Structure and Performance Analysis of various optical fiber connectors

Structure and Performance Analysis of various optical fiber connectors

When installing any optical fiber system, you must consider connecting optical fiber or optical fiber cables with low loss to achieve optical link connection. Fiber link connection can be divided into permanent and active two types. The permanent connection is mostly implemented by welding, bonding, or fixed connectors. The active connection is generally implemented by the active connector. This article briefly introduces the active connector.

An Active Optical Fiber Connector, commonly known as a live connector, is a passive device that can be used to connect two optical fiber or optical fiber cables to form a continuous optical connection, it has been widely used in optical fiber transmission lines, optical fiber distribution frames, optical fiber testing instruments and meters. It is currently the most widely used passive optical devices.

General Structure of Optical Fiber Connector

The main purpose of the optical fiber connector is to achieve the connection of the optical fiber. Fiber optic connectors have been widely used in optical fiber communication systems. They have various types and different structures. However, the basic structure of various types of optical fiber connectors is the same, that is, the vast majority of optical fiber connectors generally use high-precision components (composed of two pins and one coupling tube) achieve optical fiber connection.

In this way, the optical fiber is inserted and fixed in the plug-in, and the plug-in surface is polished, and then aligned in the coupling tube. The external components of the pin are made of metal or non-metallic materials. The pin end must be ground, and the other end usually uses bending restriction components to support optical fiber or optical fiber cables to release stress. The coupling tube is generally made of two semi-synthetic, fastening cylindrical components made of ceramic, bronze and other materials. It is equipped with a flange of metal or plastic to facilitate the installation and fixation of connectors. In order to align the optical fiber as accurately as possible, the machining precision of the plug-in and coupling tubes is very high.

Performance of optical fiber connectors

The performance of the optical fiber connector is first of all the optical performance. In addition, the interchangeable, repeatability, tensile strength, temperature and plugging times of the optical fiber connector are also considered.

(1) optical performance: the requirements for optical performance of optical fiber connectors are mainly the insertion loss and Return Loss parameters.

Insertion Loss (Insertion Loss) refers to the Loss of link effective optical power caused by the import of the connector. The smaller the insertion loss, the better. The general requirement should be no greater than 0.5dB.

Return Loss (Return Loss) refers to the ability of the connector to suppress optical power reflection on the link. Its typical value should be no less than 25 dB. In practical applications, the surface of the pin is specially polished to increase the return loss, which is generally not lower than 45dB.

(2) interchangeable and repetitive

Fiber optic connectors are commonly used passive devices. For the same type of fiber optic connectors, they can be used in any combination and can be used multiple times, the additional consumption of the import is generally within the range of 0.2dB.

(3) tensile strength

For fiber optic connectors, the tensile strength is generally not lower than 90N.

(4) Temperature

Generally, optical fiber connectors must be at-40 ℃ ~ + 70 ℃ can be used normally.

(5) plugging times

Currently, the optical fiber connectors can be plugged in more than l000 times.

Some common optical fiber connectors

According to different classification methods, optical fiber connectors can be divided into different types, according to different transmission media can be divided into single-mode optical fiber connectors and multi-mode optical fiber connectors; different types of connectors can be divided into FC, SC, ST, D4, DIN, Biconic, MU, LC, and MT. Pin End Faces of connectors can be divided into PCs (upcs) and APC; by the number of fiber cores and single-core, multi-core points.

In the actual application process, we generally differentiate the Optical Fiber Connector structure. The following briefly introduces some common optical fiber connectors:

(1) FC Optical Fiber Connector

This connector was first developed by NTT in Japan. FC is the abbreviation of Ferrule Connector, indicating that the external reinforcing mode is a metal sleeve, and the fastening mode is a screw. The earliest, FC type connector, the ceramic pin is connected to the end of the Plane Contact Mode (FC ). This type of connector is simple in structure, easy to operate, and easy to create. However, the optical fiber end face is sensitive to dust, and is easy to generate freell reflection, which makes it difficult to improve the return loss performance. Later, this type of connector was improved by using a spherical pin (PC) on the docking face, but the external structure was not changed, which greatly improved the insertion loss and Return Loss Performance.

(2) SC-type Optical Fiber Connector

This is an optical fiber connector developed by NTT. The housing is rectangular. The structure and size of the plug-in and the coupling sleeve are identical to those of the FC type. The End Face of the plug-in adopts PC or APC grinding; the fastening mode is plug-and-Remove pin latches without rotation. This type of connector is low in price, easy to plugging, small fluctuation of interference loss, high compressive strength, high installation density (the most used for vro switches ).

(3) ST-type Optical Fiber Connector

ST-type Optical Fiber Jumper: This patch cord is often used in optical fiber distribution frames. The housing is circular and the fastening mode is screw buckle. (For 10Base-F connections, the connector is usually of the ST type. Used in optical fiber distribution frames)

(4) LC Optical Fiber Connector

The LC connector was developed by the famous Bell Research Institute and is made using a convenient modular Jack (RJ) locking mechanism. The size of the plug-in and sleeve is half of the size of ordinary SC, FC, etc., 1.25mm. This improves the density of optical fiber connectors in the optical distribution frame. At present, in the single-mode SFF aspect, the LC type connector has occupied a dominant position, and applications in the multi-mode aspect have also grown rapidly.

(5) double cone Connector (Biconic Connector)

The most representative products of these optical fiber connectors were developed and developed by Bell Laboratory, USA, it consists of two precision-molded end headers, A Conical Cylinder plug and a coupling component with a double-taper plastic sleeve.

(6) DIN4 Optical Fiber Connector

This is a connector developed by Germany. The connector adopts the same structure size as the FC type of the plug-in and coupling sleeve, and the end face processing adopts the PC grinding mode. Compared with FC connector, its structure is more complex. The internal metal structure has a spring with control pressure, which can avoid damage to the end face due to the insertion pressure. In addition, the mechanical precision of this connector is high, so the intervention loss value is small.

(7) MT-RJ Connector

The MT-RJ is a NTT-developed MT connector with the same latch mechanism as the RJ-45-type LAN electrical connector and is aligned with the optical fiber through a guide pin mounted on both sides of the small casing to facilitate connection with the optical transceiver, the connector end optical fiber is designed for dual-core (with an interval of 0.75mm) arrangement and is the next generation high-density optical connector mainly used for data transmission.

(8) MU Connector

The MU connector is the world's smallest single-core optical fiber connector developed by NTT based on the currently most widely used SC connector. It adopts a 25mm diameter casing and self-retaining mechanism, its advantage lies in its ability to achieve high-density installation. Using the l. 25mm diameter casing of MU, NTT has developed the series of MU connectors. They have socket-type optical connectors for optical fiber connection (MU-A series), bottom board connectors with self-retaining mechanism (MU-B Series) and a simplified socket (MU-SR series) used to connect the LD/PD module with the plug. With the rapid development of the optical fiber network towards larger bandwidth and larger capacity and the wide application of DWDM technology, the demand for MU-type connectors will also grow rapidly.

Conclusion

With the continuous development of optical fiber communication technology, especially the development of high-speed LAN and optical access networks, optical fiber connectors will be widely used in optical fiber systems. At the same time, it also puts forward more and higher requirements for optical fiber connectors. Its main development direction is: Small appearance, low cost, and higher performance requirements. In the future, various newly developed optical fiber connectors will work with traditional FC, SC and other connectors to form an "all-in-one and all-in-one" pattern.