Journals >Chinese Optics Letters
Contents
2007
Volume: 5 Issue 2
20 Article(s)
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Research Article
Performance evaluation for 160-Gb/s optical phase conjugation systems considering dispersion mapping and third-order dispersion
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The impact of third-order dispersion (TOD) is investigated by numerical simulations in 160-Gb/s single-channel systems incorporated with dispersion mapping and optical phase conjugation (OPC). System performances using retrun-to-zero (RZ) or carrier-suppressed RZ (CSRZ) modulation format are evaluated on the optimized The impact of third-order dispersion (TOD) is investigated by numerical simulations in 160-Gb/s single-channel systems incorporated with dispersion mapping and optical phase conjugation (OPC). System performances using retrun-to-zero (RZ) or carrier-suppressed RZ (CSRZ) modulation format are evaluated on the optimized dispersion map. The results indicate that even though TOD has been fully compensated, the intra-channel nonlinearity induced by local TOD would degrade the system performance in nonlinear regime. The scheme with an optimized dispersion map provides a much higher performance and offers a larger tolerance on a variation of pre-compensation. CSRZ modulation format is more robust due to its tradeoff between tolerances on intra-channel nonlinearity and dispersion..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 2, 63 (2007)
A novel time-to-live countdown scheme based on asymmetric Mach-Zehnder interferometer and Fabry-Perot semiconductor optical amplifier
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We propose a novel optical time-to-live (TTL) processing scheme using asymmetric Mech-Zehnder interferometer (AMZI) and Fabry-Perot semiconductor optical amplifier (FP-SOA). AMZI transfers M TTL pulses into M-1 pulses and two residual pulses with 6-dB power difference. FP-SOA enhances the power difference between the MWe propose a novel optical time-to-live (TTL) processing scheme using asymmetric Mech-Zehnder interferometer (AMZI) and Fabry-Perot semiconductor optical amplifier (FP-SOA). AMZI transfers M TTL pulses into M-1 pulses and two residual pulses with 6-dB power difference. FP-SOA enhances the power difference between the M-1 pulses to the residual pulses to more than 10 dB. A numerical model is established for verifying the feasibility of this scheme..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 2, 66 (2007)
Generation of modified duobinary return-to-zero format using polarization-maintaining fiber loop mirror
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Modified duobinary return-to-zero (MD-RZ) format is an improvement of optical duobinary (ODB) format. This paper proposes a novel, all-optical method to generate MD-RZ format by using a polarization maintaining fiber loop mirror (PMFLM). Operation principle for all-optical format conversion is theoretically analyzed anModified duobinary return-to-zero (MD-RZ) format is an improvement of optical duobinary (ODB) format. This paper proposes a novel, all-optical method to generate MD-RZ format by using a polarization maintaining fiber loop mirror (PMFLM). Operation principle for all-optical format conversion is theoretically analyzed and the output spectrum is simulated. 40-Gb/s MD-RZ data format generation is experimentally demonstrated..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 2, 69 (2007)
Focal depth extending using rotational symmetric pupil masks
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Optical systems are analyzed with three kinds of rotational symmetric pupil masks: annular Gaussian ring mask, supergaussian ring mask, and quartic phase mask. In these masks, the quartic phase mask is found to be the best one to extend focal depth. Point spread function (PSF) and Strehl ratio (SR) are used to evaluateOptical systems are analyzed with three kinds of rotational symmetric pupil masks: annular Gaussian ring mask, supergaussian ring mask, and quartic phase mask. In these masks, the quartic phase mask is found to be the best one to extend focal depth. Point spread function (PSF) and Strehl ratio (SR) are used to evaluate the imaging quality of the system with different defocus parameters. Without decoding needed, the focal depth of the system with quartic phase mask is four times as deep as aberration-free system. Different from the others, it suffers no obvious loss in the light throughput and lateral resolution. With twice focal depth extension, supergaussian ring mask suffers less loss in light throughput and lateral resolution than annular Gaussian ring mask..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 2, 71 (2007)
A new adaptive nonuniformity correction algorithm for infrared line scanner based on neural networks
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The striping pattern nonuniformity of the infrared line scanner (IRLS) severely limits the system performance. An adaptive nonuniformity correction (NUC) algorithm for IRLS using neural network is proposed. It uses a one-dimensional median filter to generate ideal output of network and can complete NUC by a single framThe striping pattern nonuniformity of the infrared line scanner (IRLS) severely limits the system performance. An adaptive nonuniformity correction (NUC) algorithm for IRLS using neural network is proposed. It uses a one-dimensional median filter to generate ideal output of network and can complete NUC by a single frame with a high correction level. Applications to both simulated and real infrared images show that the algorithm can obtain a satisfactory result with low complexity, no need of scene diversity or global motion between consecutive frames. It has the potential to realize real-time hardware-based applications..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 2, 74 (2007)
Image edge detection based on adaptive weighted morphology
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A novel morphological edge detector based on adaptive weighted morphological operators is presented. It judges image edge and direction by adaptive weighted morphological structuring elements (SEs). If the edge direction exists, a big weight factor in SE is put; if it does not exist, a small weight factor in SE is put.A novel morphological edge detector based on adaptive weighted morphological operators is presented. It judges image edge and direction by adaptive weighted morphological structuring elements (SEs). If the edge direction exists, a big weight factor in SE is put; if it does not exist, a small weight factor in SE is put. Thus we can achieve an intensified edge detector. Experimental results prove that the new operator's performance dominates those of classical operators for images in edge detection, and obtains superbly detail edges..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 2, 77 (2007)
An improved computing method for the image edge detection
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The framework of detecting the image edge based on the sub-pixel multi-fractal measure (SPMM) is presented. The measure is defined, which gives the sub-pixel local distribution of the image gradient. The more precise singularity exponent of every pixel can be obtained by performing the SPMM analysis on the image. UsingThe framework of detecting the image edge based on the sub-pixel multi-fractal measure (SPMM) is presented. The measure is defined, which gives the sub-pixel local distribution of the image gradient. The more precise singularity exponent of every pixel can be obtained by performing the SPMM analysis on the image. Using the singularity exponents and the multi-fractal spectrum of the image, the image can be segmented into a series of sets with different singularity exponents, thus the image edge can be detected automatically and easily. The simulation results show that the SPMM has higher quality factor in the image edge detection..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 2, 79 (2007)
Two image denoising approaches based on wavelet neural network and particle swarm optimization
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Two image denoising approaches based on wavelet neural network (WNN) optimized by particle swarm optimization (PSO) are proposed. The noisy image is filtered by the modified median filtering (MMF). Feature values are extracted based on the MMF and then normalized in order to avoid data scattering. In approach 1, WNN isTwo image denoising approaches based on wavelet neural network (WNN) optimized by particle swarm optimization (PSO) are proposed. The noisy image is filtered by the modified median filtering (MMF). Feature values are extracted based on the MMF and then normalized in order to avoid data scattering. In approach 1, WNN is used to tell those uncorrupted but filtered by MMF and then the pixels are restored to their original values while other pixels will retain. In approach 2, WNN distinguishes the corrupted pixels and then these pixels are replaced by MMF results while other pixels retain. WNN can be seen as a classifier to distinguish the corrupted or uncorrupted pixels from others in both approaches. PSO is adopted to optimize and train the WNN for its low requirements and easy employment. Experiments have shown that in terms of peak signal-to-noise ratio (PSNR) and subjective image quality, both proposed approaches are superior to traditional median filtering..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 2, 82 (2007)
Modulation properties of spatial three-waveguide system using weakly coupled mode theory
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Based on the weakly coupled mode theory, the modulation properties of three-waveguide system are analyzed in general. We examine the modulation behavior for two cases that a voltage is applied on the beam-launched waveguide or non-beam-launched waveguide. The analytical intensity distributions in both cases are given. Based on the weakly coupled mode theory, the modulation properties of three-waveguide system are analyzed in general. We examine the modulation behavior for two cases that a voltage is applied on the beam-launched waveguide or non-beam-launched waveguide. The analytical intensity distributions in both cases are given. Applications of the spatial multi-waveguide coupling systems include spatial light modulators, optical switches, optical interconnection, and spatial optical signal processing..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 2, 86 (2007)
Generation and application of the twisted beam with orbital angular momentum
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The twisted Laguerre-Gaussian beam was generated by transforming of Hermite-Gaussian beams through an optical system consisting of three rotated cylindrical lenses. The intensity distribution and phase structure of the twisted hollow beam were theoretically analyzed by using Collins diffraction integral. By utilizing tThe twisted Laguerre-Gaussian beam was generated by transforming of Hermite-Gaussian beams through an optical system consisting of three rotated cylindrical lenses. The intensity distribution and phase structure of the twisted hollow beam were theoretically analyzed by using Collins diffraction integral. By utilizing the method of mode decomposition, the theory of transformation was analyzed. In the experiment, micro particles were trapped and rotated by this twisted beam..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 2, 89 (2007)
High-peak-power, high-repetition-rate intracavity optical parametric oscillator at 1.57 microns
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We report a high-peak-power, high-repetition-rate diode-side-pumped Nd:YAG Q-switched intracavity optical parametric oscillator (IOPO) at 1.57 microns with a type-II non-critically phase-matched x-cut KTP crystal. The average power of 1.15 W at 1.57 microns is obtained at 4.3-kHz repetition rate. The peak power of the We report a high-peak-power, high-repetition-rate diode-side-pumped Nd:YAG Q-switched intracavity optical parametric oscillator (IOPO) at 1.57 microns with a type-II non-critically phase-matched x-cut KTP crystal. The average power of 1.15 W at 1.57 microns is obtained at 4.3-kHz repetition rate. The peak power of the pulses amounts to 33.4 kW with 8-ns duration. The average conversion efficiency from Q-switched 1.064-micron-wavelength input power to OPO signal output power is up to 10.5%..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 2, 93 (2007)
Injection-switchable erbium-doped fiber laser with two output ports
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An injection-switchable erbium-doped fiber laser (EDFL) with two output ports based on a ring structure is proposed. Wavelength switching together with the switching of the dominating output port of the fiber laser is achieved by controlling the power of a tunable injection laser. The characteristics of the wavelength An injection-switchable erbium-doped fiber laser (EDFL) with two output ports based on a ring structure is proposed. Wavelength switching together with the switching of the dominating output port of the fiber laser is achieved by controlling the power of a tunable injection laser. The characteristics of the wavelength switching for different levels of the pump laser power and different wavelengths of the injection laser are studied experimentally..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 2, 96 (2007)
Demonstration of fiber pulsed light source at 1.6 microns with adjustable pulse duration
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A novel practical 1.66-micron pulse light source with adjustable pulse duration is proposed. A 2.5-km Raman fiber is placed into a ring type Q-switched erbium-doped fiber laser (Q-EDFL), serving as both delay line fiber and Raman gain medium so that in addition to the wavelength shifted to 1.6 microns, the pulse duratiA novel practical 1.66-micron pulse light source with adjustable pulse duration is proposed. A 2.5-km Raman fiber is placed into a ring type Q-switched erbium-doped fiber laser (Q-EDFL), serving as both delay line fiber and Raman gain medium so that in addition to the wavelength shifted to 1.6 microns, the pulse duration and the buildup time can be relatively extended. By properly controlling the fall edge of the acousto-optic switch (AOS), the pulse duration of 30-345 ns for ~770-Hz repetition frequency with power of 1-1.6 W is achieved..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 2, 99 (2007)
Theoretical analysis of backscattered polarization patterns of turbid media containing glucose
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Single scattering model and Stokes-Mueller formalism are introduced to investigate the influence of glucose on backscattered polarization patterns in turbid media. Glucose molecules rotate the polarization plane and induce changes in backscattered Mueller matrix patterns. Some Mueller matrix elements present higher optSingle scattering model and Stokes-Mueller formalism are introduced to investigate the influence of glucose on backscattered polarization patterns in turbid media. Glucose molecules rotate the polarization plane and induce changes in backscattered Mueller matrix patterns. Some Mueller matrix elements present higher optical rotation as the concentration of glucose augments. Using image subtraction and integration, linear relationship between low glucose concentration in the physiological range and optical rotation degree can be derived..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 2, 102 (2007)
Raman spectroscopy of Chinese human skin in vivo
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A novel and compact near-infrared (NIR) Raman system is developed using 785-nm diode laser, volume-phase technology (VPT) holographic system, and NIR intensified charge-coupled device (CCD). Signal-to-noise ratio (SNR) and resolution are improved compared with ordinary acquisition method by a specially designed opticalA novel and compact near-infrared (NIR) Raman system is developed using 785-nm diode laser, volume-phase technology (VPT) holographic system, and NIR intensified charge-coupled device (CCD). Signal-to-noise ratio (SNR) and resolution are improved compared with ordinary acquisition method by a specially designed optical fiber detector and the spectrograph image aberration correction with a parabolic-line fiber array. In 1-5 s, Raman spectra of different parts of Chinese human skin are acquired. Autofluorescence is subtracted from the raw spectrum by polynomial fitting and skin Raman spectrum is then smoothed for further analysis..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 2, 105 (2007)
Research on refractive index of optical cement used in Glan-Thompson prisms
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The influence of the refractive index n2 of optical cement on the structure angle, field angle, and transmission of Glan-Thompson prism has been studied in detail. The results show that the structure angle will increase with the decrease of n2 under the condition of the largest field angle. Thus, the ratio of length toThe influence of the refractive index n2 of optical cement on the structure angle, field angle, and transmission of Glan-Thompson prism has been studied in detail. The results show that the structure angle will increase with the decrease of n2 under the condition of the largest field angle. Thus, the ratio of length to width (L/A) of the prism will decrease, which means more materials can be saved. When the value of L/A is 3.0 or 2.5 in the routine design, the field angle will firstly increase and then decrease with the increment of n2. Two routine designs with the n2 values of 1.47 and 1.45 have the optimal field angle. In addition, n2 also has great influence on light intensity transmittance of the prism. Considering all these factors, it will be the best choice with L/A=2.5 and n2=1.45-1.46..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 2, 108 (2007)
Multi-impurity effects on the entanglement of anisotropic Heisenberg ring XXZ under a homogeneous magnetic field
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The effects of multi-impurity on the entanglement of anisotropic Heisenberg ring XXZ under a homogeneous magnetic field are studied. The impurities make the equal pairwise entanglement in a ring compete with each other so that the pairwise entanglement exhibits oscillation. If the impurities are of larger couplings, boThe effects of multi-impurity on the entanglement of anisotropic Heisenberg ring XXZ under a homogeneous magnetic field are studied. The impurities make the equal pairwise entanglement in a ring compete with each other so that the pairwise entanglement exhibits oscillation. If the impurities are of larger couplings, both the critical temperature and pairwise entanglement can be improved..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 2, 111 (2007)
Effects of spacing on dynamics of two coupled Bose-Einstein condensates in two finite traps
D. N. Wang
Interaction between two coupled Bose-Einstein condensates (BECs) is investigated by the variational approach in two finite traps, and the effects of the spacing between the two traps on dynamics of the two BECs are analyzed. The spacing determines the stable condition of stationary states, affects the existence conditiInteraction between two coupled Bose-Einstein condensates (BECs) is investigated by the variational approach in two finite traps, and the effects of the spacing between the two traps on dynamics of the two BECs are analyzed. The spacing determines the stable condition of stationary states, affects the existence condition of each BEC, and changes the switching and self-trapping effects on the two BECs. The dynamic mechanism is demonstrated by performing a coordinate of classical particle moving in an effective potential field, and confirmed by the evolution of the atom population transferring ratio..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 2, 114 (2007)
Correlation recognition for range image of laser radar
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The target recognition of laser radar becomes hot research in recent years, because laser radar can produce high space resolution and collect rich target information, such as range image, intensity image and Doppler image. In the vertical detection of laser radar, the problem of in-plane target rotation invariance is fThe target recognition of laser radar becomes hot research in recent years, because laser radar can produce high space resolution and collect rich target information, such as range image, intensity image and Doppler image. In the vertical detection of laser radar, the problem of in-plane target rotation invariance is firstly solved. In the paper, a new support vector machine (SVM) correlation filter is presented, which simultaneously has the attractive attributes of SVM and common correlation filter. Exploiting the idea of margin of separation maximization, the design criterion is produced. The filter is synthetic by the multiple training images which are generated by rotating one image. The real range images of laser radar are used to finish the correlation experiments. The results show that the filter is not sensitive to the noise, the correlation peak is changed slightly for the different testing images, and the precision of location is high. This design way can be used in other recognition fields..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 2, 118 (2007)
Fiber-distributed multi-channel open-path H2S sensor based on tunable diode laser absorption spectroscopy
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Tunable diode laser based gas detectors are now being used in a wide variety of applications for safety and environmental interest. A fiber-distributed multi-channel open-path H2S sensor based on tunable diode laser absorption spectroscopy (TDLAS) is developed, the laser used is a telecommunication near infrared distriTunable diode laser based gas detectors are now being used in a wide variety of applications for safety and environmental interest. A fiber-distributed multi-channel open-path H2S sensor based on tunable diode laser absorption spectroscopy (TDLAS) is developed, the laser used is a telecommunication near infrared distributed feed-back (DFB) tunable diode laser, combining with wavelength modulation spectroscopy technology, a detection limit of 20 ppm.m is demonstrated. Multi-channel detection is achieved by combining optical fiber technique. An on-board reference cell provides on-line sensor calibration and almost maintenance-free operation. The sensor is suitable for large area field H2S monitoring application..
Chinese Optics Letters
- Publication Date: Jan. 01, 1900
- Vol. 5, Issue 2, 121 (2007)
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