Optical fiber is a medium that transmits information from one end to the other. It is a kind of glass or plastic fiber as a transmission medium, allowing information to pass through. Generally, the terms "optical fiber" and "optical cable" are easily confused. Most optical fibers are coated with several protective structures before use, and the coated optical cable is called "optical cable". The protective structure of the outer layer of the optical fiber can prevent the surrounding environment from damaging the optical fiber, such as water, fire and electric shock. Optical fiber can be divided into optical fiber, buffer layer and coating. Optical fiber is similar to coaxial cable, except that there is no mesh shielding layer. The center is the glass core of light propagation. In multimode fiber, the diameter of the fiber core is 1.5 μ m ~ 50 μ m, which is roughly equivalent to the thickness of human hair. The diameter of single-mode fiber core is 8 μ m ~ 10 μ m, and the fiber core is wrapped by glass cladding with lower refractive index than the fiber core, so that the fiber is kept in the fiber core. Outside is a thin plastic coat to protect the envelope. Optical fibers are usually bundled and protected by a housing. The fiber core is usually a double-layer concentric cylinder with a small cross-sectional area, which is made of timely glass, fragile and easy to break, and needs a protective layer. Optical fiber communication refers to a communication mode in which voice, image and data signals to be transmitted are modulated on an optical carrier and optical fiber is used as the transmission medium. Inherent: it is the inherent loss of optical fiber, including Rayleigh scattering and inherent absorption. 2. Bending: When the optical fiber is bent, some light in the optical fiber will be lost due to scattering, resulting in loss. 3. Squeeze: Loss caused by slight bending of optical fiber when squeezed. 4. Impurities: Impurities in optical fibers absorb and scatter light propagating in optical fibers, resulting in losses. 5. Uneven: Loss caused by uneven refractive index of optical fiber materials. 6. Butting: Losses caused by fiber butt joint, such as different axes (the coaxiality of single-mode fiber is required to be less than 0.8μm), uneven end faces, mismatched butt diameters and poor welding quality. 7. Multimode fiber: The central glass core is thick (50 or 62.5μm), which can transmit multiple modes of light. However, its large intermodal dispersion limits the frequency of transmitting digital signals, and it will become more serious with the increase of distance. For example, a 600MB/KM optical fiber has only 300MB bandwidth at 2KM. Therefore, the transmission distance of multimode fiber is relatively short, generally only a few kilometers. 8. Single-mode fiber: The glass core in the center is thin (the core diameter is generally 9 or 10μm), which can only transmit one mode of light. Therefore, its intermodal dispersion is very small, which is suitable for long-distance communication, but its dispersion plays a major role. Therefore, single-mode fiber requires high spectral width and stability of light source, that is, narrow spectral width and good stability. 9. Conventional optical fiber: optical fiber manufacturers optimize the transmission frequency of optical fiber at a single wavelength, such as 1300μm.10. Dispersion-shifted optical fiber: optical fiber manufacturers optimize the transmission frequency of optical fiber at two wavelengths, such as1300μ m and1550μ m./kloc-0. It has low cost and high dispersion between modules. Suitable for short-distance low-speed communication, such as industrial control. However, due to the small dispersion between modes, single-mode fibers are all abrupt. 12. Graded fiber: The refractive index decreases gradually from the central core of the fiber to the glass cladding, which can make the high-mode light propagate in sinusoidal form, reduce the intermodal dispersion, increase the bandwidth of the fiber and increase the transmission distance, but the cost is higher. Nowadays, multimode fibers are mostly graded fibers. 13. The main task of electric transmitter is pulse code modulation and signal multiplexing. Multiplexing refers to combining multiple signals into a physical channel for transmission, and then separating each signal with special equipment at the receiving end. Multiplexing can greatly improve the utilization rate of communication lines. In optical fiber communication system, binary optical pulse "0" code and "1" code are transmitted in optical fiber, which are generated by switching modulation of light source by binary digital signal. Digital signals are generated by sampling, quantizing and coding continuously changing analog signals, which is called PCM (pulse code modulation), that is, pulse code modulation. This electrical digital signal is called digital baseband signal, which is generated by PCM electrical terminal. 14. sampling refers to the process of discretely extracting some samples from the original analog signal with continuous time and amplitude and converting them into digital signals with discrete time and amplitude. 15. Coding refers to representing the sampled m kinds of signals with a set of binary or other binary numbers according to certain rules. Each signal can be represented by n binary numbers, and m and n satisfy M=2N. For example, if there are 8 quantized amplitude values, each amplitude value needs to be represented by 3 binary sequences when encoding. 16. Time division multiplexing: When the data transmission rate of a channel is greater than the sum of the data transmission rates of various signals, the time for using the channel can be divided into time slices (time slots) and these time slices can be allocated to various signals according to certain rules. Each signal can only be transmitted in its own time slice, so the signals will not interfere with each other. 17. Frequency division multiplexing: When the channel bandwidth is greater than the total bandwidth of each signal, the channel can be divided into several subchannels, and each subchannel is used to transmit a signal. In other words, the frequency is divided into different frequency bands, and signals of different paths are transmitted in different frequency bands, so signals of different paths can be transmitted at the same time. This is frequency division multiplexing (FDM). 18. Code Division Multiple Access (CDMA): This technology is mainly used in mobile communication. Different mobile stations (or mobile phones) can use the same frequency, but each mobile station (or mobile phone) is assigned a unique "code sequence", which is different from all other "code sequences", so there is no interference between users. Because different mobile stations (or mobile phones) are distinguished by different "code sequences", it is called "code division multiple access" (CDMA) technology. 19. Spatial division multiple access (SDMA): This technology uses spatial division to form different channels. For example, multiple antennas are used on a satellite, and the beam of each antenna points to different areas of the earth's surface. Earth stations in different areas of the ground will not interfere with each other even if they work at the same time and use the same frequency. Spatial division multiple access (SDMA) is a channel capacity expansion method, which can realize frequency reuse and make full use of frequency resources. Spatial division multiple access (SDMA) can also be compatible with other multiple access methods, thus realizing combined multiple access technologies, such as SD-CDMA. 20. Line coding: also known as channel coding, its function is to eliminate or reduce DC and low-frequency components in digital electrical signals, so as to facilitate transmission, reception and monitoring in optical fibers. Generally, it can be divided into three categories: scrambling binary code, word conversion code and insertion code. 2 1. modulation mode: analog communication can adopt various modulation modes such as amplitude modulation, frequency modulation and phase modulation. When digital modulation is adopted, it is called amplitude shift keying (ASK), frequency shift keying (FSK) and phase shift keying (PSK) accordingly. A signal with only two states is called on-off key control (OOK). At present, the digital communication system adopts OOK-PCM format, which belongs to IM-DD communication mode and is the simplest and most primary communication mode. Coherent communication system can adopt ASK, FSK or PSK-PCM format, which is a complex and advanced communication mode. 22. The sensitivity of an optical receiver is defined as the minimum input optical power required by the receiver under the condition of ensuring the required bit error rate. 22. Optical coupling is to split or combine optical power with the same wavelength. Through optical coupler, we can combine two optical signals into one. 23. Optical isolator is a passive optical device that only allows one-way light to pass through. Its working principle is based on the nonreciprocal Faraday rotation. 24. Magneto-optical isolators can also be said to be unidirectional light guides. The isolator is placed in front of the laser and optical amplifier to prevent the reflected light in the system from affecting or even damaging the performance of the device. 25. A filter is a wavelength selective instrument. It can choose the desired wavelength from many wavelengths, and all light outside this wavelength will be rejected. It can be used for wavelength selection, noise filtering of optical amplifiers, gain equalization and multiplexing/demultiplexing. Filters based on interference principle: fused tapered fiber filter, Fabry-Perot filter, multilayer dielectric film filter, Mach-Zehnder interference filter. Filters based on grating principle: volume grating filter, arrayed waveguide grating filter (AWG), fiber grating filter, acousto-optic tunable filter. 26. An optical fiber connector is a device for connecting optical fibers. It plays an indispensable role in optical fiber communication systems and measuring instruments. It is different from the fixed optical fiber connector and can be disassembled and used flexibly, so it is also called optical fiber movable connector or optical fiber movable connector. Generally speaking, optical fiber connectors are required to be small in size, low in access loss, repeatable in disassembly, high in reliability, long in service life and low in price. 27. An optical attenuator is a device for attenuating optical power. It is mainly used for index measurement of optical fiber system, signal attenuation of short-distance communication system and system test. Optical attenuator requires light weight, small volume, high precision, good stability and convenient use. It can be divided into fixed, graded variable and continuously adjustable. 28. Optical amplification refers to pumping energy (electricity or light) to realize population inversion (except nonlinear optical fiber amplifier), and then amplifying incident light through stimulated radiation. 29.MDF main distribution frame, main distribution frame. 30. Intermediate distribution frame, distribution frame. 3 1 and OC OC (optical carrier) are the transmission speeds defined in SONET specification. OC defines the transmission speed of optical equipment and STS defines the transmission speed of electrical equipment. 32.SC user connector (optical fiber connector) User connector (optical fiber connector). 33.ST straight-pointed, straight-through optical fiber connector. 34.SONET SONET (Synchronous Optical Network) is an optical fiber transmission system for high-speed data communication. SONET is deployed by telephone companies and public communication companies, and its speed ranges from 5 1Mb/s to several gigabits per second. SONET is an intelligent system that provides advanced network management and standard optical fiber interface. It adopts self-recovery ring structure, and if a line fails, it can be shunted. SONET trunk is widely used to collect low-speed T 1 and T3 lines. SONET is defined by the broadband ISDN(B-ISDN) standard. The corresponding standard in Europe is SDH. SONET uses time division multiplexing (TDM) technology to transmit multiple data streams at the same time. 35. Optical cable terminal box The optical cable terminal box is mainly used for fixing optical cable terminals, welding optical cables and pigtails, and accommodating and protecting remaining optical fibers. 36. optical fiber box optical fiber box uses optical fiber technology to transmit digital and similar voice, video and data signals. Optical fiber box can be installed directly or on the desktop. Especially suitable for high-speed optical fiber transmission. 37. Optical fiber panels Optical fiber panels have the characteristics of high optical transmission efficiency, low interstage coupling loss, clear and true image transmission, and zero optical thickness. The most typical application is as the optical input and output window of low-light-level image intensifier, which plays an important role in improving the quality of imaging devices. Widely used in all kinds of cathode ray tubes, camera tubes, CCD coupling and other instruments and equipment that need to transmit images. 38. Optical fiber Coupler (coupler), also known as splitter, is an element that divides the optical signal in an optical fiber into multiple optical fibers. It belongs to the field of optical passive devices, and will be applied to telecommunication networks, cable television networks, subscriber loop systems and local networks. The largest item is used for the classification of passive devices with optical fiber connectors. Optical fiber couplers can be divided into standard couplers (two branches, unit 1×2, that is, optical signals are divided into two powers), star/tree couplers, wavelength multiplexers (WDM, which belongs to DWDM if the wavelength is high density, that is, the wavelength spacing is narrow), and the manufacturing methods include fuses, micro-optics and optical waveguides. 39. Optical fiber distribution frame (cabinet) Optical fiber distribution frame (cabinet) has the following functions: fixing, protecting and grounding optical cables; Fusion of fiber core and tail fiber of optical cable: adjust optical path and provide measuring port; Storage management of redundant optical fibers and pigtails. 40. Optical fiber distribution box Optical fiber distribution box is especially suitable for optical fiber terminal points in optical fiber access networks. It has the functions of cable distribution and welding, and can realize flexible cable adjustment and fiber core storage. 4 1. Jumpers Jumpers are cable pairs or cable units without connectors, which are used to connect various links on the distribution frame. 42. The junction box is mainly suitable for the straight-through and bifurcated joints of overhead cables, directly buried optical cables and pipeline wells, and plays a protective role for the joints. 44. 10BaseF 10Mbit/s baseband Ethernet specification refers to the optical cable connection on Ethernet 10BaseFB, 10BaseFl and 10BaseFL standards. 45. 10BaseFB refers to the specification of 10Mbit/s baseband Ethernet connected by optical cable. It is a part of IEEE 10BaseF specification. It is not used to connect user workstations. Instead, it is used to provide a synchronous signaling backbone network, allowing additional network segments and repeaters to connect to the network. The network segment length of 10BaseFB can reach 2km. 46. 10BaseFL refers to the specification of 10Mbit/s baseband Ethernet connected by optical cable. It is a part of IEEE 10 Basel specification. Although it can interoperate with FOIRL, it was developed to replace the FOIRL specification. If it is used with FOIRL, the network segment length of 10BaseFL can reach1km; However, if only 10BaseFL is used, the network segment of 10BaseFL can reach 2km. 47. 10BaseFP refers to the specification of 10Mbit/s passive optical fiber baseband Ethernet connected by optical cable. It is a part of IEEE 10BaseF specification. It organizes multiple computers into a star topology without using repeaters. The network segment length of 10BaseFP can reach 500m. 48. 10BaseFX refers to 100Mbit/s baseband fast Ethernet specification, which uses two multimode optical fiber cables in each link. To ensure correct signal timing, the 100BaseFX link cannot be longer than 400 meters. It is based on IEEE802.3 standard. 49.4B/5B fiber refers to 4-byte /5-byte local fiber. It is the fiber channel physical medium of FDDI and ATM, and supports the rate as high as 100Mbit/s on multimode fiber. 50, 8B/ 10B optical fiber 8 bytes/10 bytes local optical fiber. Refers to the Fibre Channel physical medium that supports up to 149.76Mbit/s on multimode fiber. 5 1, FDDI II second generation optical fiber distributed data interface. American National Standards Institute (ANSI) specification for improved fiber distributed data interface (FDDI). It provides synchronous transmission for connectionless data circuits and connection-oriented sound and image circuits. 52.FDDI/CDDI was formulated by X3T9.5 of ANSI. The rate is100 Mbps; CDDI is FDDI based on copper cable (twisted pair). FDDI technology is mature, and the network can be extended to 100 km. Because of its ring structure and excellent management ability, it has high reliability. Expensive, complex installation, perfect standards, mature technology and rich software and hardware products. 53. Time taken to propagate a delayed signal through a cable or system. 54. Propagation delay skew The transmission delay difference between the slowest and fastest pairs in a cable or system. 55. Single-mode optical fiber in which light travels in a single path. An optical fiber with a laser as the light source 56 is multimode, and light passes through the optical fiber in multiple paths. Light emitting diodes or lasers are used as light sources. 57. Optical fiber, that is, optical fiber, is a small and flexible medium that can transmit optical signals. An optical cable is composed of multiple optical fibers. Compared with twisted pair and coaxial cable, optical cable meets the requirements of current network for long-distance transmission of large-capacity information and plays a very important role in computer network. 58. Plane cables include connection ports in the workspace, distribution cables and connection hardware in the telecom cabinet. 59. The number of attenuated signals lost through the optical cable or system 60. When the clock rate difference between any two digital switching devices in the sliding code digital network exceeds a certain value, there will be a speed difference between the reading and writing clocks of the buffer memory of the receiving signal switch, and when this difference exceeds a certain value, sliding codes will be generated. This sliding code will lead to error code or out-of-step of the received digital stream. Responder: Mingsk- assistant level 2 2008-6- 19 07:38 Let me comment >>