In the installation of any optical fiber system, it is necessary to consider the method of connecting optical fiber or optical cable with each other in order to realize the connection of optical link. The connection of optical fiber link can be divided into permanent and active. The permanent connection is mostly realized by welding, bonding or fixed connector; the movable connection is generally realized by the movable connector. This article will make a brief introduction to the active connector.
The optical fiber movable connector, commonly known as the flexible joint, is a kind of 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 the most widely used optical passive device.
2. General structure of optical fiber connector
The main purpose of optical fiber connector is to realize the connection of optical fiber. Now, optical fiber connectors have been widely used in optical fiber communication system, which have many kinds and different structures. However, the basic structure of various types of optical fiber connectors is the same, that is, most optical fiber connectors generally use high-precision components (composed of two pins and a coupling tube, a total of three parts) to realize the alignment and connection of optical fibers.
In this method, the optical fiber is inserted and fixed in the pin, and the surface of the pin is polished to achieve alignment in the coupling tube. The outer components of the pin are made of metal or non-metallic materials. The butt end of the pin must be ground, and the other end is usually supported by a bending restraint member to release stress. The coupling pipe is usually made of ceramic, bronze and other materials, which is composed of two parts and is made of tight cylindrical components. It is usually equipped with metal or plastic flange plate to facilitate the installation and fixation of connector. In order to align the optical fiber as accurately as possible, the machining accuracy of the pin and coupling tube is very high.
3. Performance of optical fiber connector
The performance of optical fiber connector, first of all, is the optical performance. In addition, the interchangeability, repeatability, tensile strength, temperature and insertion times of optical fiber connector should be considered.
(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 (i.e. connection loss) refers to the loss of effective optical power of the link caused by the introduction of connectors. The smaller the insertion loss, the better. The general requirement should be no more than 0.5dB.
Return loss refers to the ability of the connector to suppress the optical power reflection of the link, and its typical value should not be less than 25dB. In practical application, the contact pin surface has been specially polished, which can make the return loss larger, generally no less than 45dB.
(2) Interchangeability and repeatability
Optical fiber connector is a general passive device. For the same type of optical fiber connector, it can be used in any combination, and can be used repeatedly. The additional loss caused by this is generally less than 0.2db.
(3) Tensile strength
For a good optical fiber connector, the tensile strength should be no less than 90N.
In general, the optical fiber connector must be able to work normally under the temperature of – 40 ℃ ~ + 70 ℃.
(5) Number of times of plug and pull
At present, the optical fiber connector can be plugged and plugged more than 1000 times.