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Clear Conception---90% Of The People Are Confused About The Fiber Connector
Dec 13, 2018

A fiber optic connector is a physical device used to connect fiber optic cables that permanently or detachably couples two fibers together with a contiguous portion of the protective component.

ST, SC, FC fiber optic connectors are the standards developed by different enterprises in the early days. The effects are the same, each has its own advantages and disadvantages. The following is a detailed introduction for everyone.

ST, SC connector connectors are commonly used in general networks.


After the ST head is inserted, it has a bayonet fixed for half a rotation, and the disadvantage is that it is easy to break;

The C connector is directly inserted and removed, which is convenient to use, and has the disadvantage that it is easy to fall out;

The FC connector is generally used in a telecommunication network. A nut is screwed onto the adapter. The advantage is that it is reliable and dustproof. The disadvantage is that the installation time is slightly longer.

The MTRJ type fiber optic patch cord consists of two high precision plastic molded connectors and fiber optic cables. The outer part of the connector is a precision plastic part, which includes a push-pull insertion and clamping mechanism. Suitable for indoor applications in telecommunications and data network systems.




Type of fiber interface connector


Optical fiber connectors, that is, fiber connectors that are connected to optical modules, are also various and cannot be used interchangeably with each other. People who are not always in contact with fiber optics may mistake the fiber optic connectors of GBIC and SFP modules for the same type, but they are not. The SFP module is connected to the LC fiber connector, and the GBIC is connected to the SC fiber optic connector. The following is a detailed description of several commonly used fiber optic connectors in network engineering:

1 FC type fiber optic connector: The external reinforcement method is a metal sleeve, and the fastening method is a turnbuckle. Generally used on the ODF side (the most used on the patch panel)


2 SC type optical fiber connector: The connector that connects the GBIC optical module. Its outer casing is rectangular, and the fastening method is plug-and-pull type without rotating. (most used on router switches)

3 ST type optical fiber connector: commonly used in optical fiber distribution frame, the outer casing is round and the fastening method is screw buckle. (For 10Base-F connections, the connector is usually ST type. Commonly used for fiber distribution frames)

4 LC fiber optic connector: A connector that connects to an SFP module and is made with a convenient modular jack (RJ) latch mechanism. (used by routers)

5 MT-RJ: Transceiver integrated square fiber connector, one double fiber transceiver




Introduction to various fiber interface types

Fiber optic connector

FC round with thread (most used on patch panels)

ST card type round type;

SC card type square (most used on router switches)

PC microsphere polishing and polishing;

APC is at an angle of 8 degrees and is micro-spherical polished

MT-RJ square type, one double fiber transceiver (one useful on Huawei 8850)


Fiber optic modules: generally support hot swap,

GBIC Giga Bitrate Interface Converter, the fiber interface used is mostly SC or ST type

SFP small package GBIC, the fiber used is LC type



The optical fiber connector

A fiber optic connector is a detachable (active) connection between an optical fiber and an optical fiber. The two ends 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 also affect the reliability and performance of optical transmission systems.


Optical fiber connectors can be divided into common single-mode and multi-mode connectors of silicon-based fibers according to different transmission media, and other fiber-optic connectors such as plastics; the structure of connectors 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 of the more common fiber connectors:


(1) FC type optical fiber connector

This connector was originally 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. The earliest, FC type connector used was the docking port of the ceramic pin. Such a connector has a simple structure, is easy to operate, and is easy to 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 modified to use a mating pin (PC) with a spherical end face, and the external structure was not changed, resulting in a significant increase in insertion loss and return loss performance.

(2) SC type optical fiber connector

This is a fiber optic connector developed by NTT Corporation of Japan. The outer casing is rectangular, and the pin and coupling sleeve are identical in size to the FC type. The end face of the pin is mostly made of PC or APC type; the fastening method is plug-and-pull type, which does not need to be rotated. 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.


(3) Double Cone 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.

(4) 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 processing 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 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.


(5) 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 pins mounted on both sides of the small sleeve for easy transmission and reception. Connected to the machine, the connector end face fiber is a two-core (interval 0.75mm) array design, which is the next generation high-density fiber optic connector mainly used for data transmission.

(6) LC type 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 fiber 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.

(7) 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 features a 1.25mm diameter bushing and self-retaining mechanism for the high density installation. Using MU's l.25mm diameter bushings, NTT has developed the MU connector series. They have socket type connectors for fiber optic cable connections (MU-A series); 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 in the direction of larger bandwidth and larger capacity and the widespread use of DWDM technology, the demand for MU-type connectors will also grow rapidly.

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