Optical fiber is the abbreviation of optical fiber, which is a fiber made of glass or plastic that can be used as a light transmission tool. The transmission principle is "total reflection of light". Optical fiber communication has good characteristics, such as confidentiality, high capacity, high speed, etc. Therefore, optical fiber is widely used, roughly in the following categories:
1. Backbone transmission network (SDH/SONET): such as submarine optical cables between major cities and the bottom of the ocean;
2. Ethernet (GBE): including the current fiber to the home (FTTH), to the building (FTTB), to the community, etc., mainly our home and office networks;
3. Data network (Fiber channel): various storage devices, databases, including the developing cloud computing service system;
4. Cable TV transmission (PIN reception);
5. Other special-purpose transmission: such as fighter jets and ships.
Here are 21 basic knowledge points about optical fiber cables summarized for you
1. Briefly describe the composition of optical fiber
Answer: Optical fiber consists of two basic parts: the core and cladding made of transparent optical materials, and the coating.
2. What are the basic parameters that describe the transmission characteristics of optical fiber lines?
Answer: They include loss, dispersion, bandwidth, cutoff wavelength, mode field diameter, etc.
3. What are the causes of optical fiber attenuation?
Answer: The optical power in the optical fiber gradually decreases along the longitudinal axis. The reduction in optical power is related to the wavelength. In optical fiber links, the main reasons for the reduction in optical power are scattering, absorption, and optical power loss caused by connectors and fusion joints. The unit of attenuation is dB.
Causes: There are many reasons for the attenuation of optical fiber, mainly including: absorption attenuation, including impurity absorption and intrinsic absorption; scattering attenuation, including linear scattering, nonlinear scattering and structural incomplete scattering, etc.; other attenuation, including microbend attenuation, etc. Among them, the most important is the attenuation caused by impurity absorption.
4. What does the bandwidth of an optical fiber relate to?
Answer: The bandwidth of an optical fiber refers to the modulation frequency when the amplitude of the optical power is reduced by 50% or 3dB compared to the amplitude of the zero frequency in the transfer function of the optical fiber. The bandwidth of an optical fiber is approximately inversely proportional to its length, and the product of the bandwidth and length is a constant.
The phenomenon of optical pulse broadening caused by different group velocities of different wavelengths in the spectral components of the light source in the optical fiber.
5. How to describe the dispersion characteristics of signals propagating in optical fibers?
Answer: It can be described by three physical quantities: pulse broadening, optical fiber bandwidth, and optical fiber dispersion coefficient.
6. What is the cutoff wavelength?
Answer: It refers to the shortest wavelength that can only transmit the fundamental mode in the optical fiber. For single-mode optical fiber, its cutoff wavelength must be shorter than the wavelength of the transmitted light.
7. What impact will the dispersion of optical fiber have on the performance of the optical fiber communication system?
Answer: The dispersion of optical fiber will cause the optical pulse to be broadened during the transmission process in the optical fiber. Affect the size of the bit error rate, the length of the transmission distance, and the size of the system rate.
8. What is the testing principle of the optical time domain reflectometer (OTDR)? What are its functions?
Answer: OTDR is made based on the principle of backscattering and Fresnel reflection of light. It uses the backscattered light generated when light propagates in the optical fiber to obtain attenuation information. It can be used to measure optical fiber attenuation, joint loss, optical fiber fault point location, and understand the loss distribution along the length of the optical fiber. It is an indispensable tool in the construction, maintenance and monitoring of optical cables. Its main indicators and parameters include: dynamic range, sensitivity, resolution, measurement time and blind area.
9. What does "1310nm" or "1550nm" in common optical test instruments refer to?
Answer: It refers to the wavelength of the optical signal. The wavelength range used in optical fiber communication is in the near-infrared region, with a wavelength between 800nm and 1700nm. It is often divided into short-wavelength band and long-wavelength band, the former refers to 850nm wavelength, and the latter refers to 1310nm and 1550nm.
The working wavelength of optical fiber communication is in the near-infrared region, and the bands are:
O band: 1260nm to 1310nm
E band: 1360nm to 1460nm
S band: 1460nm to 1530nm
C band: 1535nm to 1565nm
L band: 1565nm to 1625nm
U band: 1640nm to 1675nm
Single-mode optical fiber usually operates at 1310nm, 1550nm and 1625nm.
10. Among the currently commercial optical fibers, which wavelength of light has the smallest dispersion? Which wavelength of light has the smallest loss?
Answer: Light with a wavelength of 1310nm has the smallest dispersion, and light with a wavelength of 1550nm has the smallest loss.
11. How are optical fibers classified according to the different light wave modes transmitted in the optical fiber?
A: It can be divided into single-mode fiber and multi-mode fiber. The core diameter of single-mode fiber is about 1 to 10 μm. At a given working wavelength, it only transmits a single fundamental mode, which is suitable for large-capacity and long-distance communication systems. Multi-mode fiber can transmit multiple modes of light waves, with a core diameter of about 50 to 60 μm, and its transmission performance is worse than that of single-mode fiber.
12. What are the most common optical cable structures?
Answer: There are two types: layer-twisted type and skeleton type.
13. What are the main components of optical cables?
Answer: It is mainly composed of: fiber core, optical fiber grease, sheath material, PBT (polybutylene terephthalate) and other materials.
14. What does the armor of optical cable refer to?
Answer: It refers to the protective element (usually steel wire or steel belt) used in optical cables for special purposes (such as submarine optical cables, etc.). The armor is attached to the inner sheath of the optical cable.
15. There are two most basic performance parameters for optical fiber connectors. What are they?
Answer: Optical fiber connectors are commonly known as live joints. For the requirements of the optical performance of single-fiber connectors, the focus is on the two most basic performance parameters of insertion loss and return loss.
16. How many types of commonly used optical fiber connectors are there?
Answer: According to different classification methods, optical fiber connectors can be divided into different types. According to different transmission media, they can be divided into single-mode optical fiber connectors and multi-mode optical fiber connectors; according to different structures, they can be divided into various types such as FC, SC, ST, D4, DIN, Biconic, MU, LC, MT, etc.; according to the pin end face of the connector, they can be divided into FC, PC (UPC) and APC. Commonly used optical fiber connectors: FC/PC optical fiber connector, SC optical fiber connector, LC optical fiber connector.
17. Fiber fusion diagram
18. What are the main optical fibers currently used for transmission network construction?
Answer: There are three main types, namely G.652 conventional single-mode fiber, G.653 dispersion-shifted single-mode fiber and G.655 non-zero dispersion-shifted fiber.
19. What is PON (passive optical network)?
Answer: PON is a fiber-optic loop optical network in the local user access network, based on passive optical devices such as couplers and splitters.
20. Fiber Optic Connectors
The cross-section of fiber optic connectors should be divided into PC, UPC, and APC.
PC and UPC are fiber optic microsphere end faces that are parallel to the end faces of the ceramic body, and the industrial standard return losses are -35dB and -50dB respectively.
The APC cross-section has an 8-degree tilt angle. In order to reduce reflection, the industrial standard return loss is -60dB.
21. Fiber Coupler
Fiber coupler, also known as splitter, is a component that splits optical signals from one fiber to multiple fibers.
Coupler is a bidirectional passive device, and its basic forms include tree type and star type.
Source: Dongguan HX Fiber Technology Co., Ltd
Optical fiber is the abbreviation of optical fiber, which is a fiber made of glass or plastic that can be used as a light transmission tool. The transmission principle is "total reflection of light". Optical fiber communication has good characteristics, such as confidentiality, high capacity, high speed, etc. Therefore, optical fiber is widely used, roughly in the following categories:
1. Backbone transmission network (SDH/SONET): such as submarine optical cables between major cities and the bottom of the ocean;
2. Ethernet (GBE): including the current fiber to the home (FTTH), to the building (FTTB), to the community, etc., mainly our home and office networks;
3. Data network (Fiber channel): various storage devices, databases, including the developing cloud computing service system;
4. Cable TV transmission (PIN reception);
5. Other special-purpose transmission: such as fighter jets and ships.
Here are 21 basic knowledge points about optical fiber cables summarized for you
1. Briefly describe the composition of optical fiber
Answer: Optical fiber consists of two basic parts: the core and cladding made of transparent optical materials, and the coating.
2. What are the basic parameters that describe the transmission characteristics of optical fiber lines?
Answer: They include loss, dispersion, bandwidth, cutoff wavelength, mode field diameter, etc.
3. What are the causes of optical fiber attenuation?
Answer: The optical power in the optical fiber gradually decreases along the longitudinal axis. The reduction in optical power is related to the wavelength. In optical fiber links, the main reasons for the reduction in optical power are scattering, absorption, and optical power loss caused by connectors and fusion joints. The unit of attenuation is dB.
Causes: There are many reasons for the attenuation of optical fiber, mainly including: absorption attenuation, including impurity absorption and intrinsic absorption; scattering attenuation, including linear scattering, nonlinear scattering and structural incomplete scattering, etc.; other attenuation, including microbend attenuation, etc. Among them, the most important is the attenuation caused by impurity absorption.
4. What does the bandwidth of an optical fiber relate to?
Answer: The bandwidth of an optical fiber refers to the modulation frequency when the amplitude of the optical power is reduced by 50% or 3dB compared to the amplitude of the zero frequency in the transfer function of the optical fiber. The bandwidth of an optical fiber is approximately inversely proportional to its length, and the product of the bandwidth and length is a constant.
The phenomenon of optical pulse broadening caused by different group velocities of different wavelengths in the spectral components of the light source in the optical fiber.
5. How to describe the dispersion characteristics of signals propagating in optical fibers?
Answer: It can be described by three physical quantities: pulse broadening, optical fiber bandwidth, and optical fiber dispersion coefficient.
6. What is the cutoff wavelength?
Answer: It refers to the shortest wavelength that can only transmit the fundamental mode in the optical fiber. For single-mode optical fiber, its cutoff wavelength must be shorter than the wavelength of the transmitted light.
7. What impact will the dispersion of optical fiber have on the performance of the optical fiber communication system?
Answer: The dispersion of optical fiber will cause the optical pulse to be broadened during the transmission process in the optical fiber. Affect the size of the bit error rate, the length of the transmission distance, and the size of the system rate.
8. What is the testing principle of the optical time domain reflectometer (OTDR)? What are its functions?
Answer: OTDR is made based on the principle of backscattering and Fresnel reflection of light. It uses the backscattered light generated when light propagates in the optical fiber to obtain attenuation information. It can be used to measure optical fiber attenuation, joint loss, optical fiber fault point location, and understand the loss distribution along the length of the optical fiber. It is an indispensable tool in the construction, maintenance and monitoring of optical cables. Its main indicators and parameters include: dynamic range, sensitivity, resolution, measurement time and blind area.
9. What does "1310nm" or "1550nm" in common optical test instruments refer to?
Answer: It refers to the wavelength of the optical signal. The wavelength range used in optical fiber communication is in the near-infrared region, with a wavelength between 800nm and 1700nm. It is often divided into short-wavelength band and long-wavelength band, the former refers to 850nm wavelength, and the latter refers to 1310nm and 1550nm.
The working wavelength of optical fiber communication is in the near-infrared region, and the bands are:
O band: 1260nm to 1310nm
E band: 1360nm to 1460nm
S band: 1460nm to 1530nm
C band: 1535nm to 1565nm
L band: 1565nm to 1625nm
U band: 1640nm to 1675nm
Single-mode optical fiber usually operates at 1310nm, 1550nm and 1625nm.
10. Among the currently commercial optical fibers, which wavelength of light has the smallest dispersion? Which wavelength of light has the smallest loss?
Answer: Light with a wavelength of 1310nm has the smallest dispersion, and light with a wavelength of 1550nm has the smallest loss.
11. How are optical fibers classified according to the different light wave modes transmitted in the optical fiber?
A: It can be divided into single-mode fiber and multi-mode fiber. The core diameter of single-mode fiber is about 1 to 10 μm. At a given working wavelength, it only transmits a single fundamental mode, which is suitable for large-capacity and long-distance communication systems. Multi-mode fiber can transmit multiple modes of light waves, with a core diameter of about 50 to 60 μm, and its transmission performance is worse than that of single-mode fiber.
12. What are the most common optical cable structures?
Answer: There are two types: layer-twisted type and skeleton type.
13. What are the main components of optical cables?
Answer: It is mainly composed of: fiber core, optical fiber grease, sheath material, PBT (polybutylene terephthalate) and other materials.
14. What does the armor of optical cable refer to?
Answer: It refers to the protective element (usually steel wire or steel belt) used in optical cables for special purposes (such as submarine optical cables, etc.). The armor is attached to the inner sheath of the optical cable.
15. There are two most basic performance parameters for optical fiber connectors. What are they?
Answer: Optical fiber connectors are commonly known as live joints. For the requirements of the optical performance of single-fiber connectors, the focus is on the two most basic performance parameters of insertion loss and return loss.
16. How many types of commonly used optical fiber connectors are there?
Answer: According to different classification methods, optical fiber connectors can be divided into different types. According to different transmission media, they can be divided into single-mode optical fiber connectors and multi-mode optical fiber connectors; according to different structures, they can be divided into various types such as FC, SC, ST, D4, DIN, Biconic, MU, LC, MT, etc.; according to the pin end face of the connector, they can be divided into FC, PC (UPC) and APC. Commonly used optical fiber connectors: FC/PC optical fiber connector, SC optical fiber connector, LC optical fiber connector.
17. Fiber fusion diagram
18. What are the main optical fibers currently used for transmission network construction?
Answer: There are three main types, namely G.652 conventional single-mode fiber, G.653 dispersion-shifted single-mode fiber and G.655 non-zero dispersion-shifted fiber.
19. What is PON (passive optical network)?
Answer: PON is a fiber-optic loop optical network in the local user access network, based on passive optical devices such as couplers and splitters.
20. Fiber Optic Connectors
The cross-section of fiber optic connectors should be divided into PC, UPC, and APC.
PC and UPC are fiber optic microsphere end faces that are parallel to the end faces of the ceramic body, and the industrial standard return losses are -35dB and -50dB respectively.
The APC cross-section has an 8-degree tilt angle. In order to reduce reflection, the industrial standard return loss is -60dB.
21. Fiber Coupler
Fiber coupler, also known as splitter, is a component that splits optical signals from one fiber to multiple fibers.
Coupler is a bidirectional passive device, and its basic forms include tree type and star type.
Source: Dongguan HX Fiber Technology Co., Ltd
