Multimode fiber can transmit multiple modes of light. However, the dispersion between the modes is large, which limits the frequency of transmitting digital signals, and will increase with distance. Therefore, the transmission distance of multimode fiber is relatively short, generally only 2 kilometers.
1, the introduction of fiber optics The full name of the optical fiber called optical fiber English name is OPTIC FIBER, also called OPTICALFIBER, is the use of pure quartz (glass) with a special process to pull into the medium thinner than the hair medium, can be in a very short Pass a huge amount of information in time.
Below is a drawing of a high-temperature drawing process using a preform (ie, a high-purity glass rod). The middle shiny part is a melted glass.
This is a preform that is drawn into an optical fiber by melting it at a high temperature on a draw tower. The optical fiber pulled out from under the picture is still very thick. When the drawing speed reaches the normal level, the pulled out optical fiber will become a uniform finished optical fiber. During a fiber-drawing process, a preform will produce a certain amount of sub-standard optical fibers in the front and rear sections. If the process is poorly controlled in the middle, waste fibers or low-grade fibers may also be generated. Some fiber manufacturers will sell these waste fibers or low-grade fibers at a very low price to some fiber optic cable factories that do not attach importance to reputation, and the produced fiber optic cables have large adverse effects such as large attenuation and easy breakage.
2, the characteristics of optical fiber transmission speed, distance, content, and free from electromagnetic interference, not afraid of lightning strikes, it is difficult to eavesdropping on the outside, non-conductive, there is no ground between the equipment in trouble.
3. Types of optical fibers Optical transmission modes in optical fibers can be classified into: single-mode optical fibers and multi-mode optical fibers.
Multi-mode fiber: The central light transmission part has a diameter of 50 μm and an outer diameter of 125 μm (micrometer), which is a European standard. Therefore, the model is called 50/125 (A1a A1 or OM2 conventional model ⁄OM3 10G model). 62.5μm, outside diameter is 125μm too, it is the American standard, so the model is called 62.5/125 (A1b or OM1).
Multimode fiber can transmit multiple modes of light. However, the dispersion between the modes is large, which limits the frequency of transmitting digital signals, and will increase with distance. Therefore, the transmission distance of multimode fiber is relatively short, generally only 2 kilometers.
MMF (Multimode Fiber) Description:
OM1 fiber or multimode fiber (62.5⁄125), giga transmission distance only 275 meters OM2⁄O3 fiber (G.651 fiber or multimode fiber (50⁄125)) OM2 giga transmission distance of 550 meters OM3 fiber The central transmission section is also 50 micron, which is 10 Gigabit fiber. The subdivision models are:
The OM3-150 reaches 10G within a distance of 150 meters.
The OM3-300 reaches 10 Giga within a distance of 300 meters.
The OM3-550 reaches 10G within a distance of 550 meters.
Transmission band: Multimode generally uses laser transmission signals with a wavelength of 850nm (nanometers) or 1300nm.
Single-mode fiber: The center glass core is fine (the core diameter is generally 9μm in some countries is also called 8.3μm or 10μm, the outer diameter is 125μm), so the model is called 9/125.
Only one mode of light can be transmitted. Due to the small dispersion between modules, the transmission distance is several hundred kilometers and it is suitable for remote communication. Carriers usually use single-mode fiber for long-distance transmission.
Single-mode fiber additional description:
G652B, also denoted by B1.1 as a commonly used single-mode fiber G652D, is also represented by B1.3 (low water peak fiber). Carrier backbone network projects use this type of fiber.
G652D is 10 yuan more than a kilometer than G652B fiber.
Transmission band: Single-mode laser transmission signals with a wavelength of 1310 nm (nanometers) or 1550 nm are generally used. High-purity quartz glass is used as the optical fiber. The attenuation at the wavelength of 1550 nm is minimized (close to the theoretical limit of 0.2 dB/Km).
Zero Water Peak Fiber is a single mode fiber from Corning Incorporated.
Some fiber-to-the-home projects use G657 fiber (bending resistant fiber) which is 70 yuan more than a kilometer than G652B. This kind of fiber bend radius is very small, suitable for small turning angles.
4. Applying an Optical Fiber Optical fiber drawn from a drawing tower generally needs to be coated with a UV-cured acrylic resin coating layer having a diameter of 0.25 mm on the skin. This can protect the fiber.
5, other optical fiber industry, medical and low-speed network: 100/140μm, 200/230μm
Plastic: 98/1000μm, for automotive control.
Indoor cable
Indoor fiber optic cable: Indoor fiber optic cable is mainly composed of tight fiber optics, aramid and PVC outer sheath. According to the actual application needs, single mode or multimode optical fiber can be selected for production. The color of the outer sheath of the single mode indoor cable is yellow, the outer jacket color of the multimode indoor cable is orange, and the outer jacket color of some indoor cables is gray.
Tightly sleeved fiber: After the surface of the bare fiber is further squeezed with a layer of plastic, the fiber in the tight fiber sleeve is tightly bound by the sleeve and can not be loosened in it. It is an integral structure with the plastic sleeve. The average user needs an outer diameter of 0.9 mm after the optical fiber is sheathed, and a small amount needs to use 0.6 mm. The tightly packed material is generally PVC, LSZH (low-smoke halogen-free) or nylon, and the like.
Aramid: It is called “Poly(p-phenylene terephthalamide)” and in English is Aramidfiber (DuPont's trade name is Kevlar). It is a new type of high-tech synthetic fiber with ultra-high strength and high temperature resistance. , acid and alkali resistance, light weight and other excellent performance, its strength is 5 to 6 times the steel wire, in the temperature of 560 degrees, does not decompose, do not melt. It has good insulation and anti-aging properties. The discovery of Kevlar is considered to be a very important historical process in the material world. In today's body armor, military helmets are generally made of aramid. The purpose of aramid fibers in fiber optic cable is tensile and flame retardant.
High-strength yarn: also known as domestic aramid, polyester yarn. Due to the high price of aramid, it needs to be imported. Now many manufacturers use high-strength yarns as reinforcements for indoor optical cables. The advantage is that the tensile strength is close to aramid, and the price is less than one tenth of that of aramid. The disadvantage is that it is not resistant to high temperatures and is not flame retardant.
Indoor cable sheath material: When it comes to indoor fiber optic cable, we will meet many customers in the future to specify the sheath material.
PVC sheathing material: This kind of sheathing is the most commonly used, the advantage is that the raw material is easy to purchase, the cost is low, the appearance is beautiful, there is a little flame retardant. The disadvantage is that it is not resistant to ultraviolet rays and can not rain, so the fiber optic cable made of this material can not be directly under the sun, nor can it be exposed to water for a long time, otherwise it will be easy to age. Generally only used as indoor cable sheath.
LSZH (low-smoke and halogen-free) jacket material: According to statistics, 90% of the deaths caused by fires are due to the suffocation and coma caused by the strong and even toxic smoke generated during the fire, which makes people lose their chance of escape. Therefore, in some important indoor environments, once the fire is used, the fiber optic cable will be fire-retardant and will not generate large amounts of smoke and toxic gases. This material is much more expensive than PVC, the density is much larger than PVC, and the skin looks a bit like rubber.
Single core cable: This is a cross-section of a single-core cable. We look at the cross-section. The middle black represents the optical fiber, the white part is the tight cladding, and the outer periphery is added with aramid or high-strength yarn to strengthen the pulling force of the optical cable. Or low-smoke halogen-free jacket. On the right is a physical map.
This kind of cable is generally used for jumper plants to make fiber jumpers. It is not specified to be low-smoke and halogen-free (LSZH), and generally PV is used as a sheath.
There is usually a tight packing material that is low-smoke and halogen-free and is PVC. The outer sheath is low-smoke and halogen-free. Rarely tight packing is also LSZH. General outer diameter 2.8-3.0MM or 1.8-2.0MM
Twin jump cable: The cable structure of this model is the same as single-core cable, but there are many optical fiber jumpers that need to be double-cored together. The process requirements ensure that when tearing, one of the core skins will not be torn and the outer diameter of the two cores cannot deviate too much.
The material is also PVC or low-smoke halogen-free.
Outer diameter: General outer diameter 2.8-3.0MMX2 or 1.8-2.0MMX2
The single mode is generally yellow, and the multi mode is generally orange.
Multi-core indoor cable:
The picture above is a physical map of an indoor cable. Such a multi-core indoor cable is generally used for wiring in a building.
Let's look at the cross-section below. There are multiple 0.9 tightly packed optical fibers inside, plus an aramid (or high-strength yarn) for reinforcement. The outer skin is PVC, and there is also a designated LSZH. of.
Because aramid is yellow, when we do the cross-sectional view, we use the outer skin as a common multi-mode orange. When we see the outer shell of the physical map is light yellow, we should judge it as a single mode indoor cable.
We did not find that the tightly packed optical fiber in our indoor optical cable is colorful, so that it is convenient for a cable to find the corresponding optical fiber when the two terminals are constructed. 12 colors are ordered optic fiber: blue, orange, green, brown, gray, white, red, black, yellow, purple, pink, green <br> <br>
indoor drop cable: When some indoor applications require many cores of fiber, or some fibers need to be split into different units when wiring, we must use a branch cable.
Let's look at the cross-sectional view above. The structure is to twist four indoor 4-core cable optical cables and use a non-metallic reinforcement core. After wrapping with a polyester tape, the outer sheath is squeezed.
