What are the commonly used optical fiber specifications? What are the types of optical fibers, let's take a look!
Common fiber optic specifications are:
Single mode: 8/125μm, 9/125μm, 10/125μm
Multimode: 50/125μm, (European standard)
62.5/125μm, (US standard)
The optical fibers used in optical fiber communication systems include silica optical fibers, plastic-coated optical fibers, single-mode optical fibers, and multi-mode optical fibers.
Silica Fiber is an optical fiber that uses silicon dioxide (SiO2) as the main raw material and controls the refractive index distribution of the core and cladding according to different doping amounts. Quartz (glass) series optical fibers have the characteristics of low consumption and broadband, and are now widely used in cable TV and communication systems. The advantage of quartz glass optical fiber is low loss. When the light wavelength is 1.0-1.7μm (about 1.4μm), the loss is only 1dB/km, and the lowest at 1.55μm is only 0.2dB/km.
Plastic clad fiber (Plastic Clad Fiber) is a step-type optical fiber that uses high-purity silica glass as the core and plastics such as silica gel with a slightly lower refractive index than silica as the cladding. Compared with silica fiber, it has the characteristics of high core rent and high numerical aperture (NA). Therefore, it is easy to combine with light-emitting diodes and LED light sources, and the loss is also small. Therefore, it is very suitable for local area network (LAN) and short-range communication.
Single-mode fiber refers to the fiber that can only transmit one propagation mode in the working wavelength, usually referred to as single-mode fiber (SMF: Single Mode Fiber). At present, it is the most widely used optical fiber in cable TV and optical communication.
Multimode fiber The fiber in which the optical fiber is multi-mode according to the working wavelength and its propagation possible mode is called a multimode fiber (MMF: MUlti ModeFiber). The fiber core diameter is 50 μm, and since the transmission mode can reach several hundred, the transmission bandwidth is mainly dominated by the mode dispersion compared with SMF.
Optical fiber transmission has many outstanding advantages:
1. Bandwidth: The width of the frequency band represents the size of the transmission capacity. The higher the frequency of the carrier, the larger the bandwidth of the signal that can be transmitted;
2. Low loss: when transmitting 1.31um light, the loss per kilometer is less than 0.35dB; if transmitting 1.55um light, the loss per kilometer is even smaller, up to less than 0.2dB;
3. Light weight: The optical fiber is glass fiber with small specific gravity, which makes it have the characteristics of small diameter and light weight, and it is very convenient to install;
4. Strong anti-interference ability: Because the basic component of optical fiber is quartz, it only transmits light, does not conduct electricity, and is not affected by electromagnetic fields. Strong resistance;
5. High fidelity: Because optical fiber transmission generally does not require relay amplification, it will not introduce new nonlinear distortion due to amplification. As long as the linearity of the laser is good, the TV signal can be transmitted with high fidelity;
6. Reliable working performance: the optical fiber system contains a small number of devices (unlike the cable system that requires dozens of amplifiers), and the reliability is naturally high. In addition, the life of the optical fiber devices is very long, and the trouble-free working time reaches 500,000 ~750,000 hours;
7. The cost continues to decrease: due to the rich source of materials (quartz) for making optical fibers, the cost will be further reduced with the advancement of technology.
As a mainstream way of broadband access, optical fiber has the advantages of large communication capacity, long relay distance, good confidentiality performance, strong adaptability, small size and light weight, wide source of raw materials and low price, etc. Therefore, the role of optical fiber in communication systems The application is more and more extensive.
