When wiring, what is the single -mode fiber and what is the multi -mode fiber?

When many friends are wiring, there are always friends who have been asking related questions about optical fibers, so today we have a detailed understanding of the fiber through this article.

1. Multi -mode fiber

When the geometric size of the fiber (mainly the diameter D1) of the fiber is far greater than that of the optical wavelength (about 1µm), there will be dozens of or even hundreds of communication modes in the fiber. Different communication modes have different transmission speeds and aspects, resulting in long -distance transmission and delay and light pulse width. This phenomenon is called the color scattered (also known as the color scatter) of the optical fiber.

The mode of color dispersion will make the bandwidth of the multi -mode fiber narrow and reduce its transmission capacity. Therefore, the multi -mode fiber is only suitable for small -capacity optical fiber communication.

Most of the refractive index distribution of multi -mode optical fibers is the distribution of parabolic lines, that is, gradient refractive index distribution. Its core diameter is about 50芯m.

Second, single -mode fiber

When the geometric size (mainly core diameter) of the optical fiber can be similar to the light wavelength, such as the core diameter D1 in the range of 5-10µm, the optical fiber only allows one mode (base model HE11) to spread. This kind of fiber is called single -mode fiber.

Because it has only one mode spread and avoids the problem of the mode color, the single -mode fiber has a very wide bandwidth and is especially suitable for large -capacity optical fiber communication. Therefore, in order to achieve single -mode transmission, the amount of ginseng of the fiber must meet certain conditions. It can be calculated through the formula that when the optical fiber of NA = 0.12 is calculated, the radius of the optical fiber core should be implemented above the λ = 1.3µm. ≤4.2µm, that is, the diameter of its core d1 ≤ 8.4µm.

Because the diameter of the core of the single -mode fiber is very small, it has put forward more demanding requirements for its manufacturing process.

3. What are the advantages of using fiber?

1) The frequency band of the fiber is very wide, and the theory can reach 30T.

2) No relay support length can reach tens of to 100 kilometers, and the copper line is only hundreds of meters.

3) It is not affected by electromagnetic fields and electromagnetic radiation.

4) Light weight and small volume.

5) Optical fiber communication is not charged, and it can be used in places such as flammable and violent use.

6) Use the environmental temperature range wide.

7) Long service life.

Fourth, how to choose the optical cable?

In addition to the optical fiber core and the type of optical fiber, the choice of optical cables must also choose the structure and outer sleeve of the optical cable according to the environment of the optical cable.

1. When the outdoor optical cable is buried directly, a loose armor optical cable should be selected. When overheading, you can choose a loose optical cable with two or multi -rooted black PE outer condoms.

2. The optical cables used in the building should choose tightly lit cables and pay attention to their flame retardant, poison and smoke characteristics. Generally, flame retardant but smoke type (Plenum) or flammable non -toxic types (LSZH) can be selected in the pipeline or forced ventilation. In the exposed environment, flame retardant, non -toxic and smoke -free type (RISER) should be selected.

3. When vertical or horizontally cloth cables in the building, you can choose tight -set optical cables, wiring optical cables or branches of optical cables in the building.

4. Select single -mode and multi -mode optical cables according to network applications and optical cable applications. Usually indoor and short -range applications are mainly multi -mode optical cables, and long -distance applications are mainly single -mode optical cables.

5. In the connection of optical fiber, how to choose different applications for fixed connection and activity connection?

The optical fiber activity connection is achieved through the fiber connector. A activity connection point in the light link is a clear division interface. In the selection of activity connections and fixed connections, the advantages of fixed connection are reflected in low cost and small light loss, but poor flexibility, and activity connection is opposite. During the design of the network design, the use of activities and fixed connections should be flexibly selected according to the entire link situation to ensure both flexibility and stability, so as to give full play to their respective advantages. The activity connection interface is an important interface for testing, maintenance, and changes. The activity connection is relatively easy to find the fault point in the link than the fixed connection, which increases convenience to the replacement of fault devices, thereby improving system maintenance and reducing maintenance costs.

Fifth, optical fiber is getting closer to the user terminal. What factors need to pay attention to when the significance of “fiber to the desktop” and system design?

In the application of horizontal subsystems, the relationship between the “fiber to the desktop” is indispensable with the copper cable. Optical fiber has its own unique strengths, such as long transmission distance, stable transmission, non -influence of electromagnetic interference, supporting bandwidth, and no electromagnetic leakage. These characteristics make the fiber play an irreplaceable role in some specific environments:

1. When the transmission distance of the information point is greater than 100m, choose to use copper cables. You must add a relay or increase the network equipment and weak electricity, thereby increasing costs and hidden dangers of faults, and using optical fiber can easily solve this problem.

2. In a specific working environment (such as factories, hospitals, air -conditioned machine rooms, electric power rooms, etc.), there are a large number of e -electromagnetic interference sources. Fiber can be unintected by electromagnetic interference, and stable operation in these environments.

3. There is no electromagnetic leak in the fiber. It is very difficult to detect the signal transmitted in the fiber. It is a good choice (such as military, research and development, auditing, government and other industries) in a high level of confidentiality.

4. The environment with a high demand for bandwidth reaches more than 1G, and fiber is a good choice.

The application of optical fiber is gradually extending from the trunk or computer room to the desktop and residential users, which means that more and more users who do not understand the characteristics of the fiber have begun to reach the fiber system. Therefore, when designing the optical fiber link system and selection of products, the current and future application needs of the system should be fully considered, and compatible systems and products should be used to maximize maintenance and management, and adapt to the actual situation of the ever -changing field and user installation needs.

5. Can the fiber connecter be directly connected to 250µm optical fiber?

Can’t. The loose optical cable contains naked fiber with an outer diameter of 250mm. This is a very small size and fragile. It cannot be fixed for fiber fiber. At least need to be wrapped in the optical fiber of 250 µm of the fiber of 250mm, so as to provide protection and support the connecter.

6. Can the FC connector be connected directly with the SC connector?

Yes, these are just different connections of two different types of connectors.

If you need to connect them, you must choose a mixed adapter, and you can connect the FC connectors and SC connectors at both ends with the FC/SC adapter. This method requires that the connectors should be grinding. If you must connect to the oblique angle (APC) connector, the second method of preventing damage must be used.

The second method is to use a mixed jump line and two connection adapters. The hybrid jumper refers to the type of different fiber connectors at both ends. These connectors will be connected to where you need to connect, so that the general adapter can be connected to the system in the wiring panel, but it brings the system attenuation budget for the system attenuation budget. Increase the amount of a connector.

7. The fixed connection of optical fiber includes the continuity of mechanical fiber and thermal melt. So what are the principles of mechanical fiber continuity and hot melt?

Mechanical optical fiber is commonly known as fiber -fiber cold connection. It refers to the non -hot melt machine. It uses simple continuation tools and uses mechanical connection technology to realize the permanent optical fiber continuation method of single core or multi -core optical fiber. In general, when the optical fiber dispersed in the small cores is continued, the mechanical continuation should be replaced by the heat melting.

The mechanical optical fiber continuation technology is often used in engineering practice such as line repair and small -scale applications in special occasions. In recent years, with the large -scale deployment of optical fiber to desktop and fiber -to -house (FTTH), people recognize the significance of mechanical fiber continuity as an important optical fiber continuation method.

For optical fiber to desktop and optical fiber -to -house applications with large number of users and scattered locations, when the size of the user reaches a certain degree, the construction complexity and the time requirements of the construction personnel and the melting machine cannot meet the time requirements for users to open the service. Due to the simple operation, short personality training cycle, and small equipment investment, the mechanical optical fiber continuation method provides the optical fiber continuation solution with the highest cost efficiency deployment. For example, in the height of the corridor, in the small space, insufficient lighting, inconvenient on -site electricity, etc., mechanical optical fiber continues to provide a convenient, practical, fast, high -performance optical fiber continuity for design, construction and maintenance personnel.

8. In the optical fiber -to -house system, what is the difference between the requirements for optical cable joints in the outdoor line of the telecommunications operating merchant?

First of all, in the optical fiber -to -house system, you need to reserve the installation and end -connection, accommodation, and protection of the inlet and outlets in the connector box according to the actual needs. Because the actual situation is that the optical device may be located in facilities such as optical cable joint box, optical cable junction box, wiring box, ODF, and the end connection and allocation of optical cables.

Secondly, for the residential area, the optical cable joint box is more installed in the method of buried land, so the buried performance of the optical cable joint box is higher.

In addition, in the optical fiber -to -house project, a large number of small cores may be considered in and out.

The diameter of the multi -mode fiber is 50 ~ 62.5 μm, the diameter of the bag layer is 125 μm, the diameter of the core of the single -mode fiber is 8.3 μm, and the outer diameter of the bag layer is 125 μm. The operating wavelength of the fiber is 0.85 μm, a length of 1.31 μm and 1.55 μm. Fiber loss is generally reduced with the growth of the wavelength. The loss of 0.85 μm is 2.5dB/km, the loss of 1.31 μm is 0.35dB/km, and the loss of 1.55 μm is 0.20dB/km. Losses above μm have increased. Due to the absorption of OHˉ, there are a peak of loss in the range of 0.90 ~ 1.30 μm and 1.34 ~ 1.52 μm, and these two areas have not been fully utilized. Since the 1980s, it has tended to use more single -mode fiber, and first with a long wavelength of 1.31 μm.

Multimodal fiber

Multi Mode Fiber: The central glass core is thicker (50 or 62.5 μm), which can pass the light of various modes. However, the color scattered between its models is large, which limits the frequency of transmitting digital signals, and the increase will be more serious. For example, the optical fiber of 600MB/KM is only 300MB bandwidth at 2km. Therefore, the distance between the multi -mode fiber transmission is relatively close, generally only a few kilometers.

Single -mode optical fiber

Single Mode Fiber: The central glass core is very fine (the core diameter is generally 9 or 10 μm), and only one mode of light can be passed. Therefore, the color scattered between its models is very small and suitable for remote communication, but there are still material scattering and waveguide scatter. In this way, the single -mode fiber has high requirements for the width and stability of the light source, that is, the width of the spectrum must be narrow, the stability is stable, and the stability is stable. Good. Later, at the 1.31 μm wavelength, the color of the material of the single -mode fiber was scattered and the waveguide scatter was positive, one was negative, and the size was just equal. That is to say, at 1.31 μm wavelength, the total color of the single -mode fiber is scattered. From the perspective of the loss of optical fiber, 1.31 μm is exactly a low loss window for fiber. In this way, the 1.31 μm wavelength area has become an ideal working window for optical fiber communication, and it is also the main working band of the practical optical fiber communication system. The main parameters of the 1.31 μm conventional single -mode fiber are determined by the ITU -T of the International Telecom Alliance in G652, so this fiber is also called G652 fiber.

6. What is the difference between multi -mode fiber transceiver and single -mode fiber transceiver?

Price: Multi -mode cheap, single -mode expensive

Distance: The multi -mode is less than 2km, and the single -mode can transmit about 100km

Wave length: multi -mode 850/1310 nm, single mode 1310/1550 nm

Other else



Multi -mode transceiver and multi -mode fiber correspondence, single -mode and single -mode correspondence, cannot be mixed.

At present, the price of multi -mode transceiver is low, and the basically about 200 yuan is very good. More than 300 enterprise -level is enough. The bandwidth is 100Mbps.

Compared with the single -mode transceiver, the market has fewer supply and the price is more expensive. Basically it costs about 1,000 yuan, and the bandwidth is 1000Mbps, which is much higher than the multi -mode.

In specific applications, the amount of multi -mode is higher than the single mode, which is mainly within the wiring range below 500m. The multi -mode can be met. Although the performance is not as good as the single mode. Most of them are enterprise -level applications. Because the work stability and performance of the fiber module are greatly better than the transceiver, in the application environment with high performance requirements for single -mode, few enterprises will use the transceiver, but directly Use a module to replace it. There are fewer manufacturers who produce single -mode hair transceivers with natural production, and the price is high.


The multi -mode transceiver receives multiple transmission modes, and the transmission distance is relatively close.

The single -mode transceiver only receives a single mode. The transmission distance is relatively long.

As for the large amount of dosage, it is difficult to say that although the multi -mode is being eliminated, because the price is low, it is much used in the surveillance.


Single -mode is generally two cores, one core and one core; there are also single -fiber two -way with a core, and two -way transmission is achieved through WDM technology on the same core. Single -mode optical fiber wave division replica WDM

The multi -mode one is two cores, and there are no single cores, because the multi -mode light cable cannot do WDM.

The price of a single fiber two -way transceiver is higher, and the price of one -pair is up to the two -way two -way price.

Update of the latest weak electricity data -the construction quotation list of various systems of weak current engineering (December 21)

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