Abstract

Various approaches have recently been reported on the use of gain modulation of Erbium doped fiber amplifiers (EDFA) to add low frequency status or telemetry information to a signal as it is being amplified by an EDFA [1,2]. A simple theoretical description and experimental verification of all combinations of low frequency signal transfer from modulated pump or modulated signal has also been given [3]. Specifically, for the purposes of this work, we use pump to signal and signal to pump modulation transfer which is a single pole low pass process, with a 3 dB frequency of several hundred Hz that depends of pump and signal parameters. In the work reported here we employ a subcarrier at 30 kHz which is frequency modulated by single tones in the audio band from 300-5000 Hz to then intensity modulate the power of a 980 nm pump laser. Even though the FM carrier frequency is ~ two orders of magnitude higher than the 3 dB frequency of the pump to signal modulation transfer function excellent signal to noise ratio performance is achieved in an in-line amplifier configuration at total transmission distances to 100 km, indicating that this technique is highly suited for use by crafts personnel wishing to communicate from an amplifier site.

© 1994 Optical Society of America