1、 Foreword when installing any optical fiber system, we must consider to connect the optical fiber or optical cable with each other in a low loss way to realize the connection of optical fiber link. The connection of optical fiber link can be divided into two types: permanent and active. Permanent connection is mostly realized by welding, bonding or fixed connector; movable connection is generally realized by movable connector. This article will make a brief introduction to the active connector. Optical fiber movable connector, commonly known as flexible joint, commonly known as optical fiber connector, is a reusable passive device used to connect two optical fibers or optical cables to form a continuous optical path. It has been widely used in optical fiber transmission lines, optical fiber distribution frames, optical fiber testing instruments and meters, and is currently the most used optical passive device. 2、 The main purpose of optical fiber connector is to realize the connection of optical fiber. Now it has been widely used in optical fiber communication system, which has many kinds and different structures. However, the basic structure of various types of optical fiber connectors is the same, that is, most of the optical fiber connectors generally use high-precision components (consisting of two pins and a coupling tube in total of three parts) to achieve optical fiber alignment connection. This method is to insert and fix the optical fiber in the pin, polish the pin surface, and then realize the alignment in the coupling tube. The outer components of the pin are made of metal or non-metal materials. The butt end of the pin must be ground, and the other end is usually supported by a bent limiting member to release the stress. The coupling pipe is generally made of two half synthetic and tight cylindrical components made of ceramic, bronze and other materials, most of which are equipped with metal or plastic flange to facilitate the installation and fixation of the connector. In order to align the optical fiber as accurately as possible, the processing accuracy of pins and coupling tubes is required to be very high. 3、 The performance of optical fiber connector the performance of optical fiber connector, first of all, optical performance, in addition to the interchangeability, repeatability, tensile strength, temperature and plugging times of optical fiber connector. 1. Optical performance: for the optical performance requirements of optical fiber connector, the two most basic parameters are insertion loss and return loss. Insertion loss refers to the loss of effective optical power of the link caused by the import of the connector. The smaller the insertion loss is, the better. Generally, it should not be more than 0.5dB. Return loss refers to the connector's ability to suppress the reflection of link optical power, and its typical value shall not be less than 25dB. The practical connector and the pin surface have been specially polished, which can make the return loss larger, generally no less than 45dB. 2. Interchangeability and repeatability optical fiber connectors are general passive devices. For the same type of optical fiber connectors, they can be used in any combination, and can be used repeatedly. Therefore, the additional loss of the imported optical fiber connectors is generally less than 0.2db. 3. The tensile strength of a good optical fiber connector is generally required to be no less than 90N. 4. Generally speaking, the optical fiber connector must be able to operate normally at - 40 ℃ ~ + 70 ℃. 5. At present, the optical fiber connector can be plugged more than 1000 times. 4、 Some common optical fiber connectors According to different classification methods, optical fiber connector can be divided into different types, single-mode optical fiber connector and multi-mode optical fiber connector according to different transmission media; FC, SC, St, D4, DIN, biconic, mu, LC, MT and other types according to different structures; PC (UPC) and APC can be divided according to the end face of connector pin; single core and multi-core can be divided according to the number of optical fiber cores Points.