2013 Vol. 34, No. 4

OE System and Engineering
Technology of optoelectronic aid landing system based on shipborne optoelectronic tracking equipment
LU Pei-guo, LIU Xiao-qiang, LIU Jian-ping, WANG Hu, SHOU Shao-jun, LIU Han-ping, LIANG Xiao-dong
2013, 34(4): 553-563.
By analyzing present state of the optoelectronic aid system of carrier landing, the component, configuration, technology principle and technology target of the optoelectronic aid landing system were presented. Combining with the existing technology, the key factors of location precision were analyzed deeply by swaying experiment and simulation. Under the condition of no-swing, pitching of 2and period of 20s, or rolling of 10and period of 15s, the location error of the optoelectronic aid landing system was provided when the distance between carrier aircraft and landing site was greater or less than 1 km.
Miniature design of high resolution optical system for infrared seeker
ZHANG Ai-hong, CONG Hai-jia, FAN Zhi-gang, CHEN Gang-yi
2013, 34(4): 564-569.
A mid-wave infrared imaging guiding system with high resolution is designed. First imaging refractive system and telephoto lens groupe are used for the initialized structure. The system with three optical elements, the all field of view of 10, a focal length of 70mm, and the total length of 49mm is designed. Within -40℃~60℃, the system possesses better athermal performance. The image quality of the system almost approaches the diffraction limit. The biggest defocused spot's diameter is less than 15m. It is applicable to the infrared focal plane arrays(IR FPA)detector with the format of 640512, the pixel size of 15m and the Fnumber of 2. This system can suffice the requirements design of infrared seeker, which has the advantages of high resolution, wide field and small volume.
Collimator design for novel spectral tunable calibration source system
ZHAI Wen-chao, XU Jun, DING Le, ZHENG Xiao-bing
2013, 34(4): 570-574.
High accuracy spectral tunable calibration light source is a novel calibration light source, which especially accounts for the stringent calibration requirements of hyper-spectral remote sensors. A broadband and large aperture apochromatic collimator was designed. The lens worked in band of 400~1 000 nm, half field of view was 2.2, relative aperture F was 2.8, and focal length was 135 mm. According to the corrected formula of parial dispersion (P) and Abbe number (), the original optical structure was acquired, based on the principles of apochromatic lens design. The secondary spectrum was corrected well with the help of Zemax software. At last, the lens was apochromatic in the whole working band with secondary spectrum residual of about 0.04 mm, and other aberrations are balanced well. The Lens's MTFs are better than 0.8 at spatial frequency of 37 lp/mm, which meet the requirements of the light source system.
High resolution ultraviolet/visible wide band microscope objective
LIU Zhong-yu, ZHANG Xin-ting, WU Qian-qian
2013, 34(4): 575-578.
A high resolution ultraviolet/visible wide band microscope objective used for target detection was designed. This system with numerical aperture of 0.4, magnification of 10 times, image height of 4.7 mm, imaging wavelength range of 248 nm-656 nm, used fused silica and CaF2 to calibrate the achromaticity caused by wide band. Through the system structural design and the aberration, the cut-off frequency of transfer function curve could achieve 3 600 lp/mm,which was close to the diffraction limit. The resolution was less than 0.65 m. The root mean square of spot diagram was less than 0.650 mm. Curvature of field was less than 0.01 mm. Distortion was less than 0.5 m. This system can complete dual-band exploration mission of near ultraviolet and visible light.
Collimator with ultra-small size and long focal length
HAN Bing, ZHANG Xiao-hui, MA Hong-tao
2013, 34(4): 579-583.
A collimator with ultra-small size, long focal length and high image quality was designed, the structure of full reflection off-axis two-mirror was used. The collimator focal length was 12 000 mm, effective aperture was 400 mm, within field of view 30 mm30 mm the wavefront aberration was better than 1/20@632.8 nm. After light turning many times , the collimator dimensions were less than 1 000 mm600 mm500 mm, the total mass was less than 60 kg. By analysis and calculation, the environmental adaptability of collimator is better, and it meets the requirement of the normal launch site test .
Synchronous inner triggering design of inertial-visual compound sensor
YU Ming, LI Kai, HAN Yan
2013, 34(4): 584-587.
The long distance, high speed dynamic target measurement was realized by using the synchronous inner triggering inertial-visual compound sensor. Synchronously trigger the high precision inertial sensor ADIS16355 and ordinary monocular camera, monocular camera can achieve binocular vision by changing position, rotating optical axis angle. It can effectively solve the location problem of the three dimensional space moving target. Laser keyboard is used to mark image initial frame, at the same time high signal is produced, then the signal and the odd/even field synchronous pulse signal separated from the camera video signal are outputted through the AND gate, the output is used to realize synchronous measurement as the interrupt signal. It can eliminate frame stagger or frame lost, the precision can reach microsecond. It provides a general solution for synchronous acquisition of inertial sensor and ordinary monocular camera.
Security and early warning detection device in invisible part of stay cable anchorage system
CAI Lin, CHEN Le-geng
2013, 34(4): 588-593.
The cables in anchorage zone of cable-stayed bridge are hidden within the embedded pipe, which leads to the difficulty for detecting the damage of the cables with visual inspection. A detection device based on high-resolution video capture was built, the distance observing of invisible segment of stay cable and damage detection of outer surface of cable in the small volume were realized. The system mainly consisted of optical stents and precision mechanical support device, optical imaging system, lighting source, driving motor control and IP camera video capture system. A set of telescope objectives with three different focal lengths were designed and used in different distances of the monitors by means of converter. Lens system was far separated from lighting system, so that the imaging optical path could effectively avoid the harsh environment which was in the invisible part of cables. The practice shows that the device not only can collect the clear surveillance video images of outer surface of cable effectively, but also has a broad application prospect in security warning of the prestressed structures.
Influence of quintic nonlinearity on interaction of chirped ultrashort laser pulses
2013, 34(4): 594-598.
Based on the model of the high-order nonlinear complex Ginzburg-Landau equation including quintic nonlinearity, the interaction of chirped ultrashort laser pulses was numerically studied by using split-step Fourier transform method. The results show that the quintic-order nonlinear terms are important for the interaction between neighboring solitons, even small variation could change the transmission characteristic. The interaction among them can be well suppressed by appropriately selecting the coefficient of the quintic-order nonlinear and the transmission bit-rate in optical telecommunications is increased. The further simulation shows that two solitons preserving long-distance transmission can be achieved when the initial separation of neighboring solitons is equal to 6.8 and the quintic nonlinear coefficient value is equal to -0.001.
OE Information Acquisition and Processing
Light source validity evaluation in CCD vertical target measurement system based on image analysis
MA Wei-hong, NI Jin-ping
2013, 34(4): 599-603.
In view of the CCD vertical target application in outdoor natural environment and with active light source, a method to evaluate the validity of light source based on background image analysis was presented. On the condition same with pratical measurement, certain line background images without object were captured to determine the gray scale range f and gray mean value fmean of each pixel in these line background images. To each pixel, if the value of fmean was always bigger than two times of f, the object could be recognized after image analysis. The effectiveness and reliability of the criterion were all demonstrated by CCD vertical target application experiments in laboratory with active light and outdoors with natural light.
Platform design for massive hyperspectral data processing based on internet cluster
WANG Cai-ling, HU Bing-liang, WANG Hong-wei, LIU Xue-bin, CHEN Xiao-lai, LI Pu
2013, 34(4): 604-608.
In some large-scale image processing systems, multiple servers can achieve parallel processing image data stream to complete the complex data operations by building server cluster network. An Ethernet-based server cluster for huge hyperspectral image processing system was designed based on image characteristics. In order to achieve parallel processing, the task decomposition, algorithm pipelined processing and network load balancing were used in software design. The system is used in a hyperspectral image data processing system and the date rate can achieve 6 000 Mbps.
Feature detection method for parabola object in optical image
TANG Wei-hong, LUAN Sheng-li, LI Liang-fu
2013, 34(4): 609-613.
The parabola object feature detection of optical image is a difficult research topic in computer vision fields. A parabola feature detection algorithm based on the least square method is presented. Using Canny algorithm to detect edge, then the least square method is used to compute the coefficients of the parabola equation. The conic is constrained by parabola and the algorithm, so it can get the optimal solution without iteration computation. Finally the coordinate transformation of the parabola equation is computed and the parameters of parabola can be achieved. The experimental results of emulation data and real image show that our algorithm can efficiently detect the parabola object feature and compute the feature parameters in the optical image, and the calculation accuracy of each parameter is above 98%.
FFT-ernike combined algorithm of wavefront reconstruction in easurement of optical surfaces based on projected fringes deflectometry
LIU Jiang, CUI Mu-han, GAO Song-tao, SUI Yong-xin, YANG Huai-jiang
2013, 34(4): 614-618.
The basic principle of projected fringes deflectometry is to measure the point-o-oint relations of coordinates among free-orm surface, camera and projection screen, and then compute the reconstructed surface with calculated slope data iteratively. In order to reduce the calculating time of the wavefront reconstruction without losing accuracy, a fast Fourier transform(FFT)Zernike combined algorithm was proposed. The simulated result demonstrates the proposed algorithm can decrease the iterative procedure to 5 times using less than 20 seconds, compared with the traditional Zernike modal algorithm which has 15 iteration times using more than 1 minute. In addition, the calculating time is cut by two-hirds with the accuracy achieving the order of nanometer.
Measurement of moving object by multi-source data based on moving platform
HU Bing-ua, YAN Hui, WU Heng
2013, 34(4): 619-623.
An image data measurement system was created based on the moving target performance testing requirements and the characteristics of test platform, in order to realize video recording and external parameters measurement of the target. Multiple highspeed cameras were reasonably arranged from calculated distance of the camera and mimic diagram. Camera calibration method was used which is combined the checkerboardlattice parameter calibration in OpenCV with the linebasis field calibration. Additional, highspeed image data, midline video data and GPS data were combined to achieve the measurement of position, attitude and other external parameters. Analysis of measurement accuracy and experimental results prove that the measurement method is accurate and reliable. Its coordinate accuracy is better than 10 cm in horizontal direction and 5 cm in elevation direction, and the attitude accuracy is better than 05, which fully meet the measurement accuracy requirements..
Optical Metrology and Measurement
Calibration of nonlinear phase shifter with iterative least-square method
SU Zhi-de, SUI Yong-xin, YANG Huai-jiang, SHAO Jing
2013, 34(4): 624-628.
Since the measurement accuracy of a phase shifting interferometer is deeply affected by nonlinear phase shifts, a novel phase shifter calibration method based on iterative least-square-fit was proposed to cope with it. Several interferograms could be taken after applying voltages to the phase shifter, and the phase shifts between interferograms could be calculated by iterative inter-and intra-least-square-fit, so the relation curve between the applied voltages and phase shifts was obtained, then the curve was fitted and the voltages were finely adjusted and finally the phase shifter was calibrated accurately. The proposed calibration method is verified on a modified interferometer, and the measurement result is compared with that of a Zygo interferometer with the same component, the RMS of the difference between two results is 1.726 nm. It can be seen that the proposed calibration method can help to get high accuracy measurement result with a nonlinear phase shifter.
Absolute radiometric calibration technique of imaging spectrometer
FAN Ji-hong, ZHAO Sheng-lu, ZHAN Chun-lian, YUAN Liang, LI Zheng-qi, LU Fei, LI Yan
2013, 34(4): 629-632.
In order to realize absolute radiometric calibration of imaging spectrometer, based on stable source, a dedicated absolute radiometric calibration system was set up combined with monochromator, big caliber collimator and standard radiometer. Using substitute method, spectral irradiance of entrance pupil for measured imaging spectrometer was calibrated using standard radiometer during the calibration firstly, and then output signal of every pixel for measured imaging spectrometer was obtained. So spectral irradiance responsivity of every pixel could be calculated, the absolute radiometric calibration of imaging spectrometer in visible and infrared wavelength range was realized. The result of experiment proves that the uncertainty of absolute radiometric calibration is better than 5%.
Automatic defect inspection system for spectacle lenses
YAO Hong-bing, PING Jie, LI Liang-wan, GU Ji-nan, ZENG Xiang-bo, MA Gui-dian, ZHENG Xue-liang
2013, 34(4): 633-638.
According to the light scattering prinliple and visual inspection method, a defect inspection system of spectacle lenses was researched and developed, which was based on the machine vision. Image acquisition, simple image processing, grading and sorting of glasses were done in the system, in order to achieve the classification of glasses. The system adopted parallel institution to run. Low-angled-ring-light-emitting-diode (LED) was used for forward illumination. Clear defect-images of speckle, impurity, feather and so on, which stayed in or on the surface of the glasses were got. Normalization algorithms were used for image processing and glasses grading, and the identifying information of various defects was acquired. The experiment results show that the detection system can detect all of the lens-s defects. The system has the detection accuracy of 0.038 mm with the average detection time of each glass less than 2 s.
System error correcting method in sub-aperture stitching
WU Shi-xia, TIAN Ai-ling, LIU Bing-cai, ZHANG Peng-fei
2013, 34(4): 639-643.
In order to improve the detection accuracy of the measurement of large aperture optics stitching, a simple and effective absolute measurement was proposed to amend the system error of the sub-aperture stitching measurements. Firstly, an improved three-flat test was used to obtain the surface shape data of the reference plane and the surface error wave-front based on the Zernike polynomial was established which was used to correct the error of the subaperture measurement data. Then the directly measured values were compared with the full aperture surface stitching results, and the surface error peak value(DV) was reduced from 0.072 1 to 0.028 6 . The results show that the method is effective in reducing the system error that caused by the reference plane and can effectively improve the detection accuracy of the large aperture optics stitching.
System for parallelism detection of multi-spectrum optical axes
LI Si-zhong, YU Yun-qi, CHEN Jing, GUO Jia
2013, 34(4): 644-647.
A system for detecting the parallelism of multi-channel optical axes was introduced, and a collimator was used in the system to provide an infinite target. Based on CCD image acquisition and processing and computer technique, the parallelism errors among the infrared axis, visible axis and the laser axis were calculated by calculating the pixels span in the CCD between the target cross center and the laser spot center. Result shows that the calculation error of the system is less than 5 .
Infrared Technology
Accuracy analysis of space target infrared dual-band pyrometry
LIU Ying-qi
2013, 34(4): 648-652.
The unknown parameters between space target and ground-based telescopes infrared imaging terminal reduce the dual-band pyrometry accuracy, and the influence degree is unknown. Assuming that the target is gray body, the partial derivative of maximum likelihood estimation function about emissivity is solved. The dual-band pyrometry mathematical model based on infrared detectors to measure the electron number is established, and the Monte Carlo simulation and precision analysis of dual-band pyrometry is performed. The field calibration method of atmospheric transmittance prediction based on infrared natural star is proposed. The inversion precision of space target temperature has a close relationship with the imaging detector signal-to-noise (SNR) ratio, the earth-s thermal radiation estimation accuracy, atmospheric transmittance and emissivity difference between bands. When the SNR is above 20, emissivity difference is less than 0.03, the earth radiation prediction accuracy is better than 50%, and atmospheric transmittance prediction accuracy is better than 10%, the temperature estimation precision of dual-band pyrometry is better than 40 K.
Feasibility analysis of space target detection based on infrared polarization properties
LI Fan-ming, NIU Ji-yong, MA Li-xiang
2013, 34(4): 653-657.
Infrared polarization properties and their variation can characterize the surface and state information of the space target. Combining the latest progress of current polarization detection, the feasibility of space target detection based on infrared polarization properties is analyzed. Space target polarization properties vary with the materials as well as the orbits of the space targets, which provides a scientific basis of using infrared polarization detection technology to detect and identify space target. Through the analysis of polarization properties of different materials commonly used in space targets, and same material under different surface states and different viewing angles, the results demonstrate that the average DOP(degree of polarization) of a smooth steel plate is about 1.3 times rough steel.
Auto-switch device for non-uniformity correction of infrared camera
XU Xin-hang, YANG Hong-bo, GAO Yun-guo, WANG Bing
2013, 34(4): 658-662.
Infrared camera used for capturing and tracking target mainly was one of the most important equipment in laser weapon system, and its non-uniformity disturb influenced infrared target extraction greatly. To decrease noise disturb and improve imaging quality, a switch machine was designed to correct nonuniformity of infrared camera when it was started up. Considering confined applying conditions, a crank-link switching device was designed particularly on the basis of contrasting and analyzing auto-switch devices with different structure principle. The designed switch device was driven by tubular solenoid and drive was transferred by crank-link. Applying effect shows the sizes of designed switch machine is 68 mm36 mm37 mm and the switch time is about 0.4 s, so it is more suitable in the occasion of small space .
Low noise infrared radiometer
HU Tie-li, SHEN Yue, GUO Yu, FAN Ji-hong, MA Shi-bang, ZHANG Mei, LIU Rui-xing, XIE Yi, XIN Zhou
2013, 34(4): 663-666.
In order to solve the calibration of the infrared imager test equipment, a kind of infrared radiometer in which the temperature of interior reference blackbody was equal to the environmental temperature was designed. In order to evaluate this kind of radiometer and give guidance to the infrared radiometer design, a mathematic model for infrared radiometer noise equivalent temperature difference (NETD)was given. The NETD of infrared radiometer was estimated under different electronic bandwidths and spectral wavebands. The results show that when noise equivalent bandwidth is within 1 Hz, NETD of infrared radiometer in mid-wavelength infrared (MWIR) and long wavelength infrared (LWIR) spectral bands is smaller than 0.01℃, which can meet the requirements of the calibration of infrared imager test equipment.
LLL Night Vision Device and Imaging
Low-light level telescope based on laser range gate technology
ZHANG Yue-min, LIU Xiao-li, CHEN Zhou, ZHAO Lu-min, ZHANG Hong, ZHANG Jin-tao
2013, 34(4): 667-671.
Under the help of auxiliary lighting on low-light level system by using laser with infrared wavelength, environmental illumination and contrast of object area can be improved, making the object outstand from vision area, which can effectively enlarge the range of low-light detection and improve the observation effects. Adopting range gating technology, properly arranging the work order between laser pulse and gated image intensifier, shielding the object from troubling by inflected light around the object and stray light from airborne suspended particulates, solving coaxial illumination back scattering problem, the object only from the selected range can be observed. Through engineering practices of laser assistant low-light level binoculars, the range gating technology is successfully applied to low-light detecting area, and the recognizable range for medium tank and the truck broadside is up to 1 400 m under simple background conditions, without moonlight or starlight, with illumination of 110-3lx and atmosphere visibility of 10 km.
Minimum resolvable contrast model for direct view LLL night vision system
GAO Jiao-bo, ZHANG Fang, LI Yu
2013, 34(4): 672-675.
The general performance evaluation theory of low light level (LLL) night vision system is studied based on signal detection and human vision. Simultaneously, the minimum resolvable contrast (MRC) model is deduced. Combining the optical transfer properties with the signal-to -noise ratio of system, the mathematical relationship among target characteristic, LLL night vision system and human visual system is established. The simulation result shows that the relative error of the limited sensitivity calculated by MRC model is 3.08 %, compared with the reality of system. The MRC model mentioned in the paper is a more perfect one for evaluating the performance of LLL night vison system.
LLL image intensifier of the third generation SNR measurement technology
WANG Sheng-yun, SUN Yu-nan, SHI Ji-fang, LI Hong-guang, XIE Qi
2013, 34(4): 676-679.
Low-light-leve (LLL) image intensifier is the core component of LLL imaging technology, signal-to-noise ratio(SNR) of image intensifier is one of the important parameters of image intensifier, which is quantitative characterization of image intensifier performance in the detection of weak radiation image, and can reflect the influences of space factor and time factors on the detection of image features. SNR measurement principle and devices of LLL image intensifier were introduced. The measurement device adopted precise microporous grating, variable grating and conjugate symmetric lens system, and could realize that a diameter of 0.2 mm particular spot projected onto the cathode surface of image intensifier. Adopting photon counting technology, by studying the weak light intensity calibration method on small detection surface (probe diameter less than 4 mm), the accurate calibration of pinhole weak illumination and the accurate measurement of light source illumination SNR with diameter of 0.2 mm were solved.
Laser Technology
Miniature high-power all-solid-state Nd∶YAG slab laser with liquid metal heat conduction
TANG Gang-feng, SHENG Zhao-guo, SHANG Xu-chuan, LI Yi, DONG Tao, YANG Yi
2013, 34(4): 680-685.
In order to fulfill the requirements of small opto-electronic systems for miniature high power lasers, a heat conduction manner based on liquid metal was designed, which improved the heat transfer efficiency, and a high energy laser with a small volume was made. Using compound slab active materials integrated resonator and laser amplification technology, when the supply current was 80 A and the pulse frequency was 5 Hz, a 160 mJ pulse laser at 1.064 nm was obtained, with a pulse width of 6 ns and a divergence angle of 3 mrad.
Testing linearity error of long guideway by laser tracker
WANG Xiao-kun
2013, 34(4): 686-689.
On the basis of summing up conventional linearity error testing for guideway, a novel method for testing linearity error of very long guideway by laser tracker is proposed. The basic principle and testing processing of the method are analyzed and researched. A long guideway of 20 m is measured by this method, the linearity error of each direction is 27 m and 25 m respectively. This method enlarges the ability of the laser tracker, it can test the linearity error of long guideway precisely and swiftly, and it can separate the linearity error of two directions, the longth of measurement guideway can reach 70 m, and the testing precision is 0.4 m/m。
Pulse laser damage characteristic measurement of VO2 optical thin film
HAN Wen-qin, GUO Xi-qing, XIE Guan-bao, SUN Peng-fei, YANG Jing-xian, TANG Ya-jun
2013, 34(4): 690-694.
In order to evaluate the operational reliability of the VO2 optical film working in the photovoltaic device, a pulse laser experiment platform which could output gradient laser energy density was set up. The laser irradiation experiment was carried out by using the1 to 1 and s to 1 laser damage test means, and the results were processed through the methods of extrapolation and measureme calculation. The experiment obtained the damage characteristics of VO2 thin films under the pulsed laser with a repetition rate of 10 kHz, center wavelength of 532 nm and pulse width of 15 ps. The results indicate that there is a linear relationship between the damage probability of VO2 thin films and the energy density of the single laser pulse, moreover, the damage caused by the laser pulse repeated radiation has the cumulative effect, and the more times laser pulse radiation repeats, the more obvious the cumulative effect of damage is.
Optical Element and Fabrication
Study and preparation of mid-wave infrared 3μm~5μm broad band pass filter
ZHANG Jian-fu, YANG Chong-min, LIU Qing-long, WANG Yang-yun, XIE Hui, LI Ming, LIU Yong-qiang, YANG Hua-mei, MI Gao-yuan, LI Ming-wei
2013, 34(4): 695-699.
The plating process of the mid-wave infrared broad-band pass filter is difficult because of multi-layers, and the total thickness of film layers is very big ( the thickness is up to about 10 m). Through analysis of the design features of several infrared band pass filters, and combining with the actual plating technology, the 3 m~5 m broad-band pass filter with germanium substrate was designed by using the method of combining long-wavepass, shortwave-pass and irregular film design technology. The design reduces the total thickness of film ( about 8.65 m) greatly as well as the deposition time, and the firmness of the film is improved. The film obtains excellent spectral properties by changing the evaporation rate of film materials, correcting the scan mode of the electron gun when vaporizing the ZnS material, and adjusting the loading method of the evaporation material in the crucible. The average transmittance is more than 96% in the passband and less than 1% in cut-off region.
Alignment technology of offsetting image rotation prism in periscopic sight
HUI Gang-yang, YANG Hai-cheng, JIANG Feng, ZHANG Yan, WANG Zhang-li
2013, 34(4): 700-705.
When the reflection optical system of periscope mirror rotates around mechanical shaft, the reflected image in the view field rotates around the optical axis which greatly affects observation. Offsetting image rotation prisms can eliminate the influence by spinning in the opposite direction. Though the analysis of two widely used offsetting image rotation systems, the criterion of the assembly process is raised, two typical methods for offsetting image rotation prisms are concluded, and the detection of offsetting image rotation prism fixed before and after the resolution in parallel light is put forward to ensure the imaging quality. The method is proved to be effective in reducing the difficulties in alignment of offsetting image rotation prism system and improving image quality. The windage between the optical axis of the offsetting image rotation prisms and system norm axis can be controlled less than 30.
Fiber Sensing and Optical Communication
Diffraction intensity distribution of varied line-space blazed grating for broadband source
WANG Dong-hui, LIU Lin, LI Bing-shi, BAO Yan, ZHENG Pu-chao, ZHANG Bing, ZHANG Chao
2013, 34(4): 706-710.
The varied line-space grating displacement sensor is a novel wavelength encoding displacement sensor, it is one of the vital components of developing fly by light (FBL) control technology. A varied line-space grating with high diffraction efficiency is necessary to enhance measurement precision and decrease the cubage of lamp-house. First, the calculation formula of diffraction intensity of the varied line-space blazed grating was deduced based on classical optical. It was theoretically improved that the varied line-space blazed grating could increase diffraction intensity of the sensor. In addition, the prototypes of the varied line-space blazed grating were fabricated and the feasibility of process was verified. Comparative experimental researching on diffraction intensity of varied line-space blazed grating and varied line-space rectangular grating was made at the same conditions. The experimental results show that the diffraction intensity of varied line-space blazed grating is 1.7 times than varied line-space rectangular grating which is consistent with the result of calculation formula of diffraction intensity.
All-optical regeneration technologies in optical switching nodes
WU Bao-jian, WEN Feng, ZHOU Xing-yu, QIU Kun
2013, 34(4): 711-717.
Several schemes on all-optical signal regeneration in optical switching nodes are compared. The clock extraction experiments using fiber optical parametric oscillator (FOPO) and magneto-optical four-wave mixing (MO-FWM) 2R regeneration are analyzed. The principle of the idler-power-based feedback control technique to effectively enhance the stability of the FOPO for clock extraction is illustrated in terms of the experimental data. The power transfer characteristics of four FWM-based regeneration schemes are simulated and the MO-FWM-based regeneration experiment is implemented by using clock pump and idler filtering. It is shown that, the receiver sensitivity is further improved by 2 dB when the direct current (DC) magnetic field of 180 Gs is applied along the high nonlinear fiber. It is also pointed out that all-optical regeneration technologies trend to the evolution of multi-channel and integration from a long-term point of view.
Development of monitoring and early warning fiber sensor of water inrush from coal steam floor
NING Dian-yan
2013, 34(4): 718-721.
Aiming at the the special requirement of water inrush from coal steam floor monitoring and early warning system on stress sensor, according to the fiber Bragg grating sensing technology, the new fiber stress sensor is developed. The fundamental properties, service temperature range and fatigue durability of sensor system are tested. In 0 C ~ 40 C, the sensitivity coefficient of developed sensor is 1.23 pm/, the strain range is 1 000 , the transverse effect is 0.39 %, the mechanical hysteresis is 1.18 , the creep is 1.53 , the linearity is 0.13 %, the repeatability is 0.16 %, and the performance meets the design requirements. Results show that the new fiber sensor can fully satisfy the requirement of data acquisition of the real-time monitoring and early warring system under the condition of water inrush. Through the monitoring and early warring experiment on the mining face 9 028, the practicality and efficiency of new fiber sensor which used for the water inrush from coal steam floor monitoring and early warning system are able to be carried out within the range of 80 m from the monitoring points.