A fiber laser with a semiconductor saturable absorption mirror (SESAM) and a graphene-polymer composite (GPC) film is constructed for achieving different soliton bunching patterns. The SESAM is used as a mode locker for self-started pulse generation, while the GPC provides a nonsaturable absorption effect for achieving a bunching in the laser cavity. There are three extra temporal patterns observed in the experiments through adjusting polarization controllers. They are chaotic bunching, weak coherent bunching and modulated harmonic bunching. The experimental investigation shows that dynamic nonsaturable absorption effect of an absorber is beneficial for generating different bunching patterns. Our work can have a deeper understanding of the formation of the complex soliton bunching patterns in pulsed lasers.
A novel dispersion-compensation superstructure fiber Bragg grating (SFBG) based comb gain equalizer for fiber optical
parametric amplifier (FOPA) is proposed. It is characterized by its eight-channel 100GHz DWDM-channel separations
and 80 km dispersion compensation function. The object reflectivity spectra of gain equalizer are calculated in two parts
independently. Inner channel part for every channel is designed according to the gain spectrum of fiber OPA. Inter-channel
part is calculated with Gaussian hypergeometric function (-0.5dB bandwidth 0.1nm, -45dB bandwidth 0.3nm) to
obtain slower rising and descending edges than the simply zeroed case. Then the SFBG is designed with layer-peeling
inverse scattering technique. Simulation results show that this SFBG satisfies all requirements. Using this SFBG as
comb gain equalizer, the gain of fiber OPA is flattened in every channel to within ±0.4dB among 8 ITU-T regulated
channels, with 80 km dispersion compensated.
Widely tunable All-optical wavelength conversion between picoseconds pulses based on Four-wave mixing is proposed
and experimentally demonstrated in cascaded highly nonlinear fiber. The signal pulse with 40-GHz repetition rate and
1.57-ps pulse width is adopted. The converted idler wavelength can be tuned continuously from 1540.6 to 1594.8 nm as
the CW laser wavelength is changed from 1514.5 to 1565.7 nm. No obvious changes of the pulse shape and width, also
no chirp are observed in the converted idler pulse.
The evolution properties of the self-similar parabolic pulse(similariton) with higher-order effects in microstructured fiber
amplifier with normal group-velocity dispersion are investigated in this paper. The numerical results show that the
higher-order effects greatly distort similariton's waveform, frequency and the linearity of chirp. The drift of pulse center
increases with distance. The influence of different higher-order effects on similariton is analyzed. High quality
propagation of similariton can be attained by manipulating the geometrical parameters of the microstructured fiber
amplifier. These results are significant in the further study of similariton propagation in high-power ultrashort fiber
amplifier, laser and transmission system.
Vector soliton is obtained in erbium-doped fiber laser via nonlinear polarization rotation techniques. In experiment, we
observe the every 4- and 7-pulse sinusoidal peak modulation. Temporal pulse sinusoidal peak modulation owes to
evolution behavior of vector solitons in multiple polarization states. The polarizer in the laser modulates the mode-locked
pulses with different polarization states into periodical pulse train intensities modulation. Moreover, the
increasing pumping power lead to the appearance of the harmonic pulses and change the equivalent beat length to
accelerate the polarization rotation. When the laser cavity length is the n-th multiple ratios to the beat length to maintain
the mode-locking, the mode-locked vector soliton is in n-th multiple polarization states, exhibiting every n-pulse
sinusoidal peak modulation.
A novel 16-channel comb filter based on superstructure fiber Bragg grating (SFBG) is proposed for the first time. It is characterized by single-grating structure, equal reflectivity peaks, narrow channel bandwidth, flat-top, high bandwidth utilization ratio, standard 50 GHz channel-spacing, and realizing dispersion compensation and wavelength filtration simultaneously. Based on ameliorated layer-peeling algorithm, that is adopting channel-by-channel windowing method rather than all-channel integral windowing method, this novel SFBG is synthesized successfully. According to the grating structure of the synthesized SFBG, reflectivity spectrum, group delay and group delay ripper are analyzed based on the method of transfer matrix. The results show this SFBG does an almost perfect job of reproducing the desired spectrum.
A novel superstructure fiber Bragg grating (SFBG) based comb gain equalizer for fiber optical parametric amplifier (OPA) is proposed. This gain equalizer is characterized by its comb reflectivity spectrum. It can have two functions at least, one is flattening the gain in multi ITU-T regulated channels, the other is it can be used as multi-channel isolation filters taking full advantage of its comb reflectivity spectrum. In addition it can be dispersionless or have dispersion compensation function. A one-bump fiber OPA, 30dB bandwidth >15nm, is designed with one of its peak gains (41dB) located at the center of work wavelengths in a 16-channel 100GHz spaced WDM optical transmission system according to corresponding Chinese criterion (1548.51nm~ 1560.61nm). The object reflectivity spectra of gain equalizer are calculated in two parts independently. Inner channel part for every channel is designed according to the gain spectrum of fiber OPA. As a comb filter, its inter-channel part reflectivities are the smaller the better. But inter-channel part reflectivities can not be simply zeroed, for which would result in the rising and descending edges of reflectivity spectrum being too sharp to be performed by any filter. To split the difference, inter-channel part reflectivities are calculated with Gaussian hypergeometric function (-0.5dB bandwidth 0.1nm, -45dB bandwidth 0.3nm) to obtain slower rising and descending edges than the simply zeroed case, which is very necessary and important to be sure the object reflectivity spectrum not only has sharp enough edges to take the shape of comb but also is physically realizable. Adopting channel-by-channel windowing method to apodize the object reflectivity spectrum, a superstructure fiber Bragg grating is designed with lay-peeling inverse scattering technique. At last, according to the coupling coefficient calculated, reflection spectrum and group time delay are analyzed based on the method of transformation matrix. Calculation results show that this SFBG satisfies all requirements. Further calculation results show that, using this SFBG as comb gain equalizer, the gain of fiber OPA is flattened in every channel to within ±0.4dB among 16 channels, with channel isolation high up to -35dB. It needs to point out that this method can also be used to design gain equalizer for other optical amplifiers.