With the rapid introduction of the 100G Ethernet standard, the industry gradually appeared another voice: 25G optical module to meet the needs of future network upgrades, 40G light module will soon carry on. What is the reason? This tutorial will compare 25G Ethernet and 40G Ethernet.

40G Ethernet

40G Ethernet network layer’s core is a pair of fiber optic cable (OM3 / OM4 cable) connected optical module. The optical module is then inserted into a network device such as a network server or a network interface card, switch, or the like.

Solutions of 40G Ethernet optical module & cable

40G optical module standard package style has undergone a series of changes, CFP optical module is the first generation of 40G optical module, it has 12 optical signal transmission channel and 12 optical signals receiving channel, the transmission rate of each channel is 10Gbps. So a total of three 40G Ethernet ports or one 100G Ethernet port can be provided to support multimode fiber optic cable and copper applications.

With up to 24 transmit and receive channels, we can imagine that the volume of CFP optical modules is very large, so this optical module does not meet the growing demand for high-density ports.

As a result, engineers have developed CXP optical modules, which, like CFP optical modules, have 24 optical signal transceivers and support multimode fiber optic cable and copper applications, but are smaller in size than CFP optical modules Much more.

Now the most common 40G optical module on the market is QSFP optical module, its volume and CXP optical module are similar, but only four optical signal transmission channel and four optical signals receiving channel can support single-mode fiber optic cable, multi-mode fiber optic cable And copper applications.

Fiber cabling and copper cabling can be used in 40G Ethernet, it should be noted that the cable routing transmission distance than the copper cabling transmission distance is much more.

For data center of the 40G Ethernet cabling, the use of OM3 / OM4 cable is a more respected cabling solution, because this wiring is more flexible than the copper cabling solution configuration than single-mode fiber optic cable solutions Lower cost.

In addition, the common connector in 40G Ethernet cabling is the MPO / MTP connector (the common connector for traditional network cabling is a duplex LC connector) because the 802.3ba standard specifies that the multimode optical module should be connected to the MPO / MTP Device to transmit data over multiple parallel fiber channels.

25G Ethernet

25G Ethernet optical module & cable solution

There are two main types of optical modules for 25G Ethernet: SFP28 (1x25 Gbps) and QSFP28 (4x25 Gbps).

25GBASE-SR SFP28 optical module is a working wavelength of 850nm 25G optical module, and other optical modules is different, this optical module internal transmitter is a vertical cavity surface emitting laser (VCSEL, Vertical Cavity Surface Emitting Laser), And therefore need to be used with 50 / 125μm OM3 / OM4 multimode fiber.

The transmission distance of the 25GBASE-SR SFP28 optical module and the OM3 multimode fiber is 70m, and the transmission distance used with the OM4 multimode fiber is 100m. For interconnection applications in data center switches, the use of SFP28 high-speed cables is a more common and cost-effective solution. In addition, QSFP28 to 4xSFP28 high-speed cable is 100G switch and 25G switch short-distance connection of the ideal solution.

25G Ethernet VS 40G Ethernet

It turns out that compared to 40G Ethernet, 25G Ethernet seems more suitable for cloud data centers and network scale data center applications, and the cost is lower. This is because 25G Ethernet can re-use 10G and 100G Ethernet components, help network operators more easily expand its data center.

40G Ethernet deployment VS 25G Ethernet deployment

Advantage of 25G Ethernet compared to 40G Ethernet 

1.Best input/output (I / O) performance and fiber capacity;

2.2.5 times the performance of 10G Ethernet;

3.Port density is higher;

4.Save capital expenditure;

5.Save operating expenses;

6.The number of ToR switches and cables required is less;

7.Lower cost, less power consumption;

8.Conforms to the 100G Ethernet standard;