## 2 Beyond 100 Gb/S Era
### Ethernet Standards and Optical Transceiver Applications
#### 2.3.1 Optical Transceivers and the Related Ethernet Standards  
Some classifications regarding the link reach, transceiver form factor, interface connector type, fiber type, and speed have to be taken into consideration when choosing the most suitable transceiver. For short-range (SR) applications (\(\sim\)500 m), interfaces such as SFP+, SFP28, QSFP+, QSFP28, and QSFP-DD are the most widely used. Similarly, CFP, CXP, and CPAK are preferred interfaces for long-range (LR) and high-speed applications [66; 67]. Depending on the application, both single-mode fiber (SMF) and multimode fiber (MMF) can be used for data transmission using the aforementioned transceivers. For instance, they can be used for certain SR 40 G and 100 G applications. However, SMF with Dense-WDM is normally employed in the LR transmission. This results in higher data rates and longerranges (\(\sim\)40 km). It should be noted that 400 G deployment in the hyperscale data centers will be largely supported by quad small form factor pluggable-double-density (QSFP-DD) transceivers. Table 1 summarizes key parameters for the different transceivers with a range of specifications for various applications [66]. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Speed** & **Nomenclature** & **Standard** & **Medium** & **Form Factor** & **Interface** & **Reach** \\ \hline \multirow{8}{*}{ \begin{tabular}{} \end{tabular}  } & \multirow{8}{*}{10 GBASE-SR} & \multirow{8}{*}{10 GBASE-LR} & \multirow{8}{*}{ \begin{tabular}{} \end{tabular}  } & SPP+ \({}^{a}\) & \multirow{8}{*}{LC Duplex \({}^{a}\)} & OMI—33 m \\  & & & (@8850 nm) & X2 & SC Duplex & OMI—28 m \\  & & & XPAK & & OMI—300 m \({}^{a}\) \\  & & & XFP & & OMI—400 m \({}^{a}\) \\ \cline{2-6}  & \multirow{8}{*}{10 GBASE-LR} & \multirow{8}{*}{10 GBASE-LR} & \multirow{8}{*}{802.3 ae-2002 (CL49/S2)} & Single-mode Fiber & SPP+ \({}^{a}\) & \multirow{8}{*}{SC Duplex \({}^{a}\)} \\  & & & (@1310 nm) & X2 & SC Duplex & \\  & & & XPAK & & & \\  & & & XFP & & & \\ \cline{2-6}  & \multirow{8}{*}{10 GBASE-ER} & \multirow{8}{*}{ \begin{tabular}{} \end{tabular}  } & Single-mode Fiber & SPP+ \({}^{a}\) & \multirow{8}{*}{SC Duplex \({}^{a}\)} \\  & & & (@1550 nm) & X2 & SC Duplex & \\  & & & XFP & & & \\ \hline \multirow{8}{*}{ \begin{tabular}{} \end{tabular}  } & \multirow{8}{*}{25 GBASE-SR} & \multirow{8}{*}{802.3 by-2016 (CL112)} & Multi-mode Fiber & \multirow{8}{*}{SFP28 \({}^{a}\)} & \multirow{8}{*}{LC Duplex \({}^{a}\)} \\  & & & (@850 nm) & & & OMI—70 m \({}^{a}\) \\ \cline{2-6}  & \multirow{8}{*}{25 GBASE-LR} & \multirow{8}{*}{802.3 cc-2017 (CL114)} & Single-mode Fiber & \multirow{8}{*}{SFP28 \({}^{a}\)} & \multirow{8}{*}{LC Duplex \({}^{a}\)} \\  & & & (@1310 nm) & & & \\ \cline{2-6}  & \multirow{8}{*}{25 GBASE-ER} & \multirow{8}{*}{802.3 cc-2017 (CL114)} & Single-mode Fiber & \multirow{8}{*}{SFP28 \({}^{a}\)} & \multirow{8}{*}{LC Duplex \({}^{a}\)} \\  & & & (@1550 nm) & & & \\ \hline \multirow{8}{*}{ \begin{tabular}{} \end{tabular}  } & \multirow{8}{*}{40 GBASE-SR4} & \multirow{8}{*}{802.3 ba-2010 (CL82/86)} & Multimode Fiber & \multirow{8}{*}{CFP+} & MPO \({}^{a}\) & OMI—100 m \({}^{a}\) \\  & & & (@850 nm) & QSFP+ & OMI—150 m \({}^{a}\) \\ \cline{2-6}  & \multirow{8}{*}{40 GBASE-LR4} & \multirow{8}{*}{802.3 ba-2010 (CL82/87)} & Single-mode Fiber & \multirow{8}{*}{CFP+} & \multirow{8}{*}{LC Duplex \({}^{a}\)} \\  & & & (WDM) & & & \\ \cline{2-6}  & \multirow{8}{*}{40 GBASE-ER4} & \multirow{8}{*}{802.3 bm-2015 (CL82/87)} & Single-mode Fiber & \multirow{8}{*}{QSFP+} & \multirow{8}{*}{LC Duplex \({}^{a}\)} \\  & & & (WDM) & & & \\ \hline \multirow{8}{*}{ \begin{tabular}{} \end{tabular}  } & \multirow{8}{*}{100} & \multirow{8}{*}{802.3 ba-2010 (CL82/86)} & Multimode Fiber & \multirow{8}{*}{CFP} & MPO (\(2\times 12\)) \({}^{a}\) & OMI—100 m \({}^{a}\) \\  & & & (@850 nm) & & & OMI—150 m \({}^{a}\) \\ \cline{2-6}  & \multirow{8}{*}{100 GBASE-SR10} & \multirow{8}{*}{ \begin{tabular}{} \end{tabular}