This PDF file contains the front matter associated with SPIE Proceedings Volume 10822 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

Optical communication technology has made great strides for several decades and various multiplexing technologies have been developed to greatly increase the communication capacity, such as time division multiplexing technology, wavelength division multiplexing technology, polarization division multiplexing (PDM) technology and mode division multiplexing technology (MDM), etc. The high-speed development of these multiplexing technologies motivate the demands for measurement of these optical parameters, such as mode, polarization and frequency. In this paper, we will review some research advances on the measured methods of mode distribution and polarization state of light in our group, including measurement of orbital angular momentum modes, linearly polarized modes and polarization modes. These works represent new progresses in spatial mode analysis and polarization analysis, showing great potential for applications in communication systems with MDM and PDM.

Aiming at fast detection speed and significant cost reduction, a photonic system exploring both wavelength- and time-division multiplexing is presented in this paper. The system is primarily consisted of a coherent dual electro-optical frequency comb which slices the broadband microwave spectrally in the optical domain, and an optical storage which snap-shots the input for later read-out. The proof-of-concept experimental setup measures a microwave burst of ~ 1 μs with up to 8 GHz bandwidth within 20 μs at ~ 1 MHz resolution, making the system especially attractive for a wide range of applications for microwave spectral analysis.

A real-time distributed acoustic sensing system with ten thousand channels is proposed to detect dynamic signal along the fiber. The phase-sensitive optical domain reflectometry and phase-generated carrier algorithm are used to acquire the phase information of Rayleigh backscattering along the whole fiber. The sensing length of this system could be 10km with the sample resolution of 0.4m, which means that up to 25000 channels signal processing is realized in real time with Field-Programmable Gate Array module and host computer. The working principle of coherent Rayleigh backscattering interference, phase-generated carrier algorithm and the signal processing flow are introduced, and the experimental results are given in this paper.

In this paper, a microwave photonic dual band radar based on a photonic-assisted de-chirp processing receiver is proposed. The dual band operation is realized independently and simultaneously with a single set of hardware. At a transmitter end, two linear frequency-modulated signals separately located in C-band and Ku-band are transmitted, echoes are collected and sent to a receiver to implement photonic-assisted de-chirp processing. At the receiver end, a main modulator with a special structure, which consists of four parallel sub-modulators, is employed. The echoes and reference signals of C-band and Ku-band are applied to two pairs of sub-modulators of the main modulator, which are biased at the peak points for C-band and biased at the null points for Ku-band. In this case, the intermediate frequency signals of C-band and Ku-band produced by de-chirp processing locate at two different frequencies. Thus operation in different bands based on a unified system is achieved. An experiment operating in C-band and Ku-band with a bandwidth of 700 MHz and 3600 MHz is conducted. The results verify the concept of the dual band radar and show the potential of photonic technology to improve the performance of modern radar system.

A Scanning Near-field Optical Microscope (SNOM) devoted to a commercial Environmental Scanning Electron Microscope (ESEM) is demonstrated in this paper. The system can be applied to biological samples and optoelectronic devices at the nanoscale to obtain their surface topography information and fluorescence spectroscopic information in situ. Optical microscopes can characterize function and material components by means of fluorescence spectroscopic technology. However, the spatial resolution of conventional optical microscopes is limited by the diffraction limit. Owing to fine surface topography information of the sample, a SNOM combined with environmental scanning electron microscopy can obtain fluorescence images and fine surface topography images simultaneously. An Atomic Force Microscope (AFM), which utilizes the same optical fiber probe with the SNOM, is added to the system. The fluorescence signal acquired by the SNOM and the surface topography signal acquired by the AFM have the same coordinate. The surface topography images of the AFM are matched to the surface topography images of the ESEM. Therefore, the fluorescence images are located to the ESEM images. A quartz tuning fork offers feedback signals to control the distance between the optical fiber probe and the samples. The samples are scanned by a high-precision scanner with 0.3 nm resolution in X and Y directions. Coase approach to samples and selection of scanning area are achieved by a micromanipulator. Quantum dots samples and polystyrene (PS) spheres samples are prepared, and their surface topography images and fluorescence images are obtained. The spatial resolution of the SNOM applied to the commercial ESEM is less than 100 nm.

Photonic enabled RF self-interference cancellation for full-duplex communication by using phase modulation and optical sideband filtering is proposed. Based on the inherent out-of-phase property between the left and right sidebands of phasemodulated signal and optical sideband filtering, the RF self-interference cancellation is achieved by tuning the delay time and amplitude in the optical domain. The operational principle of the proposed scheme is theoretically analyzed and the feasibility is experimentally demonstrated. The optical sideband filtering for the phase modulated signals is measured and the RF self-interference cancellation at different carrier frequencies is studied. The results show a good performance of the proposed photonic scheme for RF self-interference cancellation. The full-duplex communication based on the photonic enabled RF self-interference cancellation is also investigated.

High-quality microwave generation and frequency up-conversion are demonstrated utilizing a photonic integrated two-section DFB laser. Both the DFB lasers are fabricated by the reconstruction-equivalent-chirp (REC) technique. We acquire microwave signals by optical heterodyne. High-quality microwave signal can be generated by the optical injection locking technique with low phase noise of -96.3 dBc/Hz at 10-kHz and narrow linewidth of a few kHz level. Besides, Frequency-doubled and frequency-quadrupled signals are achieved respectively.

We propose an optical frequency comb (OFC) generator for ultra-flat and multiple frequency-spaced OFC. By appropriately set the amplitude and phase of radio frequency (RF) signals fed to the parallel phase modulators, an ultraflat OFC with multiple frequency spacing can be generated. Since the frequency spacing of the generated OFC can be multiplied, it can be much larger than the typical modulation bandwidth of electro-optic modulators. Previously reported ultra-flat and multiple frequency-spaced OFC generators suffer from complex and invalid configuration since they employed either more than one-stage modulators or single-stage modulators attached with other components such as optical switches, which suffer from light leakage and limited extinction ratio in practice. Compared with previously reported method, Our scheme has much simpler configuration since only single-stage parallel modulators are used. The operating conditions for generation of multiple frequency spacing and spectrum flattening are clarified. The concept is verified in numerical analysis for generation of N×25GHz-spaced OFC. Performance analysis of the proposed scheme is also investigated.

This paper focuses the data processing and then the multi-class classification of suspended particles using a new polarized light measurement scheme. Detection of multidimensional polarization parameters keeps the advantages of fast detection speed and non-invasive local analysis of light scattering method, and increases the information dimension of the analyzed particles. However, the polarization indices are numerous and interrelated. It is difficult to complete classification prediction by a few specific indices. More advanced algorithms are needed. In our research, we selected six kinds of representative particles and three typical machine learning algorithms. k-NN, Neural network and SVM methods were used to construct the classification models and solve different classification tasks. By comparison, we evaluated these models in terms of their performance for classification tasks in different aspects. Furthermore, we discuss how to improve the models by feature selection, and a rough prediction of the capability of each polarization index to reflect the particulate features was made.

A tunable self-mixing chaotic laser based on high frequency electro-optical modulation is proposed. A laser dynamics system is designed and tested for tunable chaotic laser generation and provides optical feedback and electro-optic modulation with two degrees of freedom. The chaotic laser is generated by optical feedback, and it becomes tunable by high frequency electro-optic modulation. The frequency is modulated from 0 to 6 GHz to test this system, and the spectrum of the chaotic laser is obtained with an electrical spectrum analyzer (ESA). The experimental results show the generation of a wide range of tunable chaotic lasers via electro-optic modulation. At the same time, this tunable chaotic laser has a highly sensitive dynamic response, free regulation, and wide band via adjustments in the feedback intensity and the modulation signal, and this system is proved to be suitable for applications in high-speed broadband communication and sensing.

Auto-focus is a common function in consumer digital cameras and smart phones, but less applied into stereo microscopes, which often require repeated manual focusing to obtain a clear image. To be less time-consuming and labor-consuming during focusing operation with stereo microscopes, this paper presents a real-time and feasible continuous auto-focus algorithm. Firstly, a direction decision method is proposed to determine the beginning direction of motor for sensor moving. Secondly, an auto-focus search algorithm is improved to find the best focus position. Thirdly, in order to guarantee higher efficiency and accuracy of motor movement, an adaptive step size method is introduced to optimize the value of focus objective function. Lastly, to meet the need of continuous auto-focus, an auto-focus monitoring algorithm utilizing a finite-state-machine model is proposed to determine when to refocus and enhance the stability and responsiveness of auto-focus system. This approach has been implemented on the prototype of our stereo microscope camera to verify the auto-focus performance. Experimental results show that the proposed auto-focus algorithm can almost resist the interference in the focusing process, and achieve a good balance between accuracy and efficiency.

A Ka-band microwave photonic imaging radar demonstrator with 10.02 GHz-bandwidth is proposed and experimentally demonstrated. Continuous linear frequency waveform is optically generated in the transmitter and processed in the receiver. The range resolution of the demonstrator is tested to be 1.68 cm. Out-field tests while demonstrator works at inverse synthetic aperture radar (ISAR) and synthetic aperture radar (SAR) mode are carried out to image different targets.

Dual-comb spectroscopy is an emerging spectral detection technology with high resolution, high sensitivity, broad bandwidth and fast detection speed. By using a pair of coherent optical frequency combs, asynchronous light sampling is realized and pico-scale theoretical resolution can be achieved without mechanical scanning components. However, coherence between dual combs suffers from the frequency jitter, which causes distortion of spectral information. Furthermore, since jitter noise components in the experiment are complex, widely sourced, and difficult to control. It is impractical to study the effects of a specific jitter noise and observe how jitter correction algorithm works through an actual dual-comb spectroscopy experimental system. To solve this problem, a simulation method is proposed for dualcomb spectroscopy with jitter noise to verify the effectiveness of data processing algorithm. Two Gaussian random jitter sequence with a standard deviation of 0.16fs are generated as time jitter for dual-comb spectroscopy simulation system. The simulation results show that the time jitter causes the calculated spectral center wavelength δν to have a random jitter of standard deviation of ~40GHz. The time-domain averaging method and the frequency-domain averaging method are applied to the data obtained from the simulation system. Through 100 time-domain averaging, there is no visible compensation effect on the deviation of calculated spectral center wavelength, and the SNR becomes worse as the average number increases. On the contrary, 100 frequency-domain averaging reduces the standard deviation of the spectral center wavelength deviation to ~2.6GHz and can obtain 10 times the SNR of 100 time-domain averaging.

In this paper, a Sagnac interferometer with polarization maintaining fiber (PMF) for vector transversal loading measurement has been proposed and experimentally demonstrated. The light propagated in different axes of the PMF has different velocity because of fiber birefringence, which results in phase difference, and thus interferometer pattern is produced. When the birefringence parameters are affected by transversal loading, the phase difference of the light propagating in different axes will change, and as a result of the interferometer pattern of the Sagnac loop shifts. When transversal loading with the opposite direction is applied on the sensing fiber, the interferometer pattern also shifts, but oppositely to longer or shorter wavelength, by monitoring which vector transversal loading measurement can be achieved. The sensing characteristics when transversal loading is applied in different angles have also been studied. The proposed measurement method has a simple structure, and is easy to implement, which shows a good application prospects in the sensing field.

This paper proposed a fast human action recognition algorithm which utilized two features that can be described as iconic posture and fast moving. At first, a human detection algorithm is used to detect human object in every frame. Then regions marked as human are sent into a trained deep classification network to match trained iconic postures in key frame. Then several frames before key frame and after key frame are examined by frame differences, which are used to compensate background movement and perform human motion speed judgment. After the key frame pinning and speed judgment, the final recognition results are determined.

Pedestrian detection is the major task of many infrared surveillance system. Due to the technical limitation of sensor or the high cost of advanced hardware, the resolution of infrared images is usually low, which is not capable of meeting the high quality requirement of various applications. Compressed sensing capturing and represents compressible signals at a sample rate significantly below the Nyquist rate, is considered as a new framework for signal reconstruction based on the sparsity and compressibility. Thus, the compressed sensing theory enlightens a computational way to reconstruct a high resolution image on the basis of a sparse signal, i.e. the low resolution image. The proposed method use low resolution and high resolution infrared pedestrian images to train an over-complete dictionary through K-SVD algorithm, by which the pedestrian are sparsely well-represented. Two distant infrared cameras in the same scene are used to capture high and low resolution image to make sure same pedestrian pair is sparsely represented under the over-complete dictionary. Therefore the similarities are learning between input low resolution image patches and high resolution image patches. The popular greedy algorithm Orthogonal Matching Pursuit (OMP) is utilized for sparse reconstruction, providing optimal performance and guaranteeing less computational cost and storage. We evaluate the quality of reconstructed image employing root mean square error and peak signal to noise. The experimental results show that the reconstructed images preserve wealthy detailed information of pedestrian, and have low RMSE and high PSNR, which are superior to the traditional super-resolution methodologies.

Abstract-In digital coherent optical receivers for various polarization-multiplexed high-order modulation formats such as BPSK、QPSK、8PSK and 16QAM signals, we propose and investigate a blind modulation format recognition method using the Chinese Restaurant Process, a kind of Dirichlet model, which is based on the observation of samples in Stokes space. The recognition rates of different number of data points under different optical signal-to-noise ratios (OSNRs) are investigated in detail for four modulation formats. In addition, the recognition characteristics of the proposed method are compared with other format recognition methods in Stokes space. It is shown that the approach has a better performance with higher recognition rates, particularly under a lower OSNR.