A clear understanding of the article: fiber optic transceiver use and troubleshooting

Many friends have been asking about the role and use of fiber optic transceivers, so in this issue we will learn about the contents of the fiber optic transceiver.

First, what is a fiber optic transceiver

It is an Ethernet transmission medium conversion unit that exchanges short-distance twisted pair electrical signals and long-distance optical signals, and is also called a photoelectric converter in many places. Products are generally used in actual network environments where Ethernet cables cannot be covered and must use optical fibers to extend the transmission distance, and are usually located in access layer applications of broadband metropolitan area networks; for example, high-definition video image transmission for monitoring security engineering; It also played a huge role in connecting the last mile of the fiber to the metro and the outer network.

Second, the role of fiber optic transceiver

Maybe what is the fiber transceiver above? Everyone doesn't understand very well, so you can understand it from its purpose.

Due to the limitation of the maximum transmission distance of the commonly used network cable (twisted pair), the maximum transmission distance of the twisted pair is 100 meters. Therefore, when we are deploying a larger network, we have to use a relay device. Optical fiber is a good choice. The transmission distance of optical fiber is very long. Generally speaking, the transmission distance of single-mode fiber is more than 10 kilometers, and the transmission distance of multimode fiber can reach 2 kilometers. When using fiber optics, we often use fiber optic transceivers:

To understand how a fiber optic transceiver is used, it is important to know what the fiber optic transceiver does. Simply put, the role of a fiber optic transceiver is the mutual conversion between optical and electrical signals. The optical signal is input from the optical port, and the electrical signal is output from the electrical port (common RJ45 crystal head interface), and vice versa. The process is probably: converting an electrical signal into an optical signal, transmitting it through an optical fiber, converting the optical signal into an electrical signal at the other end, and then accessing a router, a switch, and the like.

Therefore, fiber optic transceivers are generally used in pairs. For example, the optical transceivers (possibly other devices) in the equipment room of the operator (Telecom, Mobile, China Unicom) and your fiber transceiver. If you want to build your own LAN with a fiber optic transceiver, you have to use it in pairs. Generally, the optical transceiver is the same as the general switch. It can be used by plugging in and can be used without any configuration. Optical fiber insertion port, RJ45 crystal head plug. However, pay attention to the transmission and reception of optical fibers, one for each other, if not, change each other.

for example:

E.g:

If there is a distance between some access layer switches and the core switch, a transition switch can be added between the access layer switch and the core layer switch to perform the relay. This will extend the distance. We know that the transmission distance of the network cable is 100 meters, so what about the distance? For example, seven or eight hundred meters, or even further, then do not use the switch to do the relay,

A pair of fiber optic transceivers can be used, one connected by a network cable next to the core switch and the other by the access layer switch. The two fiber optic transceivers are connected by fiber optics.

However, it is important to note the problems of single mode fiber and multimode fiber. If it is a single-mode fiber, the transceiver must also be single-mode. Only one fiber needs to be used. The length and length of the problem are not considered within a few kilometers, because the distance traveled by the single-mode fiber is far.

If it is a multimode fiber, the transceiver must be a multimode fiber, a pair of fibers, a distance of five or six hundred meters, and more than 2 kilometers.

Then it may involve a question, in the end, use single mode or multimode? This complements the difference

In fact, there is no difference between good and bad, only the use is different, multi-mode fiber is mostly used in short-distance building wiring closet, communication between core equipment and core equipment, the advantage is that communication bandwidth is large, and more support for 10G, the disadvantage is that It has a shorter transmission distance than single mode fiber.

Third, the use of optical transceivers

Generally, the optical transceiver is the same as the general switch. It can be used by plugging in and can be used without any configuration. Optical fiber insertion port, RJ45 crystal head plug. However, pay attention to the transmission and reception of optical fibers, one for each other, if not, change each other.

Fourth, the use of optical transceivers

1. The panel structure diagram of each type of optical transceiver (the following is an example) is as follows.

The schematic diagram of the application of the optical transceiver is as follows. The fibers are all one pair. You can connect to your LAN from the optical transceiver.

The meaning of the panel above is as follows:

1000 - when illuminated, it represents 1000M speed

100 - when illuminated, represents the 100M rate

FX - when it is on, it means that the pigtail is connected, and the flashing means that the data is being transmitted.

FX LINK/ACT - when it is on, it means that the Internet cable is connected, the flashing means that the number of transmissions is PWR - when it is on, it means that the power cord is connected.

TX LINK/ACT - when it is on, it represents the full-duplex rate, and when it is off, it represents the half-duplex.

2, the indicator light:

PWR: power indicator

FX: optical port link/status indicator

FX LINK/ACT: optical port link/status indicator

FDX: optical port working mode indicator

TX-100: electrical port signal indicator

TX LINK/ACT: electrical link / status indicator

If the fiber transceiver is working properly, the PWR power indicator must be steady on. The FX-LINK/ACT fiber link indicator and the TX-LINK/ACT network link indicator should be on or blinking. If the LINK/ACT indicator is off. Check whether the link is normal. The FDX working mode indicator, FX-100 fiber rate indicator, and TX-100 network rate indicator are not lit.

Five, fiber optic transceiver connection

There are many different types of fiber optic transceivers, and most of the actual use is in the categories that are differentiated by fiber connectors: SC connector fiber transceivers and FC/ST connector fiber transceivers. When using a fiber optic transceiver to connect different devices, you must pay attention to the different ports used. Here is an example of a 10100BASE-TX device:

1. Connection of fiber optic transceiver to 100BASE-TX device (switch, hub):

Make sure that the length of the twisted pair cable is no longer than 100 meters. Connect one end of the twisted pair cable to the RJ-45 port (Uplink port) of the fiber transceiver and the other end to the RJ-45 port of the 100BASE-TX device (switch, hub). (ordinary mouth).

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

Make sure that the length of the twisted pair cable is no longer than 100 meters. Connect one end of the twisted pair cable to the RJ-45 port (100BASE-TX port) of the fiber transceiver and the other end to the RJ-45 port of the network card.

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

Make sure that the length of the fiber does not exceed the range that the device can provide. One end of the fiber is connected to the SC/FC/ST connector of the fiber 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 use optical transceivers as long as the length of the fiber can be used within the maximum distance that single mode fiber or multimode fiber can support. In fact, this is a misunderstanding. This kind of 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 has a certain limit.

Sixth, fiber transceiver failure judgment method

There are many types of optical transceivers, but the method of fault diagnosis is basically the same. To sum up, the faults that occur in optical transceivers are as follows:

1. Power light does not light: Power failure

2. If the light path Link light is not lit, the fault may be as follows:

A. Check if the fiber line is open.

B. Check if the fiber line loss is too large and exceed the receiving range of the device.

C. Check whether the fiber interface is connected accurately. The local TX is connected to the remote RX, and the remote TX is connected to the local RX.

D. Check whether the fiber connector is properly inserted into the device interface, whether the jumper type matches the device interface, whether the device type matches the fiber, and whether the device transmission length matches the distance.

3. If the circuit Link light is not lit, the fault may be as follows:

A. Check if the network cable is open.

B. Check whether the connection type matches: devices such as network cards and routers use cross-wires, and switches, hubs, etc. use straight-through lines.

C. Check if the device transmission rate matches.

4. The network packet loss may be severe as follows:

A. The electrical port of the transceiver is connected to the network device, or the duplex mode of the interface of the two devices does not match.

B. There is a problem with the twisted pair and the RJ-45 head for testing.

C. Fiber connection problem, whether the jumper is aligned with the device interface, whether the pigtail and jumper and coupler type are matched.

5, the fiber transceiver can not communicate after the two ends are connected

A, the fiber is reversed, and the fiber is connected to the TX and TR.

B. The RJ45 interface is not properly connected to the external device (focus on straight-through and splicing)

The fiber interface (ceramic ferrule) does not match. This fault is mainly reflected in the 100M transceiver with photoelectric mutual control function. If the pigtail of the APC ferrule is connected to the transceiver of the PC ferrule, it will not be able to communicate normally. The photoelectric intercommunication transceiver has no effect.

6, time pass and break phenomenon

A. It may be that the optical path attenuation is too large. At this time, the optical power of the receiving end can be measured by the optical power meter. If the receiving agility range is around four weeks, the optical path fault can be basically judged within the range of 1-2 dB.

B. The switch connected to the transceiver may be faulty. In this case, the switch is replaced by a PC, that is, the two transceivers are directly connected to the PC, and the two ends are connected to PING. If the switch is not present, the switch may be basically faulty.

C. It may be a transceiver failure. At this time, connect the transceiver to the PC at both ends (do not pass the switch). After both sides have no problem with PING, transfer a large file (100M) from one end to the other end, observe it. Speed, such as slow speed (file transfer of less than 200M for more than 15 minutes), can be basically judged as a transceiver failure.

7, after a period of communication, crash, that is, can not communicate, return to normal after restart

This phenomenon is generally caused by the switch. The switch performs CRC error detection and length check on all received data. It checks that the packet with the error will be discarded and the correct packet will be forwarded. However, some packets with errors in this process are not detected in the CRC error detection and length check. Such packets will not be sent out during the forwarding process and will not be discarded. They will accumulate in the dynamic cache ( Buffer), can never be sent out, wait until the buffer is full, it will cause the switch to crash. Because restarting the transceiver or restarting the switch at this time can restore the communication to normal, the user usually thinks it is a problem with the transceiver.

8, transceiver test method

If you find a problem with the transceiver connection, please test it as follows to find out the cause of the failure.

A, near-end test

Both ends of the computer to PING, if you can PING通, then confirm that the fiber transceiver is no problem, such as the near-end test can not communicate can be judged as the fiber transceiver failure.

B, remote testing

If the computer at both ends is PING, if the PING is unreachable, it must check whether the optical path connection is normal and whether the transmitting and receiving power of the optical transceiver is within the agreed range. If PING is passed, it proves that the optical path is connected properly. You can determine the problem with the fault on the switch.

C, remote test to determine the point of failure

First connect one end to the switch, and both ends to PING. If there is no end fault, it can be judged as failure of another switch.