Linewidth characteristics of a filterless tunable erbium doped fiber ring laser

Abstract

The linewidth characteristics of a continuous wave erbium doped fiber ring laser whose tunability is controlled by intracavity loss are studied in this work. The spectral linewidth of such a filterless laser is measured experimentally, and its characteristics are analyzed using the existing analytical model of fiber laser. The long length of the cavity results in lasing into multiple longitudinal modes, thus leading to a broad linewidth. The extent of this broadening is found to depend on the intracavity attenuation and pump powers. Under the given experimental conditions, for a fiber of length 12m, the linewidth increases up to 4.5nm corresponding to an additional cavity loss of 5dB, while it increases up to 8nm for a loss of 1.2dB for a fiber of length 4.6m. The linewidth decreases with further increase in intracavity loss for both cases. In this work, the linewidth dependence on the intracavity loss is directly linked to the spectral dependence of the threshold power for each length. The linewidth increases with pump power irrespective of the intracavity attenuation, and this is explained through the nature of the amplified spontaneous emission from the fiber at different pump powers. The experimental results and the subsequent analysis are useful for the design of a filterless tunable laser with a narrow linewidth using erbium doped fiber in the ring configuration.

Multi-Wavelength Fiber Lasers

“…A systematically effort to study these causes has been carried out. Based on previous experience these studies have been focused on optimization of some the following parameters: pump power [19], doped fiber length and ions concentration [26], output coupling ratio [7], total cavity length [26], spectral hole-burning effect [27] or the cavity losses [28]. However, polarization control seems not very important for the multimode regime [7].…”

All-fiber tunable ring laser source near 2 μm designed for CO2 sensing

“…The linewidth characteristics of the Tm-doped fiber ring laser output has been explained by studying the wavelength dependence of the threshold pump power, considering that the wavelength for which the threshold pump power is the minimum, is subsequently observed as the lasing wavelength at the output [25]. This threshold power variation with wavelength for different losses of 0-5 dB in steps of 1 dB has been shown in Fig.…”

Spectral characteristics of continuous wave broadband from a fiber laser with a low dispersion fiber in the cavity

“…27 This natural linewidth of the laser is one of the primary factors that influence the extent of spectral broadening when a DSF is introduced into the fiber ring cavity. In order to quantify the extent of broadening due to the nonlinear effects, the spectral width is measured with different lengths of DSF introduced into the cavity.…”