This paper presents a study on the quality of interference fringes formed from a pulsed UV ( 255\text{\hspace{0.17em} nm} , 5.6\text{\hspace{0.17em} kHz} , and 40\text{\hspace{0.17em} ns} ) source for an application in writing fiber Bragg gratings (FBGs). The interference fringes of separation of about 8\mu \text{m} , formed by a biprism of apex angle 2°, were studied for their contrast, evolution of contrast, and positional and intensity stability over a period of 5\text{\hspace{0.17em} min} (over {10}^6 pulses). Second harmonic UV \left(255\text{\hspace{0.17em} nm}\right) sources of different spatial coherence and pointing stability characteristics were employed as the inputs. It is established that the UV fringes contrast and interference pattern stability with time is largely controlled by the optical resonator geometry of the fundamental wavelength \left(510\text{\hspace{0.17em} nm}\right) copper vapor laser (CVL) oscillator. In particular, the generalized diffraction filtered resonator (GDFR) CVL produced the highest quality second harmonic beam with the highest fringes contrast and stability. The implications of these results were studied by employing these UV sources for the fabrication of the C-band FBGs by a 24° apex angle biprism.