Grant numbers : This work was funded in part by the project DESTELLO (TEC201569256R).© 2017 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.

In-band OSNR measurement for CO-OFDM systems using high-resolution spectral analysis is experimentally demonstrated. It is shown that signal and noise levels can be monitored by direct optical spectrum analysis, avoiding the need for data demodulation.