Detailed explanation of the selection method of fiber optic transceivers!


1. Classification of fiber optic transceivers

Optical fiber transceivers, also known as photoelectric converters, are Ethernet transmission media conversion units that exchange short-distance twisted-pair electrical signals and long-distance optical signals.


Different viewing angles make people have different understandings of fiber optic transceivers:

For example, according to the transmission rate, it is divided into single 10M, 100M fiber optic transceivers, 10/100M adaptive fiber optic transceivers and 1000M fiber optic transceivers;


According to the working mode, it is divided into optical fiber transceivers working at the physical layer and optical fiber transceivers working at the data link layer;


From a structural point of view, it is divided into desktop (stand-alone) fiber optic transceivers and rack-mounted fiber optic transceivers;


According to the different access fibers, there are two types of multi-mode optical fiber transceivers and single-mode optical fiber transceivers.

mpo lc

In addition, there are single-fiber fiber optic transceivers and dual-fiber fiber optic transceivers, built-in power fiber optic transceivers and external power supply fiber optic transceivers, as well as managed fiber optic transceivers and unmanaged fiber optic transceivers.


Optical fiber transceivers break the 100-meter limitation of Ethernet cables in data transmission. Relying on high-performance switching chips and large-capacity caches, while truly achieving non-blocking transmission and switching performance, they also provide balanced traffic, isolation and conflict. Error detection and other functions ensure high security and stability during data transmission.


2. Scope of application

In essence, the optical fiber transceiver only completes the data conversion between different media, and can realize the connection between two switches or computers within 0-120Km, but the practical application has more expansion.


1. Realize the interconnection between switches.


2. Realize the interconnection between switches and computers.


3. Realize the interconnection between computers.


4. Transmission relay: When the actual transmission distance exceeds the nominal transmission distance of the transceiver, especially when the actual transmission distance exceeds 120Km, if the site conditions permit, use 2 transceivers for back-to-back relay or use optical- It is a very cost-effective solution for relaying by optical converters.


5. Single-multi-mode conversion: When a single-multi-mode fiber connection is required between networks, a single-multi-mode converter can be used for connection, which solves the problem of single-multi-mode fiber conversion.


6. Wavelength division multiplexing transmission: When the long-distance optical cable resources are insufficient, in order to improve the utilization rate of the optical cable and reduce the cost, the transceiver and the wavelength division multiplexer can be used together, so that the two channels of information can be transmitted on the same pair of optical fibers.


3. Precautions for use

We know that there are many different classifications of fiber optic transceivers, but in actual use, most of the attention is paid to the categories distinguished by different fiber optic connectors: SC connector fiber optic transceivers and ST connector fiber optic transceivers.


When using fiber optic transceivers to connect different devices, you must pay attention to the different ports used.


1. Connection of fiber optic transceivers to 100BASE-TX devices (switches, hubs):


Confirm that the length of the twisted pair does not exceed 100 meters;


Connect one end of the twisted pair to the RJ-45 port (Uplink port) of the optical transceiver, and the other end to the RJ-45 port (common port) of the 100BASE-TX device (switch).


2. The connection of the optical transceiver to the 100BASE-TX device (network card):


Confirm that the length of the twisted pair does not exceed 100 meters;


Connect one end of the twisted pair to the RJ-45 port (100BASE-TX port) of the optical transceiver, and the other end to the RJ-45 port of the network card.


3. Connection of optical transceiver to 100BASE-FX:


Confirm that the fiber length does not exceed the distance range that the device can provide;


One end of the optical fiber is connected to the SC/ST connector of the fiber optic transceiver, and the other end is connected to the SC/ST connector of the 100BASE-FX device.


In addition, it is necessary to add that many users think when using optical fiber transceivers: as long as the length of the optical fiber is within the maximum distance supported by single-mode optical fiber or multi-mode optical fiber, it can be used normally. In fact, this is a wrong understanding. This understanding is correct only when the connected devices are full-duplex devices. When there are half-duplex devices, the transmission distance of the optical fiber is limited to a certain extent.


Four, ST, SC, FC, LC interface difference

There are also many types of optical fiber connectors, that is, optical fiber connectors that connect to optical modules, and they cannot be used with each other. People who are not in frequent contact with optical fibers may mistakenly think that the optical fiber connectors of GBIC and SFP modules are the same kind, 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 fiber connector.


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

① FC-type fiber optic connector: The external strengthening method is a metal sleeve, and the fastening method is a turnbuckle. Generally used on the ODF side (the most used on the patch panel)


② SC-type optical fiber connector: the connector for connecting the GBIC optical module, its shell is rectangular, and the fastening method is the plug-in type, which does not need to be rotated. (Most used on router switches)


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


④ LC-type fiber optic connector: a connector for connecting SFP modules, which is made with a modular jack (RJ) latch mechanism that is easy to operate. (commonly used by routers)


⑤ MT-RJ: a square fiber optic connector with integrated transceiver, one dual-fiber transceiver integrated


Introduction of various fiber optic interface types (optical fiber connectors):

FC round with thread (most used on patch panels)

ST snap-on round

SC card connection type (the most used on router switches)

PC microsphere grinding and polishing

APC is at an 8-degree angle and is ground and polished with microspheres

MT-RJ square, one dual fiber transceiver

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