Low-Threshold Broadband Spectrum Generation by Amplification of Cascaded Stimulated Raman Scattering in an Ytterbium-Doped Fiber Amplifier

We present an experimental study on low-threshold broadband spectrum generation mainly due to the amplirfication of the cascaded stimulated Raman scattering （SRS） effect in a four-stage fiber master oscillator power amplifier system. The cascaded SRS is achieved by using a long passive fiber pumped by a pulsed fiber laser cen： tered at wavelength 1064 nm. The amplified spontaneous emission during the amplification process is efficiently suppressed by cutting the length of the passive fiber and by using a double-clad ytterbium-doped fiber amplifier. The generated broadband spectrum spans from 960nm to 1700nm with maximum average output 13.6 W and average spectral power density approximately 17. 7 mW/nm.

Investigation on the pre-compensation and post-compensation cascaded multi-channel-chirped fiber Bragg gratings for a repeaterless transmission system

We experimentally designed dispersion-managed repeaterless transmission systems with a pre-compensation and post-compensation technique using multi-channel-chirped fiber Bragg gratings. The repeaterless transmission link supports a single channel（1548.51 nm） with a 10 Gbps repeaterless transmission system over 300 km standard single-mode fiber（SSMF）. In the system design, two distributed Raman amplifiers（DRAs） were used to improve the signal level propagated along the 300 km SSMF. The co-propagating DRA provided 15 dB on–off gain and the counter-propagating produced 32 dB on–off gain at the signal wavelength. The experiment results show that the post-compensation configuration achieves an optimal performance with a bit error rate at 1 × 10-9.

Theoretical Modelling of Cascaded Er3+-Doped, Tm3+-Doped and Nd3+-Doped Fibers for 0.4 to 2.0 μm Emission Spectra

We present a cascaded system designed with Er^3+-Doped,Tm^3+-doped and Nd^3+-doped fibers to realize amplified spontaneous emission(ASE)spectra covering 0.4—2.0μm.The system is excited with a pump laser emitting 808 nm photons with 500 m W pump power.The emission spectra of the cascaded system covering0.4—2.0μm are realized with the Er^3+,Tm^3+and Nd^3+ion doping densities optimized to 8×10^19,2×10^20 and8×10^20 ion/m^3,respectively,and the fiber length optimized to 1 m.Numerical methods reveal that the peak ASE power for the cascaded system can reach 20.9 m W.A minimum ASE power of 4.39 m W is attainable.Using numerical calculations and analytical techniques,we provide a detailed insight into optimized Er^3+-doped,Tm^3+-doped and Nd^3+-doped fiber lengths and their doping concentrations for ASE power spectra covering 0.4—2.0μm.We believe that the cascaded system can potentially provide significant applications in various optical fields which include but not limited to wavelength-division multiplexing,various optical communications and other salient medical imaging processes.

Tunable fiber laser based on a cascaded structure consisting of in-line MZI and traditional MZI

A tunable erbium-doped fiber(EDF) laser with a cascaded structure consisting of in-line Mach-Zehnder interferometer(MZI) and traditional MZI is proposed. The transmission spectrum of the in-line MZI is modulated by the traditional MZI, which determines the period of the cascaded structure, while the in-line MZI's transmission spectrum is the outer envelope curve of the cascaded structure's transmission spectrum. A stable single-wavelength lasing operation is obtained at 1 527.14 nm. The linewidth is less than 0.07 nm with a side-mode suppression ratio(SMSR) over 48 d B. Fixing the in-line MZI structure on a furnace, when the temperature changes from 30 °C to 230 °C, the central wavelength can be tuned within the range of 12.4 nm.