An optically pumped cesium frequency standard system is being developed. Laser diodes are used in the system as optical sources. An optical feedback technique utilizing a Fabry-Perot interferometer is used for frequency stabilization and reduction of spectral linewidth. Linewidth of the spectral-narrowed laser diodes was reduced to 1/200 times that of free-running condition. Characteristics of the laser diodes and the frequency standard system at CRL are described here.