The TLD1827 Optical Fiber Identifier is a instrument designed to detect optical signals without disrupting traffic. During maintenance, installations, rerouting or restorations, by inserting the fiber into its adapter head, it can identify SM optical fibers without any damage by detecting the optical signals being transmitted through them so as to avoid the opening of the fiber at the splice point for identification, and thus avoids the interruption of the service .In the presence of traffic, the intermittently audible tone is activated. The TLD1827 optical fiber identifier also allows relative core power display and identification of the 270Hz,1kHz and 2kHz frequencies.