Optical fiber connector principle and classification

In fiber optic communication (transmission) links, in order to implement different modules. The need for flexible connection between equipment and systems, there must be a device capable of detachable (active) connection between optical fibers, so that the optical path can be transmitted according to the required channels to achieve and complete the intended or desired purpose And requirements, the device that can achieve this function is called a connector.

The optical fiber connector is to precisely butt the two end faces of the optical fiber, so that the light energy output by the transmitting optical fiber can be coupled to the receiving optical fiber to the maximum extent, and the impact on the system due to its involvement in the optical link is minimized. , which is the basic requirement for fiber optic connectors. To a certain extent, fiber optic connectors also affect the reliability and performance of optical transmission systems.

ZR Cable Fiber Connector

Fiber Connection Classification

1. The main method of optical fiber connection

1. Fixed connection. It is mainly used for permanent connection between optical fibers in optical cable lines. It is characterized by small joint loss and high mechanical strength. Equipment requires fusion splicer

2. Active connection. It is mainly used for the connection between optical fiber and transmission system equipment and instruments, mainly through optical connection plugs. The characteristic is that the connector is more flexible, the connection point is convenient to exchange, and the loss and reflection are large, which are the shortcomings of this connection method. Now the insertion loss is also very good, and you can buy the finished product directly. If you want loose parts, you also need end-face polishing and grinding equipment, which is too expensive. It is recommended to buy jumpers directly.

3. Temporary connection. This method is generally used to measure the coupling connection between the pigtail and the fiber under test. It is characterized by convenience and flexibility, low cost, and low requirements for loss. This method is often used for temporary measurement. It can also be glued with a fusion splicer or a V-groove

2. Requirements for fiber optic connection

1. Requirements for fixed connection Optical fiber fixed connection is a key technology in optical cable lines. The requirements for fixed connection are as follows: the connection loss is small and the consistency is good; the connection loss stability is better, and there should be no additional loss in the general temperature difference range; sufficient mechanical strength and service life; operation should be as simple as possible , easy to construct; the joint volume is small, easy to place and protect; the cost is low, and the material is easy to process.

2. Requirements for Active Connections For optical fiber connections that require detachable connections, mechanical connectors are currently used. The main requirements are as follows: the connection loss should be small, and the single-mode fiber loss should be less than 0.5dB; it should have good repeatability and interchangeability. After many times of plugging and exchanging accessories, there is still good consistency; it has good stability, the insertion loss is stable after the connector is tightened, and it is not affected by temperature changes; the volume should be small and the weight should be light; there are A certain strength; affordable.

3. Requirements for temporary connection The temporary connection of optical fibers can also be spliced ​​with a fusion splicer. The loss is required to be as low as possible. When connecting the V-shaped groove and the capillary, the proportioning liquid must be added, otherwise the Fresnel reflection cannot be eliminated.

3. Factors caused by optical fiber connection loss

After the optical fiber is connected, the light passing through the joint will produce a certain loss, which is called the optical fiber connection transmission loss, that is, the joint loss. Now mainly analyze the factors of single-mode fiber connection loss.

1. Intrinsic factors The single-mode fiber that has the greatest impact on the connection is the mode field diameter. When the mode field diameters are mismatched by 20%, more than 0.2 dB loss will occur. It is of great significance to use the optical fiber with the smaller mode field diameter as much as possible to reduce the splice loss.

2. External factors The main external factors for the splicing loss of single-mode optical fibers are axial dislocation and axial inclination. For mechanical connections, there are also factors such as longitudinal splitting and fusion core deformation.

(1) The axis is dislocated. When the dislocation reaches 1.2 μm, the loss caused can reach 0.5 dB, which improves the accuracy of the connection positioning and can effectively control the influence of the axial dislocation.

(2) Axial tilt. When the tilt reaches 1°, a loss of 0.2 dB will be incurred. Use high-quality fiber cleavers to improve the loss caused by axial tilt.

(3) Core deformation. When the current, propulsion, discharge current and time of the automatic fusion splicer are set reasonably, the loss caused by the core deformation can be less than 0.02 dB.

Fourth, the method and comparison of optical fiber connection

1. Fusion splicer fusion splicing This method is mainly used for the connection of optical fiber connectors. At present, it is mostly used in automatic fusion splicers for fusion splicing. The fusion splicer is divided into single-core and multi-core fusion splicers. Before the formal connection, the parameters of the fusion splicer should be tested to determine the alignment accuracy, discharge size, propulsion and other parameters of the fusion splicer, so as to adapt to the specific working conditions of the spliced ​​fiber, and control the loss within the set within the specified indicators. After the connection is completed, the optical time domain reflectometer should be used to measure the loss in time. When the loss meets the requirements of the index, the reinforcement process can be carried out until the connection is completed.

2. Mechanical connection The connection characteristics of the three most common mechanical connectors are as follows: FO-type process connector. This fiber optic connector is the standard form of connection for single-core fibers. Most of the current products grind the end face into a spherical shape, and use the principle of optical refraction to converge the light beam to reduce its connection loss.

This fiber optic connector is mostly used on fiber optic distribution frames and test instruments for switching. NTT Multicore Fiber Connectors. This optical fiber connector can connect up to 12 optical fibers at a time, and has the characteristics of large capacity, simple manufacturing process, and low splice loss. Therefore, it has a wide range of applications in the optical fiber connection of users with lower requirements. This method is mostly used for short-distance relays of optical fibers and user relays, and the effect is better.

Wiring sub connectors. With the development of technology, the average splicing loss of wiring terminals can be below 0.1 dB, and the 50% joint loss can be below 0.05 dB, and the adaptability to ambient temperature and humidity is also relatively good. Since this splicing method does not require an expensive fusion splicer, and has a variety of specifications such as single-core and multi-core, it is flexible and convenient to use.

In the development of optical cable communication, the connection technology is a very critical technology. Simplifying the connection technology and improving the connection quality will play a positive role in expanding the application field of optical fibers.