Variable 1.7 µM TO 2 µM amplifier and fiber laser based on ase suppressed TDFA

Abstract

Thulium-doped fiber amplifiers (TDFA) operating around 1.9 µm provide the broadest gain spectrum of all rare-earth doped optical amplifiers. The amplified spontaneous emission (ASE) suppression method is one of the possible ways to shift functional amplification range and change operating laser wavelength. Partial ASE suppression methods involve suppressing a portion of the unwanted ASE spectrum so that the gain of the requisite transmission window can improve accordingly. This chapter describes low pass filter and its application for 1.7 µm to 1.9 µm band thulium-doped fiber amplifier (TDFA) and thulium-doped fiber laser (TDFL) based on photonics crystal fiber (PCF) partial ASE suppression. The low-pass long cut-off wavelengths of the proposed PCF were achieved by enlarging the air holes surrounding the doped core region. We show that the optimized PCF geometrical structures resulted in long cut-off wavelengths of 1.85 µm and 1.75 µm to achieve the intended transmission characteristics. The experimental loss spectrum has been verified through numerical transmission characteristics using fullyvectorial finite element method (V-FEM). Finally, the proposed optical low-pass filter was applied in a TDFA system to partially suppress the ASE in the 1.9 µm region. We also show that the ASE peak and operating laser wavelengths could be shifted towards shorter wavelengths by rescaling the opto-geometrical parameters of the PCF fibers. © 2017 Nova Science Publishers, Inc.