The optical fiber connector

A fiber optic connector is a detachable (active) connection between an optical fiber and an optical fiber. The two end faces of the optical fiber are precisely butted together so that the optical energy output from the transmitting optical fiber can be coupled to the receiving optical fiber to the maximum extent. It also minimizes the impact on the system due to its involvement in the optical link, which is a basic requirement for fiber optic connectors. To some extent, fiber optic connectors affect the reliability and performance of optical transmission systems.

Basic introduction
A connecting device for re-plugging between optical fibers, also called a fiber optic movable joint. The main performance parameters (and typical values) are: insertion loss (<0.5dB), plug-and-repeat repeatability and interchangeability between connectors (500 changes). When used in a large-capacity high-speed transmission system, reflection is also required to be small.
Introduction
Optical fiber connectors can be divided into single-mode and multi-mode connectors of common silicon-based fibers according to different transmission media, and other fiber-optic connectors such as plastics; the structure of the connector can be divided into: FC , SC, ST, LC, D4, DIN, MU, MT, etc. Among them, ST connectors are usually used for wiring equipment terminals, such as fiber distribution frames, fiber modules, etc.; and SC and MT connectors are usually used for network equipment terminals. According to the shape of the end face of the fiber, there are FC, PC (including SPC or UPC) and APC; according to the number of cores of the fiber, there are also single core and multi-core (such as MT-RJ). Fiber optic connectors are used in a wide variety of applications. In the actual application process, we generally distinguish according to the structure of the fiber optic connector. Here are some common fiber connectors:
FC type fiber optic connector
   This connector was first developed by NTT Japan. FC is an abbreviation of Ferrule Connector, which indicates that the external reinforcement method is a metal sleeve and the fastening method is a turnbuckle. At the earliest, FC type connectors, the mating end faces of the ceramic pins used were planar contact (FC). The connector has the advantages of simple structure, convenient operation and easy manufacture, but the fiber end face is sensitive to fine dust, and Fresnel reflection is easy to occur, and it is difficult to improve the return loss performance. Later, this type of connector was improved by using a pin (PC) with a spherical end face, and the external structure was not changed, so that the insertion loss and return loss performance were greatly improved.
SC type fiber optic connector
   This is a fiber optic connector developed by NTT Corporation of Japan. The outer casing has a rectangular shape, and the structure of the pin and the coupling sleeve is exactly the same as that of the FC type. The end face of the pin is mostly made of PC or APC type; the fastening method is a plug-and-pin type, which is not required. Rotate. Such connectors are inexpensive, easy to insert and remove, have small fluctuations in insertion loss, high compressive strength, and high installation density.
The ST and SC interfaces are two types of fiber connectors. For 10Base-F connections, the connectors are usually ST type. For 100Base-FX, the connectors are mostly SC type. The core of the ST connector is exposed and the core of the SC connector is inside the connector.
Biconic Connector
   The most representative of these types of fiber optic connectors was developed by Bell Laboratories of the United States. It consists of two precision-molded ends with frusto-conical cylindrical plugs and a double-conical plastic sleeve inside. The coupling assembly of the barrel.
DIN47256 fiber optic connector
   This is a connector developed by Germany. The connector and coupling sleeve of this type of connector have the same structural dimensions as the FC type, and the end face treatment adopts PC grinding. Compared with the FC type connector, the structure is more complicated, and the internal metal structure has a spring that controls the pressure, so as to avoid damage to the end surface due to excessive insertion pressure. In addition, the mechanical accuracy of such a connector is high, and the value of the insertion loss is small.
MT-RJ type connector
   MT-RJ started with the MT connector developed by NTT, with the same latching mechanism as the RJ-45 LAN electrical connector. The optical fiber is aligned with the guide pin mounted on both sides of the small sleeve for easy transmission and reception. The machine is connected, and the connector end face fiber is a double-core (interval 0.75mm) arrangement design, which is the next-generation high-density optical connector mainly used for data transmission.
LC connector
   The LC connector was developed by the famous Bell Institute and is manufactured using a convenient modular jack (RJ) latch mechanism. The size of the pins and sleeves used is half that of ordinary SC, FC, etc., which is 1.25 mm. This can increase the density of the fiber optic connectors in the optical distribution frame. At present, in the single-mode SFF, the LC type connector has actually occupied a dominant position, and the application in multi-mode has also grown rapidly.
MU type connector
   The MU (Miniature Unit Coupling) connector is the world's smallest single-core fiber optic connector developed by NTT based on the most widely used SC-type connector. The connector uses a 1.25mm diameter bushing and self-retaining. The advantage of the organization is that it enables high-density installation. With MU's l.25mm diameter bushings, NTT has developed a series of MU connectors. They have socket type optical connectors (MU-A series) for fiber optic cable connection, backplane connectors with self-holding mechanism (MU-B series), and simplified sockets for connecting LD/PD modules and plugs (MU-SR series) )Wait. With the rapid development of fiber-optic networks to larger bandwidths and larger capacity and the widespread use of DWDM technology, the demand for MU-type connectors will also grow rapidly.
MC connector
In 2012, the domestic communication company independently developed a smaller and denser MC connector than the LC connector. The Nippon MC Fiber Optic Active Connector is a high-density single-core fiber optic connector for high-density applications such as high-capacity central rooms and high-density data centers. The MC fiber optic connector has a high density and can double the LC connector in the same space, making it the world's smallest and densest connector.
The main parameters:

General structure
The main purpose of fiber optic connectors is to achieve fiber optic connections. Optical fiber connectors that have been widely used in optical fiber communication systems are numerous in variety and structure. However, the basic structure of various types of fiber optic connectors is consistent, that is, most fiber optic connectors are generally made of high-precision components (composed of two pins and one coupling tube). Alignment of the fiber.
In this method, the fiber is inserted into 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 pins are made of metal or non-metal materials. The butt end of the pin must be ground and the other end typically uses a bend limiting member to support the fiber or fiber optic cable to relieve stress. The coupling tube is generally made of two semi-synthetic, fastened cylindrical members made of ceramic, or bronze, and is equipped with a metal or plastic flange to facilitate the mounting and fixing of the connector. In order to align the fiber as precisely as possible, the processing precision of the pin and the coupling tube is very high.
Performance
The performance of fiber optic connectors, first of all, optical performance, in addition to the interchangeability, repeatability, tensile strength, temperature and number of insertions and removals of fiber optic connectors.
(1) Optical performance: For the optical performance requirements of the optical fiber connector, the two most basic parameters of insertion loss and return loss are mainly used.
Insertion loss (InsertionLoss) is the loss of the effective optical power of the link caused by the introduction of the connector. The smaller the insertion loss, the better. Generally, the requirement should be no more than 0.5dB.
ReturnLoss (ReflectionLoss) refers to the ability of the connector to suppress the reflection of the link optical power, and its typical value should be no less than 25dB. In the practical application of the connector, the surface of the pin has been specially polished to make the return loss larger, generally not less than 45dB.
(2) Interchangeability and repeatability
The fiber optic connector is a universal passive device. For the same type of fiber optic connector, it can be used in any combination and can be used repeatedly. Therefore, the additional loss introduced is generally less than 0.2 dB.
(3) Tensile strength
For a good fiber optic connector, the tensile strength is generally required to be no less than 90N.
(4) Temperature
Generally, fiber optic connectors must be able to operate at temperatures between -40oC and +70oC.
(5) Number of insertions and removals
The fiber optic connectors used can be plugged and unplugged more than 1000 times.
Connection step
1. The Fiber Optic Quick Connector is an innovative field termination connector that includes factory pre-installed fiber, pre-cast ceramic ferrules, and a mechanical splice mechanism.
2. When the termination is completed, only the introduction fiber or the indoor fiber can be inserted into the mechanical connection mechanism, without using other tools, the termination process takes only about 2 minutes, which greatly saves the installation time.
3. The ferrule and end face of the fiber optic quick connector are pre-ground and pre-polished at the factory, and the mechanical connection mechanism is located at the end of the ferrule to fix the inserted fiber.
4. The mechanical connection mechanism is mainly composed of a V-shaped groove and a clamping element; when a fiber needs to be inserted, the V-shaped groove is opened by a wedge-shaped clamp to facilitate the smooth insertion of the optical fiber.

5. When the fiber is inserted into the V-groove and fixed, remove the wedge clamp from the V-groove.

In order to facilitate users to better understand and select fiber optic connectors, Konnra Electronics hereby organizes the knowledge and classification of fiber optic connectors, and hopes to be helpful to the majority of users.