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What is a fiber optic adapter?

1. What is an optical fiber adapter?

Fiber optic adapter (also known as fiber optic coupler), also called fiber optic connector, is the centering connection part of fiber optic connector. Optical fiber adapters are the most widely used optical passive components in optical fiber communication systems. Most optical fiber adapters are composed of three parts: two optical fiber connectors and a coupler. Two optical fiber connectors are installed into the two optical fiber tail ends; the coupler acts as an alignment sleeve. In addition, the couplers are mostly equipped with metal or non-metal flanges to facilitate the installation and fixation of the adapters.

Both ends of the fiber optic adapter can be inserted into fiber optic connectors of different interface types to realize the conversion between different interfaces such as FC, SC, ST, LC, MTRJ, MPO, E2000, etc. It is widely used in optical fiber distribution frames (ODF), optical fiber communication equipment, Instruments, etc., have outstanding performance, stability and reliability. Some fiber optic adapters on the market are also called fiber optic connectors. In fact, these are two different products.

SC-Simplex-Green-White-Adapter-with-shutter

2. Features of optical fiber adapter

2.1 Passed 100% optical performance testing, ceramic (zirconia) casing, processed by imported high-precision machine tools, with high product finish, precise axis positioning, ensuring product coaxiality and cocircularity accuracy coefficient

2.2 Unique design of integrated internal structure, simpler structure, easier to use, easy to assemble, and improve efficiency

2.3 Good stable performance, small insertion loss in continuous plug test

sc adapter with metal shutter-1

3. Performance indicators of fiber optic adapters

  • Insertion loss: ≤0.2dB
  • Return loss: ≥40dB
  • Interchangeability: ≤0.2dB
  • Working temperature (℃): -30―+80
  • Storage temperature (℃): -40―+85
  • Vibration test: ≤0.1dB (10-60Hz, 1.5mm amplitude)
  • Tensile strength test: ≤0.1dB
  • Repeatability: ≥1000 times

LC QUAD Lime Green OM5 Adapter

4. The classification of fiber optic adapters

There are various forms of optical fiber adapters. Generally, the adapters used in EPON networks are APC connectors. The end face of the APC is ground to an 8 degree angle in order to reduce reflection. The industry standard return loss is -60dB . The APC connector has precise, predetermined angle, predetermined radius, and pre-polished sleeve, which can provide excellent performance and can be used with compact key configurations with or without NTT-FC standard.

According to the application scope and requirements of the fiber optic adapter, in order to fix it on various panels, the fiber optic adapter is also designed with a variety of fine fixing flanges. The adapter type fiber optic adapter can connect different types of fiber optic patch cord interfaces and provide different The connection between the sections, double connection or multiple connection can increase the installation density. According to the difference of the shape structure and the connection section, the fiber optic adapter can be roughly divided into the following common models: FC, SC, ST, LC, FC-SC, FC-ST, ST-SC, in addition to some male to female transfer Connect the fiber optic adapter.

4.1 FC fiber optic adapter:
The external reinforcement method is a metal sleeve, and the fastening method is a turnbuckle. The FC type adapter uses the butt end of the ceramic pin. This type of adapter has simple structure, convenient operation, and easy manufacture, but the fiber end is more sensitive to fine dust, and is prone to Fresnel reflection, which makes it difficult to improve the return loss performance. Later, this type of adapter was improved by adopting a spherical pin (PC) with the mating end surface without changing the external structure, which greatly improved the insertion loss and return loss performance.

4.2 SC fiber optic adapter:
Its shell is rectangular, and the structure size of the pin and coupling sleeve used is exactly the same as that of FC type. Among them, the end face of the pin mostly adopts the PC or APC type grinding method; the fastening method is the plug-in latch type, without rotation. Equipped with metal shrapnel for easy concealed use. This type of adapter is cheap, easy to plug and unplug, small fluctuations in insertion loss, high compressive strength, and high installation density.

4.3 ST fiber optic adapter:
It is a keyed buckle type locking structure to ensure accurate alignment during connection, has strong tensile strength, metal key positioning, improves the repeatability and durability of the adapter, and uses precision ceramic or copper sleeves to ensure Long-term stable mechanical and optical properties. Rectangular structure, easy to install and use by tapping and riveting.

4.4 LC fiber optic adapter:
It is made with a convenient modular jack (RJ) latch mechanism. The size of the pins and sleeves used is small, which improves the density of optical fiber adapters in the optical fiber distribution frame. The use of precision ceramic sleeves ensures long-term stable mechanical and optical performance.

LC-Duplex-Adapter-with-Outer-Shutter

5. Common fiber optic Adapters

(1) FC type optical fiber adapter

This kind of adapter was first developed by Japan NTT. FC is the abbreviation of FERRULE , indicating that the external reinforcement method is a metal sleeve and the fastening method is a turnbuckle. The earliest FC type adapter used ceramic pin butt ends. This type of adapter has simple structure, convenient operation, and easy manufacture, but the fiber end is more sensitive to fine dust, and is prone to Fresnel reflection, which makes it difficult to improve the return loss performance. Later, this type of adapter was improved by adopting a spherical pin (PC) with the mating end surface without changing the external structure, which greatly improved the insertion loss and return loss performance.

(2) SC type optical fiber adapter

This is an optical fiber adapter developed by Japan’s NTT company. Its shell is rectangular, and the structural dimensions of the pins and coupling sleeves used are exactly the same as the FC type. Among them, the end face of the pin mostly adopts the PC or APC type grinding method; the fastening method is the plug-in latch type, without rotation. This type of adapter is cheap, easy to plug and unplug, small fluctuations in insertion loss, high compressive strength, and high installation density.   ST and SC interfaces are two types of optical fiber adapters. For 10BASE-F connection, the adapter is usually ST type, and for 100BASE-FX, the adapter is 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 adapter (BICONICCONNECTOR)

The most representative product of this type of optical fiber adapterwas developed by Bell Laboratories in the United States. It consists of two precision molded cylindrical plugs with frusto-conical ends and a double-cone plastic sleeve inside. The tube is composed of coupling components.

(4) DIN47256 optical fiber adapter

This is a adapter developed by Germany. The structure size of the pin and coupling sleeve used in this adapter is the same as that of the FC type, and the end face treatment adopts the PC grinding method. Compared with the FC type adapter, its structure is more complicated. The internal metal structure has a spring to control the pressure, which can avoid damage to the end surface due to excessive insertion pressure. In addition, the mechanical accuracy of this adapter is high, so the insertion loss value is small.

(5) MT-RJ type adapter

MT-RJ started from the MT adapter developed by NTT. It has the same latch mechanism as the RJ-45 LAN electrical adapter. The guide pins installed on both sides of the small sleeve are aligned with the optical fiber to facilitate the transmission and reception of light. It is connected to the machine, and the end face of the adapter is a dual-core (0.75mm spacing) arrangement design. It is a next-generation high-density optical fiber adapter mainly used for data transmission.

(6) LC type adapter

LC type adapter is researched and developed by the famous BELL research institute, and it is made of modular jack (RJ) latch mechanism that is easy to operate. The size of the pins and sleeves used is half the size of ordinary SC, FC, etc., which is 1.25MM. This can increase the density of optical fiber adapters in the optical fiber distribution frame. At present, in terms of single-mode SFF, LC-type adapters have actually occupied a dominant position, and applications in multi-mode have also grown rapidly.

(7) MU type adapter

MU (MINIATURE UNITCOUPLING) adapter is the smallest single-core optical fiber adapter in the world developed by NTT based on the most used SC adapter. The adapter uses a 1.25MM diameter sleeve and self-retaining mechanism, and its advantage is that it can achieve high-density installation. Using MU’s L.25MM diameter sleeve, NTT has developed the MU adapter series. They have socket type adapters (MU-A series) for optical cable connection; backplane connectors with self-holding mechanism (MU-B series) and simplified sockets (MU-SR series) for connecting LD/PD modules and plugs Wait. With the rapid development of optical fiber networks towards greater bandwidth and greater capacity and the widespread application of DWDM technology, the demand for MU adapters will also grow rapidly.

LC ADAPTER

6. The role of fiber optic adapters

Like the fiber optic adapter, the fiber optic adapter is also a connecting element in the fiber optic line. The difference is that the fiber optic adapter can only be used to connect the same type of fiber optic cable or the same type of equipment. Once it encounters two connected fiber optic cables If it does not match the model of the device, it will be blinded. The fiber optic adapter is different. There are multiple input ports and output ports of different types on the box, which can be easily connected regardless of the type of fiber optic lines and equipment. The fiber optic adapter has another function, which is to establish a signal branch. As mentioned above, there are several outlets on the box of the fiber optic adapter, and each outlet can establish a branch line.

The application range of optical fiber adapters is very wide. First of all, it plays an indispensable role in optical fiber communication networks. Our current network signals use optical fibers, so optical fibers have almost reached thousands of households. Can not do without the role of fiber optic adapter. Then there is a cable TV network. Some TV signals are also transmitted by optical fiber. In such a cable TV network, a signal source such as a voltage-controlled oscillator is first used to generate an electrical signal, and then it is converted into an optical signal by a photoelectric element. It can be transmitted by optical fiber, and the optical fiber adapter also has a very wide range of uses in such an optical fiber TV signal network. In addition, optical fibers can also be used to build some local area networks for internal use by some units, and to establish data connections between some electronic devices. These are also inseparable from optical fiber adapters. It can be seen that the role of fiber optic adapters in fiber optic communication networks is just as essential as the role of power adapters in circuits.

7. Application range of fiber optic adapter

  • Optical fiber communication system
  • TV network
  • Local area network, optical area network
  • Fiber to the home (FTTP)
  • Video transmission
  • Test equipment

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