We report an optical parametric oscillator (OPO) system operating at 1574 nm using KTP crystals, with output peak power of more than 5 megawatts, output pulse energy of up to 30 mJ per pulse, and pulse width of less than 6 nanoseconds at full width half maximum (FWHM). The OPO was pumped by a diode pumped Nd:YAG Q-switched laser, with pump energy of about 95 mJ and pulse width of approximately 7 ns. The conversion efficiency from 1064 nm Nd:YAG laser to OPO output at 1574 nm is more than 30%. The complete Nd:YAG / OPO system, compactly packed inside a case with foot print measuring 15 '' x 9 '' x 5.3 '', was tested over an operating temperature range of -20 degrees C to +35 degrees C and a storage temperature range of -40 degrees C to +50 degrees C without significant power or performance variations.