Optical/Digital Fringe Multiplication in Projection Moire

In this paper, the optical/digital fringe multiplication (O/DFM) is realized in projection moiré using digital image processing (DIP). Both deformed grating and reference grating are captured using a CCD camera. The reference grating can also be produced using DIP. With the O/DFM, the pattern is multiplied with an image processing software, which is developed using MATLAB 6.5. Also with DIP, the phase shifting can become much simpler, and the automation can be adopted. The multiplied pattern is much thinner and easier to read, and sensitivity of measurement can be enhanced.

Spectral-domain optical coherence tomography dynamic changes and steroid response in multiple evanescent white dot syndrome

Dear Editor,Multiple evanescent white dot syndrome （MEWDS） was first described in 1984 as a rare, acute, unilateral,multifocal retinochoroidal disorder, typically affecting young myopic women. Previous studies with fluorescein angiography （FA） and electrophysiology suggested that MEWDS to be a disease in the retinal pigment epithelium （RPE） or outer retina, while recent studies with spectral- domain optical coherence tomography （SD-OCT） suggested it may be an outer retinal disease due to observation of hyperreflective material in outer retina and subtle disruptionsof the ellipsoid zone without RPE disruption.

A new distribution scheme of decryption keys used in optical verification system with multiple-wavelength information

A new distribution scheme of decryption keys used in optical verification systems is proposed. The encryption procedure is digitally implemented with the use of an iteration algorithm in computer. Three target images corresponding to three wavelengths are encoded into three sets of phase-only masks （POMs） by a special distributing method. These three sets of POMs are assigned to three authorized users as the personal identification. A lensless optical system is used as the verification system. In the verification procedure, every two of the three authorized users can pass the verification procedure cooperatively, but only one user cannot do. Numerical simulation shows that the proposed distribution scheme of decryption keys not only can improve the security level of verification system, but also can bring convenience and flexibility for authorized users.

Optical coherence tomography and T cell gene expression analysis in patients with benign multiple sclerosis

Benign multiple sclerosis is a retrospective diagnosis based primarily on a lack of motor symptom progression. Recent findings that suggest patients with benign multiple sclerosis experience non-motor symptoms highlight the need for a more prospective means to diagnose benign multiple sclerosis early in order to help direct patient care. In this study, we present optical coherence tomography and T cell neurotrophin gene analysis findings in a small number of patients with benign multiple sclerosis. Our results demonstrated that retinal nerve fiber layer was mildly thinned, and T cells had a distinct gene expression profile that included upregulation of interleukin 10 and leukemia inhibitory factor, downregulation of interleukin 6 and neurotensin high affinity receptor 1（a novel neurotrophin receptor）. These findings add evidence for further investigation into optical coherence tomography and m RNA profiling in larger cohorts as a potential means to diagnose benign multiple sclerosis in a more prospective manner.

A NEW DECODER OF SYNCHRONOUS OPTICAL CODE DIVISION MULTIPLE ACCESS SYSTEMS USING SEGMENTED CORRELATION

A new segmented correlating decoder of synchronous optical CDMA using modified prime sequence codes is proposed. The performance of the proposed system is analyzed under the assumption of Poisson shot noise model for the receiver photodetector. The decoder technique is shown to be more effective to improve the bit error probability performance than the method using an optical hard-limiter.

A study of retinal parameters measured by optical coherence tomography in patients with multiple sclerosis

AIM: To investigate the difference of retinal nerve fiber layer (RNFL) thickness and macular fovea thickness/volume between multiple sclerosis (MS) patients and healthy normal individuals using optical coherence tomography (OCT) and assess its association with visual field parameters. METHODS: Thirty consecutive MS patients and 28 healthy controls were recruited in this prospective study. Comprehensive standardized ophthalmic examinations included visual acuity, cycloplegic refraction, intraocular pressure, gonioscopy, visual field, and RNFL thickness and macular fovea thickness/volume detection using Humphrey OCT. Mean values for the thickness of the peripapillary RNFL and macular volume were calculated. Associations between visual field parameters and RNFL thickness/macular volume were analyzed by Pearson correlation analysis. RESULTS: The RNFL thicknesses in each quadrant, the average macular thickness, and the average macular volume in MS patients were all less than those in healthy controls, with statistically significant differences. The RNFL thickness and macular fovea thickness/volume were greater in eyes without optic neuritis than in eyes with optic neuritis. The average visual field parameters had positive correlations with the RNFL thickness and negative correlations with macular parameters in MS patients. CONCLUSION: OCT measurements can effectively identify the nerve changes of MS patients, which provide more data for the diagnosis of MS.

Multiple Scanning Effects in Radiochromic Film Dosimetry: A Method to Reduce the Increase of Optical Density

In this work, a method to reduce increase in optical density (OD) caused by multiple scanning in radiochromic film dosimetry in combination with a flatbed scanner is presented. Gafchromic EBT3 films are scanned with Epson Pro 1680 Expression scanner and time intervals of 15 minutes and 30 minutes are observed between consecutive scans to reduce the increase in temperature of the scanner. The maximum variations in OD after consecutive scans are calculated and compared to the values obtained for scans without interruption. For film irradiated to 3 Gy, a time interval of 15 minutes between two successive scans leads to a reduction of the OD increase of 56.2% compared to when films are scanned without interruption. Reductions of OD increase of 86.72% and 78.72% respectively for film irradiated to 1 Gy and 2 Gy are obtained when a time interval of 30 minutes is left between two successive scans. These results show that when time intervals are observed between consecutive scans, the increase in OD has significantly reduced. However, the method has the drawback of increasing the time needed to perform radiochromic film dosimetry.

Fabrication and optical properties of InGaN/GaN multiple quantum well light emitting diodes with amorphous BaTiO_3 ferroelectric film

BaTiO3 （BTO） ferroelectric thin films are prepared by the sol,el method. The fabrication and the optical properties of an InGaN/GaN multiple quantum well light emitting diode （LED） with amorphous BTO ferroelectric thin film are studied. The photolumineseence （PL） of the BTO ferroelectric film is attributed to the structure. The ferroeleetric film which annealed at 673 K for 8 h has the better PL property. The peak width is about 30 nm from 580 nm to 610 nm, towards the yellow region. The mixed electroluminescence （EL） spectrum of InGaN/GaN multiple quantum well LED with 150-nm thick amorphous BTO ferroelectric thin film displays the blue-white light. The Commission Internationale De L＇Eclairage （CIE） coordinate of EL is （0.2139, 0.1627）. EL wavelength and intensity depends on the composition, microstructure and thickness of the ferroelectric thin film. The transmittance of amorphous BTO thin film is about 93% at a wavelength of 450 nm-470 nm. This means the amorphous ferroelectrie thin films can output more blue-ray and emission lights. In addition, the amorphous ferroelectric thin films can be directly fabricated without a binder and used at higher temperatures （200 ℃-400 ℃）. It is very favourable to simplify the preparation process and reduce the heat dissipation requirements of an LED. This provides a new way to study LEDs.

A Large-Scale Scheduling Method for Multiple Agile Optical Satellites

This study investigates the scheduling problem ofmultiple agile optical satelliteswith large-scale tasks.This problem is difficult to solve owing to the time-dependent characteristic of agile optical satellites,complex constraints,and considerable solution space.To solve the problem,we propose a scheduling method based on an improved sine and cosine algorithm and a task merging approach.We first establish a scheduling model with task merging constraints and observation action constraints to describe the problem.Then,an improved sine and cosine algorithm is proposed to search for the optimal solution with the maximum profit ratio.An adaptive cosine factor and an adaptive greedy factor are adopted to improve the algorithm.Besides,a taskmerging method with a task reallocation mechanism is developed to improve the scheduling efficiency.Experimental results demonstrate the superiority of the proposed algorithm over the comparison algorithms.

Performance Analysis of Multiple User Optical Code Division Multiple Access

In this paper, we discuss and analyze an optical code division multiple access for multiple user system. Media access control implementation has been considered. For fulfilling the huge need of bandwidth services, technology tends to move to optical networks and three major optical systems come into existence. Code division of the optical network is most used and real concept interacted with users up to this time. Optical code division multiple access provides complete spectrum to each and every user for the time of accessing the channel. In the paper, we have proposed network architecture with optical encoder and decoder along with optical code translator which is supporting multiple user systems. We integrate the code translator with encoding and decoding of optical code to use the optical network at full extent and present the simulation validation results of 6 Gb/s 3-hop transmission by use of proposed architecture. Further, we have implemented experimentation with 6 users 3 Gb/s optical code division multiple access network. Through simulation structure, it is shown that the combination of encoding with EDFA in multiple user environment system provides improvement in bit error rate and also improves the multiple access interference. With increase of users in the network, MAI value increases and our proposed scheme controls interference in the network.

A passive optical network based on optical code division multiplexing and time division multiple access technology

A passive optical network （PON） scheme based on optical code division multiplexing （OCDM） for the downstream traffics is proposed and analyzed in detail. In the PON, the downstream traffics are broadcasted by OCDM technology to guarantee the security, while the upstream traffics pass through the same optical fiber by the common time division multiple access （TDMA） technology to decrease the cost. This schemes are denoted as OCDM/TDMA-PON, which can be applied to an optical access network （OAN） with full services on demand, such as Internet protocol, video on demand, tele-presence and high quality audio. The proposed OCDM/TDMA-PON scheme combines advantages of PON, TDMA, and OCDM technology. Simulation results indicate that the designed scheme improves the OAN performance, and enhances flexibility and scalability of the system.

Evaluating visual outcomes using optical coherence tomography(OCT)in pediatric multiple sclerosis and other neuroinflammatory conditions

Optical coherence tomography(OCT)is a technology that is widely used to assess structural abnormalities in the retina for a variety of pediatric conditions.The introduction of this instrument has allowed for widespread access to minimally invasive standardized,reproducible quantified structural assessments of the optic nerve and retina.This has had important implications in pediatric optic neuropathies,populations in whom monitoring of disease activity is essential to make treatment decisions.OCT has had particular relevance for inflammatory optic neuropathies,as onset of an inflammatory optic neuropathy may herald the onset of a chronic inflammatory disorder of the central nervous system(CNS)such as multiple sclerosis,neuromyelitis optica spectrum disorder(aquaporin 4 antibody positive),and myelin oligodendrocyte glycoprotein(MOG)associated disorders.This paper will focus on the application of OCT technology to this group of disorders in pediatrics.After reviewing pediatric-specific anatomic and practical issues pertinent to OCT,we will review knowledge related to the use of OCT in inflammatory pediatric optic neuropathies,with a focus on structural outcomes and their correlation with functional outcome metrics.

Designs of All-Optical Higher-Order Signed-Digit Adders Using Polarization-Encoded Based Terahertz-Optical-Asymmetric-Demultiplexer (TOAD)

Various designed circuits for multiple-valued all-optical arithmetic are demonstrated. The terahertz-optical-asymmetric-demultiplexer (TOAD) switch is used as the basic structure unit in the proposed circuits due to its compact size, thermal stability, and low power operation. The designs of trinary and quaternary signed-digit numbers based adders are presented using different polarized states of light. These proposed polarization-encoded based adders use much less switches and their speeds are higher than the intensity-encoded counterparts. Further, it will be shown that one of the proposed trinary signed-digit adders is twice as fast as a recently reported modified signed-digit adder.

Mathematical demonstration of correlation of optical prime code

Starting from the configuration of the optical prime code, a kind of key signature code for the optical code-division multiple access （OCDMA） system, based on the linear congruence theory in the finite Galois field, the correlation properties of the basic prime code, the extended prime code and the modified prime code are mathematically analyzed, the distribution of cross-correlation values is given and the overlap area of ＂1＂s in the case of periodically circularly shifting is indicated. It is mathematically demonstrated that the maximum cross-correlation of the basic prime code is 2, and that of the extended prime code and the modified prime code is 1. The integrated correlation analysis process is proposed. The signal-interfere ratio （SIR） and the BER performance of the systems employing different signature codes are calculated, respectively, and the performances of OCDMA systems employing different signature codes mode are compared.

Optical coherence tomography in central nervous system demyelinating diseases related optic neuritis

AIM：To compare the thickness of the peripapillary retinal nerve fiber layer（RNFL）and ganglion cell-inner plexiform layer（GCIPL）among patients with various forms of optic neuritis（ON）and to identify whether any particular parameters or their thinning pattern can be used to distinguish the type of ON.METHODS：This prospective study was conducted at the Department of Ophthalmology,Faculty of Medicine,Siriraj Hospital,Thailand,between January,2015 and December,2016.We enlisted patients over 18 years of age with history of ON and categorized patients into 4 groups：1）aquaporin 4 antibodies（AQP4-IgG）positive;2）multiple sclerosis（MS）;3）myelin oligodendrocyte glycoprotein antibodies（MOG-IgG）positive;4）idiopathic-ON patients.Healthy controls were also included during the same study period.All patients underwent complete ophthalmological examination and spectral domain optical coherence tomography（OCT）imaging to analyze RNFL and GCIPL thickness after at least 3mo since the last episode of acute ON.The generalized estimating equation（GEE）models were used to compare the data amongst ON groups. RESULTS： Among 87 previous ON eyes from 57 patients（43 AQP4-IgG＋ON,17 MS-ON,8 MOG-IgG＋ON,and 19idiopathic-ON）,mean logMAR visual acuity of AQP4-IgG＋ON,MS-ON,MOG-IgG＋ON,and idiopathic-ON groups was 0.76±0.88,0.12±0.25,0.39±0.31,and 0.75±1.08,respectively.Average,superior,and inferior RNFL were significantly reduced in AQP4-IgG＋ON,MOG-IgG＋ON and idiopathic-ON eyes,relative to those of MS-ON.Differences were not statistically significant for RNFL or GCIPL between the AQP4-IgG＋ON and MOG-IgG＋ON groups,whereas visual acuity in MOG-IgG＋ON was slightly,but not significantly,better（0.39 vs 0.76）.Although RNFL thickness in MOG-IgG＋ON was significantly reduced as compared to MS-ON,mean visual acuity and GCIPL were not different.CONCLUSION：Thinning of superior and inferior quadrants of RNFL are more commonly seen in MOG-IgG＋ON and AQP4-IgG＋ON.Long term visual acuity in MOG-IgG＋ON is often better than AQP4-IgG＋ON,whereas the structural change from OCT is comparable.

Adaptive modulation in MIMO optical wireless communication systems

In the intensity modulation and direct detection （IM/DD） multiple-input multiple-output （MIMO） optical wireless communication systems, a direct-current-biased adaptive modulation scheme is proposed to guarantee the nonnegative property of transmitted signals, and the MIMO channel is converted to a parallel channel by using a singular value decomposition. Besides, a QR decomposition and successive interference cancellation based adaptive modulation scheme is proposed, and the MIMO channel can be simplified to a parallel channel under the bit error ratio （BER） target constraint. The power is optimally allocated to each sub-channel to maximize the data rate. Simulation results show that the proposed adaptive modulation schemes can effectively improve the transmission rate of the systems under the BER target and constant optical power constraints. The proposed adaptive modulation schemes make use of the multiplexing gain of the MIMO techniques, and can further improve the spectrum efficiency of optical wireless systems.

Overcoming the penetration depth limit in optical microscopy:Adaptive optics and wavefront shaping

Despite the unique advantages of optical microscopy for molecular specific high resolution imaging of living structure in both space and time,curent applications are mostly limited to research settings.This is due to the aberrations and multiple scattering that is induced by the inhomogeneous refractive boundaries that are inherent to biological systems.However,recent developments in adaptive optics and wavefront shaping have shown that high resolution optical imaging is not fundamentally limited only to the observation of single cells,but can be significantly enhanced to realize deep tissue imaging.To provide insight into how these two closely related fields can expand the limits of bio imaging,we review the recent progresses in their performance and applicable range of studies as well as potential future research directions to push the limits of deep tissuse imnaging.

Using CSMA/CD for Ethernet Passive Optical Network (EPON)

Using CSMA/CD for EPON can eliminate the augmentations, such as multi-point control protocol and point-to-point emulation, added to the existing 802.3 architecture due to the incompatibility of PON to Ethernet. Both full-duplex EPON system and half-duplex EPON system using CSMA/CD were proposed. In the full-duplex EPON, CSMA/CD is used as the upstream MAC protocol. In the half-duplex EPON system, both upstream and downstream traffic contend for the optical channel through CSMA/CD protocol. The upstream lightwave redirection and collision detection techniques were given. By the analysis and simulation, the throughput performance of the half-duplex EPON system is proven to be as well as that of the existing high speed half-duplex Ethernet LAN.

EFFICIENT FITTING RANGE FOR GLUCOSE MEASUREMENT WITH OPTICAL COHERENCE TOMOGRAPHY

Studies of non-invasive glucose measurement with optical coherence tomography(OCT)in tissue-simulating phantoms and biological tissues show that glucose has an effect on the OCT signal slope.Choosing an efficient fitting range to calculate the OCT signal slope is important because it helps to improve the precision of glucose measurement.In this paper,we study the problem in two ways:(1)scattering-induced change of OCT signal slope versus depth in intralipid suspensions with different concentrations based on Monte Carlo(MC)simulations and experiments and(2)efficient fitting range for glucose measurement in 3%and 10%intralipid.The results show that the OCT signal slope expresses a contrary change with scattering coefficient below a certain depth in high intralipid concentrations,so that there is an effective fitting depth.With an efficient fitting range from 100μm to the effective fitting depth,the precision of glucose measurement can be 4.4mM for 10%intralipid and 2.2mM for 3%intralipid.

Higher Speed Passive Optical Networks for Low Latency Services

Latency sensitive services have attracted much attention lately and imposedstringent requirements on the access network design. Passive optical networks (PONs) providea potential long-term solution for the underlying transport network supporting theseservices. This paper discusses latency limitations in PON and recent progress in PONstandardization to improve latency. Experimental results of a low latency PON system arepresented as a proof of concept.