This PDF file contains the front matter associated with SPIE Proceedings Volume 11555, including the Title Page, Copyright information and Table of Contents

We demonstrate in this talk a self-calibrated extraction of microwave characteristic parameters of optoelectronic devices including modulators and photodiodes with self-reference capability based on heterodyne spectral mapping. The method saves half bandwidth or extends twice measuring frequency range, since the frequency response of DUT at f is determined from the electrical components at about f/2 (modulator cases), or with two driving signals at about f/2 (photodetector case). Furthermore, we extended the spectral mapping method to segmental up-conversion for ultra-wide and scalable measurement of PDs with 2M-fold measuring frequency range (M>10). In contrast to the VNA swept frequency method, ours realizes the frequency response measurement with self-reference capability, promising for fully integrated wafer-level devices or circuits.

Tilted Bragg grating (TBG) has been intensively investigated for photonic devices such as fiber sensors and on-chip filters. In this paper, we present that TBG can be equivalently realized by designing tilted sampled Bragg grating (TSBG), which is formed by superimposing the pre-designed tilted sampling structure on the basic grating. Since the basic grating is uniform and the sampling structure is in the order of micrometer, the fabrication of TSBG can be realized with one step of holographic exposure combined with another step of micro-lithography. We designed and simulated the equivalent light responses of the TSBGs as that of the target TBG in the photonic devices. As examples, a mode converter based on TSBG has been proposed, which can be used for add-drop filter in the wavelength division multiplexing (WDM) technology combined with mode division multiplexing (MDM) technology. We also investigate the core-to-cladding mode coupling of TSBG in single-mode fiber for fiber sensing as well as the spatial filter in the α- DFB laser. The proposed technique may pave a new way for different 2D gratings with good design flexibility and easy fabrication in various photonic devices.

Recent advances in monolithically integrated multi-section semiconductor lasers (MI-MSSLs) have propelled microwave photonic technologies to new potentials with a compact, reliable, and green implementation. Much research has examined that MI-MSSLs can realize the same or even better microwave photonic functions compared to discrete lasers by taking advantages of enhanced light–matter interactions. They are beneficial towards the future of integrated microwave photonics (IMWP) once integrating the other optical components such as modulators, amplifiers, transmission waveguide and so on. Herein, these recent advances in this emerging field are reviewed and discussed. Three main kinds of MI-MSSL structures are demonstrated including passive feedback laser, active feedback laser, as well as monolithically integrated mutually injected semiconductor laser. Their pros and cons are distinguished and compared through analyzing the desired characteristic indicators in modern MWP subsystems. The focus of this paper is on the photonic microwave techniques based on the nonlinear dynamics of MI-MSSLs, consisting of electro-optic conversion characteristics enhancement, photonic microwave generation, microwave photonic filter, as well as multiwavelength laser array for wavelength division multiplexing radio-over-fiber (WDM-RoF) networks. We also take a look at the future prospective at the research directions and challenges in this area.

We demonstrate the fabrication of long-period fiber gratings (LPFGs) by using focused carbon dioxide laser. The mode coupling and characteristics of the LPFGs written in the few mode fibers were investigated experimentally. The generation and conversion of the orbital angular momentum (OAM) modes were achieved by the special designed gratings. The LPFGs could have promising application as high sensitivity optical sensors and all fiber mode converters.

A self-mixing chaotic laser which can generate ultra high frequency band is proposed.The system realize the generation of UWB through the modulation of dispersion fiber.The system enters into chaos state under optical feedback and delay feedback (the influence of dispersive fiber).In chaotic state, the Ultra bandwidth is observed on the electrospectrum analyzer by adjusting the length of dispersive fiber.In this paper, two waveforms with unimodal and bimodal are obtained by adjusting the temperature of the phase-shifting grating and adjusting the bias controller.The maximum bandwidth under single peak is 36.78GHz, and the maximum bandwidth under twin peaks is 40.57GHz.By comparison, the bandwidth generated under the bimodal peaks is larger and more complex.The experimental results show that the system bandwidth enlargement effect is very obvious in the case of the selected parameters.The system is suitable for chaotic optical communication and sensing.

Real-time sensing for gas, liquid, and fine particulate matter are challenging to optical fibers since the probe light cannot interact with the molecules or particle directly. One approach of extending fiber based system to gas or fine particulate matter sensing is taking the advantage of evanescent field that is generated around a microfiber. We report our progress in fluoride microfiber environmental sensor based on the absorption or scattering properties of the generated evanescent field.

Photonic down-conversion sampling is a promising technique that can directly and adaptively transfer a high-frequency microwave signal to a low-frequency replica in the first Nyquist zone, thanks to the large bandwidth of the electro-optic modulator and the ultra-short optical pulse train. Therefore, this technique is beneficial to achieving broadband microwave measurement by using a low-speed photodetector together with a low-frequency and narrowband digital (or analog) receiver. In this presentation, we will discuss broadband high-resolution microwave frequency measurement schemes based on low-speed photonic sampling, which are applicable for multi-tone signal. We will also discuss calibration-free microwave characterization of broadband electro-optic modulators based on low-speed photonic sampling, where the microwave response of either a phase modulator or an intensity modulator can be obtained through low-frequency detection.

Microwave frequency measurement (MFM) is to estimate frequencies of intercepted microwave signals, which is critical to modern military and civil radio-frequency (RF) systems, such as wireless communications, electronic countermeasure (ECM), radar warning and electronic intelligence systems. In this paper, a photonic-assisted MFM method based on harmonic down-conversion with semiconductor optical amplifiers (SOAs) is proposed. Two optical harmonic intensifiers consisting of an electro-optic intensity modulator and a SOA are used to generate high-order optical harmonics based on cascaded four-wave mixing in the SOA, which has low-frequency and tunable spacing. It enables ultra-wide harmonic down-conversion of microwave signals under test in the electrical domain with low-frequency local oscillator (LO). The microwave frequency is therefore unequivocally determined by cross-referencing two pairs of harmonic down-converted tones within the LO frequency. It enables multi-tone frequency measurement and eliminates the trade-off between the measurement range and frequency-resolution. Moreover, it avoids the limitation of deadband by the cross-referenced frequency discrimination.

The simultaneous distance and velocity measurement system based on a bidirectional chirped fiber Bragg grating (CFBG) is proposed. By using the bidirectional CFBG, a dual-chirp optical signal with large bandwidth is generated. After the dechirp processing in the optical domain, both the distance and velocity information can be obtained simultaneously. A simulation is carried out. A dual-chirp optical signal with a bandwidth of 0.208 THz is generated. The simultaneous distance and velocity measurement is achieved, with the ranging resolution of 0.9 mm and the velocity resolution of 0.058 km/s, respectively.

Conventional parity-time (PT) symmetric systems consist of two physically separated resonators to form one-dimensional spatial potential symmetry, with the gain and loss modes localized in respective resonators. We show that PT-symmetry can be implemented between subspaces in non-spatial parameter spaces, in which the gain and loss modes can perfectly overlay spatially but are distinguishable in the designated parameter space. Such optical parameter spaces can be implemented by optical wavelength, wavevector and polarization, etc. The resultant spatial singularity enables the possibility in implementing PT-symmetric systems with increased structural simplicity, integration density and long-term stability. In this talk, PT-symmetric optoelectronic oscillators (OEOs) are implemented in the parameter space of optical wavelength and wavevector; a PT-symmetric laser is implemented in the parameter space of optical polarization. All systems are shown to operate with stable single-mode oscillation and with low structural complexity. We believe that PTsymmetric system in non-spatial parameter spaces can find great applications in optical instrumentation due to its capability for low phase noise signal generation.

Our proposed optical performance monitoring (OPM) technique, based on the multi-task learning, is able to realize modulation format identification (MFI), baud rate identification (BRI), chromatic dispersion identification (CDI), and optical signal-to-noise ratio (OSNR) estimation simultaneously. This OPM technique can be used in the intermediate nodes of optical networks, which is cost-effective since it can monitor systems by direct detection. To further reduce the cost, PD and ADC with low bandwidth are used. Therefore, we investigate the effect of different bandwidths of direct detection receiver on the performance of OPM, to find the optimal low bandwidth of receiver to achieve relatively high OPM performance. The comparison experiment between different bandwidths of receivers has been carried out where signals with two formats, quadrature phase shift keying (QPSK) and 16 quadrature amplitude modulation (16QAM), two baud rates, 14 GBaud and 28 GBaud, and three CD situations, 0 ps/nm, 858.5 ps/nm, and 1507.9 ps/nm, are adopted. And the test bandwidths of receiver are 0.5 GHz, 1 GHz, 2.5 GHz, 5 GHz, 7.5 GHz, 10 GHz, and the original 33 GHz. It is found that the model with 5 GHz bandwidth receiver has the relatively highest performance, except the model with original 33 GHz bandwidth receiver. The identification accuracies of model with 5 GHz receiver are 99.92%, 99.11%, and 99.94% for MFI, BRI, and CDI, respectively. The OSNR estimation error of this model is 0.594 dB.

A new type of single-photon spectrograph combining a tunable optical filter and a dispersive element is presented for measurement of the spectral properties of the two-photon state. In comparison with the previous single-photon spectrograph which is merely based on the dispersive Fourier transformation (DFT) technique, this scheme avoids the need for additional wavelength calibration and the electronic laser trigger for coincidence measurement; therefore, its application is extended to continuous wave (CW) pumped two-photon sources. The achievable precision of the spectrum measurement has also been discussed in theory and demonstrated experimentally with a CW pumped periodically poled lithium niobate (PPLN) waveguide-based spontaneous parametric down conversion photon source. Such a device is expected to be a versatile tool for the characterization of the frequency entangled two-photon state.

It is found that the two pulsating solitons exhibit the same evolving process with identical period. However, the soliton characteristics including spectral profile, spectral bandwidth and sideband intensity are asynchronized integrally. The time difference between the evolving trajectories of two pulsating solitons is four roundtrip period. To best of our knowledge, it is the first unambiguous observation of multi-soliton pulsation with overall asynchronous evolution.

A nonlocal wavelength-to-time mapping method based on the entangled photon sources is proposed for nonlocal wavelength measurement. In this approach, the spectrally modulated optical carrier from the signal path is detected the single-photon detector. The dispersive medium is applied on the idler path before the idler photons reaches another SPD. With the help of GVD, the frequency correlation is transformed to the correlation of arrival time, when observed in coincidence count. As a result, the spectral pattern of the signal photon can be nonlocally transformed into temporal shape, even though there is no dispersion in the signal path. A proof-of-concept experiment demonstrates the wavelength measurement around 1560 nm, with a resolution of 0.2 nm.

Coherent lasers with ultra-narrow linewidth play a crucial role in high-precision metrology and coherent communication. Countless well-developed frequency stabilizations compensate mostly the low-frequency phase noise and facilitate an ultra-narrow linewidth down to quantum limit. Nevertheless, the precise characterization of its intrinsic linewidth of a coherent laser remains challenging. Here, a novel approach to characterize the linewidth of a coherent laser source relying on distributed Rayleigh scattering speckle in optical fiber was proposed and demonstrated. Phase noise statistics was revealed in a delay-time-resolved manner by correlation-based phase retrieval from Rayleigh scattering-induced heterodyne beating signals, facilitating precise measurement of a sub-kHz laser linewidth.

Lithium niobate on insulator (LNOI) thin film maintains the attractive material properties of lithium niobate, while also offering a stronger optical confinement and a high optical element integration density. The structure of integrated chips needs to be redesigned because the LNOI chip is quite different from the single crystal LN one. Beam splitter has been widely used in integrated optical devices, such as MZM modulator, AM modulator and light switch. In this paper, two kinds of beam splitters, including directional coupler (DC) and Multi-Mode interference (MMI) structure were designed by using finite difference time domain. The gap and coupling length of directional coupler were analyzed. An MMI beam splitter structure was designed and simulated. The key parameters of beam splitter such as free spectral range, splitting ratio and propagation loss were compared. The analysis of the two beam splitter structures can supply guidance for the design of the LNOI devices.

Recently, microplastics (MP) have emerged as global contaminants that seriously affect human and ecological health. However, rapid identification of MP is still a challenge, whether from oceans, wastewater, sediment or soil. A system based on laser-Raman spectroscopy analysis for qualitative testing of MP was established. The monitoring system can realize in-situ real-time detection and nondestructive testing, which provide a large amount of Raman spectroscopy of MP for Marine environmental analysis. A database suitable for microplastics analysis was presented based on the characteristic of Raman spectroscopy. Extra Trees algorithm was presented for the automatic identification of MP in this paper. The algorithm network is trained to detect random MP based on the established database, which including pure MP and mixed MP. The experiment result shows that several MP samples, including pure polystyrene (PS), Polymethyl methacrylate (PMMA), polyethylene terephthalate (PET), polyethylene (PE), Polyamide (PA), polyvinyl chloride (PVC) and polypropylene (PP) could be individually and automatically identified. The experiment result demonstrated that over 98.82% mixed particles could be correctly identified. The results were consistent with Extra Trees model built for identifying six types of MP, indicating Extra Trees model was highly robust for more than six of MP detection. The spectroscopy analysis method in this paper provides data support for systematically understanding the microplastic contamination.

The key to improve the capability of photoelectric detection and countermeasure system is to improve the detection ability of the system. System resolution, detection distance, detection range, response time, system signal-to-noise ratio are important criteria, and system optics is the core of its engineering implementation. From the global perspective, the adaptive algorithm establishes a new theory which superior to the traditional method, and solves the problem of freely determining the core optical solution, and opens up a new field for the development of accurate detection system.

Single suspended particle detection and recognition are tasks of significance in the context of both biomedical science and environment monitoring. In this work, we develop a system which is capable of both fluorescence and polarization real-time measurement for single suspended particle in the air. In our system, laser of 523nm is generated in light source and adjusted to light sheet in the detection area. Suspended particles fly through detection area and we real-time collect signals on both scattering, fluorescence and polarization channels for each particle. Our system provides the ability for further research on the airborne transmission route for pathogen and real-time detection of toxic pollutants in aerosol which usually emitting fluorescence for specific wavelength laser exciting.

The integrated electro-optic modulator plays an important role in the broadband wireless communication and phase-coded radar etc. The electro-optic modulator using a lithium niobite (LN) ridge waveguide is easy to be integrated and has excellent electro-optic response. However, its fabrication and coupling still face great challenge. In this paper, an intensity modulator (IM) based on heterogeneous platform with LN and silicon nitride (Si3N4) is designed. The optical mode field distribution is simulated as the waveguide size changes. The parameters such as the width and height of loadinged strip are optimized to ensure that the light power is highly concentrated in the LN layer (over 90%). The propagation loss of the IM with different Y-junction shapes is analyzed. In addition, the influence of different electrode parameters on half-wave voltage is discussed systematically. The results demonstrate that the designed IM has a low half wave voltage of 2.1V, characteristic impedance of 53Ω and propagation loss of -0.2dB. The proposed IM has the advantages of convenient fabrication and coupling, which provides an alternative modulation unit for multi-level or large-scale modulation integrated chips.

A Fabry-Perot cavity with chirped fiber gratings(CFGs) has been proposed and experimental demonstrated We use an ordinary single-mode fiber manufacturing two CFGs with reflection center wavelength 1549.74 nm by ultraviolet irradiation methods of phase mask method, two chirp fiber gratings with the same parameters: the length of the grating region is 10 mm, reflectivity is 95%, and bandwidth is 2.72 nm, chirp rate of 2 nm/cm, 1, 3 and 5 cm of two CFGs spacing. The Fabry-Perot (FP) cavity is composed of two CFGs as reflection faces. When an optical signal is input into the resonant cavity, the wavelength within the bandwidth of the CFGs satisfies the resonance condition, so the resonance is formed within the bandwidth. The structure is analyzed theoretically and the relationship between resonance spectrum and parameters is discussed. Wavelength changes are monitored by a spectral analyzer in real time. The experimental results show that the tunable laser output can be realized in optical communication system by changing the structure and parameters of the resonator.

Some Earth satellites are to be deployed in equatorial orbit in order to realize their particular objectives. For these satellites, the data transmission between ground stations and satellites has become one of the difficulties when the satellite engineering is to be realized. To make a quantitative assessment, simulations of data transmission are carried out for two typical orbits, of which the altitude are roughly 500km and 550km,and the inclination is 0 deg. Ground stations for data transmission include the such stations as Sanya China, Kourou France, Malindi Kenya. The longitude is 109.3 deg E., and the latitude is 18.3 deg N. for the station of Sanya. The longitude is 40.2 deg E., and the latitude is -3.0 deg S. for the station of Malindi. The longitude is -52.8 deg W., and the latitude is 5.3 deg N. for the station of Kourou. For Sanya, the cutoff angle for data transmission are 10 deg. For both Malindi and Kourou, the cutoff angles for data transmission are 5 deg. Two antenna for data transmission are fixed in the satellite body along +Z axis and –Z axis respectively, and the half beam angle of the boresight is 1 deg. Antenna for data transmission can scan +/-70deg both in X axis and in Y axis. Two cases are considered herein. Case 1 is that data transmission is only allowed when the celestial objects in question are obstructed by the Earth. Case 2 is that data transmission is allowed without considering the celestial objects obstruction by the Earth. For orbit altitude of 500km, 35 times data transmission are available, the average data transmission period is 305 sec,178 minutes are available for data transmission each day in Case 1; For orbit altitude of 550km, 36 times for data transmission are available, the average data transmission period is 322 sec,193 minutes are available for data transmission each day in Case 1. For orbit altitude of 500km, 9.5 times data transmission are available, the average data transmission period is 266 sec,42 minutes are available for data transmission each day in Case 2; For orbit altitude of 550km, 9.9 times for data transmission are available, the average data transmission period is 278 sec,46 minutes are available for data transmission each day in Case 2. The simulations of data transmission will support finalizing the data transmission planning before the satellite engineering project comes true.