Investigations Of L-band Erbium-doped Superfluorescent Fiber Source

Erbium-doped superfluorescent fiber source (SFS) has been widely used in dense wavelength division multiplexing (WDM) systems, optical sensor systems and fiber optic gyroscopes (FOG) for its excellent characteristics. In particular, the erbium-doped SFS is the best choice for the source of high precious FOG. In the past decades, the conventional band (C-band, 1525-1565nm) SFS based on erbium-doped fiber (EDF) amplified spontaneous emission (ASE) has been intensity researched. The mean wavelength stable SFS was achieved by designing the source configuration and optimizing the structural parameters. However, the scheme to broaden the spectral linewidth should be taken into account in the C-band SFS because the linewidth in C-band is narrow for the reason of the intrinsic peak spectrum around 1532nm.The long wavelength band (L-band, 1565-1605nm) SFS has the advantage of much more flat output spectrum. The spectrum is intrinsically flat about 40nm in the L-band with less than 1dB ripples. Therefore, the spectral linewidth in the L-band is much broader than the C-band. As been well known, the coherent noise, phase noise caused by the Rayleigh scattering, and phase drift caused by Kerr effect can be reduced by use of the source with broader linewidth in the FOG. Therefore, the L-band SFS is more suitable for application in the high precious FOG than the C-band SFS for the advantage of broader linewidth. However, there are no reports on the mean wavelength stable L-band SFS up to date to the best of our knowledge. It is the goad of this thesis to develop the mean wavelength stable L-band SFS. The configurations have been designed to achieve the L-band SFS with the characteristics of mean wavelength stability and broadening spectral linewidth as well. The high efficiency and linewidth broadening L-band SFS is also useful in the DWDM systems applications with the requirement of linewidth in rapid development of fiber optics communication.This thesis includes the following three parts:Firstly, the characteristics of output power was improved and the linewidth was broadened by designing and optimizing the conventional cascaded forward pumped two-stage L-band SFS configuration. A kind of synchronous pump technique was proposed to avoid the mean wavelength vibration caused by the individual pump to the two stages. Furthermore, a new single forward pumped L-band SFS with a segment of un-pumped fiber was developed to obtain the mean wavelength stability.Secondly, the high efficiency bi-directionally pumped one-stage L-band SFS was investigated. The mean wavelength stable L-band SFS was achieved with the usage of synchronous pump technique in the bi-directionally pumped configuration. An improved bi-directionally pumped configuration with a segment un-pumped fiber was proposed and demonstrated to improve the tenability of linewidth.Thirdly, a novel cascaded backward pumped two-stage L-band SFS was presented and realized for the first time. Characteristics of high pumping efficiency and mean wavelength stability was achieved in the proposed cascaded backward pumped L-band SFS with the usage of synchronous pump technique. Furthermore, a new single backward pumped stable L-band SFS with a segment of un-pumped fiber was developed. Analysis of the effect of the un-pumped fiber on the output characteristics was carried out to achieve a practical mean wavelength stable L-band SFS with one pump.The Background of this thesis includes a fund of New Century Excellent Talents in Fujian Province University and a project of Fujian Provincial National Science Foundation of China. The research achievements of this thesis partially contributed to fulfill these projects successfully.The innovation points and highlights of this thesis include:1. It has been put forward and realized for the first time that mean wavelength stable L-band SFS based on amplified spontaneous emission in erbium-doped fiber. The L-band SFS is a good candidate for the source used in the FOG since it poccesses the characteristics of good spectral flatness, broad spectral linewidth and high output power.2. A novel cascaded backward pumped two-stage L-band SFS was presented and realized for the first time. Characteristics of high pumping efficiency and mean wavelength stability was achieved in the proposed cascaded backward pumped L-band SFS with the usage of synchronous pump technique.3. The high mean wavelength stable L-band SFS with one pump, i.e. improved single forward or backward pumped configuration with an un-pumped fiber, was proposed. The single pumped stable L-band SFS is superiors to the synchronous pumping technique in the aspects on avoiding the complicated configuration and rigorous requirement of structural parameters. As a results, it makes much practical progress of the L-band SFS used in the high precious FOG.