Fiber optic connectors, that is, fiber optic connectors for accessing optical modules, also have many kinds, and they cannot be interused with each other. People who do not often touch optical fibers may mistakenly think that the optical fiber connectors of GBIC and SFP modules are the same, but they are not. The SFP module is connected to the LC fiber optic connector, while the GBIC is connected to the SC fiber optic connector.

ST, SC, FC fiber optic connector is the early development of different enterprises to form the standard, the use of the same effect, each have advantages and disadvantages.

ST, SC connector connectors are commonly used in general networks. After the ST head is inserted, there is a bayonet to fix it for half a rotation. The disadvantage is that it is easy to break. The SC connector is directly plugged and unplugged, which is very convenient to use, but the disadvantage is that it is easy to fall out. The FC connector is generally used in telecommunication networks. A nut is screwed onto the adapter. The advantage is that it is firm and dust-proof. The disadvantage is that the installation time is slightly longer.

MTRJ type fiber optic patch cord consists of two high precision plastic molded connectors and fiber optic cable. The external parts of the connector are precision plastic parts, including push-pull plug-in clamping mechanism. Suitable for indoor applications in telecommunication and data network systems.

Fiber optic connectors, that is, fiber optic connectors for accessing optical modules, also have many kinds, and they cannot be interused with each other. People who do not often touch optical fibers may mistakenly think that the optical fiber connectors of GBIC and SFP modules are the same, but they are not. The SFP module is connected to the LC fiber optic connector, while the GBIC is connected to the SC fiber optic connector.

The following is a detailed description of several commonly used optical fiber connectors in network engineering:

① FC type optical fiber connector: the external reinforcement method is to use a metal sleeve, and the fastening method is a turnbuckle. Generally used on the ODF side (most used on the distribution frame)

② SC type optical fiber connector: the connector connected to the GBIC optical module, its shell is rectangular, the fastening method is to use the plug pin latch type, do not need to rotate. (Most used on router switches)

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

④ LC type fiber optic connector: connector for connecting SFP modules, which is made of modular jack (RJ) latch mechanism for easy operation. (Router commonly used)

⑤ MT-RJ: Send and receive integrated square optical fiber connector, a dual-fiber transceiver

Several common optical fiber line optical fiber interface Daquan

Introduction to various fiber optic interface types Fiber optic connectors

FC round with thread (most used on distribution frame) ST snap-on round

SC card-in square type (most used on router switches) PC micro spherical grinding and polishing

APC is 8 degrees angle and do micro spherical grinding and polishing

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

Optical fiber module: generally support hot plug,

GBIC Giga Bitrate Interface Converter, the optical fiber interface used is mostly SC or ST type SFP small package GBIC, the optical fiber used is LC type

Optical fiber used:

Single Mode: L, Wavelength 1310 Single Mode Long Range LH Wavelength 1310,1550 Multimode: SM Wavelength 850

SX/LH indicates that single mode or multimode fiber can be used

In the label of pigtail joint, we can often see "FC/PC", "SC/PC", etc., its meaning is as follows:

The front part of "/" indicates the connector model of the pigtail

"SC" joint is a standard square joint, using engineering plastics, with high temperature resistance, not easy to oxidation advantages. SC connector is generally used for optical interface of transmission equipment side

The "LC" connector is similar in shape to the SC connector and is smaller than the SC connector.

The "FC" joint is a metal joint, which is generally used on the ODF side. The number of pluggable metal joints is more than that of plastic.

There are many kinds of signals for connectors. In addition to the three described above, there are MTRJ, ST, MU, etc. For the specific appearance, please refer to the figure below.

Picture

The following indicates the cross-section process of the optical fiber joint, that is, the grinding method.

"PC" is the most widely used in the equipment of telecom operators, and its joint section is flat. The attenuation of "UPC" is smaller than that of "PC" and is generally used for equipment with special needs.

FC/UPC is used for fiber hopping inside the ODF rack, mainly to improve the index of ODF equipment itself.

In addition, the "APC" model is more widely used in radio and television and early CATV, and its pigtail head adopts an inclined end face, which can improve the quality of TV signals, mainly because the TV signal is analog light modulation,

When the joint coupling face is vertical, the reflected light returns along the original path. Due to the uneven refractive index distribution of the fiber will return to the coupling surface again. At this time, although the energy is very small, the noise cannot be completely eliminated due to the analog signal,

Therefore, it is equivalent to superimposing a weak signal with time delay on the original clear signal, which is a ghost on the screen. The pigtail headband tilt angle may cause the reflected light to not return along the original path. General digital signals generally do not have this problem

fiber optic connector

The optical fiber connector is a detachable (movable) connection device between the optical fiber and the optical fiber. It precisely butts the two end faces of the optical fiber so that the optical energy output by the transmitting optical fiber can be coupled to the receiving optical fiber to the maximum extent,

And minimize the impact on the system due to its intervention in the optical link, which is the basic requirement of optical fiber connectors. To a certain extent, fiber optic connectors also affect the reliability and performance of optical transmission systems.

Optical fiber connectors can be divided into common silicon-based optical fiber single-mode and multi-mode connectors according to different transmission media, and other optical fiber connectors such as plastic and other transmission media. According to the structure of the connector, it can be divided into FC, SC, ST, LC, D4, DIN, MU, MT and other forms.

Among them, ST connectors are usually used for wiring equipment, such as optical fiber distribution frames, optical fiber modules, etc.; and SC and MT connectors are usually used for network equipment. According to the shape of optical fiber end face, there are FC, PC (including SPC or UPC) and APC. According to the number of optical fiber cores, there are also single-core and multi-core (such as MT-RJ).

Fiber optic connectors are widely used and have a wide variety of applications. In practical applications, we generally distinguish between different structures of optical fiber connectors.

Here are some of the more common fiber optic connectors:

(1)FC type fiber optic connector

This connector was first developed by NTT in Japan. FC is an abbreviation for Ferrule Connector, indicating that its external reinforcement is a metal sleeve and the fastening method is a turnbuckle.

This type of connector is simple in structure, easy to operate, and easy to manufacture, but the end face of the optical fiber is more sensitive to fine dust, and it is easy to generate Fresnel reflection, and it is difficult to improve the return loss performance.

Later, this type of connector was improved by using a spherical pin (PC) with a butt end surface, and the external structure was not changed, which greatly improved the insertion loss and return loss performance.

(2)SC type fiber optic connector

This is an optical fiber connector developed by Japan's NTT company. The housing is rectangular, and the structural dimensions of the pins and coupling sleeves used are exactly the same as the FC type.

The end face of the pin is mostly PC or APC type grinding method; the fastening method is to use the plug pin latch type without rotation. This kind of connector is cheap, easy to plug operation, small fluctuation of insertion loss, high compressive strength and high installation density.

ST and SC interfaces are two types of fiber optic connectors. For 10Base-F connections, the connectors are usually ST types, and for 100Base-FX, the connectors are mostly SC types. The core of the ST connector is exposed, and the core of the SC connector is inside the connector.

(3) Double taper connector (Biconic Connector)

The most representative product of this type of optical fiber connector is developed by Bell Laboratories in the United States. It consists of two cylindrical plugs with frustoconical ends formed by precision molding and a coupling assembly with a double conical plastic sleeve inside.

(4)DIN47256 type fiber optic connector

This is a connector developed by Germany. The structural dimensions of the pins and coupling sleeves used in this connector are the same as those of the FC type, and the end face is processed by PC grinding.

Compared with the FC type connector, its structure is more complicated, the internal metal structure has a spring to control the pressure, which can avoid damage to the end face due to excessive plug pressure.

In addition, the mechanical accuracy of this connector is high, and therefore the insertion loss value is small.

(5)MT-RJ type connector

MT-RJ MT connector developed by NTT started with the same latching mechanism as the RJ-45 LAN electrical connector. The optical fiber is aligned with the guide pins installed on both sides of the small sleeve. In order to facilitate connection with the optical transceiver, the optical fiber at the end face of the connector is designed to be arranged with double cores (0.75mm apart). It is the next generation of high-density optical fiber connector mainly used for data transmission.

(6) Type LC connector

The LC connector is developed by the famous Bell (Bell) Research Institute and is made of a modular jack (RJ) latch mechanism that is easy to operate.

The size of the pin and sleeve used is half of the size used in ordinary SC, FC, etc., which is 1.25mm. This can increase the density of fiber optic connectors in the fiber distribution frame.

At present, in terms of single-mode SFF, LC type connectors have actually occupied a dominant position, and their applications in multimode are also growing rapidly.

(7)MU Type Connector

MU(Miniature unit Coupling) connector is the world's smallest single-core optical fiber connector developed by NTT based on the most used SC connector.

The connector uses a 1.25mm diameter sleeve and a self-retaining mechanism, which has the advantage of enabling high-density mounting. NTT has developed the MU connector series using the MU's 1.25mm diameter sleeve.

There are socket-type connectors (MU-A series) for optical cable connection, backplane connectors (MU-B series) having a self-holding mechanism, and simplified sockets (MU-SR series) for connecting LD/PD modules and plugs.

With the rapid development of optical fiber networks towards larger bandwidth and larger capacity and the wide application of DWDM technology, the demand for MU-type connectors will also grow rapidly.

Optical fiber distribution box: The optical fiber distribution box is suitable for the wiring connection between the optical cable and the optical communication equipment. Through the adapter in the distribution box, the optical signal is led out by the optical jumper to realize the optical wiring function. It is also suitable for the protective connection of optical cables and wiring pigtails.

As shown in the figure for 3M company's 8200 indoor optical fiber distribution box, suitable for optical fiber access network in the use of optical fiber terminal point.

Optical transceiver: At present, one end of the commonly used optical transceiver is connected to the optical transmission system (usually SDH optical synchronous digital transmission network), and the other end (user end) is 2M interface. In addition, the optical transceiver also has PDH (quasi-synchronous digital series).

Optical transceiver is much more complicated than optical fiber transceiver. In addition to photoelectric coupling, there are also signal encoding processes such as multiplexing-demultiplexing, insinuating-insinuating.

Optical fiber transceiver: Simply speaking, one end of the optical fiber transceiver is connected to the optical transmission system, and the other end (user end) is a 10/100M Ethernet interface.

Optical fiber transceivers are to achieve the role of photoelectric signal conversion. The main principle of optical fiber transceiver is realized by optical coupling, and there is no change in the encoding format of the signal.

At present, there are many foreign and domestic manufacturers of optical fiber transceivers, and the product line is also extremely rich. In order to ensure full compatibility with other manufacturers' network cards, repeaters, hubs, switches and other network equipment, fiber optic transceiver products must strictly comply with Ethernet standards such as 10Base-T, 100Base-TX, 100Base-FX, IEEE802.3 and IEEE802.3u.

In addition, the EMC protection against electromagnetic radiation should comply with FCC Part15 standards. Nowadays, as the major domestic operators are vigorously building community networks, campus networks and enterprise networks, the amount of optical fiber transceiver products is also increasing to better meet the needs of access network construction.

Fiber optic transceivers usually have the following basic characteristics:

1. Provide ultra-low latency data transmission.

Fully transparent to network protocols.

3. Multi-purpose ASIC chips are used to realize data line speed forwarding. Programmable ASIC concentrates multiple functions on one chip, which has the advantages of simple design, high reliability and low power consumption, and can make the device get higher performance and lower cost.

4. The equipment adopts 1 1 power supply design, supports ultra-wide power supply voltage, realizes power supply protection and automatic switching.

5. Support ultra wide working temperature range.

6. Support complete transmission distance (0~120km).