In the installation of any optical system, must be considered low loss method of optical fiber cable or the connected to each other, in order to realize the light in the link. In the fiber optic link, and can be divided into permanent and activity of the two. In most of the permanent, the welding method, adhesive method or fixed connectors to realize; In the activity, use commonly activities to achieve the connector. This paper will be to do a simple activities connectors are introduced.

   Optical fiber connectors, commonly known as the live joint activities, commonly known as the optical fiber connectors, is used to connect the two root optical fiber cable or form a continuous light path can be repeated use of passive components, have been widely used in the optical fiber transmission lines, optical fiber distribution frames and optical fiber testing instrument and meter, is currently used in the largest number of optical passive components.

Optical fiber connectors general structure:

   The main purpose of the optical fiber connectors is used to make in the optical fiber. Now already is widely used in the optical fiber communication system of optical fiber connectors, the type, structure of each different. But looked up, all kinds of optical fiber connectors basic structure is the same, that is, the vast majority of the optical fiber connectors generally USES the high precision components (by two put the needle and a coupling tube were three parts) to implement the optical fiber on connection.

   The method is to optical fiber inserted and fixed in the needle, and will put into the needle on the surface polishing processing in the coupling of the tube, realize alignment. Put the needle equipment adopts metallic and non-metallic material is made. Put the needle to deal with the docking grinding, the other side is usually restricted to support the bending members or optical fiber soft cable to release stress. Coupling tube is generally by the ceramic, or bronze etc material made of two and a half synthetic, fastening of cylindrical components to make, with more of the metal or plastic flanges, in order to provide the fixed installation. For as far as possible on the precise optical fiber, to put the needle and coupling tube process accuracy is very high.

Optical fiber connectors performance:

   The performance of the optical fiber connectors, first is optical performance, in addition to consider optical fiber connectors replacement, repeatability, tensile strength, temperature and inserted number, etc.

(1) optical properties: for optical fiber connectors light performance requirements, and mainly is the insertion loss and return loss the two most basic parameters. Insertion Loss (Insertion Loss) linking Loss, refers to the introduction of the connector caused by the Loss of light power link effective. Smaller may be more beautiful insertion loss, general requirement should be no more than 0.5 dB. Return Loss (pressing, Reflection Loss) Loss is to point to to link light power connector inhibition of Reflection ability, the typical values should not be less than 25 dB. The practical application of connectors, put the needle through the special surface polishing treatment, can make the return loss bigger, generally not be less than 45 dB.

(2) the interchangeability, repeatability: optical fiber connectors is general passive components, for the same type of optical fiber connectors, generally can be arbitrary combination to use, and can repeat DuoCi use, from this and import the additional loss of the general all in less than 0.2 dB range. (3) tensile strength: for the optical fiber connectors to general requirement, the tensile strength shall not be lower than 90 N.

(4) temperature: general requirement, optical fiber connectors in-40 oC must be ~ + 70 oC to the temperature of the normal use.

(5) inserted number: current use of optical fiber connectors generally can be inserted l000 times more. Part of the common optical fiber connectors in accordance with the different classification method, optical fiber connectors can be classified into different types according to the transmission medium, can be divided into single-mode optical fiber connectors and multimode fiber connectors; According to the structure can be divided into FC, SC, ST, D4, DIN, Biconic, MU, LC, MT, etc. Various kinds of type; According to the needle inserted end connector can be divided into FC, PC (UPC) and APC; According to the optical fiber some points and single core, many of the core points.

   In practice, we generally according to optical fiber connectors of the different structure to distinguish. The following simple introduce some at present more common optical fiber connectors:

(1) the FC type optical fiber connectors

   This is the earliest it is to be made by Japan's NTT connector development. FC Ferrule is the abbreviation of by that its external strengthen way was using the metal sleeve and tighten for LuoSiKou way. The earliest, FC type of connectors, the ceramics in the end is plane needle docking contact (FC). Such connector of simple structure, easy operation, is easy to make, but fiber end face is sensitive to dust, and easy to produce the Fresnel reflections, improve return loss performance more difficult. Later, the type of connector, the improved end is inserted spherical docking needle (PC), while the external structure, make no change insertion loss and return loss performance had relatively substantially improved.

(2) the SC type optical fiber connectors

   This is a kind of Japan's NTT by company developed the optical fiber connectors. The rectangular in shell, adoption of needle inserted with coupling sleeve of size and structure of the same type, including the FC needle inserted of end used more PC or APC type grinding method; Tighten way is to use the swaps pin bars type, do not need to rotate. Such connector low prices, inserted convenient operation, small fluctuations in loss, high compressive strength, the high density of installation.

(3) double cone type Biconic connectors (by)

   This kind of optical fiber connectors the most representative of products developed by the bell LABS, it consists of two precision moulding by the end of the forming a section head conical cylinder plugs and an internal equipped with double tapered plastic sleeve of coupling components.

(4) DIN47256 type optical fiber connectors

   This is a German development by the connector. The connectors used in the structure of the sleeve and the coupling needle size and type, the same face FC treatment using PC grinding way. Compared with FC connector, the structure of complicated some internal metal structure, in the spring of the pressure control, can avoid the plug-and-socket pressure and damage end. In addition, this kind of mechanical precision connector, and intervention in smaller values of the loss.

5) MT-RJ type connector

   MT-RJ began in the development of MT connectors, NTT with and RJ-45 type LAN electrical connectors of the same bars lock in small casing, through the installation guide pin on both sides of the optical fiber, for convenience and optical transceiver letter to end optical fiber connectors, machine for double core (0.75 mm) between alignment design, is mainly used for the next generation of high density data transmission light connector.

(6) LC type connector

   LC type connector is famous Bell research institute of development of the convenient operation, out of modularization socket (RJ) latch-up mechanism is made. Its the needle into the size of the common and sleeve SC, such as the size of the FC used half, of 1.25 mm. This can improve the distribution frames in the density of the optical fiber connectors. At present, in the single-mode SFF, LC type of connector actual has held a dominant position in the mold, the application of rapid growth also.

(7) MU type connector

   MU (Miniature unit.and Coupling) connector is currently use most of the SC type connectors as the foundation, developed by NTT out of the world's smallest single core optical fiber connectors, this connector use 1.25 mm diameter of the casing and keep the organization, its advantage is to realize high density installation. Use of MU l. 25 mm diameter casing, NTT has developed MU connectors series. They are used for fiber optic cable connection type light socket connector (MU-A series), which has since keep institution of the backplane connector (MU-B series) and for the connection LD/PD module and the plug to simplify the socket (MU-SR series), etc. As the optical fiber network to a bigger more bandwidth capacity of the rapid development and direction of DWDM technology applications of MU type of connector demand will also growing rapidly.

   With the development of the optical fiber communication technology, especially the development of high-speed LAN and light access network, optical fiber connectors in the application of optical fiber system will be more widely. At the same time, also to the optical fiber connectors puts forward more and higher requirements, the main development direction is: look, low cost, the miniaturization of the requirements of high performance is more and more. In the future for a period of time, all sorts of new developed with the traditional optical fiber connectors, SC, FC together to form the connector "show director, each with the pattern of" have.