Supercontinuum spectra generation in the single-mode optical fibre with concave dispersion profile

In this paper, a new method is proposed to generate broad supercontinuum （SC） spectra in the single-mode optical fibre with concave dispersion profile, We numerically simulate pulse evolutions and discuss physics mechanism in detail for SC spectrum generation in the optical fibre with concave dispersion profile. Furthermore, general criteria are presented for specifying the shape of SC spectrum by introducing normalized parameters, which are related to the fibres and the initial pump pulses. The results show that the flat and broad SC spectra are indeed generated in our proposed optical fibre.

Optical SDMA for applying compressive sensing in WSN

In order to apply compressive sensing in wireless sensor network, inside the nodes cluster classified by the spatial correlation, we propose that a cluster head adopts free space optical communication with space division multiple access, and a sensor node uses a modulating retro-reflector for communication. Thus while a random sampling matrix is used to guide the establishment of links between head cluster and sensor nodes, the random linear projection is accomplished. To establish multiple links at the same time, an optical space division multiple access antenna is designed. It works in fixed beams switching mode and consists of optic lens with a large field of view（FOV）, fiber array on the focal plane which is used to realize virtual channels segmentation, direction of arrival sensor, optical matrix switch and controller. Based on the angles of nodes＇ laser beams, by dynamically changing the route, optical matrix switch actualizes the multi-beam full duplex tracking receiving and transmission. Due to the structure of fiber array, there will be several fade zones both in the focal plane and in lens＇ FOV. In order to lower the impact of fade zones and harmonize multibeam, a fiber array adjustment is designed. By theoretical, simulated and experimental study, the antenna＇s qualitative feasibility is validated.

Optic nerve compression:the role of the lamina cribrosa and translaminar pressure

AIM： To describe the morphological changes of the lamina cribrosa （LC） in patients with optic nerve compression. METHODS： Cross-sectional study. Twenty eyes with optic nerve compression, affected by Graves＇ ophthalmopathy （GO） were compared with 18 refractive error-matched healthy eyes. The following examinations were performed： best-corrected visual acuity （BCVA）, intraocular pressure, optic nerve echography, visual field, SD-OCT including the retinal nerve fiber layer （RNFL）, ganglion cell complex （GCC）, and LC thickness and extent. RESULTS： A-scan revealed significant differences in the subarachnoid space （SAS） between the affected and control groups. LC thickness and LC area were 233 pm （SD 23） and 0.41 mm2 （SD 0.19）, respectively. Average GCC thickness （P=-0.0005）, LC thickness （P=-0.001）, MD （P=-0.001） and PSD （P=-0.001） differed significantly between the two groups; whereas LC area （P=-0.2） and average RFNL （P=-0.1） did not. CONCLUSION： Optic nerve compression reduces the SAS thereby altering the morphology of LC thickness and causing GCC damage.

Reconfigurable single-shot incoherent optical signal processing system for chirped microwave signal compression

We propose and demonstrate a reconfigurable and single-shot incoherent optical signal processing system for chirped microwave signal compression, using a programmable optical filter and a multiwavelength laser(MWL). The system is implemented by temporally modulating a specially shaped MWL followed by a suitable linear dispersive medium. A microwave dispersion value up to 1.33 ns/GHz over several GHz bandwidth is achieved based on this approach. Here we demonstrate a singleshot compression for different linearly chirped microwave signals over several GHz bandwidth. In addition, the robustness of the proposed system when input RF signals are largely distorted is also discussed.

Construction of deterministic sensing matrix and its application to DOA estimation

Compressive sensing（CS） has emerged as a novel sampling framework which enables sparse signal acquisition and reconstruction with fewer measurements below the Nyquist rate.An important issue for CS is the construction of measurement matrix or sensing matrix.A new deterministic sensing matrix,named as OOC-B,is proposed by exploiting optical orthogonal codes（OOCs）,Bernoulli matrix and Singer structure,which has the entries of 0,＋1 and-1 before normalization.We have proven that the designed deterministic matrix is asymptotically optimal.In addition,the proposed deterministic sensing matrix is applied to direction of arrival（DOA） estimation of narrowband signals by CS arrays（CSA）processing and CS recovery.Theoretical analysis and simulation results show that the proposed sensing matrix has good performance for DOA estimation.It is very effective for simplifying hardware structure and decreasing computational complexity in DOA estimation by CSA processing.Besides,lower root mean square error（RMSE） and bias are obtained in DOA estimation by CS recovery.

Fabricating lifted Haar transform image compression optical chip based on femtosecond laser

In this paper,a lifted Haar transform(LHT)image compression optical chip has been researched to achieve rapid image compression.The chip comprises 32 same image compression optical circuits,and each circuit contains a 2×2 multimode interference(MMI)coupler and aπ/2 delay line phase shifter as the key components.The chip uses highly borosilicate glass as the substrate,Su8 negative photoresist as the core layer,and air as the cladding layer.Its horizontal and longitudinal dimensions are 8011μm×10000μm.Simulation results present that the designed optical circuit has a coupling ratio(CR)of 0:100 and an insertion loss(IL)of 0.001548 d B.Then the chip is fabricated by femtosecond laser and testing results illustrate that the chip has a CR of 6:94 and an IL of 0.518 d B.So,the prepared chip possesses good image compression performance.

Improving the intensity and efficiency of compressed echo in rare-earth-ion-doped crystal

We investigate the intensity and efficiency of a compressed echo, which is important in arbitrary waveform generation（AWG）. A new model of compressed echo is proposed based on the optical Bloch equations, which exposes much more detailed parameters than the conventional model, such as the time delay of the chirp lasers, the nature of the rare-earth-iondoped crystal, etc. According to the novel model of compressed echo, we find that reducing the time delay of the chirp lasers and scanning the lasers around the center frequency of the inhomogeneously broadened spectrum, while utilizing a crystal with larger coherence time and excitation lifetime can improve the compressed echo＇s intensity and efficiency. The theoretical analysis is validated by numerical simulations.