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How to Trouble Shoot Optical Transceiver?

Author Tao

Date 10/29/2021

As we know, fiber optic transceivers are the core of data center networks. When using a large number of transceiver modules, it is inevitable to encounter some troubles. This article will introduce the common issues in use and the corresponding solutions, such as: unsupported transceiver, SFP modules note detected, CRC error, invalid error detected, link flap, SFP unqualified etc.

Fiber Optic Transceiver Common Alarm Information Troubleshooting


this engineer is trouble shooting optical transceivers

                                                                    This engineer is trouble shooting optical transceivers.


Transceiver module not supported


When you found the following warning info in your logs such as Unsupported transceiver, Unknown, unqualified sfp+ module detected, authentication failed. There are generally three reasons for all the above errors:


a. The current version of the switch does not support your optical module, and a version update is required. For instance, the version information of Cisco equipment can be found at https://tmgmatrix.cisco.com, and the minimum software version requirements of the fiber module can be queried. If you want to use qsfp28 sr4 in N9K-C93180YC-EX, the minimum version should be NX-OS 7.03I4.2 or ACI-N9KDK9-11.3(2).


the version required of c93180yc-ex

b. Encoding compatibility issues. If you use codes such as Aruba or other manufacturers in Cisco switch, this will happen with a high probability. Besides, the OEM vendors will use a specific code on some devices, even if the code is the same vendor, it can not be used on these devices either. For example, the Cisco N7K device has a special SR code. For other types of incompatible modules, you can try the following command after logging in to the switch:



Switch#conf ter

Switch(configure)#inter eth 9(board number)/23(port number)

Switch(configure)#service unsupported-transceiver

Switch(configure)#no errdisable detect cause gbic-invalid

In most cases, replacing the transceiver modules is the best choice. Of course, if you purchase a fiber module from a third-party manufacturer like QSFPTEK. Then you can directly contact the manufacturer to provide a suitable code.


c. The device hardware does not support your optical module. In this case, the current module can only be replaced with an optical module supported by the device.


Optic modules Transmission Failed Troubleshooting

CRC error

interface status


CRC is a common detection technique for data transmission errors. The sent message is divided into predetermined lengths, and these lengths are divided by a fixed divisor. According to the calculation, the remainder is appended to and sent with the message. When a message is received, the computer recalculates the remainder and compares it with the sent remainder. If the numbers do not match, an error is detected.

Therefore, CRC error is a tricky type of error. There are generally 4 common reasons:

a. The first is the quality of the module. Reading DDM information, if there is abnormal receive power or abnormal voltage, current, temperature, etc. it can basically be judged as a hardware problem. In this case, you can consider replacing the module directly. 

b. The second is the problem of the link, such as the quality of the cable or the quality of the connector. You can use the near-end test with attenuators to simulate long-haul use. 

c. The third is that the hardware of the fiber module does not match the device. For example, some series of Aruba devices have special requirements for the hardware of the module. If the corresponding optical module is not purchased, even if the code matches, the hardware can’t meet the requirements of the device.

d. Codes are not matched with the device. When you see the info in log: gbic-security check fail, it is obvious that it is a coding problem. Need to change the appropriate code according to the device.


Link flap or Link down

When you encounter a link flap, all the reasons for this failure are hardware problems. Generally, there are two situations, one is the quality of the cable, and the second is the quality of your optical module. Both of these situations can be resolved by replacing the product. QSFPTEK can provide you with a 90-day replacement service and a 3-year warranty service for your fiber optic module, so there is no need to worry about quality problems.


There could be many reasons for the link down. If the link down occurs after a period of normal use, it can be judged that it is a quality problem of the cable or optical module. Additionally, the switch can recognize the module normally but there is always a link down, you can check the TX and RX power of the transceiver by reading the DDM information to confirm whether the quality of the module is normal. In some cases, it is because the hardware of the fiber optic module doesn't meet the requirements of the switch, which results in the inability to transmit. In this case, you need to contact the manufacturer to provide a solution.


Transceiver Hardware Issues Troubleshooting 

First, you need to confirm that the interface of the transceiver module is not dirty. Including the TX side and RX side. Furthermore, it is necessary to confirm that the gold finger is not oxidized or other visible appearance damages.


The internal component of the module is relatively fragile. If it is exposed to static electricity, it may cause the I2C chip to be broken down by static electricity. Moreover, the module does not have the characteristics of waterproof and dustproof. If water vapor enters the module, causing corrosion, etc. it will seriously affect the performance of the module or even fail to work. Non-professionals generally have no way to trouble shoot the module at the hardware level, and generally need to send it back to the manufacturer for diagnosis and repair.




Some of the above common problems need to be solved by after-sales service. Therefore, you need to carefully consider whether the vendor's after-sales service is complete and whether the product quality has been verified when purchasing optical modules. QSFPTEK can provide 90-days replacement service and 3-year warranty service. At the same time, QSFPTEK has many quality testing equipments and  50+ network switches of different brands for testing compatibility. What is more, QSFPTEK also has its own database to record past customer usage. Welcome to experience QSFPTEK's service.



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