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This paper proposed a hybrid hour-ahead forecast model, which combines multiple superimposed long and short term memory (LSTM) network and back-propagation neural network (BPNN), for the purpose of the load forecast on a building-level. The model (hybrid LSTM-BPNN) takes full consideration of the influence of the meteorological information, time information, the information of persons and devices and indoor thermal parameters. A method (LSTM-BPNN + BPNN) is further developed based on the forecasting advantages of sensible heat by hybrid LSTM-BPNN and latent heat by BPNN, in which the cooling load was split into sensible heat and latent heat to forecast separately. The results show that the method achieves the best performance for hour-ahead load forecasting compared with several classic forecasting models. An operation strategy based on the proposed LSTM-BPNN + BPNN method and LSTM model is applied to an improved ground source heat pump system integrated with cooling storage (GSHPs-CS) which was equipped with two storage tanks to achieve the variable volume control of stored chilled water. The system model is established by TRNSYS. Compared to conventional GSHPs-CS, the energy consumption and operating cost of the improved GSHPs-CS system were reduced by 11.5% and 7.5%, respectively.

Reconfigurable photonic integrated devices and circuits are very important for many applications. Among various mechanisms for realizing reconfigurability, thermo-optic effect is popular because of the availability for many materials, the design simplicity and the fabrication ease. In particular, silicon has a large thermo-optic coefficient as well as a high heat conductivity, and thus it is promising to realize efficient thermally-reconfigurable silicon photonic integrated devices and circuits. Recent progress is reviewed in this paper. First, thermally-tunable silicon photonic filters based on different structures are summarized, including microring resonators (MRRs) and MRRs-assisted Mach-Zehnder interferometers (MZIs). Second, silicon photonic switches based on MZIs and MRRs are reviewed. Finally, a review is given for thermally-reconfigurable silicon photonic integrated circuits developed for the applications in quantum photonics, microwave photonics, and optical interconnects.

A parametric collaborative optimization method for ground source heat pump-radiant ceiling (GSHP-RC) system is proposed to find the optimum setpoint combinations by maximizing system performance and reducing operating costs while ensuring indoor thermal comfort. The method integrates response surface method (RSM) and fast non-dominated sorting genetic algorithm (NSGA-II) to search the nonlinearity relationship between the controllable factors and the response factors and execute multi-objective optimization (MOO) progressively. A GSHP-RC system in an office building is investigated based on TRNSYS. Three controllable factors, the water supply temperature of radiant ceiling, the indoor set temperature and the water supply temperature of the heat pump, were used to analyze the influence mechanism on the system. The system performance, thermal comfort and economy are evaluated by seasonal performance factor (SPF), predicted mean vote (PMV) and the operating cost (OC). Two optimal cases were determined with the SPF of 3.741 and 3.734, the OC of CNY 23525 and 24613, and the PMV of 0.225 and -0.223 respectively. The optimization can realize 17.3% and 13.0% of the operating cost saving for the optimal cases respectively with the significant improvement in SPF under the premise of indoor thermal comfort compared with the reference case with conventional parameters.

Low-loss and compact optical waveguides are key for realizing various photonic integrated circuits with long on-chip delay lines, such as tunable optical delay lines, optical coherence tomography, and optical gyroscopes. In this paper, a low-loss and compact silicon photonic waveguide spiral is proposed by introducing broadened Archimedean spiral waveguides with a tapered Euler S-bend. A 100-cm-long waveguide spiral is realized with a minimal bending radius as small as 10 μm by using a standard 220-nm-thick silicon-on-insulator foundry process, and the measured propagation loss is as low as 0.28 dB/cm. Furthermore, the present waveguide spirals are used to realize a 10-bit tunable optical delay line, which has a footprint as small as 2.2 mm × 5.9 mm and a dynamic range of 5120 ps with a fine resolution of 10 ps.

Integrated photonics have experienced a rapid advance in the past few decades, and various materials/platforms for integrated photonic devices and circuits have been developed successfully, such as silicon-on-insulator, silicon nitride, and indium phosphide. The realization of on-chip polarization rotators (PRs) is often challenging as a planar optical waveguide usually has a very good ability of polarization maintaining. Waveguide gratings have attracted intensive attention because of the possibility of enabling the free spectral range-free optical filtering. The development of reconfigurable photonic integrated devices and circuits is important for making optical networks intelligent so that the bandwidth/channels can be utilized optimally and flexibly. MEMS-based silicon photonic devices also provide a good option for achieving ultra-low power consumption. It is also possible to develop some non-volatile silicon photonic devices with the help of phase-change materials. Therefore, in order to develop powerful silicon PICs in the future, it is useful to introduce other functional materials “X” and versatile structures on silicon.

Phase change material G e 2 S b 2 T e 5 (GST) has recently emerged as a highly promising candidate for photonic device applications owing to its high optical contrast, self-holding bi-stability, and fast material response. Here, we propose and analyze a 1 × 2 tunable switch using a GST embedded silicon microring resonator exploiting high optical contrast during GST phase change and a high thermo-optic coefficient of amorphous phase GST. Our device exhibits high extinction ratios of 25.57 dB and 18.75 dB at through and drop ports, respectively, with just a 1 µm long GST layer. The two states of the switch are realizable by electrically inducing phase change in GST. For post phase change from amorphous to crystalline and vice versa, the fall time down the 80% of phase transition temperature is ∼ 66 n s and ∼ 45 n s , respectively. The resonance wavelength shift per unit active length is 0.661 nm/µm, and the tuning efficiency is 1.16 nm/mW. The large wavelength tunability (4.63 nm) of the proposed switch makes it an attractive option for reconfigurable photonic integrated circuits.

Silicon photonics is recognized as one of the most promising platforms for on-chip optical interconnects. In order to further enhance the on-chip optical-interconnect link capacity, silicon photonic devices for advanced multiplexing technologies have been widely investigated, including wavelength-division-multiplexing (WDM), mode-divisionmultiplexing (MDM), as well as the hybrid multiplexing. This paper gives a review for our recent progresses in the development of silicon-based on-chip wavelength/mode-division-multiplexers.

A dual-polarization waveguide superlattice is designed and realized by using 340 nm-thick silicon photonic waveguides. The silicon waveguide superlattices are formed with periodically arranged waveguides. Each period consists of five optical waveguides with core-widths designed optimally for minimizing the crosstalk among the optical waveguides. The optimized core-widths are 390 nm, 320 nm, 260 nm, 360 nm, and 300 nm when the separation between two adjacent waveguides is as small as 0.8 µm. With this design, the silicon waveguide superlattice works with low crosstalk (nearly –18 dB or less) for both polarizations within the range of 1530 nm to 1560 nm, which agrees well with the theoretical analysis.

Structural health monitoring (SHM) has been extensively used in civil infrastructures to assess structural condition and situation. Here, we develop a novel type of mechanical sensing technique using the structural instability of cylindrical cells detected by fiber Bragg grating (FBG). The cylinders are fabricated using a 3D printing technique, which are coiled by the FBG wires to detect the transverse deformation. Structural instability under axial compression is obtained in the experiments and the force–displacement relations are validated by the numerical simulations with satisfactory agreements. The wavelength variation of the FBG, caused by the structural instability, is observed and compared with the predefined threshold. Defining the variation larger than the threshold as “1” and smaller as “0”, the pattern recognition algorithm is used to convert the FBG results into binary data, which can, therefore, be analyzed to indicate the structural conditions. In the end, we envision the potential applications of the reported sensing technique, such as wireless sensors for structural health monitoring (SHM) in civil infrastructures.

A design rule for a Mach-Zehnder interferometer (MZI) sensor is presented, allowing tunable sensitivity by appropriately choosing the MZI arm lengths according to the formula given in this paper. The present MZI sensor designed by this method can achieve an ultra-high sensitivity, which is much higher than any other traditional MZI sensors. An example is given with silicon-on-insulator (SOI) nanowires and the device sensitivity is as high as 106 nm/refractive-index -unit (or even higher), by choosing the MZI arms appropriately. This makes it possible for one to realize a low-cost optical sensing system with a detection limit as high as 10&minus, 6 refractive-index-unit, even when a cheap optical spectrum analyzer with low-resolution (e.g., 1 nm) is used for the wavelength-shift measurement.

Under the guidance of “ensuring that children do not drop out of school due to poverty China has established a broad and universal subsidy system for poverty-stricken students in colleges and universities, which has achieved phased results. However, during the implementation, there are still some bad phenomena such as “fake poverty-stricken students This paper will focus on the application of big data technology to solve the above problems through technical means. It also studies the optimization of the system from three aspects: logical structure design, physical structure design and flow chart design of the big data service platform for poverty-stricken college students.

We present a silicon racetrack-resonator based on a modified Euler curve for high-performance microwave photonic filters. It has a high Q-factor of 7×105, free spectral range of 0.73 nm, and tuning range of 92 GHz. © 2020 The Author(s)

A multilayer coal bed methane system with a complex superimposed relationship developed vertically in the Gujiao block. Taking the cumulative thickness of mudstone between neighbouring coal seams and open faults as object of research, the key strata for the division of different CBM systems was defined. The connection of an open fault for the fluid pressure system and the spatial distribution of the CBM system were analysed. The results showed that the porosity of compact mudstone is extremely low. When the mudstone thickness of the roof and floor increases, the gas content increases. Taking the Lijiashe and Wangzhimao faults as the boundary lines, the fluid pressure gradient between the Shanxi and Taiyuan formations is less than 0.08 MPa /100 m in the northern fracture zone, such as the Zhenchengdi, the Xiqu, the Tunlan, and the northern Dongqu well fields. The vertical gas units of different strata may belong to the same CBM system. The structure is simple in the southern Lijiashe fault. The vertical gas units in the southern Lijiashe fault belong to different CBM systems. Combined with the minimum thickness of the mudstone layer (2 m) and coal seam (0.5 m) standards, the spatial distribution of CBM systems was analysed.

We present a 10-GHz granularity reconfigurable WDM superchannel filter in a photonic integrated circuit. The filter uses a ring-resonator-assisted tapped-delay-line topology. An example configuration with two ring resonators and four tapped delay lines provides a spectral filter with a flat-top passband, a roll-off factor of 8%, a tunable central wavelength, and a selectable free spectral range, i.e., 2× or 4× the 3-dB passband bandwidth. The device was fabricated in a silicon nitride (Si3N4/SiO2) waveguide with a chip area of 0.36 cm2 and has a fiber-to-fiber insertion loss of 5 dB. We experimentally demonstrate the filter for selecting a subchannel from a WDM superchannel comprising 10-GHz subchannels with 10% and zero guard bands. Owing to the infinite impulse responses of ring resonators, this filter requires a significantly smaller area and fewer tuning elements compared with designs based on only tapped-delay-line finite-impulse-response filters. This paper contributes to the creation of chip-scale all-optical WDM superchannel transceivers and reconfigurable optical add/drop multiplexers (ROADMs).

The roof, floor and gangue samples of coal seams were collected from a borehole in the Gujiao mining area. The vertical distribution of major elements, trace elements and rare earth elements (REEs) was tested through X-ray fluorescence spectrometry and inductively coupled plasma-mass spectrometry (ICP-MS). The formation environment and material source of the strata were analysed. The results showed that the major elements of the coal seam roof, floor and gangue are Si and Al, followed by Fe, K, and Ti. In the Shanxi Formation, Sn, B, Ta, Bi, Th, U, Li, Be, Nb, In, Cs and Hf are enriched. In the Taiyuan Formation, B, Bi, U, Li, Sr, Mo and Sb are enriched. Sn, B, Th, U, and Be of the Shanxi Formation and B, U, Mo, and Sb of Taiyuan Formation are enriched hazardous elements. The ratios of Sr/Ba, U/Th, Ni/Co and V/Cr could indicate the paleosalinity and redox conditions. The Shanxi Formation was mainly formed in an oxic environment. The roof and floor of the No. 7 coal and the roof of the No. 8 coal are limestone, indicating anoxic and suboxic to dysoxic environments. The lithology of the Shanxi Formation and Taiyuan Formation material source is complex, including sedimentary rocks, granite and alkaline basalt. Most samples are distributed at the intersection of the granite and alkaline basalt, indicating dual sourcing from the granite and alkaline basalt.

Chip-scale integrated optical signal processors promise to support a multitude of signal processing functions with bandwidths beyond the limit of microelectronics. Previous research has made great contributions in terms of demonstrating processing functions and device building blocks. Currently, there is a significant interest in providing functional reconfigurability, to match a key advantage of programmable microelectronic processors. To advance this concept, in this work, we experimentally demonstrate a photonic integrated circuit as an optical signal processor with an unprecedented combination of two key features: reconfigurability and terahertz bandwidth. These features enable a variety of processing functions on picosecond optical pulses using a single device. In the experiment, we successfully verified clock rate multiplication, arbitrary waveform generation, discretely and continuously tunable delays, multi-path combining and bit-pattern recognition for 1.2-ps-duration optical pulses at 1550 nm. These results and selected head-to-head comparisons with commercially available devices show our device to be a flexible integrated platform for ultrahigh-bandwidth optical signal processing and point toward a wide range of applications for telecommunications and beyond.

Coalbed methane (CBM) resources are abundant in Gujiao blocks, Xishan coalfield, China. However, there is little previous geological research regarding coalbed methane. Using a quantitative and qualitative index, the hydrocarbon source rocks and preservation conditions of No. 2, 8 and 9 coalbed methane systems in Gujiao blocks were evaluated through a multi-level fuzzy method. On this basis, the comprehensive favourable area of three CBM systems and multi-layer commingled production were predicted. The results showed that the comprehensive score trend of hydrocarbon source rocks in Gujiao blocks gradually increases from southeast to northwest. The comprehensive score trend of preservation conditions increases gradually from north to south. The No. 2 coalbed methane system of the Shanxi formation is given priority over level II, which is distributed in the central and southern study area. The No. 8 coalbed methane system of the Taiyuan formation is given priority over level III, followed by level IV. The No. 9 coalbed methane system of the Taiyuan formation is given priority over level II and level III, which is distributed in the central and southern study area. Most of the area is suitable for individual CBM exploitation of No. 8 coal. The favourable area for the No. 2+8 coal layer is located in parts of the central, south-western and south-eastern study area. The favourable area for No. 8+9 coal layer is located in the Dongqu well field and the southern Tunlan well field. The favourable area for No. 2+8+9 coal layer is located in the eastern Yang Zhuang well field.

Integrated optical signal processors have been identified as a powerful engine for optical processing of microwave signals. They enable wideband and stable signal processing operations on miniaturized chips with ultimate control precision. As a promising application, such processors enables photonic implementations of reconfigurable radio frequency (RF) filters with wide design flexibility, large bandwidth, and high-frequency selectivity. This is a key technology for photonic-assisted RF front ends that opens a path to overcoming the bandwidth limitation of current digital electronics. Here, the recent progress of integrated optical signal processors for implementing such RF filters is reviewed. We highlight the use of a low-loss, high-index-contrast stoichiometric silicon nitride waveguide which promises to serve as a practical material platform for realizing high-performance optical signal processors and points toward photonic RF filters with digital signal processing (DSP)-level flexibility, hundreds-GHz bandwidth, MHz-band frequency selectivity, and full system integration on a chip scale., Nanophotonics, 7 (2), ISSN:2192-8614

Adsorption and desorption of coal to methane are substantially related to coal facies, referring to the production potential of a coalbed methane (CBM) well. Based on analyses of the stratified channel samples from coal seams No. 2, No. 4 and No. 9 in the Xiqu Drainage Area, Gujiao CBM Block, North China, the relationship between coal facies and adsorption-desorption behaviors was first proposed and discussed. Using the coal facies diagrams suggested by previous investigators, four types of coal facies were distinguished in the coal seams, including the upper delta plain wet forest swamp (I), the lower delta plain fen (II), the lower delta plain marsh (III) and the back barrier low moor (IV). The upper delta plain wet forest swamp occurred dominantly, developing at the bottom and top of all the coal seams. Both the ash yield and groundwater index (GWI) tend to increase from coal facies I to IV, whereas the volatile compounds, fixed carbon, organic sulfur, total sulfur, micropore volume and specific surface area, tissue preservation index (TPI) and vegetation index (VI) decreased, which indicates changes in the vegetation types, water supplements and disturbance, acid-base properties and redox conditions in the paleomires. Paleomire evolution accompanied the rise and drop of the sea level, with a transgression or regression process that could be represented by the coal facies sequence. Coal seams No. 2, No. 4 and No. 9 were discriminated into two, three and two evolving stages, respectively, and these stages were characterized by complete cycles, except stage 4-I from the lower delta plain marsh. Mudstone partings in the coal seams deposited during the highest sea level. Collectively, paleomire environments, especially the variation of vegetation types and mire water condition, result in adsorption and desorption divergences among different coal facies. Arborescent plants decrease from coal facies I to IV as the hydrodynamic intensity increases, leading to corresponding changes in botanical tissue preservation, medium oxidizability, mineral content and, ultimately, adsorption and desorption behaviors. In view of the gas content and desorption capacity of the coal layers in the same coal seam, the layers from the upper delta plain wet forest swamp may have the best potential for CBM drainage, followed by those from the lower delta plain fen and marsh, while those from the back barrier low moor may have the worst potential.

// Ying Wang 1, 3, * , Bingyu Chen 3, * , Zhen Wang 3 , Wei Zhang 4 , Ke Hao 3 , Yu Chen 4 , Kaiqiang Li 3 , Tongtong Wang 4 , Yiwei Xie 3 , Zhihui Huang 1, 2 , Xiangmin Tong 1, 4 1 Key Laboratory of Laboratory Medicine, Ministry of Education, Wenzhou Medical University, Wenzhou, Zhejiang, 325035, China 2 Institute of Neuroscience and Hypoxia Medicine, Wenzhou Medical University, Wenzhou, Zhejiang, 325035, China 3 Department of Blood Transfusion, Zhejiang Provincial People’s Hospital, Hangzhou, Zhejiang, 310014, China 4 Clinical Research Institute, Zhejiang Provincial People’s Hospital, Hangzhou, 310014, China * These authors have contributed equally to this work Correspondence to: Xiangmin Tong, email: tongxiangmin11@163.com Zhihui Huang, email: hzhzju021@163.com Keywords: Marsdenia tenacissimae extraction, T-cell acute lymphoblastic leukemia, proliferation, apoptosis, PTEN Received: June 29, 2016 Accepted: October 03, 2016 Published: October 14, 2016 ABSTRACT Marsdenia tenacissimae extraction (MTE) as a traditional Chinese herb has long been used to treat some diseases such as tumors in China. However, the potential effectiveness of MTE in leukemia has not yet been fully understood, and the related molecular mechanism is still unknown. In the present study, we aimed to evaluate the effects of MTE on the proliferation and apoptosis of Jurkat cells (T-ALL lines) and lymphocytes from T-ALL (T-cell acute lymphoblastic leukemia) patients. Firstly, CCK8 assays and flow cytometry assays revealed that MTE dose-dependently reduced the proliferation of Jurkat cells by arresting cell cycle at S phase. Secondly, Annexin V-FITC/PI-stained flow cytometry and TUNEL staining assays showed that MTE promoted the apoptosis of Jurkat cells. Mechanistically, MTE enhanced PTEN (phosphatases and tensin homolog) level and inactivated PI3K/AKT/mTOR signaling pathway in Jurkat cells, which mediated the inhibition of cell proliferation by MTE and MTE-induced apoptosis. Finally, MTE significantly inhibited the proliferation and promoted the apoptosis of lymphocytes from T-ALL patients, compared with lymphocytes from healthy peoples. Taken together, these results reveal an unrecognized function of MTE in inhibiting the proliferation and inducing the apoptosis of T-ALL cells, and identify a pathway of PTEN/PI3K/AKT/mTOR for the effects of MTE on leukemia therapy.

A novel wavelength-selective 2 × 2 optical switch based on a Ge 2 Sb 2 Te 5 (GST)-assisted microring-resonator (MRR) is proposed. The present GST-assisted MRR consists of two access optical waveguides and an MRR coupled with a bent GST-loaded silicon photonic waveguide. The 2 × 2 optical switch is switched ON or OFF by modifying the GST state to be crystalline or amorphous. In particular, the microring waveguide and the bent GST-loaded waveguide are designed to satisfy the phase-matching condition when the GST is crystalline. As a result, the MRR becomes highly lossy and the resonance peak is depressed significantly. On the other hand, when it is off, there is little coupling due to the significant phase mismatching. Consequently, one has a low-loss transmission at the drop port for the resonance wavelength. In this paper, the simulation using the three-dimensional finite-difference method shows that the extinction ratio of the designed photonic switch is ∼ 20 dB at the resonance wavelength, while the excess losses at the through port and drop port are 0.9 dB and 2 dB. In particular, the resonance wavelength changes little between the ON and OFF states, which makes it suitable for multichannel wavelength-division-multiplexing systems.

Radio frequency (RF) switches are essential for implementing routing of RF signals. However, the increasing demand for RF signal frequency and bandwidth is posing a challenge of switching speed to the conventional solutions, i.e., the capability of operating at a sub-nanosecond speed or faster. In addition, signal frequency reconfigurability is also a desirable feature to facilitate new innovations of flexible system functions. Utilizing microwave photonics as an alternative path, we present here a photonic implementation of an RF switch providing not only the capability of switching at a sub-nanosecond speed but also options of frequency doubling of the input RF signals, allowing for flexible output waveforms. The core device is a traveling-wave silicon modulator with a device size of 0.2 mm × 1.8 mm and a modulation bandwidth of 10 GHz. Using microwave frequencies, i.e., 15 GHz and 20 GHz, as two simultaneous RF input signals, we experimentally demonstrated their amplitude and frequency switching as well as that of the doubled frequencies, i.e., 30 GHz and 40 GHz, at a switching frequency of 5 GHz. The results of this work point to a solution for creating high-speed RF switches with high compactness and flexibility.

An ultrahigh-Q silicon racetrack resonator is proposed and demonstrated with uniform multimode silicon photonic waveguides. It consists of two multimode straight waveguides connected by two multimode waveguide bends (MWBs). In particular, the MWBs are based on modified Euler curves, and a bent directional coupler is used to achieve the selective mode coupling for the fundamental mode and not exciting the higher-order mode in the racetrack. In this way, the fundamental mode is excited and propagates in the multimode racetrack resonator with ultralow loss and low intermode coupling. Meanwhile, it helps achieve a compact 180° bend to make a compact resonator with a maximized free spectral range (FSR). In this paper, for the chosen 1.6 μm wide silicon photonic waveguide, the effective radius R eff of the designed 180° bend is as small as 29 μm. The corresponding FSR is about 0.9 nm when choosing 260 μm long straight waveguides in the racetrack. The present high-Q resonator is realized with a simple standard single-etching process provided by a multiproject wafer foundry. The fabricated device, which has a measured intrinsic Q-factor as high as 2.3 × 10 6 , is the smallest silicon resonator with a > 10 6 Q-factor.

The Gujiao blocks are abundant in coalbed methane (CBM) resources. The reservoir pressure and pressure gradient in this area vary different for different mine fields. With increasing burial depth, the reservoir pressure increases. The reservoir pressure gradient ranges from 0.41 to 0.95 MPa/100 m; therefore, the reservoir can be classified as an under-pressurized reservoir. The southern region of the study area is a groundwater retention area, whereas the northern region is a runoff area. The gas content gradually increases from north to south. Taking the Miaogou limestone (L 1 ) and Xiedao limestone (L 4 ) as the boundary, three separate gas-bearing units can be divided vertically. The sequence stratigraphy structure is closely related to the quality of the CBM systems. The transgressive system formation provides a good sealing barrier that can be vertically divided into three CBM systems. In controlling the coal reservoir and the tectonic and hydrology conditions, components of the CBM system can communicate with each other in fracture development areas, which are suited for multi-layer drainage. However, we must design a method of development according to the law of diminishing fluid pressure of different CBM systems.

Active photonic circuits use combinations of active semiconductor devices and passive elements to support many applications. We present four functions on a single active photonic integrated circuit (4.5 mm × 4 mm).

Optical delay lines implemented in photonic integrated circuits (PICs) are essential for creating robust and low-cost optical signal processors on miniaturized chips. In particular, tunable delay lines enable a key feature of programmability for the on-chip processing functions. However, the previously investigated tunable delay lines are plagued by a severe drawback of delay-dependent loss due to the propagation loss in the constituent waveguides. In principle, a serial-connected amplifier can be used to compensate such losses or perform additional amplitude manipulation. However, this solution is generally unpractical as it introduces additional burden on chip area and power consumption, particularly for large-scale integrated PICs. Here, we report an integrated tunable delay line that overcomes the delay-dependent loss, and simultaneously allows for independent manipulation of group delay and amplitude responses. It uses a ring resonator with a tunable coupler and a semiconductor optical amplifier in the feedback path. A proof-of-concept device with a free spectral range of 11.5 GHz and a delay bandwidth in the order of 200 MHz is discussed in the context of microwave photonics and is experimentally demonstrated to be able to provide a lossless delay up to 1.1 to a 5 ns Gaussian pulse. The proposed device can be designed for different frequency scales with potential for applications across many other areas such as telecommunications, LIDAR, and spectroscopy, serving as a novel building block for creating chip-scale programmable optical signal processors.

We characterize an integrated silicon 4×5 Gb/s OFDM transmitter PIC (2.1×4.8 mm2) with four modulators and an optical Fourier transform. This PIC features a channel spacing of 5 GHz and an 80-GHz free spectral range.

Few-mode-fiber (FMF) based mode division multiplexing (MDM) is a promising technique to further increase the transmission capacity of single mode fibers. We propose and numerically investigate a fiber-optical mode converter (MC) using long period gratings (LPGs) fabricated on the FMF by point-by-point CO 2 laser inscription technique. In order to precisely excite three modes (LP 01 , LP 11 , and LP 02 ), both untilted LPG and tilted LPG are comprehensively optimized through the length, index modulation depth, and tilt angle of the LPG in order to achieve a mode contrast ratio (MCR) of more than 20 dB with less wavelength dependence. It is found that the proposed MCs have obvious advantages of high MCR, low mode crosstalk, easy fabrication and maintenance, and compact size.

This paper proposed and experimentally demonstrated an all-fiber tunable and programmable bandpass filter using a linearly chirped fiber Bragg grating (CFBG). The center wavelength and spacing of the transmission peaks could be independently tuned via computer. The tunable range is about 18 nm. With this filter we demonstrated a tunable fiber ring laser which has an output power of about -7 dBm, full-width at half- maximum linewidth of ~0.017 nm which is limited by the resolution of the optical spectrum analyzer (OSA). Furthermore, a spacing tunable dual-wavelength fiber laser was achieved with the same setup. This all-fiber laser features advantages like simple structure, low cost, flexible and digital tuning capability.

We proposed and experimentally demonstrated an all-fiber structured programmable optical bandpass filter (waveshaper) based on a linearly chirped fiber Bragg grating and a digital-controlled thermal array. The key parameters of this filter such as the number of transmission channels, passing bandwidth per channel, central wavelength as well as the channel spacing can be reconfigured independently and flexibly by a program-controlled circuit. We have achieved in experiments the tunable passing bandwidth ranging from < 0.04 to 1.55 nm, adjustable central wavelength ranging from 1,547.16 to 1,558.64 nm, and a minimum wavelength spacing of 0.91 nm. The insertion loss of the whole device and the sideband rejection ratio are about 1.76 and 28 dB, respectively.

We propose and demonstrate by simulations a novel Nyquist-WDM (N-WDM) superchannel transmitter based on an arrayed waveguide grating router (AWGR). This approach can generate Nyquist pulses at multiple wavelengths using a single AWGR. Results for a 3-channel 960-Gbit/s QPSK superchannel system show that a 10% guard band reduces the inter-channel interference (ICI) sufficiently. The design introduces less than 0.16-dB penalty when the waveguide loss is 2 dB/cm and 0.73-dB penalty when the standard deviation of phase error is 10°. Such Nyquist pulse shapers can be realised on a chip scale using photonic integrated circuits technology, and could be compactly integrated with other functional components to create single-chip N-WDM superchannel transmitters.

Orthogonal time division multiplexing (OrthTDM) interleaves sinc-shaped pulses to form a high baud-rate signal, with a rectangular spectrum suitable for multiplexing into a Nyquist WDM (N-WDM)-like signal. The problem with generating sinc-shaped pulses is that they theoretically have infinite durations, and even if time bounded for practical implementation, they still require a filter with a long impulse response, hence a large physical size. Previously a method of creating chirped-orthogonal frequency division multiplexing (OFDM) pulses with a chirped arrayed waveguide (AWG) filter, then converting them into interleaved quasi-sinc pulses using dispersive fiber (DF), has been proposed. This produces a signal with a wider spectrum than the equivalent N-WDM signal. We show that a modification to the scheme enables the spectral extent to be reduced for the same data rate. We then analyse the key factors in designing an OrthTDM transmitter, and relate these to the performance of a N-WDM system. We show that the modified transmitter reduces the required guard band between the N-WDM channels. We also simulate a simpler scheme using an unchirped finite-impulse response filter of similar size, which directly creates truncated-sinc pulses without needing a DF. This gives better system performance than either chirped scheme.

We report a photonic integrated circuit implementation of an optical clock multiplier, or equivalently an optical frequency comb filter. The circuit comprises a novel topology of a ring-resonator-assisted asymmetrical Mach-Zehnder interferometer in a Sagnac loop, providing a reconfigurable comb filter with sub-GHz selectivity and low complexity. A proof-of-concept device is fabricated in a high-index-contrast stoichiometric silicon nitride (Si3N4/SiO2) waveguide, featuring low loss, small size, and large bandwidth. In the experiment, we show a very narrow passband for filters of this kind, i.e. a −3-dB bandwidth of 0.6 GHz and a −20-dB passband of 1.2 GHz at a frequency interval of 12.5 GHz. As an application example, this particular filter shape enables successful demonstrations of five-fold repetition rate multiplication of optical clock signals, i.e. from 2.5 Gpulses/s to 12.5 Gpulses/s and from 10 Gpulses/s to 50 Gpulses/s. This work addresses comb spectrum processing on an integrated platform, pointing towards a device-compact solution for optical clock multipliers (frequency comb filters) which have diverse applications ranging from photonic-based RF spectrum scanners and photonic radars to GHz-granularity WDM switches and LIDARs.

Phase-coded radio frequency (RF) pulses are widely adopted for radar systems as an effective signal format to enable high-range resolution. However, generating such signals conventionally requires high-speed electronics and complex RF circuitry that impose burdens on the system cost and power consumption. In particular, modern radar systems desire features such as high frequencies, e.g., in the millimeter-wave region, high compactness, and high system flexibility, which pose great challenges for the conventional all-electronics solutions. In contrast, integrated microwave photonics opens a way to solutions that are able to provide those features simultaneously, together with potential for full integration and low cost fabrication. Here, we present an integrated microwave photonic method of a binary-phase-coded millimeter-wave signal generation. The core device is a silicon microring modulator with a device size of 0.13 mm×0.32 mm and a modulation bandwidth of 23 GHz. Using RF seed frequencies of 17.5 GHz and 20 GHz, respectively, we experimentally demonstrated the generation of binary-phase-coded signals at 35 GHz and 40 GHz using our proposed approach, the performance of which was verified by a pulse compression ratio of 94 and 106, respectively. The result of this work points to the realization of a chip-scale flexible millimeter-wave signal generator.

We proposed and experimentally demonstrated an all-fiber structured wavelength-tunable second-order optical temporal differentiator based on a linearly chirped fiber Bragg grating and a digital-controlled thermal array. The central frequency of the differentiation can be reconfigured from 192.141 to 192.616 THz by a programmable circuit. In the experiment, a second-order differentiator with 3 dB bandwidth of 0.086 THz is achieved with a root mean square error of 4.89%. Published version

Mode division multiplexing (MDM) transmission based on few-mode fibers (FMFs) appears to be an alternative solution for overcoming the capacity limit of single-mode fibers (SMFs). A FMF coupler-based mode division multiplexer/demultiplexer (MMUX/DeMMUX) is proposed and theoretically investigated after the fabricated FMF is characterized. MMUXs/DeMMUXs with a mode contrast ratio (MCR) of more than 20 dB can be obtained for two-mode multiplexing and three-mode multiplexing over a wavelength span of 60 and 10 nm, respectively. We numerically verify the proposed MMUX/DeMMUX which has the advantages of high MCR, easy fabrication and maintenance, and low wavelength dependence.

We propose a novel method to improve a system degraded by a low receiver electrical bandwidth. With optical pre-sampling, 4-dB sensitivity improvement at the 7% hard FEC limit is experimentally demonstrated.

We present an FPGA-based QPSK-encoded 9.375 Gb/s layered/enhanced ACO-OFDM transmitter giving a high spectral efficiency. The measured Q-factor is greater than 13 dB after 20­km standard single-mode fiber transmission.

We propose a method for generating Nyquist sine pulses, based on an arrayed waveguide grating router (AWGR) preceded by a multimode interference coupler. This outperforms previous methods using a chirped AWGR and a dispersive fiber.