulation, high voltage resistance, high temperature resistance, corrosion resistance, and can be suitable for harsh environments; large bandwidth, basically no transmission, long transmission distance, and the confidentiality is high. Although the network integrated wiring basically uses the traditional twisted pair network cable, since the optical fiber has so many advantages, the popularization of the optical fiber can be expected in the future; the network cable transmits the electrical signal, and the optical fiber transmits the optical signal. Although electrical signals and optical signals are incomprehensible, in contrast, the transmission of optical signals is even more elusive. How does optical fiber transmit optical signals?
Optical fiber is the carrier of optical signal transmission, where does the optical signal come from? That's right, the electrical signal is converted, and the device that can realize the electro-optical conversion is called a fiber optic transmitter. In fiber optic systems, the transmitter is the signal origin of the fiber optic line. Before the transmitter receives the signal, it needs to be encoded first. The encoded electronic pulse signal comes from the copper wire cable, and then processed by the transmitter and converted into an equivalent encoded optical pulse signal. The optical pulse signal is generated by a light-emitting diode or an injection laser, and at the same time, the optical pulse signal is concentrated into the optical fiber medium through the lens, so that the optical pulse is transmitted in the optical fiber medium along the line.
The transmission of optical signals in optical fiber transmission is accomplished by the principle of total reflection of light. When the incident angle exceeds the critical angle, through the reflection of light, the light pulse can easily move along the optical fiber line, and the light cannot overflow from the glass, and vice versa. will return to the input.
The bare fiber is generally divided into three layers: the first layer: the core - the high refractive index glass core in the center; the second layer: the cladding - the low refractive index silica glass cladding in the middle; the third layer: the coating Layer - the outermost layer is a protective and strengthening coating; light is reflected through the cladding, and the optical signal is transmitted in the core. This principle is used to make a multi-core cable of the optical fiber, so that the signal is transmitted along the optical line in the form of optical pulses.
The optical signal is transmitted to the other end of the system through the optical fiber. At this time, the optical signal needs to be converted into an electrical signal. Only in this way can it be used on various network devices. The device that can achieve this function is an optical receiver. The main component of the optical receiver is the photodetector. The most important part of the photodetector is the photodiode, which requires high sensitivity. The photodiode uses the photoelectric effect of the semiconductor to restore the optical signal to an electrical signal, and then amplifies the electrical signal. After other processing, a qualified electrical signal is output, and the electrical signal is basically restored without attenuation.
All in all, optical fiber transmission is a technology that transmits in the form of optical signals between the sender (optical transmitter) and the receiver (optical receiver) and an efficient information transmission method that converts electrical signals to optical signals, and then restores from optical signals to electrical signals.