Selection of Fiber Connector Types

Optical fiber is an abbreviation for optical fiber, which is composed of thin glass filaments with a diameter of about 0.1 mm. It is transparent and slender, and although thinner than a human hair, it has a waveguide structure that encloses light in it and propagates it in the axial direction. Optical fiber communication is a communication method developed because of this magical structure of optical fiber, which uses light waves as the carrier frequency and optical fibers as the transmission medium.

Choice of Fiber Type

According to the different modes of optical fiber transmission points, optical fibers are mainly divided into two types, namely, single-mode fiber (Single Mode Fiber, SMF) and multi-mode fiber (Multi Mode Fiber, MMF). The so-called "mode" refers to a beam of light entering the fiber at a certain angular velocity.

Multimode fiber uses light-emitting diode LED as light source, and the transmission distance of 1000Mb/s fiber is 220m--550m. Multimode fiber optic cables and multimode fiber optic ports are relatively inexpensive, but have shorter transmission distances, so they are more used for vertical backbone subsystems, and sometimes for horizontal subsystems or building cluster subsystems.

The single-mode fiber uses a laser diode LD as the light source, and the transmission distance of the 1000Mb/s fiber is 550m--100km. Single-mode fiber optic cables and single-mode fiber optic ports are more expensive, but can provide longer transmission distances and higher network bandwidths, and are usually used for long-distance network or inter-building connections. That is, the building group subsystem.

Common single-mode fiber specifications are 8/125um, 9/125um and 10/125um, and common multi-mode fiber specifications are 50/125um (European standard) and 62.5/125um (American standard). In comparison, 62.5/125um optical fiber has been favored by most users and has gained a solid position in the world optical fiber market.

Fiber Gigabit Ethernet includes 4 standards including 1000Base-SX, 1000Base-LX, 1000Base-LH and 1000Base-ZX. Among them, SX (Short-wave) is short wave, LX (longwave) is long wave, LH (long-haul) and ZX (extended range) are ultra-long wave, 1000Base-SX and 1000Base-LX can use either single-mode fiber or Use multimode fiber; while 1000Base-LH and 1000Base-ZX can only use single mode fiber.

Single-mode fiber and multi-mode fiber can be easily distinguished from the size of the core. The core of single-mode fiber is very small, about 4-10um, and only transmits the main mode. In this way, modal dispersion can be completely avoided, so that the transmission frequency band is very wide and the transmission capacity is large. This fiber is suitable for large-capacity, long-distance fiber-optic communications. It is the inevitable trend of the future development of optical fiber communication and light wave technology.

Multimode fiber is further divided into multimode abrupt fiber and multimode graded fiber. The former has a larger core diameter and more transmission modes, so the bandwidth is narrower and the transmission capacity is smaller. Wide and larger transmission capacity, the latter is generally used at present.

Optical fiber product purchase

Selection of fiber optic cable types

Optical fibers are usually bundled with a protective outer casing and a tensile wire in the middle, which is called a fiber optic cable. According to different application environments, optical cables are usually divided into indoor optical cables and outdoor optical cables.

Indoor fiber optic cables have less tensile strength and poorer protective layers, but are lighter and more economical. Indoor optical cables are mainly suitable for horizontal wiring subsystems and vertical backbone subsystems.

Outdoor optical cables have higher tensile strength, thicker protective layers, and are usually armored (that is, wrapped in metal skins). Outdoor optical cables are mainly suitable for building complex subsystems, and can be laid in three ways, namely direct burial, overhead or pipeline. The optical cable is directly buried in the excavated telecommunication trench, and after the burial is completed, the soil is filled and buried, which is simple and easy to implement, and the construction cost is low. If there are telecommunication trenches or pre-buried pipelines to be excavated, pipeline optical cables can be used. When the ground is not suitable for excavation, cannot be excavated or the excavation cost is too high, it is considered to use overhead laying.

Although the termination of optical fibers and the production of patch cords are very difficult, the connection of optical fiber networks can be easily accomplished. As long as the connecting device (hub and network card) has an optical fiber connection interface, a piece of fiber optic patch cord that has been made or purchased can be used for connection. The connection method is the same as that of the twisted pair cable, the network card and the hub. However, unlike twisted pair, there are many different types of connectors for optical fibers, and there is no direct connection between different types of connectors.

Introduction to Fiber Optic Connectors

When installing any fiber optic system, consideration must be given to connecting optical fibers or cables to each other in a low-loss method to achieve optical link splicing. The connection of optical fiber links can be divided into two types: permanent and active. Permanent connection is mostly realized by welding method, bonding method or fixed connector; active connection is generally realized by movable connector. A brief introduction to active connectors will be made here.

Optical fiber active connectors, commonly known as live joints, generally called optical fiber connectors, are reusable passive devices used to connect two optical fibers or optical cables to form a continuous optical path. They have been widely used in optical fiber transmission lines and optical fiber distribution frames. It is the most widely used optical passive device among optical fiber test instruments and meters.

Classification of fiber optic connectors

According to different classification methods, fiber optic connectors can be divided into different types. According to different transmission media, they can be divided into single-mode fiber optic connectors and multi-mode fiber optic connectors; according to different structures, they can be divided into FC, SC, ST, D4 , DIN, Biconic, MU, LC, HT and other types; according to the pin end face of the connector can be divided into FC, PC (UPC) and APC; according to the difference in the number of fiber cores, there are single-core and multi-core points. In the actual application process, we generally distinguish according to the structure of the optical fiber connector.

The connector types of single-mode fiber optic connectors are FC, SC, ST, FDDI, SNA, LC, MT-RJ, etc. (Figure 3), and the connector types of multi-mode fiber optic connectors are FC, SC, ST, FDDI, SMA, LC, MT -RJ, MU and VF45, etc. Optical fiber connectors are divided into PC, UPC and APC types according to the end-face contact method.

Selection of Fiber Connector Types

FC type fiber optic connector

FC is the abbreviation of Ferrule Connector, indicating that its external reinforcement method is a metal sleeve, and the fastening method is a turnbuckle. The earliest, FC type connector, the mating end face of the ceramic pin used is the plane contact method (FC). Such connectors are simple in structure, easy to operate, and easy to manufacture, but the fiber ends are more sensitive to dust, and are prone to Fresnel reflections, making it difficult to improve return loss performance. Later, this type of connector was improved, and the contact pin (PC) with spherical end face was adopted, and the external structure was not changed, so that the performance of insertion loss and return loss was greatly improved.

SC type fiber optic connector

The shell of the SC optical fiber connector is rectangular, and the structure and dimensions of the pins and coupling sleeves used are exactly the same as those of the FC type. The end faces of the pins are mostly PC-type or APC-type grinding methods; the fastening method is to use plug-in pins. Latch type, do not need to be rotated. This type of connector is inexpensive, easy to plug and unplug, small fluctuation in insertion loss, high compressive strength, and high installation density.

ST type fiber optic connector

The ST-type fiber optic connector shell is round, and the structure and dimensions of the pins and coupling sleeves used are exactly the same as those of the FC type. The end faces of the pins are mostly PC-type or APC-type grinding methods; the fastening method is turnbuckle. This type of connector is suitable for various fiber optic networks, easy to operate, and has good interchangeability.

MT-RJ type fiber optic connector

The MT-RJ has the same latching mechanism as the RJ-45 type LAN electrical connector. The optical fibers are aligned with the guide pins installed on both sides of the small sleeve. The core (spacing 0.75mm) arrangement design is a high-density optical connector mainly used for data transmission.

LC type fiber optic connector

The LC-type fiber optic connector is developed by the famous Bell Research Institute and is made with a modular jack (RJ) latch mechanism that is easy to operate. The size of the pins and sleeves used by the connector is half the size of ordinary SC, FC, etc., which is 1.25m, which improves the density of optical fiber connectors in the optical distribution frame. At present, in terms of single-mode SFF, LC-type connectors have actually occupied a dominant position, and the application in multi-mode is also growing rapidly.

MU type fiber optic connector

MU (Miniature unit Coupling) fiber optic connector is the world's smallest single-core fiber optic connector developed on the basis of SC-type connectors. The connector uses a 1.25mm diameter sleeve and a self-retaining mechanism, which has the advantage of enabling high-density mounting. The MU connector series includes receptacle-type optical connectors (MU-A series) for fiber optic cable connections, backplane connectors with self-retaining mechanisms (MU-B series), and simplified receptacles for connecting LD/PD modules to plugs ( MU-SR series) etc. With the rapid development of optical fiber networks in the direction of larger bandwidth and larger capacity and the wide application of DWDM technology, the society's demand for rigid connectors will also increase rapidly.

Optical fiber distribution frame

Optical Fiber Distribution Frame (ODF, Optical Fiber Distribution Frame) is an important supporting equipment in the optical transmission system. It is mainly used for optical fiber fusion splicing of optical cable terminals, optical connector installation, optical path adjustment, redundant pigtail storage and optical cable. It plays an important role in the safe operation and flexible use of optical fiber communication networks.

1. The function of optical fiber distribution frame

As the terminal equipment of the optical cable line, the optical fiber distribution frame has the following four basic functions: fixed function, fusion function, deployment function and storage function.

2. Type selection of optical fiber distribution frame

Optical fiber distribution frame can be divided into wall-mounted and rack-mounted according to different structures. The wall-mounted optical fiber distribution frame can be directly fixed on the wall. It is generally a box structure and is suitable for places where the number of optical cables and the number of optical fiber cores are small. The rack-mounted fiber optic distribution frame can be directly installed in the standard cabinet and is suitable for larger-scale fiber optic networks.

The rack-mounted patch panel is divided into two types, one is the patch panel with fixed configuration, and the optical fiber coupler is directly fixed on the chassis; The corresponding modules are convenient for network adjustment and expansion.