Real-Time 4-Mode MDM Transmission Using Commercial 400G OTN Transceivers and All-Fiber Mode Multiplexers

Weakly-coupled mode division multiplexing(MDM)technique is considered a promising candidate to enhance the capacity of an optical transmission system,in which mode multiplexers/demultiplexers(MMUX/MDEMUX)with low insertion loss and modal crosstalk are the key components.In this paper,a low-modal-crosstalk 4-mode MMUX/MDEMUX for the weakly-coupled triple-ring-core few-mode fiber(TRC-FMF)is designed and fabricated with side-polishing processing.The measurement results show that a pair of MMUX/MDEMUX and 25 km weakly-coupled TRC-FMF MDM link achieve low modal crosstalk of lower than−17.5 dB and insertion loss of lower than 11.56 dB for all the four modes.Based on the TRC-FMF and all-fiber MMUX/MDEMUX,an experiment for 25 km real-time 4-mode 3-λwavelength division multiplexing(WDM)-MDM transmission is conducted using commercial 400G optical transport network(OTN)transceivers.The experimental results prove weakly-coupled MDM techniques facilitate a smooth upgrade of the optical transmission system.

Design of LCoS-Based Twin 1×40 Wavelength Selective Switch

Wavelength selective switch(WSS)is the crucial component in the reconfigurable optical add/drop multiplexer(ROADM),which plays a pivotal role in the next-generation all-optical networks.We present a compact architecture of twin 1×40 liquid crystal on silicon(LCoS)-based WSS,which can be regarded as a 4f system in the wavelength direction and a 2f system in the switching direction.It is designed with theoretical analysis and simulation investigation.Polarization multiplexing is employed for two sources of twin WSS by polarization con-version before the common optical path.The WSS system attains a coupling efficacy exceeding 96%for 90%of the ports through simulation optimization.The 3 dB bandwidth can be achieved by more than 44 GHz at a 50 GHz grid for all 120 channels at all deflection ports.This work establishes a solid foundation for developing high-performance WSS with larger port counts.

Reconfigurable optical add-drop multiplexers for hybrid mode-/wavelength-division-multiplexing systems

Dealing with the increase in data workloads and network complexity requires efficient selective manipulation of any channels in hybrid mode-/wavelength-division multiplexing(MDM/WDM)systems.A reconfigurable optical add-drop multiplexer(ROADM)using special modal field redistribution is proposed and demonstrated to enable the selective access of any mode-/wavelength-channels.With the assistance of the subwavelength grating structures,the launched modes are redistributed to be the supermodes localized at different regions of the multimode bus waveguide.Microring resonators are placed at the corresponding side of the bus waveguide to have specific evanescent coupling of the redistributed supermodes,so that any mode-/wavelength-channel can be added/dropped by thermally tuning the resonant wavelength.As an example,a ROADM for the case with three mode-channels is designed with low excess losses of<0.6,0.7,and 1.3 dB as well as low cross talks of<−26.3,−28.5,and−39.3 dB for the TE0,TE1,and TE2 modes,respectively,around the central wavelength of 1550 nm.The data transmission of 30 Gbps∕channel is also demonstrated successfully.The present ROADM provides a promising route for data switching/routing in hybrid MDM/WDM systems.

Quantitative Determination of Benoxinate Hydrochloride by Three Wavelength Spectrophotometry

hree wavelength spectrophotometry was used to determine the content ofbenoxinate hydrochloride.Using this method could effectively eliminate the devia-tion of background absorption caused by the change of concentration and the errorof quantitative anaiysis caused by asymmetric peaks, and at the same time the lean-ing degree of base line was corrected.This method was simple, the recovery was98. 62% 101. 86% and the coefficient of variation was 0. 551%.

Calibration-free wavelength modulation spectroscopy for gas concentration measurements under low-absorbance conditions

We derive the expressions of the first and second harmonic signals on the basis of absorption spectral and lock-in theories, and determine the gas concentration according to the ratio of second and first harmonic signals. It is found that the X and Y components of the harmonic signals are influenced by the phase shift between the detection and reference signal, and the phase shift can be any value in a range from 0 to 2π, which is different from the results obtained previously. Meanwhile, an additional item caused by the residual amplitude modulation will make a great contribution to the second harmonic signal, and may not be neglected under low absorbance conditions. Theoretical analysis indicates that subtracting back-ground signal from the second harmonic signal can remove the influence of this item, and can improve the measurement accuracy of gas concentration. On this basis, we select the transition of CO2 at 6527.64 cm-1 to analyse the approximation errors during the derivation by numerical simulation and then measure the CO2 concentration under low absorbance conditions, with absorbance varying from 1‰ to 6‰.

Wavelength Dependence in the Analysis of Carbon Content in Coal by Nanosecond 266 nm and 1064 nm Laser Induced Breakdown Spectroscopy

The wavelength dependence of laser induced breakdown spectroscopy （LIBS） in the analysis of the carbon contents of coal was studied using 266 nm and 1064 nm laser radiations. Compared with the 1064 nm wavelength laser ablation, the 266 nm wavelength laser ablation has less thermal effects, resulting in a better crater morphology on the coal pellets. Besides, the 266 nm wavelength laser ablation also provides better laser-sample coupling and less plasma shielding, resulting in a higher carbon line intensity and better signal reproducibility. The carbon contents in the bituminous coal samples have better linearity with the line intensities of atomic carbon measured by the 266 nm wavelength than those measured by the 1064 nm wavelength. The partial least square （PLS） model was established for the quantitative analysis of the carbon content in coal samples by LIBS. The results show that both of the 266 nm and 1064 nm wavelengths are capable of achieving good performance for the quantitative analysis of carbon content in coal using the PLS method.

A New Method to Determine Central Wavelength and Optimal Bandwidth for Predicting Plant Nitrogen Uptake in Winter Wheat

Plant nitrogen （N） uptake is a good indicator of crop N status. In this study, a new method was designed to determine the central wavelength, optimal bandwidth and vegetation indices for predicting plant N uptake （g N m-2） in winter wheat （Triticum aestivum L.）. The data were collected from the ground-based hyperspectral reflectance measurements in eight field experiments on winter wheat of different years, eco-sites, varieties, N rates, sowing dates, and densities. The plant N uptake index （PNUI） based on NDVI of 807 nm combined with 736 nm was selected as the optimal vegetation index, and a linear model was developed with R2 of 0.870 and RMSE of 1.546 g N m-2 for calibration, and R2 of 0.834, RMSE of 1.316 g N m-2, slope of 0.934, and intercept of 0.001 for validation. Then, the effect of the bandwidth of central wavelengths on model performance was determined based on the interaction between central wavelength and bandwidth expansion. The results indicated that the optimal bandwidth varies with the changes of the central wavelength and with the interaction between the two bands in one vegetation index. These findings are important for prediction and diagnosis of plant N uptake more precise and accurate in crop management.

Effects of the long wavelength-filtered continuousspectrum on natural refractive development in juvenile guinea pigs

AIM: To investigate the effects of spectral composition and light intensity on natural refractive development in guinea pigs.METHODS: A total of 124 pigmented guinea pigs(2-week-old) were randomly assigned to three groups at high(Hi;4000 lx), medium(Me;400 lx) and low(Lo;50 lx) light intensities under a 12:12 light/dark cycle for 6 wk. Each group was subdivided into subgroups with the following spectra: broad spectrum Solux halogen light(BS), 600 nm above-filtered continuous spectrum(600F), 530 nm above-filtered continuous spectrum(530F), and 480 nm above-filtered continuous spectrum(480F;HiBS: n=10, Hi600F: n=10, Hi530F: n=10, Hi480F: n=10, MeBS: n=10, Me600F: n=10, Me530F: n=10, Me480F: n=10, LoBS: n=11, Lo600F: n=12, Lo530F: n=10, Lo480F: n=11). Refractive error, corneal curvature radius, and axial dimensions were determined by cycloplegic retinoscopy, photokeratometry, and A-scan ultrasonography before and after 2, 4, and 6 wk of treatment. Average changes from both eyes in the ocular parameters and refractive error were compared among different subgroups.RESULTS: After 6 wk of exposure, high-intensity lighting enhanced hyperopic shift;medium-and low-intensity lighting enhanced myopic shift(P<0.05). Under the same spectrum, axial increase was larger in the low light intensity group than in the medium and high light intensity groups(HiBS: 0.65±0.02 mm, MeBS: 0.67±0.01 mm, LoBS:0.82±0.02 mm;Hi600 F: 0.64±0.02 mm, Me600F: 0.67±0.01 mm, Lo600F: 0.81±0.01 mm;Hi530F: 0.64±0.02 mm, Me530F: 0.67±0.01 mm, Lo530F: 0.73±0.02 mm;Hi480F: 0.64±0.01 mm, Me480F: 0.66±0.01 mm, Lo480F: 0.72±0.02 mm;P<0.05). Under 400 lx, there was a faster axial increase in the MeBS group than in the Me480F group(P<0.05). Under 50 lx, axial length changes were significantly larger in LoBS and Lo600F than in Lo530F and Lo480F(P<0.01).CONCLUSION: Under high-intensity lighting, high light intensity rather than spectrum distributions that inhibits axial increase. Under medium-and low-intensity lighting, filtering out the long wavelength inhibits axial growth in juvenile guinea pigs.

Sensitive absorption measurements of hydrogen sulfide at 1.578 μm using wavelength modulation spectroscopy

Sensitive detection of hydrogen sulfide（H2S） has been performed by means of wavelength modulation spectroscopy（WMS） near 1.578 μm. With the scan amplitude and the stability of the background baseline taken into account, the response time is 4 s for a 0.8 L multi-pass cell with a 56.7 m effective optical path length. Moreover, the linearity has been tested in the 0–50 ppmv range. The detection limit achievable by the Allan variance is 224 ppb within 24 s under room temperature and ambient pressure conditions. This tunable diode laser absorption spectroscopy（TDLAS） system for H2 S detection has the feasibility of real-time online monitoring in many applications.

A Dual Wavelength Differential First Derivative Spectrophotometric Method for Identification and Determination of Carbon Monoxide Generated During the Microsomal Metabolism of Xenobiotics in vitro

A dual wavelength differential first derivative spectrophotometric method has been developed to standardize the concentration of a saturated aqueous solution of carbon monoxide (CO) as the standard and to identify and to determine CO formed during the microsomal metabolism of xenobiotics in vitro. The method can significantly eliminate the background interference in the assay media and increase the quantitative accuracy and the sensitivity. There is a good linear relationship between CO concentration in the range of 2～10 μmol·L 1 CO and the distance D between the first derivative peak at 415 nm amd valley at 426 nm with r=0.9999(n=5),the regression equation being C (mmol·L 1 )=17.6D 0.4, the detection limit lower than 0.1 μmol·L 1 CO. The average recoveries of CO from the assay system and the sample were 102.1%, RSD=2.9% (n=7) and 79.7%, RSD=6.8% (n=12),respectively. The RSD of within day was 4.4%(n=18),and the RSD of day to day was 6.1%(n=16). By this method, four trihaloanilines and one trihalobenzene were tested, the results showed that only 2,4,5 trifluoroaniline could be converted to CO by the incubation with rat hepatic microsomes, NADPH and oxygen, the ability of phenobarbital or dexamethasone to induce rat hepatic microsomes to catalyze CO formation was 3 or 8 times higher than that of the control.

A 32-channel 100 GHz wavelength division multiplexer by interleaving two silicon arrayed waveguide gratings

A 32-channel wavelength division multiplexer with 100 GHz spacing is designed and fabricated by interleaving two silicon arrayed waveguide gratings(AWGs).It has a parallel structure consisting of two silicon 16-channel AWGs with200 GHz spacing and a Mach-Zehnder interferometer(MZI)with 200 GHz free spectral range.The 16 channels of one silicon AWG are interleaved with those of the other AWG in spectrum,but with an identical spacing of 200 GHz.For the composed wavelength division multiplexer,the experiment results reveal 32 wavelength channels in C-band,a wavelength spacing of 100 GHz,and a channel crosstalk lower than-15 dB.

Three-wavelength generation from cascaded wavelength conversion in monolithic periodically poled lithium niobate

Tunable coherent emission is generated in a single-pass, cascaded wavelength conversion process from mode-locked laser-pumped monolithic periodically poled lithium niobate（PPLN）. Three ranges of wavelength, including visible output from 628 nm to 639 nm, near-infrared output from 797 nm to 816 nm, and mid-infrared output from 3167 nm to 3459 nm,were obtained from the monolithic PPLN, which consists of a 10-mm section for 532-nm-pumped optical parametric generation（OPG） and a 7-mm section for 1064-nm-pumped sum frequency generation（SFG）. A pump-to-signal conversion efficiency of 23.4% for OPG at 50°C and a quantum efficiency of 26.2% for SFG at 200°C were obtained.

Wavelength dependence four-wave mixing spectroscopy in a micrometric atomic vapour

This paper presents a theoretical study of wavelength dependence four-wave-mixing （FWM） spectroscopy in a micrometric thin atomic vapour. It compares three cases termed as mismatched case I, matched case and mismatched case II for the probe wavelength less, equal and greater than the pump wavelength respectively. It finds that Dicke- narrowing can overcome width broadening induced by Doppler effects and polarisation interference of thermal atoms, and high resolution FWM spectra can be achieved both in matched and mismatched wavelength for many cases. It also finds that the magnitude of the FWM signal can be dramatically modified to be suppressed or to be enhanced in comparison with that of matched wavelength in mismatched case I or II. The width narrowing and the magnitude suppression or enhancement can be demonstrated by considering enhanced contribution of slow atoms induced by atom-wall collision and transient effect of atom-light interaction in a micrometric thin vapour.

An Ant Colony Algorithm Based on Cross-Layer Design for Routing and Wavelength Assignment in Optical Satellite Networks

This paper introduces an ant colony routing and wavelength assignment algorithm based on cross-layer design(CL-ACRWA),which can overcome the adverse effects of Doppler wavelength shift on data transmission in optical satellite networks. Firstly, a cross-layer optimization model is built, which considers the Doppler wavelength shift, the transmission delay as well as wavelength-continuity constraint. Then an ant colony algorithm is utilized to solve the cross-layer optimization model, resulting in finding an optimal light path satisfying the above constraints for every connection request. The performance of CL-ACRWA is measured by the communication success probability, the convergence property and the transmission delay. Simulation results show that CL-ACRWA performs well in communication success probability and has good global search ability as well as fast convergence speed. Meanwhile, the transmission delay can meet the basic requirement of real-time transmission of business.

Semi-vectorial analysis of a compact wavelength demultiplexer based on the tapered multimode interference coupler

Based on a parabolically tapered multimode interference （MMI） coupler with a deep-etched SiO2/SiON rib waveguide, a compact wavelength demultiplexer operating at 1.30 and 1.55 μm wavelengths is proposed and analysed by using three-dimensional semi-vectorial finite-difference beam propagation method （3D-SV-FD-BPM）. The results show that a MMI section of 330.0 μm in length, which is only 76% length of a straight MMI coupler, is achieved with the contrasts of 42.3 and 39.2dB in quasi-TE mode, and 38.4 and 37.8dB in quasi-TM mode at wavelengths 1.30 and 1.55μm, respectively, and the insertion losses below 0.2dB at both wavelengths and in both polarization states, The alternating direction implicit algorithm with the Crank-Nicholson scheme is applied to the discretization of the 3D-SV-FD-BPM formulation along the longitudinal direction. Moreover, a modified FD scheme is constructed to approximate the resulting equations along the transverse directions, in which the discontinuities of the derivatives of magnetic field components Hy and Hx along the vertical and horizontal interfaces, respectively, are involved.

Determination of action potential wavelength restitution in Scn5a^＋/- mouse hearts modelling human Brugada syndrome

Brugada syndrome is a primary electrical disorder of theheart, predisposing affected individuals to potentially lethal,ventricular tachy-arrhythmias. A number of mechanismshave been identified as being important increasing the riskof these rhythms. Wavelength （γ） restitution has beensuggested to predict the onset of action potential duration（APD） alternans in mouse Scn5a^＋/- hearts modelling Bru-gada syndrome.

Broad and ultra-flattened supercontinuum generation in the visible wavelengths based on the fundamental mode of photonic crystal fibre with central holes

By coupling a train of femtosecond pulses with 100 fs pulse width at a repetition rate of 76 MHz generated by a mode-locked Ti： sapphire laser into the fundamental mode of photonic crystal fibre （PCF） with central holes fabricated through extracting air from the central hole, the broad and ultra-flattened supercontinuum （SC） in the visible wavelengths is generated. When the fundamental mode experiences an anomalous dispersion regime, three phases in the SC generation process are primarily presented. The SC generation （SCG） in the wavelength range from 470 nm to 805 nm does not emerge significant ripples due to a higher pump peak power and the corresponding mode fields at different wavelengths are observed using Bragg gratings. The relative intensity fluctuations of output spectrum in the wavelength ranges of 530 nm to 640 nm and 543 nm to 590 nm are only 0.028 and 0.0071, respectively.

Simultaneous Determination of Six Constituents in Cangbaiqutong Capsule by HPLC Wavelength Switching Technique

[Objectives] To establish a high performance liquid chromatography (HPLC) wavelength switching method for the simultaneous determination of content of six constituents (phellodendrine chloride, gentiopicrin, paeoniflorin, tetrandrine, berberine hydrochloride and paeonol) in Cangbaiqutong capsules, and provide a scientific basis for the comprehensive evaluation of the quality of Cangbaiqutong capsule.[Methods] The chromatographic column of Waters XSELECT CSH-C 18 (4.6 mm × 150 mm, 5 μm), the mobile phase of acetonitrile-0.1% phosphate solution, gradient elution (0-15 min,10%-18% A;15-30 min,18%-50% A;30-35 min, 50%-10% A);the flow rate of 1.0 mL/min, wavelength switching of 284 (0-7 min, phellodendrine), 274 (7-10 min, gentiopicrin), 230 (10-14 min, paeoniflorin) and 274 nm (14-35 min, tetrandrine, berberine hydrochloride, paeonol), the injection volume of 10 μL.[Results] There was a good linear relationship between the area of chromatographic peak and the injection volume of phellodendrine chloride, gentiopicrin, paeoniflorin, tetrandrine, berberine hydrochloride and paeonol in the range of 0.150-1.504, 0.768-7.680, 1.096-10.960, 0.220-2.200, 0.296-2.956, 0.0345-0.345 μg, respectively;the average recovery rates ( n =6) were 98.3%, 99.2%, 98.8%, 98.8%, 99.1% and 98.2%, respectively;the RSD value was 1.32%, 1.46%, 1.08%, 1.31%, 1.26% and 1.21%, respectively.[Conclusions] The method can be used to determine many kinds of constituents at the same time, and the operation is simple, accurate and reproducible, and can be used for the quality control of compound Cangbaiqutong capsules.

Realization of advanced passive silicon photonic devices with subwavelength grating structures developed by efficient inverse design

Compact passive silicon photonic devices with high performance are always desired for future largescale photonic integration.Inverse design provides a promising approach to realize new-generation photonic devices,while it is still very challenging to realize complex photonic devices for most inverse designs reported previously due to the limits of computational resources.Here,we present the realization of several representative advanced passive silicon photonic devices with complex optimization,including a sixchannel mode(de)multiplexer,a broadband 90 deg hybrid,and a flat-top wavelength demultiplexer.These devices are designed inversely by optimizing a subwavelength grating(SWG)region and the multimode excitation and the multimode interference are manipulated.Particularly,such SWG structures are more fabrication-friendly than those random nanostructures introduced in previous inverse designs.The realized photonic devices have decent performances in a broad bandwidth with a low excess loss of<1 dB,which is much lower than that of previous inverse-designed devices.The present inverse design strategy shows great effectiveness for designing advanced photonic devices with complex requirements(which is beyond the capability of previous inverse designs)by using affordable computational resources.

Degradation of Japanese Lacquer under Wavelength Sensitivity of Light Radiation

Degradation of Japanese lacquer caused by light irradiation was examined at various wavelengths. By exposing lacquer specimens to a narrow monochromatic light band isolated from dispersed polychromatic light emitted by a Xe lamp source, the wavelength sensitivity characteristics of lacquer degradation could be determined on the basis of radiant energy. Tame-Urushi (brown) lacquer displayed peak degradation maxima at 220 and 315 nm. A broad shoulder peak was also observed in UVA. For Shu-Urushi (cinnabar) lacquer, in addition to peaks in the UVA–UVB range, a large degree of degradation was observed following exposure to light in the visible range. Ao-Urushi (green) lacquer showed similar characteristics, although it was less prone to degradation. Similarly, Shin-Urushi (black) lacquer showed little change in response to light, although UV light caused limited degradation. These results indicate that along with the damage caused by UVA and UVB, visible light in the range 510 - 650 nm may also have a significant degradation effect. Our results provide experimental evidence that Japanese lacquer responds differently to light of various wavelengths and that specific wavelengths, including visible light, can cause significant degradation.