The stimulated Raman adiabatic passage (STIRAP) is an important technique in controlling the atomic states and it has been widely used in atom manipulation and quantum information. Obtaining Raman laser is the first step to demonstrate the STIRAP for atoms. A system is presented for generating Raman laser for STIRAP process for Cs atom based on waveguide fiber modulation with high frequency and two pieces of interference filter. Two sidebands with frequency difference of exact 9.19 GHz are separated from the carrier and each of them can be controlled independently. The distinction ratio between the sidebands and the carrier is 21 dB. The power of each sideband is about 120 μW and the fluctuation is less than 2% in ten minutes. This system could be used in atomic state preparation and coherent control of the atomic states.