The Advantest Q8341 is an optical spectrum analyzer for visible radiation with a wavelength range of 350 nm to 1000 nm. Because it uses a Fourier spectrum system with a Michelson interferometer, the Q8341 can measure coherence. With its narrow wavelength resolution of 0.01 nm*, the Q8341 is very effective for the evaluation of not only CD/DVD laser diodes, but also for blue-violet laser diodes. In addition, the built-in He-Ne laser acts as a wavelength reference to ensure a high wavelength measurement accuracy of 0.01nm*. Finally, with its fast 0.5 s* measurement speed, the Q8341 is ideal for evaluating temperature characteristics of system components.