Fiber optic connector problem analysis

Fiber Connection Classification

1. The main way of optical fiber connection

1. Fixed connection. It is mainly used for the permanent connection between optical fibers in the optical cable line, mostly using fusion splicing, and also using bonding and mechanical connection. It is characterized by low joint loss and high mechanical strength. The equipment needs a fusion splicer, about tens of thousands of RMB

2. Active connection. It is mainly used for the connection between the optical fiber and the transmission system equipment and the instrument, mainly through the optical connection plug. The characteristic is that the connector is more flexible, and it is convenient to exchange the connection point. The loss and reflection are relatively large, which is the shortcoming of this connection method. Now the insertion loss is also very good, dozens of RMB is enough, you can buy finished products directly, if you want parts, you also need end surface polishing and grinding equipment, which is too expensive, it is recommended to buy jumpers directly.

3. Temporary connection. To measure the coupling connection between the pigtail and the optical fiber under test, this method is generally used to connect. It is characterized by convenience and flexibility, low cost, and low requirements for loss. This method is often used for temporary measurement. You can also use a fusion splicer or a V-groove to add glue

2. Requirements for fiber optic connection

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

2. Requirements for active connections Currently, mechanical connectors are used for detachable optical fiber connections. Its requirements mainly include the following aspects: the connection loss should be small, and the loss of single-mode fiber 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, and the insertion loss is stable after the connector is fastened, and it is not affected by temperature changes; it is small in size and light in weight; A certain strength; the price is right.

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

3. Factors of optical fiber connection loss

After the optical fiber is connected, the light passing through the joint will generate a certain loss, which is called the transmission loss of the optical fiber connection, that is, the joint loss. The factors that cause the connection loss of single-mode fiber are mainly analyzed now.

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

2. External factors The main factors that cause the splicing loss of single-mode optical fiber are axis misalignment and axial tilt. For mechanical connection, there are also factors such as longitudinal split and core deformation of fusion splicing.

(1) Axis misalignment. When the misalignment reaches 1.2 μm, the loss caused can reach 0.5 dB, which improves the accuracy of connection positioning and can effectively control the influence of axial center misalignment.

(2) Axial tilt. When the tilt reaches 1°, it will cause a loss of 0.2 dB. The loss caused by axial tilt can be improved by selecting a high-quality fiber cleaver.

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

Fourth, the method and comparison of optical fiber connection

1. Fusion splicer This method is mainly used for the connection of optical fiber joints. At present, it is mostly used in automatic fusion splicers for fusion splicing. Fusion splicers are divided into single-core and multi-core fusion splicers. Before the formal splicing, the parameters of the fusion splicer should be tested to determine the alignment accuracy, discharge size, propulsion amount and other parameters of the fusion splicer, so that they can adapt to the specific working conditions of the spliced optical fiber and control the loss within the set value. within the specified indicators. After the splicing is completed, the optical time domain reflectometer should be used to measure the loss in time. When the loss meets the index requirements, the reinforcement process can be carried out until the splicing 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 a standard form of connection for single-core optical fibers. Most of the current products have their end faces ground into spherical shapes, and use the principle of optical refraction to converge the beams to reduce their splicing loss. This kind of fiber optic connector is mostly used on fiber optic distribution frames and test instruments for switching purposes. NTT multi-core fiber optic connector. 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 small splicing loss. Therefore, it is widely used in optical fiber connections for users with lower requirements. This method is mostly used in short-distance relays of optical fibers and user relays, and the effect is better. Wiring sub-connector. With the development of technology, the average splice loss of the connector can be less than 0.1 dB, and 50% of the splice loss can be less than 0.05 dB, and the adaptability to ambient temperature and humidity is relatively good.