The FPI-100-0400-1 from TOPTICA Photonics is a Fabry-Perot Interferometer that operates from 380 to 430 nm. It has a free spectral range (FSR) of 1 GHz and a frequency resolution of 2.5 GHz. This confocal, scanning interferometer has an aperture of 7 mm, a typical finesse over 400, and a standard mirror with 99.8% reflectivity. It has a built-in photodetector unit and is designed for measuring and controlling the mode profiles of continuous wave (CW) lasers. This interferometer has an FC/APC fiber connector and is ideal for Telecommunication and Spectral Analysis Applications.