This paper introduces the causes and treatment methods of large attenuation points of optical cable lines, line maintenance and testing methods, and standardized operation procedures for construction and connection of optical cable lines. It also briefly introduces the composition and structure of the optical cable, the naming method and the standard chromatographic arrangement of the optical fiber. very powerful!

Maintenance and Construction of Optical Cable Lines

1. Manufacture of optical cable:
The manufacturing process of optical cable is generally divided into the following processes:
1) Screening of optical fibers: select optical fibers with excellent transmission characteristics and qualified tension.
2) Dyeing of optical fibers: use standard full chromatogram to identify, requiring high temperature not fading and not migrating.
3) Secondary extrusion: Use plastic with high elastic modulus and low linear expansion coefficient to extrude into a certain size tube, incorporate the optical fiber and fill it with moisture-proof and waterproof gel, and store it for a few days (not less than two days) .
4) Optical fiber cable twisting: twist several extruded optical fibers and strengthening units together.
5) Squeeze the outer sheath of the optical cable: add a layer of sheath to the twisted optical cable.
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2. Types of optical cables:
1) According to the laying method, there are: self-supporting overhead optical cable, pipeline optical cable, armored buried optical cable and submarine optical cable.
2) According to the optical cable structure, it is divided into: bundled optical cable, layered optical cable, tightly hugged optical cable, ribbon optical cable, non-metallic optical cable and branchable optical cable.
3) According to the use, it is divided into: optical cable for long-distance communication, short-distance outdoor optical cable, hybrid optical cable and optical cable for building.
<img src="https://www.ductcable.com/picture/ossImg/zrcable/dcfd8f6de5940dc3b955f89fd8ebc69d.jpg/defaultStyle" alt="gyta53 cable" width="900" height="900" />
3. Construction of optical cable:
Over the years, the construction of optical cables has enabled us to have a set of mature methods and experience.
Outdoor construction of optical cable:
The most important thing for long-distance cable laying is to choose a suitable path. The shortest path is not necessarily the best, but also pay attention to the right to use the land, the possibility of erection or burial, etc.
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There must be very complete design and construction drawings for convenient and reliable construction and future inspections. During construction, be careful not to put the optical cable under heavy pressure or be punctured by hard objects.
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When the optical cable turns, its turning radius is 20 times larger than the diameter of the optical cable itself.
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1) Construction of outdoor aerial optical cable:
A. The overhead method of hanging wire brackets is simple and cheap, and is the most widely used in my country, but it is time-consuming to add hooks and arrange them.
B. Hanging wire winding overhead method, this method is more stable and less maintenance work. But a special wrapping machine is required.
C. The self-supporting overhead method has high requirements on the trunk line, difficult construction and maintenance, and high cost. It is rarely used in China at present.
D. When overhead, a guiding device must be installed at the place where the optical cable leads to the trunk, and the optical cable should not be dragged to the ground. Pay attention to reducing friction when pulling the optical cable. A length of fiber optic cable should be left on each trunk for expansion and contraction.
E. Pay attention to the reliable grounding of metal objects in the optical cable. Especially in mountainous areas, high-voltage power grid areas and many areas, there are generally 3 grounding points per kilometer, and even non-metallic optical cables are used.
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2) Construction of outdoor pipeline optical cable:
A. Before construction, the occupancy of the pipeline should be checked, the plastic sub-pipes should be cleaned and placed, and the traction line should be placed at the same time.
B. Calculate the deployment length, and there must be enough reserved length.
C. The length of one laying should not be too long (generally 2KM). When wiring, it should be pulled from the middle to both sides.
D. The traction force of the cable is generally not more than 120kg, and the reinforcing core part of the optical cable should be pulled, and the waterproof and strengthening treatment of the head of the optical cable should be done.
E. The lead-in and lead-out of the optical cable must be equipped with a follow-up device, and the floor cannot be directly mopped.
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F. The pipeline optical cable should also pay attention to reliable grounding.
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3) The laying of directly buried optical cables:
A. The depth of direct buried optical cable trench should be excavated according to the standard. The standard is shown in the following table:
B. Where trenches cannot be dug, the pipelines can be laid overhead or drilled.
C. The bottom of the ditch should be flat and firm, and a part of sand, cement or support can be pre-filled if necessary
D. Manual or mechanical traction can be used when laying, but attention should be paid to guidance and lubrication.
E. After the laying is completed, the soil should be covered and compacted as soon as possible.
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4) Laying of optical cables in buildings:
A. When laying vertically, special attention should be paid to the load-bearing problem of the optical cable. Generally, the optical cable should be fixed once every two layers.
B. When the optical cable passes through the wall or floor, a protective plastic pipe with a mouth guard should be added, and the pipe should be filled with flame retardant filler.
C. A certain amount of plastic pipes can also be laid in advance in the building, and when the optical cable is to be laid in the future, the optical cable can be laid by traction or vacuum method.
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4. Selection of optical cable:
The selection of optical cables is not only based on the number of optical fibers and the type of optical fibers, but also the outer sheath of the optical cable according to the use environment of the optical cable.
1) When the outdoor optical cable is directly buried, the armored optical cable should be selected. When overhead, an optical cable with a black plastic outer sheath with two or more reinforcing ribs can be used.
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2) When selecting optical cables used in buildings, attention should be paid to their flame retardant, poisonous and smoke characteristics. Generally, the flame-retardant but smoke-bearing type (Plenum) can be used in the pipeline or forced ventilation, and the flame-retardant, non-toxic and smoke-free type (Riser) should be used in the exposed environment.
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3) When cabling vertically in the building, you can choose Distribution Cables; when laying horizontally, you can choose Breakout Cables.
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4)If the transmission distance is less than 2km, you can choose multi-mode optical cable. If it exceeds 2km, you can use repeater or choose single-mode optical cable.
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1. Manufacture of optical cable:  The manufacturing process of optical cable is generally divided into the following processes:  1) Screening of optical fibers: select optical fibers with excellent transmission characteristics and qualified tension.  2) Dyeing of optical fibers: use standard full chromatogram to identify, requiring high temperature not fading and not migrating.  3) Secondary extrusion: Use plastic with high elastic modulus and low linear expansion coefficient to extrude into a certain size tube, incorporate the optical fiber and fill it with moisture-proof and waterproof gel, and store it for a few days (not less than two days) .  4) Optical fiber cable twisting: twist several extruded optical fibers and strengthening units together.  5) Squeeze the outer sheath of the optical cable: add a layer of sheath to the twisted optical cable.

Manufacture and selection method of optical cable

The continuous updating of several optical communication technologies has driven the large-scale development of fiber-to-the-home, thereby promoting the continuous expansion of the market scale of fiber-optic quick connectors. In the process of fiber-optic wiring, there are generally two types of fiber-optic connection methods. One is It is optical fiber thermal fusion, and one is to use a quick connector for splicing. So, what is the difference between fiber optic quick connectors and cold splices?
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1. The meaning of fiber optic quick connectors and cold connectors
1. Optical fiber quick connector
Optical fiber active connectors, commonly known as live joints, generally called optical fiber connectors, are reusable passive devices used to connect two optical fibers or optical cables to form a continuous optical path. They have been widely used in optical fiber transmission lines and optical fiber distribution frames. It is the most widely used optical passive device among optical fiber test instruments and meters.
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2. Cold connector
It is used for optical fiber butt optical fiber or optical fiber docking pigtail, which is equivalent to making a joint, (fiber docking pigtail refers to the butt joint between the optical fiber and the core of the pigtail, not the pigtail head mentioned by the former), which is used for this kind of cold splicing. Something called a fiber optic cold splicer.
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Fiber Quick Connector
2. What is the difference between fiber optic quick connectors and cold connectors?
The optical fiber cold connector has the same structural principle as the pre-buried optical fiber connector. It is a sub-product of the optical fiber quick connector. Because its shape is similar to the quick connector, many people are stupid and unclear about the two.
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The difference between the cold connector and the fiber optic quick connector is that it has no movable plug. It is used to directly and fixedly connect the optical link node when the optical fiber is connected to the optical fiber or the optical fiber and the pigtail. The joint loss is about 0.1dB&mdash;&mdash; 0.2dB. It is mainly used for indoor wiring or wiring in a small space, and the installation is more convenient and flexible.
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3. How to install and use optical fiber quick connectors
Step 1: Remove the connector end cap and pass the cable through it;
Step 2: Use optical fiber strippers to strip the cable sheath, the length is about 5CM;
Step 3: Cut the exposed coating layer with the Miller clamp close to the edge of the clamp to expose the fiber;
Step 4: Wipe and clean the bare fiber with a dust-proof cloth;
Step 5: Cleave the fiber with a fixture;
Step 6: Align the optical fiber with the main body slot and insert it. When the optical fiber is initially bent, press the crimping cover down;
Step 7: Screw the end cap on the cable back to the main body of the connector and then fasten the shell.
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The installation of the optical fiber quick connector is very simple, but it should be noted that the optical fiber quick connector is extremely susceptible to contamination and damage, which will lead to the loss of optical fiber performance. During the installation process, it should be kept away from dust and contaminants, and the action should be slow when inserting.
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Fourth, what is the method of optical fiber cold splicing
First, use diagonal pliers to cut the steel wire inside the cable by about 20CM, and use the optical cable stripper to open the leather cable to expose the optical fiber, pay attention to the length. Put it in the guide groove, pull the guide groove back by 3.5CM, and use the Miller wire to peel off the plastic on the surface of the fiber, and the exposed fiber is bare fiber. Put the stripped bare fiber tape guide groove like a cutter, and push it from the inside (on one side of your body) to the outside. Put on the cold terminal and press the yellow part forward.
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The above is the whole content of the difference between the optical fiber quick connector and the cold splicer that we have brought to you. I believe that you have already answered this question here. Make the glass stick to your hands.
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The continuous updating of several optical communication technologies has driven the large-scale development of fiber-to-the-home, thereby promoting the continuous expansion of the market scale of fiber-optic quick connectors. In the process of fiber-optic wiring, there are generally two types of fiber-optic connection methods. One is It is optical fiber thermal fusion, and one is to use a quick connector for splicing. So, what is the difference between fiber optic quick connectors and cold splices?

The difference between optical fiber quick connector and cold connector

1. First, check whether the indicator light of the optical fiber transceiver or optical module and the indicator light of the twisted pair port are on?
A. If the indicator light of the optical port (FX-LINK/ACT) of the transceiver is not on, please confirm whether the optical fiber link is the correct cross-link, the optical fiber socket TX-RX; RX-TX.
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B. If the indicator light of the optical port (FXFX-LINK/ACT) of the transceiver A is on but the indicator light of the optical port (FXFX-LINK/ACT) of the transceiver B is not on, the fault is on the transceiver side of A: one possibility is: The optical transmission port of transceiver A (TX) is broken, because the optical port (RX) of transceiver B cannot receive optical signals; another possibility is: the optical fiber link of the optical transmission port of transceiver A (TX) has problem (the fiber optic cable or fiber patch cord may be broken).
<img src="https://www.ductcable.com/picture/ossImg/zrcable/0016a2a6d9bfe5a98fb6b8662a7d3dc4.jpg/defaultStyle" alt="Fiber Transceiver" width="1000" height="1000" />
C. The twisted pair (TXFX-LINK/ACT) indicator light is not on, please confirm whether the twisted pair connection is wrong or the connection is wrong? Please use a continuity tester to test (however, the twisted pair indicator of some transceivers will not light up until the optical fiber link is connected).
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D. Some transceivers have two RJ45 ports: (To HUB) indicates that the connection line connecting the switch is a straight-through line; (To Node) indicates that the connection line connecting the switch is a crossover line.
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E. There are MPR switches on the side of some transceivers: it means that the connection line connected to the switch is in a straight-through mode; DTE switch: the connection line connected to the switch is in a crossover mode.
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2. Are the fiber optic cables and fiber jumpers broken?
A. Optical cable on-off detection: use a laser flashlight, sunlight, or illuminator to illuminate one end of the optical cable connector or coupler; see if there is visible light at the other end? If there is visible light, it means that the optical cable is not broken.
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B. On-off detection of optical fiber connection: use a laser flashlight, sunlight, etc. to illuminate one end of the optical fiber jumper; see if there is visible light at the other end? If there is visible light, it means that the optical fiber jumper is not broken.
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3. Is the half/full duplex mode wrong?
Some transceivers have FDX switches on the side: full duplex; HDX switches: half duplex.
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4. Detect with an optical power meter
The luminous power of the fiber optic transceiver or optical module under normal conditions:
Multimode 2Km: between -10db-18db;
Single mode 20 kilometers: between -8db and 15db;
Single mode 60 kilometers: between -5db and 12db;
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If the luminous power of the optical fiber transceiver is between: -30db-45db, then it can be judged that there is a problem with the transceiver.
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1. First, check whether the indicator light of the optical fiber transceiver or optical module and the indicator light of the twisted pair port are on?  A. If the indicator light of the optical port (FX-LINK/ACT) of the transceiver is not on, please confirm whether the optical fiber link is the correct cross-link, the optical fiber socket TX-RX; RX-TX.

Optical Transceiver Indicator Function and Fault Judgment

This article shares common knowledge of optical fibers, optical modules and optical interfaces for everyone, hoping to help everyone.
Optical modules commonly used in Ethernet switches include SFP, GBIC, XFP, and XENPAK.
Weak current engineering
Their full English names:
SFP: Small Form-factor Pluggabletransceiver, small package pluggable transceiver
GBIC: GigaBit InterfaceConverter, Gigabit Ethernet Interface Converter
XFP: 10-Gigabit smallForm-factorPluggable transceiver 10 Gigabit Ethernet interface
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Small Package Pluggable Transceivers
XENPAK: 10-Gigabit EtherNetTransceiverPAcKage 10 Gigabit Ethernet interface transceiver package package.
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The optical fiber connector
The optical fiber connector is composed of an optical fiber and a plug at both ends of the optical fiber, and the plug is composed of a pin and a peripheral locking structure. According to different locking mechanisms, fiber optic connectors can be divided into FC type, SC type, LC type, ST type and KTRJ type.
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The FC connector adopts a threaded locking mechanism, which is an early and most used optical fiber active connector.
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SC is a rectangular connector developed by NTT. It does not need screw connection and can be plugged directly. Compared with the FC connector, it has a small operating space and is easy to use. Low-end Ethernet products are very common.
<img src="https://www.ductcable.com/picture/ossImg/zrcable/f8064f477d25d6cdb37620fb652b98d2.jpg/defaultStyle" alt="sc lc" width="900" height="900" />
LC is a Mini-type SC connector developed by LUCENT. It has a smaller volume and has been widely used in the system. It is a direction for the development of optical fiber active connectors in the future. Low-end Ethernet products are very common.
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ST connector is developed by AT&amp;T company, with bayonet locking mechanism, the main parameters and indicators are equivalent to FC and SC connectors, but it is not widely used in the company, usually used in multi-mode device connection, and other manufacturers equipment Used more when docking.
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The pins of KTRJ are made of plastic and are positioned by steel pins. With the increase of insertion and extraction times, each mating surface will wear out, and the long-term stability is not as good as that of ceramic pin connectors.
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Fiber knowledge
Optical fibers are conductors that transmit light waves. Optical fibers can be divided into single-mode fibers and multi-mode fibers from the mode of optical transmission.
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There is only one fundamental mode of light transmission in a single-mode fiber, which means that light travels only along the inner core of the fiber. Due to the complete avoidance of modal scattering, the transmission frequency band of single-mode fiber is very wide, so it is suitable for high-speed, long-distance fiber communication.
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There are multiple modes of light transmission in multimode fiber. Due to dispersion or aberration, the transmission performance of this fiber is poor, the frequency band is narrow, the transmission rate is small, and the distance is short.
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Characteristics of optical fibers
The structure of the optical fiber is drawn from a prefabricated silica optical fiber rod, and the outer diameter of the multi-mode optical fiber and single-mode optical fiber for communication is 125 &mu;m.
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The fiber body is divided into two regions: the core (Core) and the cladding layer (Cladding layer). The core diameter of single-mode fiber is 8~10&mu;m, and the core diameter of multi-mode fiber has two standard specifications, the core diameter is 62.5&mu;m (American standard) and 50&mu;m (European standard).
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The interface fiber specification has the following description: 62.5&mu;m/125&mu;m multimode fiber, where 62.5&mu;m refers to the core diameter of the fiber, and 125&mu;m refers to the outer diameter of the fiber.
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Single-mode fibers use light wavelengths of 1310 nm or 1550 nm.
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The wavelength of light used in multimode fibers is mostly 850 nm.
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Single-mode fiber and multi-mode fiber can be distinguished by color. The outer body of single-mode fiber is yellow, and the outer body of multi-mode fiber is orange-red.
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Gigabit optical port
The Gigabit optical port can work in two modes: forced and auto-negotiation. In the 802.3 specification, the Gigabit optical port only supports 1000M speed, and supports two duplex modes: Full and Half.
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The most fundamental difference between auto-negotiation and forcing is that the code streams sent when the two establish a physical link are different. The auto-negotiation mode sends the /C/ code, that is, the configuration code stream, while the mandatory mode sends the /C/ code. I/code, that is, the idle code stream.
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Gigabit optical port auto-negotiation process
1. Both ends are set to auto-negotiation mode
The two parties send /C/ code streams to each other. If three consecutive /C/ codes are received and the received code streams match the working mode of the local end, a /C/ code with an Ack response will be returned to the other party. After receiving the Ack information, the peer end believes that the two can communicate with each other, and sets the port to the UP state.
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2. One end is set to auto-negotiation, and one end is set to mandatory
The auto-negotiation end sends the /C/ code stream, and the forced end sends the /I/ code stream. The forced end cannot provide the peer end with the negotiation information of the local end, and cannot return the Ack response to the opposite end, so the auto-negotiation end is Down. However, the forced end itself can recognize the /C/ code, and think that the opposite end is the port that matches itself, so directly set the local port to the UP state.
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3. Both ends are set to mandatory mode
The two sides send /I/ stream to each other. After one end receives the /I/ stream, it considers the other end to be the port that matches itself, and directly sets the local port to the UP state.
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How does fiber optics work?
Optical fibers for communication are composed of hair-thin glass filaments covered with a plastic protective layer. The glass filament consists essentially of two parts: a core with a diameter of 9 to 62.5 &mu;m and an outer cladding of a low refractive index glass material with a diameter of 125 &mu;m. Although there are other types of fibers depending on the materials used and different sizes, the most common ones are mentioned here. Light is transmitted in the core part of the fiber by "total internal reflection", that is, after entering one end of the fiber, light is reflected back and forth between the interface between the core and the cladding, and then transmitted to the other end of the fiber. A fiber with a core diameter of 62.5 &mu;m and a cladding outer diameter of 125 &mu;m is called 62.5/125 &mu;m light.
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What is the difference between multimode and singlemode fiber?
Multimode:
Fibers that can propagate hundreds to thousands of modes are called multimode (MM) fibers. According to the radial distribution of refractive index in the core and cladding, it can be divided into step multimode fiber and graded multimode fiber. Almost all multimode fibers are 50/125&mu;m or 62.5/125&mu;m in size, and the bandwidth (the amount of information transmitted by the fiber) is typically 200MHz to 2GHz. Multimode optical transceivers can transmit up to 5 kilometers through multimode optical fibers. Light-emitting diodes or lasers are used as light sources.
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Single mode:
Fibers that can only propagate one mode are called single-mode fibers. Standard single-mode (SM) fiber has a refractive index profile similar to that of step-type fiber, except that the core diameter is much smaller than that of multimode fiber.
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Single-mode fiber is 9-10/125 &mu;m in size and has unlimited bandwidth and lower loss than multimode fiber. The single-mode optical transceiver is mostly used for long-distance transmission, sometimes reaching 150 to 200 kilometers. LDs or LEDs with narrow spectral lines are used as light sources.
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Differences and connections:
Single-mode equipment typically operates on both single-mode fiber and multi-mode fiber, while multi-mode equipment is limited to operation on multi-mode fiber.
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How about transmission loss when using fiber optic cable?
It depends on the wavelength of the transmitted light and the type of fiber used.
When 850nm wavelength is used for multimode fiber: 3.0dB/km
When 1310nm wavelength is used for multimode fiber: 1.0dB/km
When 1310nm wavelength is used for single mode fiber: 0.4dB/km
When 1550nm wavelength is used for single mode fiber: 0.2dB/km
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What is GBIC?
GBIC is the abbreviation of Giga Bitrate Interface Converter, which is an interface device that converts gigabit electrical signals into optical signals. The GBIC is designed to be hot-swappable. GBIC is an interchangeable product that complies with international standards. Gigabit switches designed with GBIC interface occupy a large market share in the market due to their flexible interchangeability.
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What is SFP?
SFP is the abbreviation of SMALL FORM PLUGGABLE, which can be simply understood as an upgraded version of GBIC. The volume of the SFP module is reduced by half compared to the GBIC module, and more than double the number of ports can be configured on the same panel. The other functions of the SFP module are basically the same as those of the GBIC. Some switch manufacturers call the SFP module a miniaturized GBIC (MINI-GBIC).
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Future optical modules must support hot swap, that is, the module can be connected or disconnected from the device without cutting off the power supply. Since the optical module is hot-swappable, network managers can upgrade and expand the system without shutting down the network. Users will have no impact. Hot swappability also simplifies overall maintenance and enables end users to better manage their transceiver modules. At the same time, due to this hot-swappable performance, the module enables network managers to make overall plans for transceiver costs, link distances, and all network topologies based on network upgrade requirements without having to replace the entire system board.
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The optical modules that support this hot swap currently include GBIC and SFP. Since SFP and SFF are similar in size, they can be directly inserted on the circuit board, saving space and time in packaging, and have a wide range of applications. Therefore, Its future development is worth looking forward to, and may even threaten the SFF market.
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What is SFF?
SFF (Small Form Factor) small package optical module adopts advanced precision optics and circuit integration technology, and its size is only half of that of ordinary duplex SC (1X9) optical fiber transceiver module. It can double the number of optical ports in the same space. Increase line port density and reduce system cost per port. And because the SFF small package module adopts the KT-RJ interface similar to the copper network, the size is the same as that of the common computer network copper interface, which is conducive to the transition of the existing copper-based network equipment to the higher-speed optical fiber network. To meet the dramatic increase in network bandwidth demand.
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Network connection device interface type
BNC interface
The BNC interface refers to the coaxial cable interface. The BNC interface is used for 75 ohm coaxial cable connection. It provides two channels of receiving (RX) and transmitting (TX), which are used for the connection of unbalanced signals.
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Fiber interface
A fiber optic interface is a physical interface used to connect fiber optic cables. There are usually SC, ST, LC, FC and other types. For 10Base-F connection, the connector is usually ST type, and the other end of the FC is connected to the fiber optic cable rack. FC is the abbreviation of FerruleConnector. Its external reinforcement method is a metal sleeve, and the fastening method is a turnbuckle. ST interface is usually used for 10Base-F, SC interface is usually used for 100Base-FX and GBIC, LC is usually used for SFP.
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RJ-45 interface
The RJ-45 interface is the most commonly used interface for Ethernet. RJ-45 is a common name, which refers to the standardization by IEC (60) 603-7 and uses 8 positions (8 pins) defined by the international connector standard. modular jacks or plugs.
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RS-232 interface
RS-232-C interface (also known as EIA RS-232-C) is the most commonly used serial communication interface. It is a standard for serial communication jointly formulated by the Electronic Industries Association (EIA) of the United States in 1970 in conjunction with Bell Systems, modem manufacturers and computer terminal manufacturers. Its full name is "Serial Binary Data Exchange Interface Technical Standard between Data Terminal Equipment (DTE) and Data Communication Equipment (DCE)". The standard stipulates that a 25-pin DB25 connector is used, and the signal content of each pin of the connector is specified, and the level of various signals is also specified.
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RJ-11 interface
The RJ-11 interface is what we usually call the telephone line interface. RJ-11 is the generic name used for connectors developed by Western Electric. Its shape is defined as a 6-pin connection device. Formerly known as WExW, the x here means "active", a contact or a needle. For example, WE6W has all 6 contacts, numbered 1 to 6, WE4W interface only uses 4 pins, the outermost two contacts (1 and 6) are not used, WE2W only uses the middle two pins (that is, the telephone line interface).
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CWDM and DWDM
With the rapid growth of Internet IP data services, the demand for bandwidth of transmission lines is increasing. Although DWDM (Dense Wavelength Division Multiplexing) technology is the most effective way to solve line bandwidth expansion, CWDM (Coarse Wavelength Division Multiplexing) technology has advantages over DWDM in terms of system cost and maintainability.
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Both CWDM and DWDM belong to wavelength division multiplexing technologies, which can couple light of different wavelengths into a single-core fiber and transmit them together.
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The latest ITU standard for CWDM is G.695, which specifies 18 wavelength channels with an interval of 20nm from 1271nm to 1611nm. Considering the influence of the water peak of ordinary G.652 fibers, 16 channels are generally used. Because the channel interval is large, the multiplexer and the laser are cheaper than DWDM devices.
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The channel spacing of DWDM has different spacings such as 0.4nm, 0.8nm, and 1.6nm according to the needs. The spacing is small and additional wavelength control devices are required, so the equipment based on DWDM technology is more expensive than equipment based on CWDM technology.
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The PIN photodiode is a layer of lightly doped N-type material, called I (Intrinsic, intrinsic) layer, between the highly doped P-type and N-type semiconductors. Because it is lightly doped, the electron concentration is very low, and a wide depletion layer is formed after diffusion, which can improve its response speed and conversion efficiency.
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The APD avalanche photodiode not only has the function of light/electrical conversion, but also has an internal amplification effect, and its amplification effect is completed by the avalanche multiplication effect inside the tube. APD is a photodiode with gain. In the case where the sensitivity of the optical receiver is high, the use of APD is beneficial to prolong the transmission distance of the system.
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This article shares common knowledge of optical fibers, optical modules and optical interfaces for everyone, hoping to help everyone.  Optical modules commonly used in Ethernet switches include SFP, GBIC, XFP, and XENPAK.  Weak current engineering  Their full English names:  SFP: Small Form-factor Pluggabletransceiver, small package pluggable transceiver  GBIC: GigaBit InterfaceConverter, Gigabit Ethernet Interface Converter  XFP: 10-Gigabit smallForm-factorPluggable transceiver 10 Gigabit Ethernet interface

Common knowledge of optical fibers, optical modules and optical interfaces in weak current engineering

Leather cable is commonly known as indoor hanging wiring cable. With the domestic optical fiber access market showing a good momentum of development, optical fiber access has become a hot spot in the field of optical communications. In the optical fiber access project, the indoor wiring close to the user is the most complicated link. The bending performance and tensile performance of conventional indoor optical cables can no longer meet the needs of FTTH (fiber-to-the-home) indoor wiring. Presumably you are not unfamiliar with the leather cable, so, do you know the laying technical requirements for the installation of the leather cable?
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ZR Cable leather cable
1. What are the laying technical requirements for the installation of leather cable
1. The laying of the leather cable should be straight, without twisting and crossing, and should not be squeezed by external forces and damaged by operation. Power cords, household leather cables and cables for other weak current systems in the building should be laid out separately. If it cannot be satisfied, corresponding isolation protection measures must be taken. For steel wire reinforced leather cable, attention should be paid to grounding the metal parts in the junction box.
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2. For important users or users with special requirements, protection should be considered, and different protection methods should be selected according to different situations.
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3. The laying of the leather cable should fully consider and strictly meet the requirements of "fire prevention, rodent prevention and extrusion prevention".
<img src="https://www.ductcable.com/picture/ossImg/zrcable/24a59c3d4f0d799e7bf0ebd61aeae911.jpg/defaultStyle" alt="ftth cable" width="900" height="900" />
4. The two ends of the leather cable should have a unified mark, and the mark should indicate the position where the two ends are connected. Label writing should be clear, correct and correct. Labels should be made of materials that should not be damaged.
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5. The bend of the leather cable should be even and smooth. The curvature radius of the ordinary G.652 fiber should be greater than 30mm, and the curvature radius of the anti-bending G.657 fiber should be greater than (A type) 10mm, (B type) 7.5mm , (C type) 5mm.
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6. When laying the leather cable, manual traction is generally used, and the traction force should not exceed 80% of the maximum allowable tension of the leather cable. The instantaneous maximum pulling force shall not exceed the maximum allowable tension of the leather cable 100N. The main traction force should be added to the cable strength member. After the cable is laid, the tension should be released to maintain a natural bending state.
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7. The leather cable reel should be used to carry the cable, and the cable tray should be used when laying the cable, so that the cable reel can automatically rotate to prevent the cable from being entangled.
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8. During the laying process of the leather cable, the tensile strength and bending radius of the optical fiber should be strictly paid attention to, so as to avoid the optical fiber from being entangled, twisted, damaged and trampled.
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The minimum bending radius of the cable laying shall meet the following requirements:
(1) The bending radius of the leather cable should not be less than 40mm during the laying process;
(2) After fixing, the bending radius of the cable should not be less than 15mm.
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9. Requirements for shafts and bridges in the building:
(1) The telecommunications shaft should pass through each floor uniformly up and down, the internal width should not be less than 600mm, and the operating distance in front of the wiring box installed in the cable shaft should not be less than 0.6m.
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(2) A grounding device should be reserved in the telecommunication shaft.
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(3) The installation of the trunking in the shaft should be more than 50% of the total cable utilization rate.
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(4) The vertical part of the home optical cable in the shaft should be bundled and fixed every 1.5 meters to prevent the damage to the fiber core caused by the falling force.
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10. Horizontal piping requirements (weak current well to user end):
(1) The diameter of the pre-embedded pipe should be &phi;20 mm - &phi;25 mm, the length of the straight embedded pipe of the hidden pipe in the building should be controlled within 30 meters, and a passage box should be added when the length exceeds 30 meters. When the hidden pipe must be bent and laid, its routing length should be &le; 15 meters, and there should be no S-bend in this section. When it is continuously bent for more than 2 times, a wire box should be installed. All turns are done with pipe benders and are standard turning radii. Three-way, four-way, etc. shall not be used.
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(2) The bending radius of the hidden pipe should be 10 times larger than the pipe diameter. When the outer diameter is less than 25 mm, the bending radius should be 6 times larger than the pipe diameter, and the bending angle should not be less than 90 degrees. The bending radius of the hidden pipe shall not be less than 6--10 times the outer diameter of the pipe.
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11. When laying the leather cable, the reserved length at both ends of the leather cable should meet the following requirements: about 1m is reserved at one end of the floor optical splitter box; about 0.5m is reserved at one end of the user leather cable terminal box.
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12. After the household leather cable is laid, the light source and optical power meter should be used to test it. The optical attenuation value of the household leather cable section at the wavelength of 1310nm and 1490nm should be less than 1.5dB. If the optical attenuation value is greater than 1.5dB, it should be repaired. If the repair has not been improved, it is necessary to re-make the optical fiber mechanical connection plug or re-lay the leather cable.
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13. If the span of outdoor leather cable exceeds 40 meters, consider adding a soft hanging method.
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14. When laying the dark (open) tube type leather wire optical cable first, when laying the dark (open) tube, the connection at the turning angle should be a hose or a passing box should not be directly applied to the turning angle; when the straight line distance exceeds 10 meters, it should be Install the pass box.
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15. In principle, the laying of the leather cable in the shaft is from top to bottom. In high-rise buildings or long-distance laying, it needs to be bundled and fixed every 1.5 meters to reduce the long-term self-weight of the leather cable. damage to come.
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16. Power cords, home leather optical cables and cables of other weak current systems in the building should be laid out separately.
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2. What are the ways to enter the home with the leather cable?
User indoor wiring
In the FTTH project, the user's indoor wiring is the most complicated link, and many factors are considered. It is necessary to ensure the safety of the line, take into account the indoor beauty, and at the same time facilitate the construction. The traditional single-core indoor optical cable can no longer meet the indoor wiring requirements of the current FTTH project. As a substitute for traditional indoor optical cables, ZR Cable can adapt to most indoor wiring conditions, such as turning with a bending radius of 20mm, and can bear the lateral pressure of people stepping on the optical cable and the pulling force caused by engineering construction . At the same time, with a variety of on-site connectors, on-site termination and docking can be realized in the shortest time. Therefore, ZR Cable is the best choice for FTTH indoor wiring.
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In-building vertical and horizontal wiring
Like the user's indoor wiring, the ZR Cable is also suitable for vertical and horizontal wiring in the building. The horizontal wiring is not very demanding on the optical cable, but the vertical wiring must require the optical cable to have a certain tensile strength. The ZR Cable leather cable can withstand the short-term 200N and long-term 100N tensile force, so it can ensure the construction safety and stable performance of the vertical wiring of the leather cable within a certain height range.
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Self-supporting overhead access wiring
Since the self-supporting "8" wiring optical cable has a metal hanging wire unit, it has stronger tensile performance and can withstand a span of 50 meters. The optical cable is laid outdoors in an overhead manner. Before entering the house, the metal suspension wire unit is cut off and fixed on a special fixture. After the remaining optical cable is stripped of the metal suspension wire, the leather wire optical cable is introduced into the room.
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Pipeline wiring
Compared with the leather cable, the pipeline mapping optical cable is harder and has higher tensile strength. At the same time, the optical cable contains water-blocking materials, which can reduce the erosion of outdoor rainwater, so it is more suitable for long-distance outdoor pipeline laying. The ZR Cable pipe mapping optical cable adopts an all-non-metal structure, thus avoiding the introduction of lightning into the room. After the optical cable enters the house, strip its outer sheath, water blocking material and reinforcements, and directly use the middle leather cable for indoor wiring, which inherits all the advantages of indoor wiring of the leather cable, while reducing the connection of outdoor and indoor optical cables.
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The sheathed optical cable is mostly single-core or double-core structure, and can also be made into a four-core structure. The cross section is in a figure-8 shape. The reinforcement is located in the center of the two circles. Metal or non-metallic structure can be used. . The optical fiber in the leather cable adopts G.657 small bending radius optical fiber, which can be laid with a bending radius of 20mm.
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Leather cable is commonly known as indoor hanging wiring cable. With the domestic optical fiber access market showing a good momentum of development, optical fiber access has become a hot spot in the field of optical communications. In the optical fiber access project, the indoor wiring close to the user is the most complicated link. The bending performance and tensile performance of conventional indoor optical cables can no longer meet the needs of FTTH (fiber-to-the-home) indoor wiring. Presumably you are not unfamiliar with the leather cable, so, do you know the laying technical requirements for the installation of the leather cable?

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