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In this paper, we describe low-noise Er-doped optical fiber amplifiers (EDFAs) achieved byexploring novel long period fibre gratings (LPFGs) written by high-frequency CO2 laser pulses. This new LPFG fabrication technique is based on the thermal shock effect of high-frequency CO2 laser pulses at several kHz. By inserting such a LPFG in the Er-doped fibre, the ASE (Amplified Spontaneous Emission) noise of the EDFA has been reduced considerably. Two low-noise EDFAshave been constructed and demonstrated. The ASE noise of the two EDFAs used as a pre-amplifier and an in-line amplifier has been successfully reduced from 4.0dB to 3.5dB and from 4.8dB to4.3dB with a small-signal gain increase of7dB for the in-line amplifier, respectively. Keywords: Er-doped optical fiber amplifiers (EDFAs), ASE noise filters, In-fiber gratings. 1. INTRODUCTION Er-doped optical fibre amplifiers (EDFAs) with a low noise figure are critical for realizing high-performance optical fibre communication systems, especially for pre- and in-line amplifiers. |
