Differences Between ST, SC, FC, and LC Fiber Connectors

NADDOD Adam Connectivity Solutions Consultant Jan 10, 2023

ST, SC, FC fiber optic connectors are the early development of different companies formed the standard, the use of the same effect, each has its advantages and disadvantages.

ST, SC connector connectors are commonly used in general networks. ST head inserted into the rotation of half a week there is a bayonet fixed, the disadvantage is easy to break; SC connector directly plug, easy to use, the disadvantage is easy to fall out; FC connector general telecommunications networks used, there is a nut screwed to the adapter, the advantage is secure, dust-proof, the disadvantage is a little longer installation time.

MTRJ type fiber patch cords consists of two high-precision plastic molded connectors and fiber optic cable. The outer parts of the connector are precision plastic parts, including a push-pull plugging and clamping mechanism. It is suitable for indoor applications in telecommunication and data network systems.

EDR transceivers

1. Type of the Fiber Optic Connector

Fiber optic connectors, that is, access to the optical transceiver connectors, there are also several kinds, and they can not be used interchangeably. People who are not always in contact with optical fiber may mistakenly think that the GBIC and SFP transceiver fiber optic connectors are the same, in fact, not. SFP transceiver to LC fiber connector, while 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: external reinforcement is used metal sleeve, fastening method is screw fastening. Generally used in the ODF side (the most used in the distribution frame)

② SC-type fiber optic connectors: connectors connected to GBIC optical modules, its shell is rectangular, fastening method is used to plug the pin latch type, do not need to rotate. (The most used on the router switch)

③ ST-type fiber optic connectors: commonly used in fiber optic distribution frame, the shell is round, fastening method is screw fastening. (For 10Base-F connection, the connector is usually ST type. Commonly used in fiber optic distribution frame)

④ LC type fiber optic connector: connector for connecting SFP modules, it is made with easy-to-operate modular jack (RJ) latching mechanism. (Commonly used in routers)

⑤ MT-RJ: transceiver square fiber optic connector, one end of the dual-fiber transceiver integration.

2. Common Types of Fiber Optic Cables

Fiber Optic Interface :




3. Introduction of the Fiber Optic Interfaces

(1) Types of Fiber Optic Connector

FC Round type with thread (most used on wiring frames)
ST Snap-on round type
SC Snap-on square type (most used in router switches)
PC micro spherical polished
APC with 8 degree angle and microspherical polishing
MT-RJ square type, a dual-fiber transceiver integrated (Huawei 8850 on the useful)
Fiber optic module: generally support hot-swap,
GBIC Giga Bitrate Interface Converter, the use of fiber optic interfaces are mostly SC or ST type
SFP small package GBIC, the use of fiber for the LC type

(2) Types of Fiber

Single-mode: L, wavelength 1310 Single-mode long-haul LH wavelength 1310,1550
Multimode: SM wavelength 850
SX/LH indicates that single mode or multimode fiber can be used
In the labeling of the pigtail connector, we often see “FC/PC”, “SC/PC”, etc., the meaning is as follows
The front part of “/” indicates the connector type of the pigtail
“SC” connector is a standard square connector, using engineering plastic, with high temperature resistance, not easy to oxidation advantages. Transmission equipment side of the optical interface is generally used SC connector
“LC” connectors are similar in shape to SC connectors, but smaller than SC connectors.
“FC” connector is a metal connector, generally used in the ODF side, metal connectors can be plugged more times than plastic.
Connector variety signal more, in addition to the three introduced above, there are MTRJ, ST, MU, etc…
After the “/” indicates the fiber optic connector cross-section process, that is, the grinding method.
“PC” in the telecom operator’s equipment is most widely used, the connector cross-section is flat.
“UPC” attenuation is smaller than “PC”, generally used in equipment with special needs, some foreign manufacturers of ODF frame internal jumpers with FC/UPC, mainly to improve the indicators of ODF equipment itself.

In addition, in the broadcast and early CATV is more often used in the “APC” model, the pigtail head with the inclination of the end face, can improve the quality of the TV signal, the main reason is that the TV signal is analog light modulation, when the coupling surface is vertical, the reflected light returns along the original path. Due to the uneven distribution of the refractive index of the fiber will return to the coupling surface again, at this time, although the energy is very small, but because the analog signal is unable to completely eliminate the noise, so the equivalent of the original clear signal superimposed on a weak signal with time delay, the performance on the screen is a double image. Pigtail head with tilt angle can make the reflected light does not return along the original path. General digital signals generally do not have this problem.

(3)Fiber Optic Connector

Fiber optic connector is a detachable connection between the fiber and the fiber device, it is the two ends of the fiber precision butt to enable the transmitting fiber output light energy can be coupled to the receiving fiber to the maximum, and its intervention in the optical link to minimize the impact on the system, which is the basic requirements of the fiber optic connector. To a certain extent, fiber optic connectors also affect the reliability and performance of the optical transmission system.

Fiber optic connectors according to the different transmission media can be divided into common silicon-based fiber single-mode, multimode connectors, and other such as plastic as the transmission medium of fiber optic connectors; according to the connector structure can be divided into: FC, SC, ST, LC, D4, DIN, MU, MT and so on various forms. Among them, ST connectors are usually used for cabling equipment, such as fiber optic patch panels, fiber modules, etc.; while SC and MT connectors are usually used for network equipment. According to the shape of the fiber end face FC, PC (including SPC or UPC) and APC; according to the number of fiber cores divided into single-core and multi-core (such as MT-RJ) points. Fiber optic connectors are widely used, a wide variety. In the actual application process, we generally follow the different structure of fiber optic connectors to distinguish. The following are some of the more common fiber optic connectors.

FC Type Fiber Optic Connector

This connector was first developed by Japan’s NTT. FC is an abbreviation for Ferrule Connector, indicating that its external strengthening method is the use of metal sleeves, fastening method for the screw fastening. The earliest, FC type connector(using the butt end of ceramic pin). This type of connector structure is simple, easy to operate, easy to produce, but the fiber end face is more sensitive to fine dust, and easy to produce Fresnel reflections, improve the return loss performance is more difficult. Later, the type of connector made improvements, the use of butt end face is spherical pin (PC), while the external structure has not changed, making the insertion loss and return loss performance has improved substantially.

SC Type Fiber Optic Connector

This is a kind of fiber optic connector developed by Japan NTT company. Its shell is rectangular, the structure of the pins and coupling sleeve size and FC type is exactly the same,. The end face of the pins are mostly PC or APC type grinding; fastening method is to use the plug and pin latch type, without rotation. Such connectors are inexpensive, easy to plug and unplug operation, small fluctuations in intervention loss, high compressive strength, high installation density.

ST and SC interface are two types of fiber optic connectors, for 10Base-F connection, the connector is usually ST type, for 100Base-FX, the connector is SC type in most cases. the core of ST connector is exposed, the core of SC connector is inside the connector.

Biconic Connector

This type of fiber optic connectors in the most representative products developed by the U.S. Bell Labs, it consists of two precision molded ends are truncated conical cylinder plug and a coupling assembly with a double conical plastic sleeve inside.

DIN47256 Type Fiber Optic Connector

This is a connector developed by Germany. This connector uses the same structural dimensions of the pin and coupling sleeve as the FC type, and the end face is treated by PC grinding. Compared with the FC type connector, its structure is more complicated, and the internal metal structure has a spring to control the pressure, which can avoid damaging the end face due to excessive plugging pressure. In addition, the mechanical accuracy of this connector is higher, and thus the intervention loss value is smaller.

MT-RJ Type Fiber Optic Connector

MT-RJ started from the MT connector developed by NTT, with the same latching mechanism as the RJ-45 type LAN electrical connector, by installing the guide pin on both sides of the small sleeve to align the fiber, in order to facilitate connection with optical transceivers, the connector end face of the fiber is a two-core (0.75mm interval) arrangement design, is mainly used for data transmission of the next generation of high-density fiber optic connectors.

LC Type Fiber Optic Connector

LC-type connector is the famous Bell (Bell) Institute of research and development, the use of easy to operate modular jack (RJ) latch mechanism made. The size of the pins and sleeves used is half of the size used in ordinary SC, FC, etc., 1.25mm. This can improve the density of fiber optic connectors in the fiber optic distribution frame. At present, in single-mode SFF, LC type connectors have actually dominated, and the application in multimode is also growing rapidly.

MU Type Fiber Optic Connector

MU (Miniature unit Coupling) connector is the world’s smallest single-core fiber optic connector developed by NTT, based on the currently most used SC-type connector. This connector uses 1.25mm diameter sleeve and self-retaining mechanism, and has the advantage of high density installation. Using the MU’s l.25mm diameter sleeve, NTT has developed the MU connector series. They are socket-type connectors for fiber optic cable connections (MU-A series); baseboard connectors with a self-retaining mechanism (MU-B series) and simplified sockets for connecting LD/PD modules to plugs (MU-SR series). With the rapid development of fiber optic networks to larger bandwidth and larger capacity and the widespread use of DWDM technology, the demand for MU-type connectors will also grow rapidly.