# The Multiband over Spatial Division Multiplexing Sliceable Transceiver for Future Optical Networks
## 6 Experimental Assessment
### Complexity/Cost Analysis of the Proposed MB(oSDM) S-Bvt  
In this paper, we have proposed to implement a MB(oSDM) S-BVT based on IM and DD to target cost efficiency when comparing with alternative implementations based on coherent detection taking advantage of cost-effective optoelectronic subsystems and simplified DSP. According to [46], the adoption of DD technology, at the receiver side, instead of coherent detection reduces the S-BVT cost of about 25-35%. Additionally, a comparison of the cost of 2 \(\times\) 50 Gb/s S-BVT based on DD and coherent solution at 100 Gb/s (4 \(\times\) 25 Gb/s) is provided in [46], showing intrinsic cost savings when adopting a DD implementation. However, the proposed MB(oSDM) S-BVT, of Figure 1, has additional elements to consider in terms of cost analysis due to the exploitation of MB technology. Figure 10: (**a**) SNR profile of the S-, C-, and L-band contributions and (**b**) achieved data rate per band after 19\(-\)cores MCF of 25.4 km. Hence, here we provide a cost analysis of the proposed transceiver solution based on external modulation and simple DD photodetection. For the cost analysis, we consider that the optical aggregator/distributor element of the MB(oSDM) S-BVT comprises WSSes shared among all the BVTs working in a specific band and BPFs to implement MB technology. Table 2, shows the number of components required to implement the proposed transceiver based on DD considering 3 transmission slices at different bands (S+C+L) at 50 Gb/s. Thus, the unitary cost of a building block in the C-band of the proposed MB(oSDM) S-BVT based on DD is:  
\[C_{BVT_{\mathrm{xC}}}=C_{LS_{\mathrm{C}}}+C_{MZM}+C_{driver}+\frac{C_{DAC}}{M} +\frac{C_{WSS_{\mathrm{xC}}}}{N}+\frac{C_{BPF}}{B} \tag{5}\]  
\[C_{BVR_{\mathrm{xC}}}=C_{PD}+\frac{C_{ADC}}{M}+\frac{C_{WSS_{\mathrm{xC}}}}{N} +\frac{C_{BPF}}{B} \tag{6}\]  
Figure 11: Power profile of the data filled in the neighbouring cores of the MCF to evaluate the XT. BS–broadband source; EDFA–erbium-doped fibre amplifier. Figure 12: Maximum achieved data rate for the C-band contribution, considering in-band XT. \(M\) and \(N\) are the number of DAC/ADC and WSS ports, respectively, and \(B\) the number of BPF outputs, corresponding to the number of bands. We have considered that the WSS working in a particular band at the transmitter and receiver are the same. The unitary cost for the L-band and S-band building blocks will depend on the same individual parts/elements which include the LS, MZM, driver, DAC, WSS, PD, ADC, and BPF. However, the cost of specific components such as LS and WSS working in S- and L-bands are higher than the ones in the C-band due to the availability and maturity of the technology in the specified bands. As an example, the cost of the S-band LS (EML) used in the experiments is almost 5 times higher than the cost of the C-band LS (TLS), which both are from the same provider/manufacturer. Additionally considering similar WSS modules from the same provider, the cost of the WSS in the L-band can be increased by a factor of 1.3 when comparing with the C-band one. Hence, we consider \(\alpha,\beta,\gamma\), and \(\epsilon\) scaling factors \(>1\) to define the relationship in terms of cost of the LS and WSS in the S- and L-band with the corresponding C-band elements, respectively. Taking into account all this, the total cost for the 150 Gb/s MB(oSDM) S-BVT (\(3\times 50\) Gb/s) can be defined as:  
\[ \begin{split} C_{S-BVT}&=(1+\alpha+\beta)\times C _{LS_{C}}+3\times C_{MZM}+3\times C_{driver}++3\times\frac{CDAC}{M}+\\ &+3\times\frac{CADC}{M}+2\times(1+\gamma+\epsilon)\times\frac{CWSS _{C}}{N}+3\times C_{PD}+6\times\frac{CBPF}{B}\end{split}  \tag{7}\]  
According to Equations (5) and (6) and reference [46], the cost of the MB(oSDM) S-BVT, when only enabling the C-band, will slightly increase compared to a S-BVT that can not enable MB technology.