# Analysis of Available Components and Performance Estimation of Optical Multi-Band Systems
## 2 Review of Commercially Available Components
### Band Filters  
Band filters are also key components for the realization of an OMB system as they can segregate and combine the optical bands at the node's ingress and egress, respectively, as well as at any amplification stage. Table 4 contains indicative band filters along with their key parameters. As it is evident, using a number of them e.g., in tandem, we can obtain a multi-band filter that can multiplex/demultiplex a number of bands. The most important parameters when selecting a band filter are (a) the wavelength range, as a cascade of different band filters may be required to split/combine the bands, (b) the insertion loss, as when a number of different filters are cascaded, the amplification gain should be higher to mitigate this loss, leading to a greater ASE noise, (c) the isolation, as an inadequate value can lead to an important channel crosstalk, degrading the physical layer performance, and (d) the return loss, which has to be as high as possible to avoid filter reflections. All in all, Table 4 reveals that a broad gamut of band filters is available, spanning from static to tunable and from filters with small spectral range of a few tens of nm to hundreds of nm.  
\begin{table}
\begin{tabular}{c c c c c} \hline \multirow{2}{*}{**Filter Type**} & \multirow{2}{*}{\begin{tabular}{c} **Output Wavelength Range** \\ **(Transmit)** \\ \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} **Output Wavelength Range** \\ **(Reflected)** \\ \end{tabular} } & \multirow{2}{*}{**Insertion Loss**} & \multirow{2}{*}{
\begin{tabular}{c} **Isolation** \\ **Transmission Port/** \\ **Reflection Port** \\ \end{tabular} } & \multirow{2}{*}{**Return Loss**} \\  & 1570–1610 nm & 1500–1564 nm & \(\leq\)0.5 dB (passband) & \(>\)30 dB/\(>\)12 dB & \(>\)50 dB \\  & (or 1500–1564 nm) & (or 1570–1610 nm) & \(<\)0.6 dB (reflect) & \(>\)30 dB/\(>\)15 dB & \(>\)50 dB \\  & 1460–1575 nm & 1610–1640 nm & \(<\)0.5 dB (reflect) & 30 dB/15 dB & \(>\)50 dB \\  & 1500–1563 nm & 1570–1640 nm & \(<\)0.7 dB (passband) & 30 dB/15 dB & \(>\)50 dB \\ Band Filter & 1410–1500 nm & 1510–1625 nm & \(<\)0.7 dB (passband) & 30 dB/15 dB & \(>\)50 dB \\  & 1310 nm \(\geq\) +50 nm & 1470–1610 nm & \(\leq\)0.70 dB (passband) & \(\geq\)45 dB/\(>\)15 dB & \(\geq\)45 dB \\  & 1310 nm \(\pm\) 2 nm & 1270–1355 nm, 1317–1355 nm & \(<\)0.80 dB (reflect) & \(\geq\)20 dB/\(\geq\)12 dB & \(\geq\)45 dB \\  & 1563–1568 nm & 1525–1561.5 nm, 1569.5–1620 nm & 0.5 dB (passband) & \(>\)30 dB/\(>\)20 dB & 50 dB \\ Passband & 1500–1520 nm & 1530–1610 nm & 0.4 dB (reflect) & 15 dB/40 dB & 50 dB \\  & 1280–1340 nm & 1350–1620 nm & \(<\)1.1 dB & \(>\)50 dB/\(>\)20 dB & 50 dB \\ \hline Tunable & varies from 1260 to 1650 nm & varies from 1260 to 1650 nm & 4.5 dB & 60 dB & N/A \\ \hline High-Isolation & & & & \(>\)18 dB \\ Filter & 1510–1590 nm & 1270–1350 nm & \(\leq\)0.6 dB (reflect) & \(\geq\)40 dB/\(\geq\)40 dB & \(\geq\)45 dB \\ \hline Pluggable Filter & & & & & \(>\)18 dB \\  & 1460–1581 nm & 1610–1660 nm & \(<\)1.2 dB & N/A & (1260–1360 nm)/ \\  & 1460–1581 nm & & & \(>\)17 dB \\  & & & & \(>\)17 dB \\  & & & & (1460–1581 nm) \\ \hline Reflector & 1260–1570 nm & 1610–1680 nm & \(<\)0.60 dB & \(>\)15 dB/\(>\)40 dB & \(>\)45 dB \\ \hline \end{tabular}
\end{table}
Table 4: Commercially available filters for OMB transmission.