In view of the application requirements of broadband optical communication system for dense wavelength division light source, the shortcomings of single wavelength laser in dense wavelength division system are pointed out, and the principle and generation method of optical frequency comb light source are introduced. This paper presents a method of generating optical frequency comb based on phase modulation, and tests the generated optical frequency comb in broadband optical communication system, and verifies the application effect of optical frequency comb as multi-wavelength light source in broadband optical communication system.