# _electronics_
## 3 Communication Potentials  
In this section, we study on-chip communication using the proposed hybrid topological waveguides. An electric-based terahertz wired channel link is modeled here for budget analyses [36]. A schematic diagram of the link as well as corresponding calculations and parameters are presented in Figure 5. At the transmitter end, terahertz carriers can be generated using a voltage-controlled oscillator followed by on-off keying modulation. The  
Figure 4: Losses as a function of frequency for (**a**) forward and (**b**) backward modes, and GVDs as a function of frequency for (**c**) forward and (**d**) backward modes for different \(h\) values.  
modulated signals are amplified and then launched into the waveguide using an antenna and a horn coupler. Our group recently demonstrated a homemade 3D-printed coupler [37], which can be customized to improve the coupling efficiency. After transmission over the waveguide, another pair of coupler and antenna receives the terahertz radiation. Next, the signals go through a low-noise amplifier for incoherent detection (a peak envelope detector is applied). Finally, the demodulated data is amplified again by a baseband amplifier for signal processing. Using the link budget model, the performance of the baseband signals, including received power (_Pr_), signal to interference plus noise ratio (_SINR_), and bit error rate (_BER_), can be evaluated as performed in the left bottom panel of Figure 5. For this on-chip communication link, we assume the generated time-domain terahertz wave has a pulse width of 25 ps, input power of 0 dBm, OOK bit rate of 10 Gbps, and other parameters, for example, the gain and noise factor of amplifiers are shown in the right bottom panel of Figure 5. In the following discussions, we calculate the _Pr_, _SINR_, and _BER_ for waveguide lengths (_L_) from 50 mm to 100 mm at four specific carrier frequencies where the forward and backward modes have either the minimum loss or zero GVD (indicated in Figure 4d).  
From the results shown in Figure 6, both waveguide loss and GVD contribute to the communication performances. In Figure 6a, all received power _Pr_ values reduce for a longer waveguide because of not only the transmission loss but also the GVD. Considering a Gaussian pulse propagating over a dispersive channel, the GVD leads to pulse broadening while the integral power of the pulse should be constant; thus, the signal power would spread into the interference. From Figure 6b,c, poor performances at a frequency of forward mode with the minimum loss can be significantly observed due to a high GVD magnitude of the mode (603 ps/THz/mm). At other carrier frequencies, the proposed waveguide could support high-SINR, low-BER (below \(10^{-3}\), which is generally considered to be the forward  
Figure 5: Top panel: schematic of terahertz waveguide communication link; left bottom panel: calculations of signal power (\(S\)), interference (\(I\)), noise (\(N\)), _Pr_, _SINR_, and _BER_; right bottom panel: parameters used in link budget analyses.  
error correction (FEC) limit) 10-Gbps on-chip communications over 50-100 mm channel lengths. Comparing the frequencies for the minimum loss and zero GVD, we conclude that for such short links (no longer than 100 mm), the communication performance of the proposed waveguide is largely GVD-dominated. Therefore, it is suggested that frequencies corresponding to near-zero GVDs can be promising carrier candidates in the context of inter/intrachip connection applications. The data rate remains a large scope of enhancement using high-order modulation techniques, such as 16-QAM. Furthermore, the proposed topological chip could support low-crosstalk, full-duplex communications between two nodes thanks to the dual unidirectional topological propagations.