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What is the working principle of optical fiber connectors

Update:07-08-2020
Summary:

Optical fiber connector is an indispensable device for […]

Optical fiber connector is an indispensable device for connecting various devices in optical fiber communication system, and it is also the most used optical fiber device at present.

Generally, the main optical characteristic indexes to measure the quality of optical fiber connectors are insertion loss and return loss. In addition, physical characteristics such as geometric parameters of the ferrule end face that affect product quality and reliability are also valued. Starting from the working principle of the optical fiber connector, we will briefly introduce the insertion and return loss of the connector:

The optical fiber connector cannot be used alone. It must be mutually matched with other connectors of the same type to form the optical path connection. At present, the more popular optical fiber connector assembly and docking method is: use epoxy resin thermosetting agent to glue the optical fiber It is fixed in the ceramic pin hole and positioned by the adapter sleeve to realize the fiber connection. Insertion loss is caused by the lateral deviation between two consecutive optical fibers, the longitudinal gap in the optical fiber connector, and the quality of the end face.


 

It can be seen that ensuring that the two butted fiber cores are in a straight line when they are in contact is the key to ensuring the excellent connection quality of the connector. It mainly depends on the physical properties of the fiber itself, the manufacturing accuracy of the connector pins, and the assembly of the connector. Processing accuracy, at the same time, the optical performance index of the optical fiber and the polishing quality of the pin end face also have a direct impact on the optical performance and reliability of the connector.

Insertion loss refers to the optical power attenuation caused by the connected connector to the system (that is, the relative decrease in the output power of the optical connector relative to the input power).

Insertion loss is mainly caused by the lateral deviation between two consecutive optical fibers. If two optical fibers are arranged in a straight line and the lateral deviation is zero, the insertion loss caused by them is minimal. But in the actual docking process of the connector, this is unlikely to be achieved because of the misalignment of the fiber core and the fiber cladding, the misalignment of the fiber cladding and the pin hole, and the concentricity of the pin hole and the outer diameter. Degree errors, etc., will cause lateral deviation between optical fibers.

Longitudinal gap and end face quality. At the same time, the longitudinal gap and end face quality in the optical fiber connector are also one of the factors that cause insertion loss. The UPC plug contact method commonly used in recent years has better solved the longitudinal gap problem. In this way, the pin and the fiber end face are polished spherically, so that the two opposite pins are meshed together under the action of external force, so that the apex of the meshed fiber is deformed and flattened to form a sufficient butt of the fiber and reduce the fiber joint The longitudinal gap.

Return loss is a parameter used to measure the size of the back-reflected light on the connector end face. The essence of echo is light reflection. According to the principle of Fresnel reflection, Fresnel reflection occurs when light encounters two interfaces with different refractive indexes during transmission, causing signal superposition or interference in the optical path. In a single-mode fiber system with a high transmission rate, especially a cable television system (CATV), the reflection phenomenon will cause a time lag in the transmission signal, which delays the time it takes for the signal to reach the user end, and causes the ghosting and sharpness of the image to decrease.

The UPC contact method of the connector joint reduces the gap between the connection end faces, in addition to reducing the insertion loss, it also reduces the reflection of the connection end face, and improves the return loss; for users such as CATV systems, the APC type The contact method is a better choice: because the spherical normal of the end face of the ceramic ferrule of the APC connector has an angle (usually 8°) with the axis of the fiber, the light reflected from the end face leaks out without returning to the core. Thereby greatly improving the return loss of the connector.

In summary, for an excellent Optical Fiber Joint Box manufacturer, in order to ensure the high quality of the product, three factors are very important. They are high-quality tight-buffered fiber optic cable, high-precision ceramic pin and Assemble parts, and excellent assembly processing technology.

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