A superfluorescent fiber source (SFS) with the low Ge-doped and Er/Ce codoped photonic crystal fiber (ECPCF) is proposed to improve the radiation resistance of SFS. The radiation effects of SFSs for an Er/Ce codoped conventional fiber (ECF) and a low Ge-doped and ECPCF are investigated in a Co60 gamma-ray environment. Results show that the low Ge-doped photonic crystal fiber exhibits better radiation tolerance than its counterpart in the Er/Ce codoped fibers, and the attenuation of the power of ECPCF-SFS is significantly smaller than that of ECF-SFS. In addition, the radiation-induced spectral variation of ECPCF-SFS with increased radiation dose is less than that of ECF-SFS. ECPCF-SFS simultaneously exhibits higher recovery performance than ECF-SFS.
The radiation resistance effect of two superfluorescent fiber sources using Er-doped photonic crystal fiber is studied under 500 Gy gamma-ray irradiation. One is trimmed into a quasi-Gaussian spectrum by a filter and the other is not trimmed. The results show that the SFS with spectrum trimming has a smaller radiation induced attenuation and a higher mean wavelength stability (2.616 dB and 24.803 ppm) than that of the SFS without spectrum trimming (3.187 dB and 611.766 ppm). Therefore, this method has practical use for improving radiation resistance in space environment.
A high-stability erbium-doped superfluorescent photonic crystal fiber source (SPCFS) is presented. Optimization of
the high-stable SPCFS is achieved by combining high-performance EDPCF, optimal fiber length, and source
structure with suitable pump power. The result shows a 56.979 ppm mean wavelength stability of a prototype SPCFS
is demonstrated with the temperature varied in the range of −40 °C—70 °C. Especially, in the room temperature, the
mean wavelength stability of a prototype SPCFS is less than 2.59 ppm, which will be approaching the requirement
for inertial-grade fiber optic gyroscopes.
Polarization maintaining (PM) photonic crystal fiber (PCF) and Er-doped PCF technologies are investigated for
interferometer fiber optic gyroscope (IFOG) applications. A PM-PCF optimized to achieve low-loss and high
polarization extinction splice-joints with conventional PM fiber pigtails of a multifunction integrated optical circuit
(MIOC) was drawn and tested under different temperature conditions. The loss and polarization crosstalk
properties of a fiber coil made from the PM PCF were measured and compared with conventional PM fiber. An
erbium-doped PCF was designed and fabricated, with which a superfluorescent fiber source (SFS) was made and tested.
The results show that an IFOG with the PM-PCF coil and the Er-doped PCF source could achieve better temperature
performance. An experimental PCF-based prototype IFOG was built and tested , and preliminary results was obtained.
A high-stable and broadband single-pass backward configuration superfluorescent fiber source based on erbium-doped photonic crystal fiber (EDPCF) is proposed. With the proper EDPCF length, pump power, and a gain flattening filter, we demonstrate that it is possible to create a high-stable and broadband erbium-doped superfluorescent photonic crystal fiber source (SPCFS). This was accomplished by replacing the conventional erbium-doped fiber with the EDPCF, the intrinsic thermal coefficient of which is four times less than the measured conventional erbium-doped fibers. The SPCFS showed that the total output power stability was less than 0.0337%, the 3-dB spectral width was broader than 42 nm, the output spectrum flatness was less than 1 dB, and the mean wavelength stability was less than 2.58 ppm over 6 h at temperatures from 24.3°C to 25.5°C, which approached the requirement for inertial-grade fiber optic gyroscopes.
Complementation image is often used as a guard technology in the trademark and paper currency. The key point of recognizing this kind of images is judging the complementary effect of complementation printing. The perspective images are usually not clear and legible, so it is difficult to recognize them. In this paper, a new method is proposed. Firstly, capture the image by reflex. Secondly, find the same norm to man-made pair printing. Lastly, judge the true and false of paper currency by the complementary effect of complementation printing. This is the purpose of inspecting the false. Theoretic analysis and simulation results reveal that the effect of man-made pair printing is good, the method has advantages such as simplicity, high calculating speed, and good robust to different RMB. The experiment results reveal that the conclusion is reasonable, and demonstrates that this approach is effective.
A novel measuring implementation based on second-harmonic generation frequency-resolved optical gating (SHG-FROG) has been presented. Both the intensity and phase of arbitrary-shaped ultra-short laser pulses can be got. According to SHG-FROG, the femtosecond pulse produced by a laser resource is split into two beams which variable time delay one another is controlled by a stepped electromotor. The second-harmonic signal field is generated by focusing these two beams to a 100um BBO crystal. Changing the delay from 0 to N (N is the samples number of time domain or frequency domain) delay units, the two-dimensional spectrum data of the second-harmonic signal field are acquired by PC2000-ISA card spectrometer and OOIwinIP of Ocean Optics. These data are provided to a pulse amplitude and phase retrieval algorithm to retrieve the parameters of the pulse. An experimental system is erected and the all software modules, including spectrum data acquiring, pulse retrieving and displaying, are based on Labwindows/CVI of National Instrument Corp. The stepped electromotor is driven by the commands coming from RS-232 interface. The results show that after 50 times iterations or so, the iterative error of the algorithm can be reduced to an enough small value and then the pulse amplitude, phase and other parameters are the desired parameters. The whole measuring process can be finished in 2~3 seconds while the spectrum data is a 64x64 matrix and the iterative times are set to 50.