Fiber optic basic knowledge of the first part of the theory of fiber optics and fiber optic structure, light and its properties: 1, light is an electromagnetic wave Visible light part of the wavelength range is: 390 ~ 760nm (millimeters).
Greater than 760nm part of the infrared light, less than 390nm part of the ultraviolet light. Fiber optic applications are: 850nm, 1300nm, 1310nm, 1550nm four.
2, light refraction, reflection and total reflection. Because the propagation speed of light in different substances is different, so the light from a substance to another substance, in the two substances at the interface will produce refraction and reflection.
Moreover, the angle of the refracted light changes with the angle of the incident light. When the angle of the incident light reaches or exceeds a certain angle, the refracted light will disappear and all the incident light will be reflected back, which is the total reflection of light.
Different substances have different refraction angles for the same wavelength of light (i.e., different substances have different optical refractive indexes), and the same substances have different refraction angles for different wavelengths of light. Fiber optic communication is based on the above principles.
Second, the structure and types of optical fiber: 1, fiber structure: optical fiber bare fiber is generally divided into three layers: the center of the high refractive index glass core (core diameter is generally 50 or 62.5 μm), the middle of the low refractive index silica glass cladding (diameter of 125 μm), the most outwardly reinforcing the use of resin coatings. 2, the value of the aperture: light incident on the end face of the optical fiber can not be all the optical fiber is transmitted, but only in a certain angle range of the incident light is transmitted. A certain angle range of incident light can be.
This angle is called the numerical aperture of the fiber. A larger numerical aperture of the fiber is advantageous for the alignment of the fiber.
The numerical aperture of optical fibers produced by different manufacturers is different (AT&TCORNING).3. Types of optical fibers: A. According to the mode of transmission of light in optical fibers can be divided into: single-touch optical fibers and multimode optical fibers.
Multi-mode fiber: the center glass core is thicker (50 or 62.5 μm), can transmit a variety of modes of light. However, its intermodal dispersion is larger, which limits the frequency of transmission of digital signals, and with the increase in distance will be more serious.
For example, a 600MB/KM fiber has a bandwidth of only 300MB at 2KM. Therefore, multimode fiber transmission distance is relatively close, usually only a few kilometers.
Single-mode fiber: the center of the glass core is thin (core diameter is generally 9 or 10 μm), can only transmit a mode of light. Therefore, its intermode dispersion is very small, suitable for long-distance communication, but its chromatic dispersion plays a major role, so that the single-mode fiber on the spectral width of the light source and the stability of the high requirements, that is, the spectral width should be narrow, the stability should be good.
B. According to the best transmission frequency window: conventional single-mode fiber and dispersion-shifted single-mode fiber. Conventional: fiber optic manufacturers will fiber optimal transmission frequency in a single wavelength of light, such as 1300nm.
Dispersion-shifted: fiber optic manufacturers will fiber optimal transmission frequency in two wavelengths of light, such as: 1300nm and 1550nm. C. According to the distribution of the refractive index: mutant and gradual change type of fiber.
Mutation type: the refractive index of the fiber center core to the glass cladding is mutated. Its cost is low and intermodal dispersion is high.
Suitable for short-haul, low-speed communication, such as: industrial control. But single-mode fiber due to the small intermodal dispersion, so single-mode fiber are used mutant.
Gradient fiber: the refractive index of the fiber center core to the glass cladding is gradually becoming smaller, so that the high-mode light propagation in the form of sinusoidal, which reduces the intermodal dispersion, improves the fiber bandwidth, increases the transmission distance, but the cost is higher, the multimode optical fiber is now more of a gradient fiber.4, commonly used optical fiber specifications: single-mode: 8/125 μm, 9/125 μm, 10/125 μm Multimode: 50/125μm, the European standard 62.5/125μm, the U.S. standard Industrial, medical and low-speed network: 100/140μm, 200/230μm Plastic: 98/1000μm, used for automotive control Third, optical fiber manufacturing and attenuation: 1, fiber optic manufacturing: fiber optic manufacturing methods now include: CVD (Chemical Vapor Deposition) method in the tube, the rod CVD method. PCVD (plasma chemical vapor deposition) method and VAD (axial vapor deposition) method.
2. Optical fiber attenuation: the main factors causing optical fiber attenuation are: intrinsic, bending, extrusion, impurities, uneven and docking. Intrinsic: is the inherent loss of the fiber, including: Rayleigh scattering, intrinsic absorption.
Bending: When the fiber is bent, part of the light inside the fiber will be lost due to scattering, resulting in loss. Squeeze: The fiber is squeezed to produce a small bend in the loss caused by.
Impurities: Impurities in the fiber absorb and scatter the light propagating in the fiber, resulting in loss. Uneven: the loss caused by the uneven refractive index of the fiber material.
Splicing: the loss generated when the fiber is docked, such as: different axes (single-mode fiber coaxiality requirements of less than 0.8 μm), the end face is not perpendicular to the axis of the end face is not flat, docking diameter does not match the fusion splicing quality is poor. Fourth, the advantages of optical fiber: 1, the optical fiber pass band is very wide. Theory up to 3 billion megahertz.
2, no relay section is long. Dozens to more than 100 kilometers, copper wire only a few hundred meters. 3, not affected by electromagnetic fields and electromagnetic radiation.
4, . Light weight and small size. For example: through 21,000 calls to the 900 pairs of twisted-pair cable, its diameter is 3 inches, weighing 8 tons / KM.
And the amount of communication for its ten times the diameter of the fiber-optic cable is 0.5 inches, weighing 450P / KM. 5, fiber-optic communication is not electrified, the use of safe for use in flammable, violent places.
6, the use of a wide range of ambient temperature. 7, chemical corrosion, long service life.
The second part of the fiber optic cable I. Manufacturing of fiber optic cables: The manufacturing process of fiber optic cables is generally divided into the following processes: 1, fiber optic screening: select the transmission characteristics of excellent and tension-qualified optical fiber. 2. 2, . Dyeing of optical fibers: the application of standard full chromatography to identify the requirements of high temperature without fading and migration.
3.. Secondary extrusion: the choice of high modulus of elasticity, low coefficient of linear expansion of plastic extrusion into a certain size of the tube, the optical fiber into and filled with moisture-proof and waterproof gel, and finally stored for a few days (not less than two days). 4, optical cable stranding: several extruded fiber and strengthen the unit stranded together.
5, extruded fiber optic cable sheath: in the stranded fiber optic cable plus a layer of sheath. Second, the types of fiber optic cable: 1, according to the laying method: self-supporting aerial cable, pipe cable, armored buried cable and submarine cable.
2. According to the structure of the fiber optic cable: bundled fiber optic cable, stranded fiber optic cable, tightly embraced fiber optic cable, banded fiber optic cable, non-metallic fiber optic cable and can be branching fiber optic cable. 3.. According to the use of: long-distance communication cable, short-distance outdoor cable, hybrid cable and building with fiber optic cable.
Third, the construction of fiber optic cables: Over the years, do the construction of fiber optic cables so that we have a set of mature methods and experience. (A) fiber optic cable.
2. Introduction to fiber optic interfaces
Fiber optic fiber from the internal can conduct light waves of different, divided into single-mode (conduct long wavelengths of laser) and multi-mode (conduct short wavelengths of laser) two kinds. Single-mode fiber optic cable connection distance up to 10 kilometers, multi-mode fiber optic cable connection distance is much shorter, is 300 meters or 500 meters (mainly depends on the different lasers, short-wavelength laser light source is generally two kinds of, one is 62.5, one is 50).
Fiber optic cable from the connector part of the different, divided into SC interface and LC interface. SC interface for 1GB interface, (SC = *** art card) LC interface for 2GB interface, (LC = Lucent Connector).
Judging optical interface single and multi-mode
1. By labeling the center wavelength. The center wavelength of 850nm is multi-mode, 1310nm or 1550nm is single mode.
2. Activate the transmitter side of the optical port, and quickly check whether the transmitter side of the red light is emitted, if so, it is a multimode port, otherwise it is a single-mode port.
Classification of fiber
Single-mode fiber and multimode fiber. The core diameter of a single-mode fiber is smaller than that of a multimode fiber.
There are two types of multi-mode fibers: 62.5 μm and 50 μm.
There are three types of single-mode fibers: 8 μm, 9 μm, and 10 μm.
Under the same conditions, the smaller the fiber diameter the smaller the attenuation, and the longer the distance can be transmitted. The transmit power of multimode port is smaller than that of single-mode port, which is directly related to the model of GBIC or SFP, generally between -9.5dBm and -4dBm; the range of single-mode optical port is generally around 0dBm, and some ultra-long-haul interfaces will be as high as +5dBm.
Received power range
The received power of multimode port is generally between -20dBm and 0dBm; the received power of single-mode is between -23 dBm to 0 dBm.
The maximum receivable power is called the overload optical power, and the minimum receivable power is called the receive sensitivity.
Engineering requirements for normal operation of the received optical power is less than the overload optical power of 3-5 dBm, greater than the receiving sensitivity of 3-5 dBm. In general, regardless of the single-mode interface or multi-mode interface, the actual received power in the -5 to -15 dBm between the more reasonable range of work. Generally support hot-swap
GBIC Giga Bitrate Interface Converter, the use of fiber optic interfaces are mostly SC or ST type
SFP small package GBIC, the use of optical fiber for LC type. Singlemode: SM, wavelength 1310 Singlemode Long-Haul LH Wavelength 1310,1550
Multimode: MM Wavelength 850,1300
SX/LH means that it can be used with either multimode or singlemode fibers, and the part in front of the "/" denotes the connector type of pigtail
"SC" is the connector type of the pigtail
SFP is a small package GBIC, which uses LC type of fiber. "SC" connector is a standard square connector, using engineering plastics, with high temperature resistance, not easy to oxidize the advantages. SC connectors are generally used for optical interfaces on the transmission side
"LC" connectors are similar in shape to SC connectors, but smaller than SC connectors. "FC" connector is a metal connector, generally used in the ODF side, the metal connector can be plugged and unplugged more often than plastic. In the labeling of pigtail connectors, we often see "FC/PC", "SC/PC" and so on. FC round type with threads (most used in patch panels) SC small square head, directly connected to the device SFP module
ST snap-on round type
PC microspherical grinding and polishing
APC at an angle of 8 degrees and microspherical grinding and polishing
SC snap-on square type (most used in routers and switches)
MT-RJ square type, the first one is a dual-fiber transceiver, the first one is a dual-fiber transceiver, the first one is a dual-fiber transceiver, the second one is a dual-fiber transceiver, the second one is a dual-fiber transceiver, the third one is a dual-fiber transceiver. A head of dual-fiber transceiver integration (Huawei 8850 on the useful)
3. broadband installation science and technology knowledge, broadband is divided into several types
1, ADSL: through the copper twisted-pair cable (that is, ordinary telephone lines) to provide broadband data transmission, that is, the spread of electrical signals;
2, the speed of light city: a. Fiber optic access to the building FTTB (PON + LAN\PON +) b. Fiber optic access to the building FTTB (PON + AD) c. Fiber optic access to the building PON + LAN\PON +) d. Fiber optic access to the building FTTB (PON + AD) AD) b, fiber to the home FTTH (so that the broadband speed than the traditional ADSL has a substantial increase)
3, FTTX + LAN: the realization of Gigabit fiber to the community (building) central switch, the central switch and the building switch connected to the 100 megabits of fiber or Category 5 network cable, the building using integrated cabling (i.e., the user's common network cable into the home)
4, fiber optic leased line: the use of Fiber optic as an information transmission medium, to provide a fixed IP address, upstream and downstream network speed symmetrical high-speed Internet access services.
4. Fiber optic access network knowledge of what
From the perspective of the entire telecommunications network, the entire network can be divided into a public network and the user premises network (CPN) two major blocks, of which the CPN is owned by the user, and therefore, the usual meaning of the telecommunications network refers to the public telecommunications network part.
The public telecom network can be divided into long-distance network, trunk network and fiber optic access network 3 parts. The long-haul network and the trunk network are combined as the core network.
Relative to the core network, fiber optic access network between the local switch and the user, mainly to complete the task of making the user access to the core network, the access network by the service node interface (SNI) and the user network interface (UNI) between a series of transmission equipment. In recent years, the Internet as a representative of the new technological revolution is profoundly changing the traditional concept of telecommunications and architecture, with the gradual opening of the market of fiber optic access network in various countries, the relaxation of telecommunications regulatory policy, competition is increasingly intensified and expanded, the rapid emergence of new business needs, wired technology (including fiber optic technology) and the development of wireless technology, fiber-optic access network has begun to become the focus of people's attention.
Driven by the huge market potential, a wide variety of fiber optic access network technologies have been generated. Fiber optic communication has the advantages of large communication capacity, high quality, stable performance, anti-electromagnetic interference, and strong confidentiality.
In trunk communications, optical fiber plays an important role, and in fiber optic access networks, fiber optic access networks will also become the focus of development. Fiber optic access network is a long-term solution for the development of broadband access.
First, the basic composition of fiber-optic access network fiber-optic access network (OAN), refers to the use of optical fiber as the main transmission medium, to achieve fiber-optic access network information transmission function. Through the optical line terminal (OLT) connected to the business node, through the optical network unit (ONU) connected to the user.
Fiber optic access network consists of a remote device - optical network unit and a local device - optical line terminal, which are connected through transmission equipment. The main components of the system are the OLTs and the remote ONUs.
They accomplish the conversion of the relevant signaling protocols from the service node interface (SNI) to the user network interface (UNI) throughout the access network. Access equipment itself also has the ability to network, can form a variety of forms of network topology.
At the same time, the access device also has a local maintenance and remote centralized monitoring functions, through transparent optical transmission to form a maintenance management network, and through the corresponding network management protocol into the network management center unified management. The role of the OLT is to provide an interface between the access network and the local switch, and communicate with the user side of the optical network unit through optical transmission.
It completely isolates the switching function of the switch from the subscriber's fiber optic access network. The optical line terminal provides maintenance and monitoring of itself and the subscriber end, and it can be placed directly with the local switch at the switching office end or set up at the remote end.
The role of the ONU is to provide a user-side interface to the access network. It can access a variety of user terminals, and at the same time, it has the optical and electrical conversion function as well as the corresponding maintenance and monitoring functions.
The main function of the ONU is to terminate the fiber from the OLT, process the optical signal and provide a service interface for multiple small businesses, utility users and residential users.
The network side of the ONU is an optical interface, while its user side is an electrical interface.
Therefore, the ONU has optical/electrical and electrical/optical conversion capabilities. It also has digital/analog and analog/digital conversion for voice.
The ONU is usually placed close to the subscriber and has great flexibility in its location. Optical access network (OAN) is divided into two categories from the system distribution: active optical network (AON, ActiveOpticalwork) and passive optical network (PON, PassiveOpticaOpticalwork).
Second, active optical access network active optical network can be divided into SDH-based AON and PDH-based AON. active optical network of the local equipment (CE) and remote equipment (RE) through the active optical transmission equipment connected to the transmission technology is the backbone network has been widely used in the SDH and PDH technology, but the SDH technology is the main focus of this paper mainly discusses the SDH (synchronous optical network) system. ) system.
SDH-based active optical network SDH concept was initially proposed in 1985 by the Bell Communications Research Institute, called synchronous optical network (SynchronousOpticalwork, SO). It is composed of a set of hierarchical standard transmission structure, suitable for a variety of adapted to deal with the net load (i.e., the network node interface bit stream can be used for telecommunications services in the part of the transmission on physical media such as optical fiber, microwave, satellite, etc.).
The standard became the new standard for the U.S. Digital System in 1986. International Telecommunication Union Standards Department (ITU-T) predecessor of the International Telegraph and Telephone Consultative Committee (CCITT) in 1988 to accept the concept of SO, and with the American Standards Institute (ANSI) agreement to modify the SO renamed synchronous digital series (SynchronousDigitalHierarchy, SDH), so that it is simultaneously adapted to the telecommunications business, the concept of SO, and the American Standards Institute (ANSI) agreement, the SO modified renamed Synchronous Digital Hierarchy (SDH), so that it is simultaneously adapted to the telecommunications business. ), making it simultaneously adapted to fiber optic, microwave, satellite transmission of the universal technology system.
SDH network is the original PDH (PlesiochronousDigitalHierarchy quasi-synchronous digital series) network of a revolution. PDH is an asynchronous rewire, in any network node fiber optic access network connected to a low-speed feeder signals have to be rewired in the node, the code conversion, code speed adjustment, timing, scrambling, de-scrambling code, etc., and the process. PDH only provides for the electrical interface, the line system and optical interface does not have uniform provisions, can not realize the establishment of a global information network.
With the introduction of SDH technology, the transmission system not only has the function of providing the physical process of signal propagation, but also provides the function of signal processing, monitoring, and other processes.SDH, through a variety of containers C and virtual containers VC, and the definition of cascading complex frame structure, so that it can support a variety of circuit layer services, such as asynchronous digital series of various rates, DQDB, FDDI, ATM, etc., and the future may appear a variety of new services. and a variety of new services that may emerge in the future.
The large number of spare channels in the segment overhead enhances the scalability of the SDH network. Through software control to make the original PDH in the manual changes in the wiring method to achieve cross-connections and plug-and-multiplex connections, providing flexible up/down circuit capabilities, and make the network topology dynamically variable, enhanced network to adapt to the development of services, flexibility and security, can be achieved in a wider geometric range of protection of circuits, the height of the optimal use of the communication capacity, thus laying the foundation for enhanced networking capabilities, just a few seconds to re-form the network. seconds to reorganize the network.
In particular, the SDH self-healing ring can be quickly restored within a few tens of milliseconds after a circuit failure.
These advantages of SDH make it the basic transmission network for broadband service digital networks.
5. Network knowledge of fiber optic connectors have a few obvious stages of development
Fiber optic connectors have two obvious stages of development: the first stage: in order to save space, to the miniaturization of the direction of the development of fiber optic connectors from the traditional FC, ST, SC development of the LC, MTRJ, E2000. the second stage: not only in order to save space, but also to meet the requirements of the use of multi-core, fiber optic connectors from the LC, ST, SC development of the E2000. The second stage: not only to save space, but also to meet the requirements of multi-core use, fiber optic connectors from LC, MTRJ, E2000 to the evolution of MU, MTP / MPO, and now a MTP / MPO multi-core connector can meet the requirements of 2-core, 4-core, 8-core, 12-core, 24-core, and currently up to 72-core.
The second stage of this development brings obvious benefits, check out the 40G, 100G on the fiber optic network transmission specification requirements know, multi-core transmission, that is, 8 or 20 cores. So that MPO/MTP is to be able to meet the requirements of high-speed network applications in a tiny space.
But for engineers in the field construction also brings a great challenge, or even impossible to complete the task. Of course there is now a good alternative, which is to manufacture factory pre-connected system products.
6. How to clean LC fiber optic connectors
Fiber optic connector cleaning tips
1, why not use cotton balls dipped in alcohol to clean the light connector? The cleaning requirements of fiber optic connectors are much higher than the cleaning requirements of camera lenses. Cotton or only lens paper fibers are coarse, easy to cause wear and tear of fiber optic connectors. Foreign countries have long since stopped using cotton balls or lens paper to clean fiber optic connectors. For fiber optic test equipment is prohibited to use cotton balls or lens paper to clean the fiber optic connector.
2. Why use OAM fiber optic connector cleaner? OAM fiber optic interface cleaner for the U.S. OMA company developed research for fiber optic communication transmission network in a variety of fiber optic interface cleaning of a high-tech products. The effect can be achieved so that the optical signal return loss to hundreds of thousands or even one millionth. OAM fiber optic interface cleaner using non-alcoholic special fibers, has the following advantages:
(1) safe and reliable: than the use of alcohol, ether and cotton balls or lens paper and other easy to cause the second pollution of the traditional cleaning methods, unique design structure and selection of materials to make each cleaning to achieve the desired results. There is no adverse effect on the environment and the operator. It can effectively prevent fire caused by alcohol and ethanol.
(2) Easy to use: no need to carry a number of other traditional supplies in the work, just a light wipe, fiber optic connection interface dust and grease that is clean.
(3) affordable: the use of new design structure, patented product materials, greatly reducing production costs. Commodity prices are only a fraction of similar imported products. Each box of cleaning tape can clean more than 500 fiber optic interfaces, and the cleaning tape in the cleaner can be replaced.
(4) Wide range of uses: can be used for optical experimental research units, but also for indoor and outdoor fiber optic communications construction, maintenance, and fiber optic equipment, parts supply manufacturers of quality assurance package.
(5) Strong applicability: can be used for various types of fiber optic interfaces such as SC, FC, LC, ST, D4, DIN and so on.
3. How to use OAM fiber optic connector cleaner? ? Push the pull button on the upper end of the fiber optic interface cleaner to open, and put the connector of the contaminated fiber optic connector into one of the cleaning grooves and wipe it once with a little force. ? After the initial cleaning, in order to ensure the cleaning effect, you can again put the connector into another cleaning slot cleaning once. ? After cleaning, release the pull button and it will close automatically. Use it again and again in this way.
4. Why use compressed gas dust remover? Compressed gas dust remover, also known as "gas brush", is especially suitable for occasions where conventional dust removal methods are difficult to work, and can safely and quickly remove dust, fiber shavings, metal ions and other pollutants from the surface of precision electronic and optical instruments. This product is widely used in a variety of fiber optic communications, printed circuit boards, electronic instruments, optical instruments, electronic computers, intelligent equipment, communications equipment, audio-visual equipment, medical equipment, advanced cameras, video cameras, cameras, and other dust removal and maintenance. This product is flexible dusting, safe and non-invasive.
5. How to use compressed gas dust remover? ? Hand-held compressed gas dust remover, can upright, 5-10cm from the cleaning object, pull off the upper part of the actuator safety piece, short, frequent press the actuator for blowing. Use an extension tube for hard-to-reach areas. Do not shake or tilt the canister when using it. Do not shake or tilt the canister during use. Doing so will cause the compressed gas in the can to flow out in a liquid form, which may freeze skin or damage glassware. ? Continuous use of the compressed gas duster will result in a loss of blowing power, but this can be restored to normal after leaving it for a period of time.
? Please use compressed gas dust remover in a ventilated environment.
7. What are the types of fiber optic interfaces Common types of optical fiber
SC square straight plug
FC round screw port
ST round T-head
Network engineering, several commonly used fiber optic connectors for a detailed description:
① FC-type fiber optic connectors: the external reinforcement is the use of a metal sleeve, the fastening method for the screw buckle. Screw buckle. Generally used in the ODF side (the most used on the distribution frame)
② SC-type fiber optic connector: connecting the GBIC optical module connector, it is a rectangular shell, the fastening method is the use of insertion and removal of the pin latch type, do not need to rotate. (Routers and switches on the most)
③ ST-type fiber optic connectors: commonly used in fiber optic distribution frames, the shell is round, the fastening method for the screw buckle. (For 10Base-F connection, the connector is usually ST type. (For 10Base-F connection, the connector is usually ST type. Commonly used in fiber optic patch panels)
④ LC-type fiber optic connector: connecting the SFP module connector, which is easy to operate modular jack (RJ) latch mechanism. (Commonly used in routers)
⑤ MT-RJ: transceiver integrated square fiber optic connector, one end of the dual-fiber transceiver integration