With the massive increase in demand for huge bandwidth requirements of private and public cloud data centers and communication service providers (telco), and because of the recent advancements in the 25G Ethernet speed technology, the ICT researchers and developers promoted 25 Gigabit Ethernet to meet the requirement of higher bandwidth for Internet users. In fact, 25GbE ports are growing rapidly in data center server access ports. This article will introduce 25GbE Ethernet and 25G SFP28 transceiver.
What Is 25G Ethernet?
25G Ethernet is a proposed Ethernet standard at 25 gigabits per second (25 GbE). 25 GbE was approved in 2016 and developed by the 25G Ethernet Consortium and IEEE 802.3by task force, which also includes 50 GbE. The 25 and 50 GbE speeds are even divisions of 100 Gigabit Ethernet, which comprises four 25 Gbps streams. Therefore, migrating in the future from 25 or 50 to 100 GbE is expected to be more economical than going from 40 to 100 GbE. 25GbE take benefit for cloud and enterprise data center environments.
25GbE leverages technology defined for 100GbE implemented as four 25Gbps lanes (IEEE 802.3bj) running on four fiber or copper pairs. Quad small form-factor and 100Gb form-factor pluggable transceiver (QSFP28/ CFP) modules have four lasers, each transmitting at 25Gbps. Each lane requires a Serializer/Deserializer (SerDes) chipset. The twisted pair standard was derived from 40GbE standards development. The following table provides a summary of key upcoming IEEE standard interfaces that specify 25GbE.
Why 25G Ethernet?
More performance improvements for 25G
25G solutions offer 2.5 times the bandwidth, but they are not much more expensive than 10G Ethernet solutions. In addition, when connected to 10G devices, they are fully backward compatible. When upgrading a data center network to 25G, you can use the 25G feature to refresh the network instead of upgrading the entire system. Compared with the 40G solution, the basic technology of 40G Ethernet is only four channels of 10G speed. It does not have the advantages of cost, power consumption and server rack density for wide speed conversion. All in all, 25G Ethernet reduces cost and power requirements, making network bandwidth cost-effective and supporting next-generation server and storage solutions in cloud and Web-class data center environments.
Lower Cost than 10G per port
25G solutions offer The proposed 25GbE standard provides 2.5 times the amount of data compared to existing 10GbE solutions. It also provides greater port density and lowers port density Cost per unit of bandwidth by leveraging switch port functionality compared to 40GbE solutions. The specification adopted by the Alliance uses single-channel 25GbE and dual-channel 50GbE link protocols. To help promote adoption, news specifications can be provided free of charge to any data center ecosystem provider or to consumers who join the alliance.
What is 25G SFP28 Transceiver
SFP28 is the dominant form factor for the 25G transceiver. It is upgrade standard relies on the 10G SFP+ (Small Form Factor Pluggable) standard for mechanical specifications. The SFP28 transceiver supports the electrical specifications that operate at 10.312Gbps to one 28Gbps lane that operates at 25Gbps+ error correction. The SFP28 form is the third generation of the SFP interconnect systems designed for 25G performance per the IEEE 802.3by specification.
Types of 25G SFP28 Transceiver and Cables
25G SFP28 SR Transceiver
25G SFP SR transceiver is a multimode 25G transceiver that operates over a pair of multi-mode fibers (MMF), using a wavelength of 850nm. It provides an ideal solution for data center applications that require up 100 meters over OM4 fiber or 70 meters over OM3 fiber interconnect.
25G SFP28 LR Transceiver
25G SFP LR transceiver is a single-mode transceiver. It is SFP28 module for duplex optical data communications supports 25G Ethernet. It is with the SFP+ 20-pin connector to allow hot plug capability. Digital diagnostic functions are available via an I2C. 25G SFP28 LR is designed for single-mode fiber and operates at a nominal wavelength of 1310nm.
25G SFP28 ER Transceiver
25G SFP ER transceiver is a single-mode extended reach transceiver. This SFP28 module is designed for duplex optical data communications to support 25Gb/s Ethernet with CDR engaged, while, 10G ethernet optical data communication can be supported when CDR is bypassed. It is with the SFP+ 20-pin connector to allow hot plug capability. Digital diagnostic functions are available via an I2C. This module is designed for single-mode fiber and operates at a nominal wavelength from 1295nm to 1310nm. The transmitter section uses a 1310nm multiple quantum well DFB laser and is a class 1 laser compliant according to International Safety Standard IEC 60825.
25G SFP28 CWDM Transceiver
25G SFP CWDM transceiver is a single-mode CWDM transceiver. It is SFP28 module for duplex optical data communications support up to 25.78Gb/s. It is with the SFP+ 20-pin connector to allow hot plug capability. Digital diagnostic functions are available via an I2C. It has a built-in clock and data recovery (CDR). This module is designed for single-mode fiber and operates at a nominal wavelength of CWDM (1271~1331nm).
25G SFP28 BiDi Transceiver
25G SFP BiDi transceiver is a single-mode Bidirectional transceiver. It is SFP28 module for duplex optical data communications supports up to 25.78Gb/s. It is with the SFP+ 20-pin connector to allow hot plug capability. Digital diagnostic functions are available via an I2C. It has a built-in clock and data recovery (CDR). This module is designed for simplex fiber and operates at a nominal wavelength of 1270 / 1330nm.
25G SFP28 DAC Cable
25G SFP28 DAC is a 25GBASE-CR direct attach copper cable for data center environment. It provides a high speed, cost-effective alternatives to fiber optics in 25GbE Ethernet applications. The cables are compliant SFF-8402 SFP28 standard. The 25G SFP cable is available in lengths up to 5m (16.4 ft) for passive DAC. Compared with SFP28 transceiver, 25G SFP DAC allows the customers to deploy the copper cabling with a far less budget.
25G SFP28 AOC Cable
25G SFP28 AOC is a 25GBASE-AOC SFP28 Active Optical Cables (AOC)