Nonlinearity of traveling-wave electroabsorption modulator according to microwave characteristics

In this paper, we introduce a model to analyze the linearity of multiple-quantum-well (MQW) traveling-wave electroabsorption modulator (TW-EAM). The device length, microwave loss (ML), velocity mismatch (VM) between lightwaves and the microwaves, and internal reflection (IR) due to impedance mismatch have effect on the linearity of a TW-EAM. ML has little effect on the intermodulation distortions (IMDs). VM also has little influence on IMD3 (third-order IMD), but severely affect IMD2 (second-order IMD), which become as high as 30 dB for the input frequency of 100 GHz, the device length of 0.8 mm, and VM of 20%. IR has different nonlinear characteristics according to the wavelength of the input frequency and the device length. As a result, it is known that IMDs improve when the device length equal to a quarter of the wavelength of the input signal and that the device length of 0.4 mm is appropriate for the analog fiber-optic communication with the frequency range of 50 GHz.