Ethernet is a computing network technology that accompanies network computing. Xerox introduced Ethernet for the first time in 1980, when the transmission speed was 10 megabits per second (10Mb/s). Improved Ethernet has been released one after another, the network speed usually increases by 10 times, and the design is often backward compatible. Over the years, the network speed has gradually evolved from 10Mb to 100Mb, 1000Mb, and 1Gb per second. After the network speed reaches 10Gb per second, the “ten-fold” growth rate will no longer be adopted, and the next speed will be 40Gb per second. The latest generation of data center networks are designed to transmit at 400Gb per second, and there are plans to increase the transmission speed to 1.6Tb per second.
 
 
 
In this article, we will use 10Gb/s Ethernet or 10 Gigabit Ethernet (10GbE) related technologies running on optical fiber links in a local area network (LAN) or data center (DC) environment as examples to explain data communication. The environment's 10GbE (ten-gigabit) network was first introduced to the market in 2002, and there are several ways to achieve 10GbE transmission: 10GBASE-SR, 10GBASE-LR, 10GBASE-ER, and 10GBASE-LX4 applied to local area networks and data centers; applications 10GBASE-SW, 10GBASE-LW and 10GBASE EW for Wide Area Network (WAN). These transmission methods have different characteristics, and different types of lasers and optical fibers are used to achieve different transmission lengths. It's worth noting that the cost points for each option vary widely. In the next few years, the choice of transmission methods available for LAN and data center applications has been reduced to three main specifications: SR (short wave, short distance), LR (long wave, long distance) and ER (ultra long wave, ultra long distance) ). The main features of each specification are listed below.
 
 
 
10GbE Ethernet switches are structured with ports that plug into transceivers (transmit / receive). The main function of the transceiver is to convert the 10 Gigabit network electrical signals (10GbE) in the switch into optical signals that are subsequently sent through the optical fiber, and convert the optical signals received through the optical fibers into 10 Gigabit network (10GbE) electrical signals. Various transceivers existed in early 10 Gigabit Ethernet, but then small hot-swappable (SFP+) transceivers based on LC duplex connectors became the de facto standard. Compared with earlier transceivers, it has a low carbon footprint and low power consumption, and a rack unit (1RU) network switch can provide 48 ports.
 
The advent of 10 Gigabit Ethernet (10GbE) has brought tremendous changes to the fiber optic networks of local area networks and data centers. These new 10GBASE-SR transceivers use VCSEL lasers (vertical cavity surface emitting lasers), which are cheaper than single-mode lasers but more powerful than previous multimode light-emitting diode (LED) transmitters. These vertical-cavity surface-emitting lasers have a very concentrated spot (approximately 30 μm in diameter) and require new laser-optimized multimode fibers. Although traditional OM1 (62.5 / 125) and OM2 (50/125) cabled optical fibers can be used, due to their limited bandwidth capacity, the transmission range is very limited (33m and 82m respectively). The new enhanced bandwidth optical fiber conforms to ISO / IEC 11801-1 standards in the form of OM3 and OM4, and the transmission distance is 300 meters and 400 meters, respectively. OM3 and OM4 cables are usually equipped with Aqua jackets to distinguish them from traditional orange or gray jacketed OM1 and OM2 cables.
 
In the specification file of 10GBASE-SR, the maximum channel insertion loss is 2.6 dB when using OM3 transmission distance over 300 meters; the maximum channel insertion loss is 2.9 dB when using OM4 transmission distance over 400 meters. Channel insertion loss refers to the total optical signal loss from the transceiver at one end of the channel to the transceiver at the other end of the channel. These two parameters are closely related-as the channel length decreases, the allowable loss value increases, and the value is greater than the optical attenuation value reduced due to the shortened fiber length. This is because, in order to compensate for the effect of signal distortion, when the transmission length reaches the maximum distance, it is necessary to increase the loss margin. By using OM4 fiber, with higher specification transceivers, the link can be extended up to 400 meters or more.
 
C-light SFP+ video

 
 
Summary: Today's 10GbE networks (10 Gigabit Ethernet) use OM3 fiber, the longest transmission distance can reach 300 meters, and OM4 fiber can reach 400 meters. With the LC duplex connector, the maximum channel insertion loss of OM3 is 2.6 dB, and the maximum channel insertion loss of OM4 is 2.9 dB. Now, 10GbE network switches can connect up to 48X 10GbE ports for devices and up to 6X 40GbE ports for network uplinks. All 10GbE ports in modern fiber optic networks are equipped with SFP + small hot-swappable transceivers.
 
How to ensure the transmit and receive power of the optical module ?

In the diagnostic information of the optical module, you can view the current optical power values sent and received, as well as the default maximum and minimum power values.
 
If the received power is low (RxPower Low), it indicates that the signal received by the local end is too low, and the port may not be UP or the packets may be discarded after receiving the UP. In this case, first check whether the transmission distance is too long and exceeds the optical module. The transmission distance, and then check the link, such as whether the optical module, optical fiber is damaged, whether the single-mode multi-mode fiber is used incorrectly, whether the quality of the splice connection is reliable, and whether the transmit power of the opposite optical module is too low.
 
If the received power is high (RxPower High), it means that the signal received by the local end is too high. The possible reason is that the optical module is a long-distance optical module, and the actual transmission distance is too short, resulting in no signal attenuation. Increase optical attenuation to protect the optical module.
 
If the transmit power is low (TxPower Low), the signal sent by the optical module is not good, which may cause the receiving power of the peer end to be low, which may cause the port not to be UP or the packet transmission and reception to be discarded after the UP. The possible reason is that the optical port of the optical module is polluted. If there is too much dust accumulation, please clean the optical module with a cotton swab, and then test whether the luminous power of the optical port returns to normal.
 
If the transmit power is high (TxPower High), it means that the optical module sends a signal that is too strong, which may cause the receiving power of the peer end to be high, which may cause the peer optical module to burn out due to the continuously high receiving power. The possible cause is the local end optical module. Failure, it is recommended to replace the optical module.
 
Therefore, after the optical module is plugged in and connected to the port, the alarm information about the transmitted or received optical power must be checked to avoid traffic or optical modules being abnormal due to low or high power.