Cisco S-Class Optics vs. Non-S-Class Optics, What is the Difference?

If you are a Procurement manager, you might be confused when purchasing transceiver modules for your company. Take the Cisco short-range 10G SFP+ module for fiber networks as an example, there are SFP-10G-SR and SFP-10G-SR-S available. However, no technical difference can be found when you browse the specifications of these two optics. In fact, these are two quite similar transceiver modules launched by Cisco. The latter one is Cisco S-class optics. So questions like “What is the difference between Cisco S-Class and Non-S-Class Optics?‘ and “Is S-Class SFP+ compatible with "normal" SFP+?” are raised in communities. This article will compare S-class SFP vs. non-S-class SFP modules to help you make a better choice.

Cisco S-Class Modules Introduction

Cisco launched the S-class optics in December 2014 to provide a cheaper solution for enterprise and data center 10G and 40G Ethernet applications. These S-class modules are only available for the most common reaches. We can find eight S-class optical transceivers in the Cisco 10GBASE SFP+ Modules Data Sheet and Cisco 40GBASE QSFP Modules Data Sheet. They are Cisco SFP-10G-SR-S, Cisco SFP-10G-LR-S, Cisco SFP-10G-ER-S, Cisco SFP-10G-ZR-S for 10 gigabit Ethernet and Cisco QSFP-40G-SR4-S, Cisco QSFP-40G-CSR-S, Cisco QSFP-40G-LR4-S, Cisco QSFP-4X10G-LR-S for 40 gigabit Ethernet. All these models are commercial temperature modules. 

 

Cisco S-Class 10GBASE SFP+

Cisco S-class 10GBASE SFP+ is optimized for enterprise and data center applications. The portfolios of products provide multiple 10-gigabit Ethernet connectivity options, ranging from short-reach to long-reach up to 80km. The table below is the detailed specification of Cisco S-class 10GBASE SFP+ optics.

 

 

Cisco S-Class 40GBASE QSFP

Cisco S-class 40GBASE QSFP is best for enterprise core, distribution and high-performance computing network applications. The portfolios of products provide multiple 40-gigabit Ethernet connectivity options, ranging from short-reach to long-reach up to 10km. The table below is the detailed specification of Cisco S-class 40GBASE QSFP+ optics.

 

 

Cisco S-Class vs. Non-S-Class Modules: What are the Differences?

Cisco non-S-class and S-class optics are identical in appearance and most transmission parameters, such as wavelength, cable type, core size, bandwidth, and Cisco S-class optics are functionally simpler than non-S-class ones. 

 

Standard

In addition, we can find another difference if you read the paragraph on the Cisco SFP-10G-ZR module. It noted that the Cisco SFP-10G-ZR module “is a multirate 10GBASE-ZR, 10GBASE-ZW, and OTU2/OTU2e module.” However, the Cisco SFP-10G-ZR-S does not mention it. We can surmise that the S-class follows a more narrow standard. And SFP S-class is not compliant with the TAA (Trade Agreements Act). 

 

FCoE

Check the Cisco 10GBASE SFP+ or 40GBASE QSFP module datasheet, we will see the obvious difference between the S-class and non-S-class of the similar mode is the last sentence in the S-class module paragraph: “XXX-S does not support FCoE.” Cisco S-class can not support Fiber Channel over Ethernet (FCoE) applications.

 

 

Protocols

Also, it is noted that the FAQs from Cisco about presale product position have pointed out that S-class optics are single-rate Ethernet only, while non-S-class modules are multi-rate optics complying with Ethernet, OTN (Optical Transport Network), and WAN-PHY (Wide Area Network Physics) protocols.

 

Application

The application range of S-class modules is narrower than that of non-S-class modules, as evidenced by Cisco QSFP-40G-SR4-S (S-Class) and Cisco QSFP-40G-LR4-S (S-Class). Cisco has specifically defined that Cisco QSFP-40G-SR4-S (S-Class) does not support 4x10G breakout connectivity. One should apply QSFP-40G-SR4 or QSFP-40G-CSR4 for such applications.

 

 

Transmission Distance

The maximum transmission distance is 80km for the 10GBASE SFP S-class optics and 10km for 40GBASE QSFP+ S-class optics. However, more reach options are available for non-S class modules, such as QSFP-40G-ER4 for 40 Gigabit Ethernet up to 40km.

 

Operating Temperature

The operating temperature range of Cisco S-class optics is commercial only, from 0 to 70℃. However, non-S-class optics have more temperature grade options: commercial (0~70℃), extended (-5~85℃) and industrial (-40~85℃) are all available.

The table below lists the differences between S-class and non-S-class we gather from the Cisco official website datasheet or Cisco community for your reference.

 

 

Is S-Class SFP+ compatible with "normal" SFP+?

Cisco S-class optical modules have been released for almost 10 years and are becoming more and more popular in the market. However, many users have questions about interoperability: Are Cisco S-class optical modules compatible with conventional optical modules? Take SFP-10G-LR-S= and X2-10GB-LR= as examples, they are compatible as they have the same specifications.

 

 

Conclusion

Compared to the Cisco non-S-class optics, Cisco S-class optics are a more affordable alternative for the most common reaches in 10G and 40G Ethernet applications. S-class modules are not specified by TAA compliance and are applied in the Ethernet only, supporting no FCoE, OTN, WAN-PHY, or any additional environment. What’s more, Cisco S-class optics are limited in transmission distance, temperature grad, and special application scenarios. For example, you should go for non-S-class optics in the following scenarios: 

-Reach beyond 10km in 40G Ethernet

-4x10G breakout connectivity solution

-Use transceivers in extreme temperature tolerance

Last Word

For most SMBs, it is costly to shop whatever Cisco S-class optics or non-S-class transceiver modules. The market has seen many third-party transceiver suppliers selling compatible Cisco S-class modules and non-S-class modules at affordable prices. You can look for a trusted third-party vendor for a compatible connectivity solution. Mind that the S-class optics provided by third-party vendors are often identical to the non-S-class modules with the same specifications. The difference between S-class and non-S-class optics may be erased among third-party modules. For instance, Cisco QSFP-40G-LR-S and QSFP-40G-LR4 compatible modules provided by QSFPTEK are exactly the same at the same price.