AbstractIn response to the problems of communication capacity and spectrum resource constraints, radio over fiber (ROF) technology has gained widespread adoption, and the quality and performance of the optical transmitter module also directly affect the transmission of the link. This paper presents the design of a direct modulation optical transmitter module in the frequency band ranging from 2.6 kHz to 206.8 MHz using OPA690 broadband voltage feedback op‐amp. The module features a tunable bias voltage range from 0 to 5 V to accommodate different threshold voltages for modulation power supply. It offers a gain of 12 dB and a signal‐to‐noise ratio exceeding 50 dB while demonstrating excellent stability, high signal purity, good spectral response characteristics, and compact size advantages. Based on this design, we further optimized the system circuit by adding a fourth‐order Butterworth filter structure, reducing the lower cut‐off frequency to about 500 Hz, increasing the gain by 6 dB, reducing the return loss to −26.91 dB, and the module's signal‐to‐noise ratio exceeding 90 dB. This optimization scheme improves the stability and signal purity of the optical transmitter module and improves the spectral response characteristics. In this paper, Multisim is used to analyze and verify the proposed optical transmitter circuit. In addition, a complete link experiment was carried out using an optical receiving module designed in the same laboratory to verify the feasibility of our proposed module.