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20 essential knowledge of optical fiber and cable (2)

2019-11-26

21, the most common cable structure there are several?


Answer: there are two types: layering type and skeleton type.

22.What is the optical cable mainly composed of?


Answer: mainly by: fiber core, fiber ointment, sheath material, PBT (polybutylene terephthalate) and other materials.



23.What is the armor of optical cable?


Answer: it is to point to the protection element that USES in the optical cable of special purpose (wait like submarine optical cable) place (usually for steel wire or steel belt). Armor is attached to the inner sheath of the cable.



24.What material is optical cable sheath?


A: the cable sheath or sheath is usually made of polyethylene (PE) and polyvinyl chloride (PVC) materials to protect the cable core from outside influences.


25.List the special optical cable used in power system.


Answer: there are three kinds of special optical cable:


Ground composite optical cable (OPGW) : the optical fiber is placed in the power line of aluminum steel stranding structure. The application of OPGW optical cable has played the double functions of ground line and communication, and effectively improved the utilization rate of power poles and towers.


Winding cable (GWWOP) : where an existing transmission line exists, the cable is wound or suspended on the ground.


Self-supporting optical cable (ADSS) : it has strong tensile resistance and can be directly hung between two power poles and towers, with a maximum span of up to 1000m.


26, OPGW cable application structure there are several?


Answer: mainly include:


1) twisted plastic pipe layer + aluminum pipe structure;


2) structure of center plastic tube + aluminum tube;


3) aluminum frame structure;


4) spiral aluminum tube structure;


5) single-layer stainless steel tube structure (central stainless steel tube structure, stainless steel tube layer stranded structure);


6) composite stainless steel tube structure (central stainless steel tube structure, stainless steel tube layer stranded structure).



27. What is the main composition of the twisted wire outside the OPGW cable core?


A: it is composed of AA wire (aluminum alloy wire) and AS wire (aluminum clad steel wire).



28, to choose the OPGW cable model, should have what technical conditions?


Answer: 1) the nominal tensile strength of OPGW cable (RTS) (kN); 2) optical fiber core number (SM) of OPGW optical cable; 3) short circuit current (kA); 4) short circuit time (s); 5) temperature range (℃).



29. How can the bending of the cable be limited?


Answer: the cable bending radius should not be less than 20 times the diameter of the cable, the construction process (non-static state) is not less than 30 times the diameter of the cable.



30, in the ADSS fiber optic cable project, what should pay attention to?


Answer: there are three key technologies: optical cable mechanical design, suspension point and the selection and installation of supporting gold.



31.What are the main optical cable hardware?


Answer: optical cable gold is to point to the hardware that installs optical cable to use, basically have: be able to bear tension line clip, overhang line clip, prevent vibration implement to wait.



32.What are the two most basic performance parameters of optical fiber connector?


Answer: the optical fiber connector is commonly known as the union, and the optical performance requirements for the single fiber connector are focused on the two most basic performance parameters, intervention loss and return loss.



33.How many types of fiber optic connectors are commonly used?


A: fiber optic connectors can be classified into different categories according to different classification methods.


According to the different transmission media can be divided into single-mode optical fiber connector and multi-mode optical fiber connector;


According to the different structure can be divided into FC, SC, ST, D4, DIN, Biconic, MU, LC, MT and other types;


According to the pin face of the connector, it can be divided into FC, PC (UPC) and APC. Commonly used optical fiber connector: FC/PC optical fiber connector, SC optical fiber connector, LC optical fiber connector.

34. The following items are commonly used in optical fiber communication systems. Please indicate their names.


A: AFC, FC type adapter ST type adapter SC type FC/APC, FC/PC type connector SC type connector ST type connector LC type jumper MU type jumper single mode or multiple mode jumper



35. What is the insertion loss of fiber optic connectors?


Answer: it is the quantity value that because connector intervenes and causes transmission line effective power to reduce, for the user, this value is smaller better. Itu-t stipulates that its value should not be greater than 0, 5dB.



36. What is the return loss of optical fiber connector?


A: it is a measure of the input power component reflected from the connector and returned along the input channel. The typical value should not be less than 25dB.



37. What is the most striking difference between the light emitted by a light-emitting diode and a semiconductor laser?


A: light-emitting diodes produce incoherent light with a wide spectrum. The laser produces coherent light with a narrow spectrum.



38. What is the most obvious difference between the performance of a light-emitting diode (LED) and a semiconductor laser (LD)?


A: there is no threshold value for LED, while there is a threshold value for LD. Only when the injection current exceeds the threshold value can laser be generated.



39.Single longitudinal mode semiconductor laser commonly used which two?


Answer: DFB laser and DBR laser are both distributed feedback lasers, whose optical feedback is provided by the distributed feedback Bragg grating in the optical cavity.



40.What are the two main types of optical receiving devices?


A: there are mainly photodiode (PIN tube) and avalanche photodiode (APD).


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