# Integrated Components and Solutions for High-Speed Short-Reach Data Transmission
## 2 Transmitter for Short-Reach Transmission Systems
### LiNbO\({}_{3}\) Mach-Zelntder Modulator  
In the early development of direct modulation components, bandwidth limitation may be the main obstacle to realize high-speed transmission rate. The external modulation component, LiNbO\({}_{3}\) MZM modulator, has been extensively reported in 100-Gbit/s and beyond 100-Gbit/s short-reach transmission systems [56; 57; 58; 59; 60]. [PERSON] et al. applied artificial neural networks as signal equalization technology to realize 120-Gbit/s PAM-8 10-km transmission [56]. [PERSON] et al. achieved beyond 100-Gbit/s single-sideband (SSB) DMT transmission over 80-km SMF assisted by dual-drive (DD) MZM [57]. [PERSON] et al. demonstrated 168-Gbit/s PAM-4 generation and C-band 1-km transmission [58]. Moreover, based on Tomlinson-Harashima precoding, [PERSON] et al. reported 168-Gbit/s PAM-4 transmission over 2-km SMF with 33-GHz brick-wall bandwidth limitation [59]. To extend transmission distance, [PERSON] et al. used a DDMZM to generate chromatic dispersion (CD) pre-compensated signal and achieve 128-Gbit/s 80-km transmission [60]. Recently, various beyond 200-Gbit/s transmission schemes have been demonstrated as listed later [61; 62; 63; 64; 65; 66; 67]. [PERSON] et al. proposed a simple nonlinear trellis-ceed-modulation scheme to realize spectral shaping for a 255-Gbit/s PAM-8 transmissions system over 10-km SMF under 20-GHz component bandwidth limitation without any optical amplifier [61]. [PERSON] et al. presented 200-Gbit/s PAM4 40-km dispersion management transmission with 14-GHz analog to digital converter (ADC) bandwidth [62]. Furthermore, probability shaping modulation format was also introduced to achieve better transmission performance. [PERSON] et al. reported single-lane 280-Gbit/s PS-PAM-8 transmission over 10-km SMF link based on pre-equalization and clipping technique [67]. The recent applications of MZM under beyond 100-Gbit/s per lane have been summarized as shown in Table 3. As mentioned above, LiNbO\({}_{3}\) MZM modulator with a large modulation bandwidth and no frequency chirp effect had been widely applied in various beyond 100-Gbit/s short  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline
**Tx** & **\(\mathbf{\lambda}\)** & **MF** & **BW** & **Rate** & **Reach** & **Fiber** & **FEC** & **Ref.** \\
**Device** & **(nm)** & & **(GHz)** & **(Gbit/s)** & **(km)** & **Type** & **Limit** & **Ref.** \\ \hline DML & 1310 & PAM-4 & 28 & 112 & 40 & SMF & \(3.8\times 10^{-3}\) & [8] \\ DML & C-band & PAM-4 & 16 & 100 & 15 & SMF & \(3.8\times 10^{-3}\) & [9] \\ DML & 1300 & PAM-4 & 55 & 112 & 2.2 & SMF & \(2\times 10^{-4}\) & [46] \\ DML & 1310 & DMT & 18 & 117 & 40 & SMF & \(1\times 10^{-3}\) & [49] \\ DML & 1308.45 & PAM-4 & 25 & 112 & 20 & SMF & \(4.6\times 10^{-3}\) & [50] \\ DML & 1286 & PAM-4 & \(>\)100 & 256 & 2 & SMF & \(3.8\times 10^{-3}\) & [47] \\ DML & 1295.48 & DMT & 104.5 & 321.24 & 2 & SMF & \(3.8\times 10^{-3}\) & [51] \\ DML & 1315 & PAM-8 & 54 & 240 & 10 & SMF & \(1.8\times 10^{-2}\) & [52] \\ DML & 1313 & DMT & 65 & 368.8 & 15 & SMF & \(1.8\times 10^{-2}\) & [53] \\ \hline \end{tabular}
\end{table}
Table 2: Incomplete summary of DML applied in beyond 100-Gbit/s per lane data transmission.  
Figure 2: (a) S\({}_{21}\) amplitude responses for a bias range from 10–36.2 mA at 25\({}^{\circ}\)C; (b) S\({}_{21}\) amplitude and frequency responses at 36.2 mA gain bias at 25\({}^{\circ}\)C; FM: Frequency modulation; AM: Amplitude modulation; (From [46], © 2017 IEEE).  
reach transmission systems, but the component cost and power consumption were still considered as the limiting factors. In recent years, combining the advantages of LiNbO3 MZM modulator, some groups are exploring various integrated MZM solutions to reduce footprint size, power consumption, and cost to meet the demands of low-cost and power-efficient short-reach transmission systems under tens of kilometers transmission distance.