The Ando AQ6315E optical spectrum analyzer (OSA) is an improved version of the well known Ando AQ6315A. This OSA can do spectrally resolved intensity measurements in the range of 350 to 1750 nm with a wavelength accuracy better than 0.05 nm and supports single-pass/double-pass monochromator mode select. In the single-pass monochromator mode, it supports the same wide range of applications as previous models. In the double-pass monochromator mode, the dynamic range is improved to -90dBm. The system is sensitive enough to measure light intensities as low as a few picowatts, and in a single measurement can cover a dynamic range of seven orders of magnitude, allowing for the simultaneous viewing of low intensity and high intensity signals such as spontaneous emission and laser emission from a laser cavity. It has several integrated measurement modes, from simple optical absorption measurements to full optical amplifier parameter analysis. This unit supports diverse analysis functions for DWDM and other optical devices (LD, LED, FBG, etc).