This paper proposed an approach to design an evenly spaced, 1.8 THz spectrally broad and 1.6 dB flat optical frequency comb (OFC) by exploiting the cross-phase modulation in highly nonlinear fiber. The OFC is realized by controlling the phase of the signals in two parallelly placed highly nonlinear fibers. The frequency and line spacing of the OFC can be tuned by simply varying the periodicity and central wavelength of input electrical and optical signal, respectively.