Abstract: This invention is directed to a spectrum analyzer system which is laser-driven and which includes a standard Bragg cell and a standard photo-diode array as the output detector. In this system, the Bragg cell is driven by a bandwidth expansion circuit which receives the typical R.F. input signal, supplies it to a variable center frequency filter or to a bank of filters which then down-converts the signal and supplies the signal to a real time signal storage memory at a first signal rate. The signals are retrieved from the memory at a second, much greater signal rate, up-converted and supplied to the Bragg cell to affect the operation thereof in the usual fashion. This time base compression circuit has the effect of producing an improved optical spectrum analyzer with expanded frequency resolution.