Characteristics in Neodymium-Doped Fiber Amplifiers at 1.06 µm


IEICE TRANSACTIONS on Electronics   Vol.E79-C    No.6    pp.863-869
Publication Date: 1996/06/25
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Opto-Electronics
Nd-doped fiber amplifier,  1.06µm,  Nd-Al co-doped fibers,  Nd: YAGlaser,  

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We have investigated the gain and noise figure characteristics of a Nd-doped silica single-mode fiber amplifier (NDFA) at 1.06 µm which is applicable to various systems using a Nd: YAG laser light source at 1.06 µm, such as free-space laser communications, a fiber sensing system, and a lidar system. A fluorescence spectrum observation of the Nd-doped fibers with various co-dopants shows that the Nd-A1 co-doped fiber is suitable for realizing a high-gain amplifier for the 1.06-µm wavelength region. The pump wavelength tolerance at around 0.81 µm , the gain bandwidth and the sufficient value of the Nd concentration and length product for achieving maximum small signal gain are clarified. A noise figure of almost 3 dB and small signal gain of more than 30 dB are attained by 50-mW pump power. The unique four-level system characteristics, even in low pumppower conditions, provide low noise amplification in the NDFA. These gain and noise characteristics are well described by a simple theoretical model. We also demonstrated high-power operation of the NDFA with four pump LD modules adoptinga polarization-multiplexing technique. More than 100-mW signal output power is available for 1-mW signal input power at 200mW launched pump power. These features of the NDFA as a compact, polarization-independent, spatial-beam -distortion-free amplifier, will allow it to replace the solid sate laser in various applications using a Nd: YAG laser light source at 1.06µm.