Fluoride Fiber is an optical fiber made of fluoride glass. The representative of fluoride optical fiber is ZBLAN optical fiber, which is composed of zirconium fluoride (ZrF2), barium fluoride (BaF2), lanthanum fluoride (LaF3), aluminum fluoride (AlF3), sodium fluoride (NaF) and other fluorides in a certain proportion. Mainly between 2-10 μ The m wavelength enables optical transmission. Due to the possibility of ultra-low loss optical fibers in ZBLAN fiber, feasibility development for long-distance communication optical fibers is underway, such as its theoretical minimum loss, which is within 3 μ At m wavelength, it can reach 10 ^ -2 to 10 ^ -3 dB/km, while quartz fiber can reach 1.55 dB/km μ At m, it is between 0.15 and 0.16dB/Km. Due to the difficulty in reducing scattering loss, ZBLAN optical fibers can only be used between 2.4 and 2.7 μ The temperature sensor and thermal image transmission of m have not yet been widely applied. Recently, in order to utilize ZBLAN for long-distance transmission, 1.3 is being developed μ Praseodymium doped fiber amplifier (PDFA) with m.
Plastic coated optical fiber
Plastic Clad Fiber is a step type fiber that uses high-purity quartz glass as the core and plastic with a refractive index slightly lower than quartz, such as silicone, as the cladding. Compared with quartz optical fibers, it has the characteristics of thick core and high numerical aperture (NA). Therefore, it is easy to combine with LED light sources, and the loss is also small. So, it is very suitable for local area networks (LANs) and close range communication.
Plastic optical fiber
This is an optical fiber that uses plastic (polymer) as the core and cladding. Early products were mainly used for decoration, lighting, and optical communication in close range optical keyways. The main raw materials are organic glass (PMMA), polystyrene (PS), and polycarbonate (PC). The loss is constrained by the inherent C-H bonding structure of plastics, typically reaching several tens of dB per kilometer. In order to reduce losses, we are developing and applying the Fluorosol series of plastics. Due to the core diameter of plastic optical fiber being 1000 μ m. It is 100 times larger than single mode quartz fiber, with simple connection and easy bending construction. In recent years, coupled with the progress of broadband, the development of multimode plastic optical fibers with gradient refractive index (GI) has received social attention. Recently, it has been rapidly applied in the internal LAN of automobiles, and may also be applied in home LANs in the future.
Single mode fiber
Single mode fiber refers to a fiber that can only transmit one propagation mode at its working wavelength, commonly referred to as a single mode fiber (SMF). In cable television and optical communication, it is the most widely used fiber optic. Due to the fine core of the optical fiber (approximately 10 μ m) Moreover, the refractive index exhibits a step like distribution. When the normalized frequency V parameter is less than 2.4, theoretically, only single mode transmission can be formed. In addition, SMF does not have multimode dispersion, and not only does it have a wider transmission frequency band with more mode fibers, but also the material dispersion and structural dispersion of SMF are combined to cancel out, resulting in a zero dispersion characteristic in its synthesis, which widens the transmission frequency band even more. There are many types of SMF due to differences in dopants and manufacturing methods. A concave clad fiber (DePr essed Clad Fiber) has a dual structure formed by its cladding. The cladding adjacent to the fiber core has a lower refractive index than the outer inverted cladding.
Multimode fiber
A multimode fiber refers to a fiber that has multiple modes of propagation according to its working wavelength, known as a multimode fiber (MMF). Fiber core diameter is 50 μ m. Due to the hundreds of transmission modes, the transmission bandwidth is mainly dominated by mode dispersion compared to SMF. In history, it has been used for short distance transmission in cable television and communication systems. Since the emergence of SMF fiber optic, it seems to have formed a historical product. However, in fact, due to the larger core diameter of MMF compared to SMF and its easy integration with light sources such as LEDs, MMF has more advantages in many LANs. Therefore, MMF is still receiving renewed attention in the field of short distance communication. There are two types of MMF classification based on refractive index distribution: gradient (GI) type and step (SI) type. The refractive index of the GI type is highest at the center of the fiber core and gradually decreases along the cladding. Due to the reflection and progression of SI type light waves in optical fibers, the time difference between different light paths is generated, resulting in distortion of the emitted light waves and significant color excitation. The result is a narrower transmission bandwidth and fewer applications of SI type MMF.
