# Analysis of Available Components and Performance Estimation of Optical Multi-Band Systems
## 2 Review of Commercially Available Components  
### Transceivers  
In this section, we decouple the types of transceivers into two categories based on their target applications. The first category incorporates transceivers for long-reach purposes, e.g., core networks, while the second one includes transceivers for short-reach applications, e.g., access and intra-data center applications. The details of the transceivers for the first category are tabulated in Table 1. To compose this table, we are based on both commercially available solutions and experimental components such as [10, 11]. The first observation is that a 200 G line rate can be attained by increasing the modulation format, from PM-QPSK to 16 QAM, simply doubling the number of bits per symbol. However, this comes with the cost of a higher value of required optical to signal plus interference ratio (OSNIR) in order to attain the same Bit Error Rate (BER), which will directly result in a smaller attainable reach. Secondly, the 400 G and 800 G line rates can be realized using a number of different options. Each alternative has its own trade-offs, e.g., lower modulation formats such as 16 QAM, require a lower OSNIR in order to attain the same BER as 64 QAM. This will lead to a higher reach for the lower cardinality modulation format; however, this reach is traded for a lower number of channels, as they consume a higher channel bandwidth. In this case, capacity is traded with connectivity, and the optimal solution is based solely on the high-level design set by the network operator. The OSNIR shown in the last column of Table 1 is calculated over the whole channel bandwidth while designating the target pre-Forward Error Correction (FEC) value. The existence of a FEC, e.g., [12], is considered, which can make a pre-FEC BER of \(10^{-3}\) shrink to a post-FEC BER of less than \(10^{-12}\). The exact resulting performance after the FEC depends on the employed algorithm and its complexity; in commercially available transceivers, a common option is soft-decision FEC. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Type**} & **Modulation** & **Symbol** & **Channel** & **Data** & **Required** \\  & **Format** & **Rate** & **Spacing** & **Rate** & **OSNIR** \\  & & & & & **(for BER = 10\({}^{-3}\))** \\ \hline
100 G & PM-QPSK & 32 Gbaud & 37.5 GHz & 100 Gb/s & 9.8 dB \\ \hline
200 G & PM-16 QAM & 32 Gbaud & 37.5 GHz & 200 Gb/s & 16.55 dB \\ \hline
400 G & PM-16 QAM & 63 Gbaud & 75 GHz & 400 Gb/s & 16.55 dB \\  & PM-64 QAM & 42 Gbaud & 50 GHz & 400 Gb/s & 22.5 dB \\  & PCS-16 QAM & 80–95 Gbaud & 100 GHz & 400 Gb/s & varies \\ \hline
800 G & PM-16 QAM & 128 Gbaud & 150 GHz & 800 Gb/s & 16.55 dB \\  & PM-32 QAM & 96 Gbaud & 112.5 GHz & 800 Gb/s & 19.5 dB \\  & PM-64 QAM & 80 Gbaud & 100 GHz & 800 Gb/s & 22.5 dB \\  & PCS-64 QAM & 90 Gbaud & 100 GHz & 800 Gb/s & N/A \\ \hline
200–800 G & Probabilistic Shaping & 60–95 Gbaud & 75–100 GHz & 200–800 Gb/s & varies \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Commercially available transceivers for regional and long-haul transmission. Next, we tabulate the details of indicative commercially available transceivers for short-reach applications (Table 2). These transceivers are part of the small form-factor pluggable (SFP) category of transceivers, which are mainly dedicated to access and/or shorter reach applications. SFP transceivers are hot-pluggable network interface modules which show some important features such as compactness, flexibility, cost-effectiveness, and high data rates. Based on their characteristics and application, they can be delineated in various categories such as simple SFP, SFP+, XFP, QSPF, and CFP. For example, XFP, where X stands for \"10\", and SFP+ are improved versions of simple SPF that can attain significantly higher data rates, e.g., 10 Gb/s compared with the 1 Gb/s rate of the simple SFP.