e with the signal quality, while InP modulators are used in compact interfaces, like transceivers, where direct laser modulation is not possible. In Table 5.6 the main characteristics of a few practical Mach-Zehnder modulators are summarized. TABLE 5.6 Characteristics of Practical InP and LiNbO3 Mach-Zehnder Modulators Electro-Optic Material LiNbO3 LiNbO Bit rate 10 Gbit/s 40 Gbit/s 10 Gbit/s Operating case temperature 0°C C-70°C 0°C -70°C 0°C -70°C Operating wavelength 1525-1605nm 1530-1600nm 1520-1600nm Optical insertion loss (connectorized) 5.0 dB 4.5 dB Insertion loss variation (EOL) -0.5 to 0.5 dB -0.5 to 0.5 Modulator chirp parameter -0.1 to 0.1 Selectable -0.2 to 0.2 Optical return loss 40 dB 35 dB 20 dB Optical on/off extinction ratio (at DC) 20 dB 10 dB E/O bandwidth (-3dB with linear fit) 12.0 GHz 42 GHz 10 GHz Vpi RF port (at 1 GHz) 5.1 V DC bias voltage range (EOL) -8 to 8 V Footprint (w/ electrical connections, 95 X 20 mm 99 X 14.5 mm 26x12mm w/o pigtail) EOL, end of life value. Technology for Telecommunications: Integrated Optics and Microelectronics 5.5.2 Electro-Absorption Modulators EA modulators are based on the change of the absorption coefficient when an electrical field is applied. This effect is known as quantum-confined Stark effect when happening in quantum well structures, and almost all the practical EA modulators are realized using quantum well structures [31]. The physical description of the effect is quite complex [39], but the final result is that the absorption coefficient, and in particular the absorption edge, that is, the wavelength at which the material lowers abruptly its absorption coefficient and behaves like a transpar- ent material, depends on the applied optical field. Since the transition between strong absorption and good transparency is quite abrupt and the Stark effect is very fast, this dependence can be used to design a modu- lator [40]. This effect is shown in Figure 5.28, where the attenuation of a packaged EA modulator is shown at different wavelengths in the fibe