This PDF file contains the front matter associated with SPIE Proceedings Volume 9619 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

Multiple-pulse generation is often achieved in a passively mode-locked fiber laser when the mode-locking mechanisms are overdriven. Under certain circumstances, passively harmonic mode-locking (HML) and bound state of multiple pulses can also be observed. In this paper, a three-state switchable dissipative soliton (DS) mode-locked fiber laser based on a semiconductor saturable absorber mirror (SESAM) has been experimentally demonstrated for the first time. With a pump power of ~175 mW, operation states of multiple pulses (two pulses), 2^nd-order HML and bound state of two DSs were observed by only adjusting the polarization controller (PC) inside the cavity. At a higher pump power level (~276 mW), operation states of multiple pulses (three pulses), 3^rd-order HML and bound state of three DSs were observed by changing the state of the PC. From the experimental results, it seems that there is a correlative relationship among the three operation states (N pulses/Nth-order HML/ bound state of N pulses) for the DS fiber laser and these states are switchable by only adjusting the cavity birefringence with a PC under the same pump power level.

We proposed a scheme of optical frequency modulated continuous wave (OFMCW) system based on the polarization diversity heterodyne receiver (PDHR) with a frequency swept distributed feedback (DFB) laser. The adoption of PDHR in OFMCW system successfully reduced the polarization-induced fading and improved the signal to noise ratio (SNR). High-sensitivity OFMCW system is achieved, which has spatial resolution of 1.5 mm for distance of 1.5 km.

Wireless laser power supply to long-distance devices is drawing more and more interest in recent years. As power receivers, laser cells are adhered on these devices. Relatively high laser cell efficiency could be obtained under a monochromatic illumination. In order to study the most efficient laser illumination conditions to the laser cell, the efficiencies of circular and rectangular cells illuminated by laser with fundamental mode are compared. The simulations show that the cell efficiency increases slowly with the increase of the laser power, and decreases with the increase of the spot size. When the rectangular cell and the circular cell have the same area, and the diameter of the circular cell and that of the laser spot are equal, the efficiency of the circular cell is higher than the rectangular cell.

We study the limitation of electrical bandwidth in QPSK optical coherent receiver with decision-aided maximum likelihood (DAML) carrier phase estimation. Before signal sampling, a low-pass rectangular filter is utilized to model the bandwidth limitation of electronic devices in the receiver. On one hand the limited bandwidth can reduce the power of additive noise, on the other hand it would distort the signal since inter-symbol interference (ISI) between adjacent symbols occurs. In this paper we discuss the effects on signal amplitude and phase caused by ISI and find original distribution of QPSK constellation points will shift due to ISI. When adjacent symbol interference, that is, the ISI effect of one previous symbol, is taken into account, the distribution changes into the form of 16-QAM, while changing as 4K+1-QAM if K previous symbols are considered. The impact on the subsequent DAML algorithm and the final bit error rate (BER) calculation due to constellation points shifts are analyzed intensively. Monte-Carlo (MC) simulation results show that 0.7 to 0.9 times symbol rate is a reasonable bandwidth range for different optical signal to noise ratios (OSNRs), and optimum bandwidth is often inside this range. Results also reveal that filter-induced ISI would degrade the BER performance of DAML receiver when OSNR is over 10 dB.

A novel integrable optical analog-to-digital converter (OADC) scheme based on phase-shifted optical quantization has been proposed for years, the quantization module of which is mainly composed of a 1×2 multi-mode interference (MMI) coupler, a phase modulator and a 4×4MMI. Although the manufacture technology of 1×2 MMI and phase modulator has been very mature, the 4×4MMI on a silicon-on-insulator (SOI) substrate with superior performance has not been realized. Since the 4×4MMI is crucial for the realization of the OADC, we designed and fabricated a 4×4 MMI coupler on SOI substrate. The width and length of the multi-mode section are 10.2 um and 182.6 um respectively. Measurement results show that the imbalance of the four output ports at 1550-nm is around 1.9 dB, while the insertion losses are 5.6 dB.

In coherent optical phase-shift-keying (PSK) system, the conventional decision-aided maximum likelihood (DA-ML) phase estimator only considers constant phase noise over the entire observation interval. In this paper, we take into account the time-varying phase noise and propose a flexible DA-ML phase estimator for carrier phase estimation. The weighted coefficients are introduced to estimate carrier phase more accurately than the conventional scheme. The phase estimation error of this flexible DA-ML receiver is analyzed and compared with results from the conventional DA-ML receiver. The analytical bit error rate (BER) follows well with Monte Carlo (MC) simulations. Simulation results also show that by using the flexible DA-ML receiver in quadrature PSK (QPSK) system, bit signal-to-noise ratio (SNR) improvement over the conventional DA-ML receiver at BER of 10^-3 is 0.2dB and 1.2dB with block length of 20 and 50, respectively, when the laser linewidth is 2MHz.

A flexible atmospheric turbulence simulator based on spatial light modulator is investigated experimentally. Phase screens generated by Fourier Transform method are used in the proposed scheme. The effect of time-varying atmospheric turbulence with different strength is successfully demonstrated. The far-field intensity and received optical power of Gauss-shaped laser beam under relatively weak, moderate and strong atmospheric turbulence are measured. Experiments show that atmospheric turbulence will cause the distortion of far-field intensity distribution and fluctuation of received optical power.

Phase error compensation is necessity for high resolution optical frequency modulated continuous wave (OFMCW). In the phase error compensation of OFMCW, the precise measurement of laser source phase is the most significant. In this paper, we proposed a phase-smooth unwrapping algorithm to settle the issue of phase leap over 2π, thus could restore precisely the real phase of laser source, then could compensated the phase error in OFMCW. With that method, OFMCW's resolution could be promoted to 0.5 mm at over 200 m.

Optical frequency domain reflectometry is a suitable and promising measurement technique for optical network components characterization; however its performance is severely limited by sweep nonlinearity of the laser chirp. We demonstrate precise linearization of broadband optical frequency chirp using optoelectronic feedback loop. The sweep rate and the laser chirp shape is locked to and determined by the frequency of a reference electronic signal, an agile, high coherence swept-frequency semiconductor laser source with a bandwidth of 66GHz in 100ms is achieved. The laser source is applied to a coherent optical frequency domain reflectometry; a transform-limited spatial resolution of 1.5mm at a distance of 200 meters is demonstrated.

Quantum key distribution can be used to share secret keys with information-theoretic security between two legitimate partners for secure communication. In the case of satellite communication, free-space channel is the only way to transmit information, thus research on its properties is of great significance to quantum cryptographic communication. In this paper, we thoroughly analyze the influence of free-space channel fading effects on continuous variable quantum key distribution and for the first time prove that random distribution (such as Rayleigh distribution, Rice distribution and et al.) of free-space channel fading coefficients can be used to increase secret information rates and improve system stability against excess noises. Our results offer academic reference for practical applications of ground-space and space-space quantum communication and global quantum communication network.

We demonstrate a stable coherent dual comb generator with two phase/intensity-modulated combs. The optical fiber path induced phase fluctuation results in the coherent dual comb beating phase noise. We transfer this phase noise to a 40MHz intermediate frequency with dual-heterodyne phase error transfer, decreasing by a phase-locked loop and optical phase locked loop. Under the scheme, stable coherent dual comb with slightly different repetition rates and offset frequency is generated.

The performance of satellite-to-ground laser communication is affected by the atmospheric environment seriously, so it is a key issue for system design and operation to analyze the link availability quantitatively according to the channel characteristics. Firstly, the basic concept of laser communication link availability is put forward. Secondly, the preliminary theory model and calculation method of geostationary satellite-to-ground laser communication link availability are established by analyzing influencing factors. Lastly, the link availability of 77°E GEO satellite-to-ground laser communication is analyzed, combining with the atmospheric statistics data of typical optical ground stations in China. The results show that, it is feasible to achieve more than 90% joint link availability by implementing two stations, or to achieve more than 95% joint link availability by implementing three stations.

Indoor Visible Light Communication (VLC) positioning is an new indoor positioning method. We discuss the method to realize 3D positioning and the how to optimize it. Build a simplified 3D fingerprint database in the condition of linear light intensity attenuation model and use it for 3D positioning. Furthermore we combined fingerprint database method with the iterative algorithm of Lambert distribution to calculate Z coordinates in order to improve the accuracy. Simulations shows that, in the subspace of 1m*1m*1m, the measurement error of fingerprint database method in X-Y plane is 4.1cm, while z direction measurement error is 5.4cm. By contrast, measurement error of 3D positioning method based on iterative algorithm reduces by 10%.

Various methods of nonlinearity estimation have been proposed. The Gaussian Noise model(GN model) is one of the most important methods which estimate the nonlinear noise in frequency domain. One of the defects of the GN model is that this model assumes that the signal transmitted into the transmission fiber is Gaussian distributed. Many signals don’t meet this assumption for different baud rates, modulation formats and pulse shapes. The Gaussian distribution of the signal can't be visualized before the proposing of Gaussian Fitting Error.

In this paper, we simulate different modulation formats(QPSK and 16QAM), different channel space (37.5 GHz and 50GHz), different pulse shapes (RZ and NRZ) and different fiber types (SMF and NZDSF). The histograms under different conditions will be used to calculate the Gaussian Fitting Error. Then proper amount of pre-dispersion is added before transmission to lower the Gaussian Fitting Error.

The results show that without pre-dispersion, the analytical simulation approximation for the GN-Model nonlinear interference power spectral density is obviously not precise under the given conditions. Different modulation formats also affect the model’s accuracy. The model goes well with different modulation format in Nyquist systems. While for non-Nyquist systems, the model is applicable only under certain conditions.

Our results suggest that the GN model is reliable when the Gaussian Fitting Error of the signal is low enough. The amount of pre-dispersion is not fixed. The Gaussian Fitting Error should be used to judge the precision of the amount of pre-dispersion to get the optimal result.

We have demonstrated an optical generation of highly stable millimeter-wave signal distribution system, which transfers a 300GHz signal to two remote ends over different optical fiber links for signal stability comparison. The transmission delay variations of each fiber link caused by temperature and mechanical perturbations are compensated by high-precise phase-correction system. The residual phase noise between two remote end signals is detected by dual-heterodyne phase error transfer and reaches -46dBc/Hz at 1 Hz frequency offset from the carrier. The relative instability is 8×10^-17 at 1000s averaging time.

Polarization-division-multiplexed(PDM) optical coherent systems is considered a promising technique for next generation optical networks. With coherent detection, various impairments in the optical transmission system can be compensated by using digital signal processing (DSP) in the electrical domain. Constant modulus algorithm (CMA), due to its simplicity and immunity to phase noise, has been widely used to demultiplex polarizations and compensate received signals. On the other hand, CMA suffers from the singularity problem which results from Polarization- Dependent-Loss (PDL) and the less sensitivity in phase of CMA. Although many people have researched the singularity problem of CMA both in theory and experiments (modify CMA to avoid singularity problem), their theoretical channel model only contains fiber birefringence and does not consider the situation of multistage channel model which is used in long distance transmission system. Then we analyse the performance of CMA in the channel with multistage channel model through simulation. We change the initial tap of the traditional CMA which can achieve correct polarization demultiplexing without singularity in one stage channel model. But it is not very suitable in multistage channel model. We analysed singularity ratio in long distance transmission system. The simulation results play an active role in following research on singularity problem and the performance of CMA.

Optical receiving antenna is usually positioned before the detector of an indoor visible light communication (VLC) system in order to collect more optical energy into the detector. Besides optical gain of the antenna, the field of view (FOV) plays also an important role to the performance of a VLC system. In this paper, the signal noise ratio (SNR) and inter-symbol interference (ISI) versus FOV of the antenna are simulated via Line-of-Sight (LOS) and non-Line-of-Sight (NLOS) links within a room with a size of 5m × 5m × 3m. Results show that, the blind area appears while the FOV is less than 40 deg. and the SNR reduces as FOV increases and keeps small when FOV is more than 70 deg.. Furthermore, the average power of ISI rises with the increase of FOV, and the rising trend is relatively moderate when FOV is below 50 deg., while there is a rapid increase between 50 deg. and 70 deg. and finally tends to be stable after 70 deg. Therefore, it is practical to determine the FOV of the optical receiving antenna in the scope of 40 to 50 deg. based on the installment of LED lights on the ceiling here so as to avoid the blind area, attain high SNR, and reduce the influence of ISI. It is also worthwhile in practice to provide an identifiable evidence for the determination of FOV of the optical antenna.

An innovative approach to realise high chip rate in OCDMA transmission system is proposed and experimentally investigation, the high chip rate is achieved through a 2-D wavelength-hopping time-spreading en/decoder based on the supercontinuum light source. The source used in the experiment is generated by high nonlinear optical fiber (HNLF), Erbium-doped fiber amplifier (EDFA) which output power is 26 dBm, and distributed feed-back laser diode which works in the gain switch state. The span and the flatness of the light source are 20 nm and 3 dB, respectively, after equalization of wavelength selective switch (WSS). The wavelength-hopping time-spreading coder can be changed 20 nm in the wavelength and 400 ps in the time, is consist of WSS and delay lines. Therefore, the experimental results show that the chip rate can achieve 500 Gchip/s, in the case of 2.5 Gbit/s, while keeping a bit error rate below forward error correction limit after 40 km transmission.

We propose a design of a multi-OAM-modes ring-core fiber with two guided modes regions which possesses relatively large effective index separations required for the vector modes. This fiber can support 28 information states bearing OAM spanning 8 OAM orders with large effective mode area by using polarization multiplexing and both signs of topological charge in the ring region, combined with two degenerate fundamental polarization modes in the core region which can hold the whole C bands. There is a high isolation between the modes in these two regions. These designed features have potential applications in the next generation fiber communication systems either in the quantum domain or in the classical domain.

Although the time-domain method, frequency-domain method and wavelet-domain method can used into signal denoising or filtering, the denoising of blood glucose photoacoustic signals are limited due to some advantages. In this paper, an improved wavelet threshold denoising method is used to remove the noise of the blood glucose photoacoustic signals. In order to overcome some drawbacks of classical wavelet threshold denoising, an improved wavelet threshold function was proposed. In the simulation experiments, the different denoising results are compared between this improved wavelet threshold function and other functions. And the experiments of this improved wavelet threshold function into the denoising of the time-resolved photoacoustic signals of glucose solution are performed. The experimental result verifies that the improved wavelet threshold function denoising is available. The improved wavelet threshold function has better flexibility than others due to the usage of two threshold values and two factors. So, the improved wavelet threshold function has the potential value in the denoising field of blood glucose photoacoustic signals.

In this paper, a noninvasive glucose concentration monitoring setup based on the photoacoustic technique was established. In this setup, a 532nm pumped Q switched Nd: YAG tunable pulsed laser with repetition rate of 20Hz was used as the photoacoustic excitation light source, and a ultrasonic transducer with central response frequency of 9.55MHz was used as the detector of the photoacoustic signal of glucose. As the preliminary exploration of the blood glucose concentration, a series of in vitro photoacoustic monitoring of glucose aqueous solutions by using the established photoacoustic setup were performed. The photoacoustic peak-to-peak values of different concentrations of glucose aqueous solutions induced by the pulsed laser with output wavelength of 1300nm to 2300nm in interval of 10nm were obtained with the average times of 512. The differential spectral and the first order derivative spectral method were used to get the characteristic wavelengths. For the characteristic wavelengths of glucose, the least square fitting algorithm was used to establish the relationship between the glucose concentrations and photoacoustic peak-to-peak values. The characteristic wavelengths and the predicted concentrations of glucose solution were obtained. Experimental results demonstrated that the prediction effect of characteristic wavelengths of 1410nm and 1510nm were better than others, and this photoacoustic setup and analysis method had a certain potential value in the monitoring of the blood glucose concentration.

In recent years, reconfigurable optical add drop multiplexers (ROADM) and multiple-dimensions optical cross-connection (OXC), as the essential devices of next-generation dynamic optical networks, have been attracted great interests by research institutions and relevant industry. 1×N Wavelength selective switches (WSSs) are one of the key components in current and next generation ROADM. Currently, WSS primarily rely on micro-electromechanical systems (MEMS) and liquid crystal on silicon spatial light modulators (LCOS-SLM) switches. LCOS-based WSSs have several advantages, including flexible spectrum coverage, adaptive alignment, and robustness. Based on a novel 2-f optical structure, we therefore propose 1×32 WSS system including a 1×32 fiber-coupling lenslet arrays, a collimating lens, a transmission grating, a cylindrical lens and a LCOS-SLM. By uploading the optimized phased holograms on the LCOS, we have successfully switched input signal with arbitrary wavelength in C-band into any output port. The output channel spacing can be adjusted flexibly and each port switches independently. Experimental results demonstrate the insertion loss is around 5~10dB and the switch crosstalk at 1550nm is -35dB. The 3dB-bandwidth of signal@100G is 40G.The research has established the theory and experiment foundation for the development of M×N WSS in future.

In recent years, due to the high stability and privacy of vortex beam, the optical vortex became the hot spot in research of atmospheric optical transmission .We numerically investigate the propagation of vector elliptical vortex beams in turbulent atmosphere. Numerical simulations are realized with random phase screen. To simulate the vortex beam transport processes in the atmospheric turbulence. Using numerical simulation method to study in the atmospheric turbulence vortex beam transmission characteristics (light intensity, phase, polarization, etc.) Our simulation results show that, vortex beam in the atmospheric transmission distortion is small, make elliptic vortex beam for space communications is a promising strategy.

Compared with traditional communication technology, laser communication technology has great advantages and broad application prospects. And the optical transceiver is the main of the space laser communication system. This paper discusses achievements on the optical transceiver among developed countries in recent years, discussing the trend of optical transceiver. Under the background of laser communication for the future platform among more types network, optical transceiver on one-many communication of optical antenna has been reported, assessing the advantages and disadvantages of all kinds of design scheme from several aspects. Finally, some new thought and analysis of optical antenna of network communication technology have been put forward.

The message-decryption process of subtracting chaotic synchronization carrier from receiving signal is explained by modeling and numerically solving the rate equations for semiconductor lasers. An experimental system of wavelength division multiplexing passive optical network (WDM-PON) based on chaotic-light secure communications is first built up. The bidirectional transmissions of downstream and upstream data are experimentally realized with only two lasers and a single wavelength channel in a WDM fiber-optic link. When the data rate is 1.25 Gb/s, the secure transmission distance can be up to 11 km with SSMF of G.652. After sampling and decision, the BER of the recovered messages is calculated to be approximately 1×10⁻⁴.

This paper focuses on a method to decrease the scattering loss induced by surface roughness through waveguide structure optimization. First, the concept of roughness is discussed briefly, and the diagram of waveguide surface roughness tested by optical profiler is given. Then, this report mainly analyzes the influence on scattering loss coefficient and total loss coefficient induced by surface roughness under different waveguide parameters. The study finds that the scattering loss coefficient and the total loss coefficient increase as roughness increasing. Last, the part produces a method to decrease scattering loss induced by roughness through waveguide structure optimization importantly. It is found that the total scattering loss coefficient can be decreased greatly if waveguide core size is in range from 60 μm to 80 μm or the parameter Δ is smaller than 0.016. When surface roughness is 200 nm, the correlation length is 4 μm, waveguide length is 100 cm, and core width (height, a=b) is from 30 μm to 70 μm, the total scattering loss coefficient can decrease from 3.37×10^-2 dB/cm to 1.65×10^-2 dB/cm.

Optical orthogonal frequency division multiplexing (OOFDM) is a promising technology in the next generation of high-speed and long-haul optical transmission, due to its high spectral efficiency, high speed of data transmission and strong ability of anti-dispersion. But optical OFDM system has a very high peak-to-average power ratio (PAPR). High PAPR will bring instantaneous high optical power to the optical OFDM system. Asymmetrically clipping and signal scrambling based on fast Hartley transform for PAPR reduction is proposed in optical OFDM system. Firstly, IFFT/FFT module in each sub-block of traditional signal scrambling technique is replaced with inverse fast Hartley transform (IFHT) and fast Hartley transform (FHT) module, which yield to the real signal in OOFDM system. Then, asymmetrically clipping technique is applied to turn it into a positive and real signal. Finally, the signal with the minimum PAPR is selected for transmission in the fiber channel. The PAPR of the optical OFDM signal can be reduced effectively. And without the Hermitian symmetry, the space and computational complexity are reduced accordingly.

The energy attenuation, fluctuations of arrival angle, light intensity scintillation, beam drift and beam spreading, which are caused by atmospheric attenuation and turbulence, will severely degrade the performance of space laser communication systems. For evaluating the laser transmission characteristics in atmosphere in Beijing, a measurement system is designed and implemented, which includes signal data acquisition unit, data processing unit data transmission unit. With this measurement system, the atmospheric parameters were measured at specific time period in one day as well as different typical climatic conditions, which lasted up to one year, and a lot of measurement data were acquired. Through a detailed analysis to these data, the laser transmission characteristics in atmosphere in Beijing are evaluated comprehensively, which supply a reference background for the real application of space laser communication technology in Beijing.

For indoor visible light communication (VLC) systems aim to achieve communication and illumination simultaneously, the channel capacity are significantly affected by illumination demands in actual scenarios. To enhance the system performance, the wavelength division multiplex (WDM) technique can be introduced. In this letter, we analyzed the demands of illuminance and chromaticity’s influence on indoor WDM visible light communication system based on color light emitting diodes (LED). The spectra distribution, crosstalk and noise of WDM VLC system were analyzed and the relative optimal total channel capacity was obtained by optimizing the number of sub-channels and their intensity at standard illumination scenario. It’s shown that by applying WDM technique, the total channel capacity of LED based VLC system can be about 4 times than the situation of single sub-channel, even with indoor illumination constraints. What’s more, the system performance can be improved by adjusting appropriate number of sub-channels and their intensity accordingly.

In an optical sampling system for high-speed optical communications, polarization controlling is one of the most important parts of the system, regardless of nonlinear optical sampling or linear optical sampling. A simple method based on variance calculation of sampled data is proposed in this paper to tune the wave plates in a motor-driven polarization controller. In the experiment, an optical sampling system base on SFG in PPLN is carried for a 10Gbit/s or beyond optical data signal. The results demonstrate that, with the proposed method, the error of estimated Q factor from the sampled data is least, and the tuning time of optimized polarization state is less than 30 seconds with the accuracy of ±1°.

With the development of optical fiber communication, dense wavelength division multiplexing (DWDM) system is important for the rapid management of multi-wavelength in the core node of the optical transmission network. In this paper, a reconfigurable optical add-drop multiplexer (ROADM) based on the tunable Fabry-Perot (F-P) array is proposed. An optical switch with high isolation and low crosstalk is designed by using the characteristics of filtering and tuning for the F-P array. The principle, structure, and function of the tunable F-P array are introduced. The characteristics of filtering and tuning for the F-P filter are also calculated, and the factor for the isolation, crosstalk, response time and insertion loss are analyzed. A single physical channel ROADM with 16 signal channels, which operates in C-band, is designed and optimized by simulation.

We propose a novel method for optical signal-to-noise ratio (OSNR) monitoring by the correction to the error of OSNR in high speed coherent optical communication systems. We calculate the total power and the total noise power by the real and imaginary part of the coherent detection signal. Then, the error of OSNR is corrected by a polynomial function. The simulation results demonstrate that, with the input power of 0.0dBm and 2.0dBm of 15-35GB QPSK optical fiber communication systems, the error of estimated OSNR is in the range of ±1dB with the reference OSNR of 15-25dB.