Technologies such as 5G, Big Data, and Artificial Intelligence all have higher requirements for data processing and network bandwidth. Therefore, in recent years, data centers need to continuously upgrade their network bandwidth to meet the demand. The most direct way is to enhance the network bandwidth of the single port, from 40G to 100G, from 100G to 200G, or even higher, thus increasing the bandwidth of the whole data center. 400G network deployment has started in 2019, and 400G switches will soon become the core switches for mega data centers. On one side, there is a strong demand for high-speed modules in data centers, and on the other side, the module failure rate remains high. So how should we reduce and avoid the failure rate of optical modules? This article will provide answers.
Why do optical modules encounter error?
Compared with 1G and 10G, the failure rate of 40G, 100G, 200G and 400G modules is much higher. Of course, the process complexity of these high-speed modules is much higher than that of low-speed modules. For example, a 40G optical transceiver is essentially bound through four 10G channels, which is equivalent to 4X10Gb/s working. As long as there is a problem in one channel, the whole 40G can no longer be used. Plus, the 40G QSFP optical modules also need to realize the coordinated work of four optical paths, accordingly the error rate is naturally higher than that of 10G module. The 100G optical transceiver is even more so, some are bound up through 10X10Gb/s channels, and some use new optical technology, all of which will increase the possibility of errors. For example, 400G is still the technology in the laboratory, and the current usage is not very much. However, with the continuous improvement of technology, it is believed that the high-speed transceivers will be gradually stable like the low-speed transceivers.
Fortunately, the failure of the optical module rarely has a great impact on the service. In a few cases, the optical module may cause equipment port failure, resulting in the hanging of the whole equipment. This situation is mostly caused by unreasonable equipment connection, in other words, the vast majority of optical modules and equipment are loosely coupled. Although they are connected together, there is no coupling relationship. Imagine getting the 1G optical module of GBIC 20 years ago. It feels like using 200G now. It is inevitable that the failure rate of the new product will increase in the short term. In fact, it is inevitable that the failure rate of new products will increase in the short term. Recall that 20 years ago when you first used a 1G GBIC optical module, it was similar to the feeling of using 200G for the first time now.
What faults usually occur in optical modules?
The failures of optical modules are mostly manifested in the phenomena that the port cannot be up, the optical module cannot be recognized, and the error packets of the CRC port. These failures are related to the equipment side, the optical module itself and the link quality. Especially for the error packet and failure to UP, it is difficult to judge the fault location from the software technology. Besides, some are even adaptation problems, that is, there are no problems with optical modules and switches, but they have not been debugged and adapted to each other, resulting in failure to work together. In practice, there are many such situations, thus many network devices will be gave a list of adaptive optical modules, so as to ensure stable availability. In case of failure, the best method is rotation test, changing link optical fiber, module and port. Through this series of tests, confirm whether it is the problem of optical module or the problem of link or equipment port. In general, this kind of fault phenomenon is easy to determine, but some are not. For example, when there is a error packet of the CRC port, pull out the optical module directly and replace it with a new one, the fault phenomenon disappears, and then replace the original optical module, and the fault will not reappear, which makes it difficult to judge whether it is an optical module problem. This situation is often encountered in practical use, which makes it difficult to make judgment.
How to reduce the failure rate of optical modules?
First, pay close attention to the source. Optical modules with higher bandwidth should not be rushed to the market. And sufficient experiments should be done. Moreover, high-speed modules need corresponding equipment to be realized, and all aspects of technology need to be relatively perfect. Don’t blindly pursue high speed. Since now network devices support multi-port binding. Like QSFP-DD 400G SR8, if a single 400G transmission can’t be realized, 8x50Gb/s can also meet the demand.
Second, network equipment manufacturers and data center customers should be cautious in using high-speed optical modules, strictly test high-speed optical modules, and resolutely filter out products with defects in quality. At present, the market competition of high-speed optical modules in the market is also fierce. They all hope to take the lead in the new high-speed modules, but the product quality and price are uneven, which requires network equipment manufacturers and data center customers to strengthen the assessment. The more high-speed modules, the more complex the verification should be.
Third, the optical module is actually a highly integrated device. The exposed optical fiber channel and internal devices are relatively fragile. When using, handle them with care, wear clean gloves to avoid falling into dust. The unused optical modules should wear optical fiber caps and put them in bags. Doing so will also reduce the use failure rate.
Fourth, the optical module shall be applied to the limit parameter value as little as possible. For example, if the 100G optical module is used near the maximum speed for a long time, or the optical module with a transmission distance of 200m is used at a distance of 200m, these limit boundary values will cause great loss to the optical module. In other words, the optical module is like a person. When people work in an air-conditioned room with a temperature of 24 ~ 26 degrees, their work efficiency is high. When they reach the outdoor high temperature environment of 35 degrees, they can’t concentrate for a long time, and their work efficiency is low. When it reaches more than 40 degrees, people are about to suffer from heatstroke. How can they work? Therefore, providing a comfortable working environment for the optical module can effectively prolong the service life of it.
What are the precautions for optical module connecting?
Data centers need to realize the coordinated operation of data, that is, the computer rooms need to be interconnected to exchange information. Storage, calculation and analysis are based on electrical signals, and optical fiber is the main transmission medium. Therefore, we need a device that can convert optical and electrical signals to each other. Optical module is undoubtedly the core device.
Optical module is an essential part of all network connection deployment. Click to know what are the internal components of an optical module. Basically, as long as there is optical fiber interconnection, optical module will be used. The application scenarios of optical module are mainly divided into Internet data center network, metropolitan area network, optical transmission network and 5G bearer network. Ordinary optical modules are mostly commercial optical modules, and the normal working temperature is 0℃~70℃, while the working temperature of industrial optical modules is -40℃~85℃, that is, they can work at a high temperature of 85 ℃ and in a harsh environment of minus 0℃. Different application environments need to select the corresponding level of optical module, otherwise it is easy to cause abnormal temperature of optical module, thus affecting normal use.
FAQ of data center optical transceiver:
·Can optical modules with different wavelengths of 1310nm and 1550nm be connected?
No, you cannot. Because the wavelengths of 1310nm and 1550nm carriers are not the same, the signal modulation will be wrong and the docking will not be able to communicate.
·Can optical modules with different transmission distances be connected?
The optical modules shall be used in pairs. The optical modules at the receiving end and the transmitting end shall have the same transmission rate, transmission distance, transmission mode and working wavelength. Optical modules with different transmission distances have different sensitivity ranges. Therefore, if you want to connect different transmission distance optical modules, you can add suitable attenuator according to the required range (non-professional please do not try), this operation will be more trouble, non-essential cases are not recommended.
·Can a high rate optical module be used as a low rate optical module?
If the GE optical module is used as the FE optical module, it can sometimes be connected, but because the working level is different from the working mode of the single board, and has not been strictly tested, the parameter indexes do not meet the requirements, and many unknown problems will occur, so it cannot be used in this way.
· Under what circumstances do you need to add attenuation to the optical module?
When the optical power transmitted by the opposite end is greater than the upper limit of the optical power received by the local optical module, it is necessary to properly attenuate the optical signal before connecting to the local optical module. When long-distance fiber optical transceiver, such as 80km and 120km optical modules, are used in short-distance applications, or when the optical module passes through the amplifier, pay attention to increase appropriate light attenuation to avoid direct burning of the optical module due to too strong optical power.
Conclusion
With the growth of massive data, the bandwidth demand of data center is higher and higher. The introduction of higher speed optical modules has become the necessary way to go, and the issue of their quality must be controlled. If the new high-speed modules frequently hit a wall in the market, they will not escape the result of being eliminated. Of course, any kind of new technology has a process of maturity, high-speed optical modules are no exception. Continuous technological innovation is needed to solve various problems, improve module quality and reduce failure probability. High speed optical module is the profit engine of module manufacturers, is a must for all generations of module manufacturers. Therefore, the quality of the newly high-speed modules should be strictly controlled.