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

Abstract

The spectral width of the continuous wave broadband generated in an erbium doped fiber ring laser containing a dispersion shifted fiber (DSF) in a filterless cavity is found to be governed by the nature of the gain spectrum of the doped fiber, in addition to the nonlinear effects. This dependence is studied experimentally with different lengths of the doped fiber and the DSF. Spectral broadening is demonstrated in the conventional (C) and long wavelength (L) bands using pump powers less than 200 mW, with an appropriate choice of cavity parameters. The generated broadband is demultiplexed in the C-band to prove its utility in optical communication systems.

Excited-state absorption in erbium-doped silica fiber with simultaneous excitation at 977 and 1531 nm

“…1͒, its brightness is drastically increased upon the assistance of signal wave radiation at wavelength s = 1531 nm. Figure 4 shows the dependence of green UCE signal 4. ͑Color online͒ Dependence of UCE power on signal power.…”

“…11,17,18 So, the results discussed below are almost free from the pairs' effect, so the nonlinearity occurring in the EDF transmission coefficient and UCE stem both solely from ESA. The first experiment was focused on the demonstration of the presence of ESA in the EDF, when it is pumped simultaneously at p = 977 nm ͑through 4 Experimentally, an EDF piece was pumped, using a wavelength division multiplexer ͑WDM͒ supporting up to 1 W of optical power, by the pump and signal beams from the same fiber side. These beams were delivered, correspondingly, from a standard fibered semiconductor laser ͑ p = 977 nm͒ and another semiconductor laser with wavelength s = 1531 nm, followed by an EDFA.…”

“…4 I 15/2 → 4 I 11/2 and "1 " → "2" : 4 I 15/2 → 4 I 13/2 ͒ results in a partial but noticeable ͑comparing to the case of excitation at only p ͒ populating of state "3" ͑ 4 I 11/2 ͒, which allows, thereafter, the populating of short-living state 4 F 7/2 through ESA transition "3 " → "5" : 4 …”

“…Our results demonstrate that ESA at p may play a notable role as a strong pump loss factor in EDF. The data for the ESA process ͑at p ͒ in the presence of signal radiation ͑at s ͒ seem to be important indeed because the presence of signal radiation in EDF results in an increased populating of state 4 trary, without the presence of signal wave in the fiber, almost all ions will be in the upper laser level 4 I 13/2 , which leads to a low pump absorption. Thus, the signal at 1531 nm switches on the ESA process at p and, thereafter, it increases the number of Er 3+ ions in the ground state, leading to an increase in the pump absorption.…”

“…1͒. The correspondent ESA processes in EDF are, respectively, 4 I 13/2 → 4 I 9/2 ͑"2 " → "4"͒ and 4 I 11/2 → 4 F 7/2 ͑"3 " → "5"͒.…”