In order to meet the requirements of low phase noise and high stability multi-carrier light source for terahertz communication over fiber, a high flat tunable optical frequency comb (OFC) signal generation scheme based on an electro-absorption modulator (EAM), an intensity modulator (IM), and an EAM cascade is presented. In the scheme, based on the primary EAM, the optical frequency comb signal is generated, the number of combs is further increased by IM, and the flatness is optimized by adjusting the drive voltage of the second EAM. The simulation results show that this scheme can generate a 21 line optical frequency comb signal with a maximum bandwidth of 800 GHz, with a flatness of 0.52 dB. Subsequently, the impact of the operating parameters of key components in the scheme on their performance is analyzed. To further verify the communication performance of generating optical frequency comb signals, the performance of single or multi-channel transmission of 256-ary quadrature orthogonal amplitude modulation (256QAM) signals is analyzed through simulation under three conditions of back to back (BTB),10 km fiber, and 15 m wireless. The results indicate that the bit error rate (BER) in each of the above cases is lower than the forward error correction coding decision threshold of 3.8×10^-3.