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Preparations and basic knowledge before optical cable installation (1) Inspection requirements for optical cables * The specifications, models, and quantity of optical cables to be used in the project must comply with the design specifications and contract requirements； * The markings attached to the optical fiber, as well as the content of the labels, should be complete and clear ； * The outer sheath of the optical cable must be intact, and the cable shall come with a certificate of quality inspection upon leaving the factory ； * After the optical cable is unpacked, it is necessary to first check that there are no damages to its exterior, and that the cable ends are properly sealed ； * The inspection of fiber optic jumpers shall comply with the following requirements: they must have fiber protection jackets that are fire-resistant, and the end connectors at both ends shall be equipped with appropriate protective caps ； The fiber type of each fiber optic connector should be clearly marked and meet the design requirements. (2) The use of wiring equipment shall comply with the relevant regulations. * The model and specifications of optical cable connection equipment shall meet the design requirements ； * The arrangement and labeling of optical cable connection equipment shall be in accordance with the design. The names of various markers should be consistent, and their positions should be accurate and clear. 3. Requirements for optical cable wiring: The optical cables should be laid straight, without any twisting or curling, and they must not be subjected to external pressure or damage. Before laying the optical cable, labels should be attached to both ends to indicate the starting and ending positions. Labels should be written clearly, neatly, and correctly. It is best to lay the optical cable in a straight line. In the event of bends, the bending radius of the optical cable should be at least 10 times the outer diameter of the cable when it is at rest, and at least 20 times that diameter during installation. 4. Optical cable installation (1) Vertical installation through the low-voltage cable shaft. There are two options for installing optical cables in the low-voltage cable shaft: pulling them upward or lowering them downward. It is usually easier to lower the cable downward rather than pulling it upward; therefore, when preparing to lower the optical cable, follow these steps: * Place the cable reel 1–1.5 meters away from the slot in the equipment room at the top of the building, so that the reel can control the cable as it rotates. Place the cable reel on the platform so that the cable remains perpendicular to the axis of the reel at all times. When positioning the reel, have the end of the cable at its top, and then pull the cable from the top of the reel. * Rotate the cable reel and pull the cable out from its top. When pulling the optical cable, it is necessary to keep it within the specified minimum bending radius and maximum tension limits. * Guide the optical cable into the installed cable tray. * Slowly pull the optical cable from the reel until the workers on the next level can take over the cable and introduce it into that level. Repeat the above steps on each floor; when the optical cable reaches the lowest floor, let it lie loosely on the ground. When laying optical cables in the low-voltage room, in order to reduce the load on the cables, they should be secured to the wall with cable ties at regular intervals (such as every 5.5 meters). With this method, the optical cable does not require intermediate support, but it is necessary to tie the cable carefully so as not to break the optical fibers. To avoid breaking the optical fibers and causing additional transmission losses, do not damage the outer protective cover of the cable when bundling it. The steps for securing the cable are as follows: * Use plastic ties to fasten the main cable to the cable tray, starting from the top of the cable ； * From top to bottom, install straps at specified intervals (5.5m) until the main optical cable is securely fastened ； * Check for any damage to the optical cable jacket, and close the cover of the cable tray. (2) Laying optical cables through the ceiling: In this system, the section of the fiber optic cable route that runs from the low-voltage junction box to the distribution room is generally laid by using the ceiling (cable tray): * Open the ceiling along the recommended fiber optic routing path ； * Use a tool to cut off a section of the optical fiber’s outer jacket; make a circular cut in the cable’s outer jacket starting from 0.3 meters from one end, and then remove the outer jacket ； * The optical fiber and reinforcing core are cut off and buried in the outer sheath, leaving only the yarn. Repeat this process for each optical cable that needs to be laid ； * Twist the yarn together with the strap ； * Tightly wrap the cable jacket over a 20 cm length using tape ； * Feed the yarn into the appropriate clip until the sheath wrapped with the tape is completely inserted into the clip ； * Wrap the tape around the clip and the optical cable, pull the optical cable to the desired location, and leave enough length of the cable for subsequent processing. 5. Main materials for fiber optic termination * Connection devices * Sleeves: black for fibers with a diameter of 3.0 mm ； Silver is used for 2.4mm single-fiber cables. * Buffer layer fiber cable holders (guides) * Expanders with threaded caps * Protection caps. 6. Method of assembling standard fiber connectors: (1) On-site installation method for ST-type armored fibers: a. Open the material bag and remove the connector unit and the rear cover ； b. Rotate the mounting platform to open it, and use the provided mounting platform base to fix the mounting tool to a workbench ； c. Insert the connector into the socket on the mounting platform, and release the tension spring so that it points upward. Push the rear shell of the connector into the socket on the mounting platform. After all the protective covers have been pushed into the sockets on the mounting platform, rotate the connector 1/4 turn clockwise and tighten it in that position. The cover remains on top. d. Tighten the tension sleeve on the rear cover of the connector (gripping the tension sleeve helps in inserting the optical fiber); first wrap the narrow end of the rear cover’s tension sleeve around the optical fiber, and then squeeze the sleeve so that it slides forward along the direction of the core fiber. e. Use a cable stripper to remove about 40–50 mm of the outer sheath from the end of the fiber; the sheath must be stripped completely, with the end face forming a right angle. f. Move the yarn ends away from the buffer layer and concentrate them towards the back; make a mark on the buffer layer at the end of the sheath, i.e., on that buffer layer. g. Hold the optical fiber at the exposed buffer layer, and peel off the 900μm buffer layer starting from 6 mm or 11 mm from the end of the fiber. * To avoid damaging the optical fiber, the buffer layer is stripped off in small sections from the fiber ； * Gripping the sleeve can prevent the fiber from moving ； h. Gently clean the exposed fiber with a piece of paper or cloth soaked in alcohol. i. Push the yarn to one side and apply the buffer layer to the fiber cutter. Use forceps to remove the discarded fiber optic cable and place it properly in the waste container. j. Insert the cut fiber into the side hole of the microscope to check whether the cut is satisfactory. * Placing the microscope on a white panel yields clearer and brighter images ； * The bottom hole of the microscope can also be used to inspect the end collar of the connector. k. Remove the rear dust cover from the connector and discard it. l. Check whether the position of the reference marks on the buffer layer is correct. Carefully insert the exposed fiber into the connector until you feel it touch the bottom of the connector. Fix the optical fiber with a clip. m. Press the piston of the mounting platform and slowly release it. n. Push the connector forward and rotate it 1/4 turn counterclockwise in order to remove the connector from the mounting platform. Place the connector into the folding tool and straighten it. Use the first notch of the folding tool to create folds in the \"buffer folding area\" on the buffer layer. o. Reinsert the connector into the socket on the mounting platform and lock it in place. Rotate the connector 1/8 turn counterclockwise, and carefully cut off the excess yarn. p. Slide the compression sleeve over the yarn, making sure it fits tightly against the buckle at the rear end of the connector; use one of the grooves in the middle of the folding tool to fold the compression sleeve. q. Release the core wire. Straighten the optical fiber and push the rear housing to combine it with the front sleeve. A slight sound will be heard when it is inserted correctly, at which point the connector can be removed from the mounting platform. (2) On-site installation method for SC-type jacketed fiber optic connectors: a. Open the material bag and take out the connector body and the rear cover. b. Rotate the mounting platform to open it, and use the provided mounting platform base to secure these tools to a workbench. c. Insert the connector into the mounting platform and release the tension spring so that it points upward. * Push the rear shell of the connector toward the socket on the mounting platform; once all the dust covers have been inserted into those sockets, rotate the connector 1/4 turn clockwise and lock it in place ； * The dust cover remains on top ； d. Put the tension sleeve over the optical fiber; by squeezing the sleeve, it slides forward along the direction of the core wire. e. Use a cable stripper to remove about 40–50 mm of the outer sheath from the end of the fiber; the sheath must be stripped completely, with the end face forming a right angle. f. Gather the yarn ends together behind the 900μm buffer fiber, and make the first mark on the buffer layer (if the fiber is thinner than 2.4mm, make the mark at the end of the protective sleeve) ； Otherwise, make a mark on the bundle holder) ； Make a second mark on the buffer layer (if the fiber is thinner than 2.4 mm, make marks at 6 mm and 17 mm) ； Otherwise, make marks at 4mm and 15mm). g. Hold the optical fiber at the exposed buffer layer, and strip off 900 μm of the buffer layer from the end of the fiber to the first marker. * To avoid damaging the optical fiber, the buffer layer is stripped off in small sections from the fiber ； * Gripping the sleeve can prevent the fiber from moving ； h. Gently clean the exposed fiber with a piece of paper or cloth soaked in alcohol. i. Push the yarn to one side and apply the buffer layer to the fiber cutter. Cut a 7mm optical fiber from the end of the buffer layer. Use forceps to remove the discarded fiber optic cable and place it properly in the waste container. j. Insert the cut fiber into the side hole of the microscope to check whether the cut is satisfactory. * Placing the microscope on a white panel yields clearer and brighter images ； * The bottom hole of the microscope can also be used to inspect the end collar of the connector. k. Remove the rear dust cover from the connector and discard it. l. Check whether the position of the reference marks on the buffer layer is correct. Carefully insert the exposed fiber into the connector until you feel it touch the bottom of the connector. m. Press the piston of the mounting platform and slowly release it. n. Carefully remove the connector from the mounting platform to loosen the optical fiber; release the bending tool and place it on the protrusion of the multi-tool, keeping it straight, ensuring that the bending tool remains horizontal, and tighten it properly (hear three soft clicks). Insert the connector into the first slot of the folding tool, use the protrusion on the tool to point at the handle of the folding tool, and apply force in the cushioning fold area of the cushioning layer to create folds. o. Grasp the handling tool and pull gently to expose about 8 mm of the East China section. Remove the handling tool and discard it. p. Gently pull the yarn in the direction of the connector, aligning the yarn neatly; slide the compression sleeve over the yarn to wind it evenly around the connector, then carefully remove the connector from the mounting platform. q. Grab the ring of the main body and slide it into the rear part of the connector until it reaches the position corresponding to the connector’s setting. (VI) Twisted pair cable transmission testing 1. Verification test of cable transmission. Common connection faults during installation include incorrect cable labeling, open circuits, incorrect wiring diagrams for twisted pair cables (including wrong pairing, reversed polarity, and cross-wiring), as well as short circuits. (1) Open circuit, short circuit: Such faults occur during construction due to issues with installation tools or wiring techniques, as well as problems related to wiring inside walls ； (2) Reverse connection: The same pair of wires is connected in reverse at the two ends; for example, one end is 1-2 while the other end is 2-1 ； (3) Wrong connection: Connecting one pair of wires to another pair at the other end; for example, if one end is 1-2, it should be connected to pins 4-5 at the other end. The most typical mistake is mixing up the color codes of T568A and T568B during wiring. (4) Stranding: This involves separating the original two pairs of wires and then recombining them into new wire pairs. Because end-to-end connectivity remains good when this fault occurs, tools such as multimeters cannot detect it; only specialized cable testers can identify it. Due to the stranding, the associated wire pairs do not kink, which results in high near-end crosstalk (NEXT) when signals pass between the wire pairs. 2. Certification testing for cable transmission (1) Certification testing standards: EIA/TIA 568A \"Standard for Telecommunications Cabling in Commercial Buildings\", TSB-67 \"Technical Specifications for Testing the Transmission Performance of Unshielded Twisted Pair Cable Installations in the Field\", ISO/IEC 11801:1995(E) International Cabling Standard. (2) Certification testing setup: To test UTP cabling systems, the horizontal connections should include information sockets/connectors, transition points, 90 meters of UTP cable (categories 3 to 5), a junction device with two termination blocks or ports, and a cable run with a total length of 10 meters. Two connection configurations are used for testing purposes. The basic connection includes a distribution cable, information sockets/connectors or conversion points, and a horizontal junction component. This is the fixed part of the connection. Channel connections include the basic connection as well as the installed equipment, users, and crossover cables. TSB-67 specifies the allowable worst-case attenuation and crosstalk for connections. The table below shows the attenuation and crosstalk limits for both basic connections and channel connections. (Refer to the comprehensive cabling testing methods on the homepage.) (3) Testing parameters: a. Wire Map: This test is used to verify the connection of the link, that is, to ensure that the wire pairs in the link are correct and that there is no splitting of pairs. The correct wiring diagram requires that the corresponding pins be connected end to end in a 1-to-1, 2-to-2, 3-to-3, 4-to-4, 5-to-5, 6-to-6, 7-to-7, 8-to-8 manner. b. Link length: If the cable length exceeds the specified value (such as 100 meters), signal attenuation is significant. c. Attenuation: Attenuation is a measure of signal loss along a link. The on-site testing equipment should measure the worst case of attenuation for each pair of wires installed, and by comparing the maximum attenuation value with the allowable attenuation value, it shall determine whether the result is Pass or Fail. d. Near-End Crosstalk (NEXT) loss: NEXT loss refers to the measurement of signal coupling from one pair of wires to another in a UTP link, and it is a key performance indicator for UTP links. To test the NEXT value on a typical four-pair UTP link, it is necessary to test between each pair of wires, namely: 12/36, 12/45, 12/78, 36/45, 36/78, 45/78. e. Impedance includes resistance, as well as inductive and capacitive reactances at frequencies ranging from 1 to 100 MHz; it is related to the distance between a pair of wires and the electrical properties of the insulator. (7) Fiber optic transmission channel testing – Fiber optic measurement parameters: (1) Fiber continuity. When performing continuity tests, a red laser, light-emitting diode, or other visible light source is injected into the fiber optic cable, and the output of light at the end of the fiber is monitored. If there is a break or other discontinuity in the fiber, the optical power at the output end of the fiber will decrease, or no light will be emitted at all. The rate of power reduction after light is transmitted through an optical fiber can also indicate the transmission performance of the fiber. If the attenuation of the optical fiber is too high, the system cannot function properly either. Optical power meters and light sources are common devices used for measuring the transmission characteristics of optical fibers. (2) Attenuation of optical fibers: The attenuation of optical fibers is mainly caused by the inherent absorption and scattering properties of the fibers themselves. The attenuation coefficient should be measured at multiple wavelengths; therefore, a monochromator is selected as the light source, or a light-emitting diode can be used as the test source for multi-mode fibers. (3) Bandwidth of optical fibers: Bandwidth is one of the important parameters in fiber optic transmission systems; the wider the bandwidth, the higher the information transmission rate. In most multi-mode systems, light-emitting diodes are used as light sources, and the light source itself also affects the bandwidth. This is because these LED light sources have a wide spectral distribution, in which light of longer wavelengths travels faster than light of shorter wavelengths. This difference in the speed of light propagation is known as dispersion, and it causes light pulses to broaden after transmission. 2. Fiber optic testing steps (refer to the structured cabling testing methods on the homepage)