Wavelength Switching Research Articles

On the Network Planning of Wavelength Switched Optical Networks With P2MP Transceivers

On the Network Planning of Wavelength Switched Optical Networks With P2MP Transceivers

Multiple visible wavelength switchable cascaded self-Raman laser based on selective wave-mixing mechanism

A diode-pumped solid-state laser with watts-level five switchable wavelengths spanning green to red is first experimentally demonstrated. The selective wave-mixing mechanism was introduced for multiple visible wavelength switchable output. The five visible wavelengths are generated by wave-mixing of the fundamental wave, the first-Stokes wave, and the second-Stokes wave in a Nd:YVO4 self-Raman laser. A β-barium borate crystal with a critical phase-matching angle cut is used for the wavelength conversion, and the angle-tuning method was used to achieve fast wavelength switching. A diffusion bonded YVO4/Nd:YVO4/YVO4 crystal was used to reduce the thermal lens effect and increase the effective length of the Raman gain medium for high output power and efficient Raman conversion. Under a pump power of 19.5 W, five visible laser output powers achieved for the green at 532 nm, lime at 559 nm, yellow at 588 nm, orange-red at 620 nm, and deep red at 657 nm are 4.01, 1.76, 2.54, 1.41, and 2.82 W, respectively. This laser system provides a convenient way for visible wavelength-switchable coherent light generation and may find potential applications where multiple visible wavelengths are required.

Traffic prediction assisted wavelength allocation in vehicle-to-infrastructure communication: A fiber-wireless network based framework

The advent of the next generation of connected and autonomous cars offers immense opportunities for both users as well as service providers. In particular, fiber-wireless (FiWi) based vehicle-to-infrastructure (V2I) network can facilitate some of the stringent requirements of sixth-generation (6G) vehicular networks, including higher capacity, lower delay, and ubiquitous connectivity. FiWi based V2I network integrates the next generation passive optical network 2 (NG-PON2) with IEEE 802.11p based V2I network. In this work, we first review the various kinds of vehicular data traffic and their desired key performance indicators (KPIs), namely throughput, delay, and reliability. Depending on the KPI requirements, the V2I traffic is classified among four classes and assigned to different transmission containers (T-CONTs) of the optical network unit (ONU). Further, in order to minimize the delay of the network, we propose a machine learning (ML) based T-CONT priority assignment wavelength allocation algorithm that minimizes the number of wavelength switching instances in the PON. The performance of the proposed ML-based wavelength allocation algorithm is compared with the other approaches, namely random and equal T-CONT based wavelength allocation algorithms. Simulation results demonstrate the efficiency of the proposed algorithm vis-a-vis other approaches in terms of end-to-end (e2e) delay, throughput, and reliability.

Wavelength switching technique for phase interrogation of Mach Zehnder interferometer-based optical sensors.

A method for determining the phase shift of a Mach Zehnder interferometer (MZI) is presented. It is based on switching the wavelength of continuous wave (CW) laser light illuminating the MZI and measuring the interferometer output amplitudes at DC and switching frequency. The method can measure the MZI phase shift unambiguously over the entire phase shift range of 2π. A practical proof of concept demonstration shows that the method can perform real-time measurement with high repeatability and accuracy limited by the optical frequency drift and power fluctuation of the lasers. The method does not require modifications of the sensor or accessing to the laser electronics and also uses simple detection. It is, therefore, suitable for bio and medical sensing applications.

Dynamically manipulation of anisotropic coherent perfect absorption in borophene metasurface

This paper proposed a borophene-based metamaterial device to achieve the anisotropic coherent perfect absorption (CPA) effect in the two-port device. By simply adjusting the polarization angle of the incident light, the dynamic switching of the CPA resonance peak wavelength can be achieved. Besides, by simultaneously modulating the electron doping concentration of borophene and the relative phase of the incident light, the coherent absorption efficiency of borophene can be continuous modulated for both polarization directions. Furthermore, the theorem of scattering matrix is utilized to elucidate the physical mechanism of CPA, and the analytical results demonstrate remarkable accordance with the numerical computations. Owing to the flexible continuous tunability, the proposed borophene CPA device is expected to open up new opportunities for optical modulators and all-optical logic chips.

Quality grade evaluation of Nvjin Pills based on traditional Chinese medicine reference drug and network pharmacology of target-focused compounds.

To improve the effectiveness of marketed drugs related to active ingredients, it is necessary to designate a more unified quality evaluation standard. Taking Nvjin Pills as an example, this study reported the development of a novel principle of analysis in traditional Chinese medicine. The core of the experiment is to prepare three batches of traditional Chinese medicine reference drugs by high-quality Chinese materia medica. The active ingredients identified in the herbal formula including glycyrrhizic acid, cinnamaldehyde, paeonol, baicalin, hesperidin, paeoniflorin, and ferulic acid were analyzed in traditional Chinese medicine reference drugs by the high-performance liquid chromatography method combined with wavelength switching. The simple prediction results of network pharmacological analysis verified the feasibility and reliability of the established quantitative analysis method for seven target-focused compounds in Nvjin Pills, which were recommended as candidate indicators for quality evaluation ultimately. Using the seven target-focused compounds as the scientific ruler, quality grade specifications of Nvjin Pills were proposed by comprehensive analysis. Accordingly, 16, 47, and 13 batches of samples were primarily graded as first grade, second grade, and unqualified grade, respectively. This study will provide a chemical basis for quality control of Nvjin Pills, which is necessary for the production process of pharmaceutical development.

TWDM-assisted passive quadrature phase demodulation for a Fabry-Perot-based ultrasound localization detection.

We propose a time and wavelength division multiplexing (TWDM)-assisted passive quadrature phase demodulation mechanism in this Letter. Combining wavelength division multiplexers (WDMs) with a programmable modulated grating Y-branch (MG-Y) laser, this method realizes both fast switching of discrete wavelengths and fast activation of multiple sensing paths simultaneously. Deploying it on a fiber-optic dual-cavity Fabry-Perot (F-P) ultrasound sensor array, we achieve high-precision localization of partial discharge (PD) signal sources in a two-dimensional (2D) plane with a maximum distance error of 1.53 cm and a maximum angle error of about 3.02°. This demodulation scheme can balance the relationship between sensitivity, sampling rate, and time-delay-induced errors, and provides an innovative solution for high-frequency phase demodulation applications of sensor arrays, which is especially significant for high-frequency detection in specific environments like partial discharges, industrial nondestructive testing, and so on.

Near- and far-field study of polarization-dependent surface plasmon resonance in bowtie nano-aperture arrays.

Bowtie nano-apertures can confine light into deep subwavelength volumes with extreme field enhancement, making them a useful tool for various applications such as optical trapping, deep subwavelength imaging, nanolithography, and sensors. However, the correlation between the near- and far-field properties of bowtie nano-aperture arrays has yet to be fully explored. In this study, we experimentally investigated the polarization-dependent surface plasmon resonance in bowtie nano-aperture arrays using both optical transmission spectroscopy and photoemission electron microscopy. The experimental results reveal a nonlinear redshift in the transmission spectra as the gap size of the bowtie nanoaperture decreases for vertically polarized light, while the transmission spectra remain unchanged with different gap sizes for horizontally polarized light. To elucidate the underlying mechanisms, we present simulated charge and current distributions, revealing how the electrons respond to light and generate the plasmonic fields. These near-field distributions were verified by photoemission electron microscopy. This study provides a comprehensive understanding of the plasmonic properties of bowtie nano-aperture, enabling their further applications, one of which is the optical switching of the resonance wavelength in the widely used visible spectral region without changing the geometry of the nanostructure.

Nano-ITLA Based on Thermo-Optically Tuned Multi-Channel Interference Widely Tunable Laser

A tunable light source with narrow linewidth, small size and low power consumption is necessary for high-speed digital coherent communication system. We have developed a monolithically integrated narrow linewidth widely tunable laser—multi-channel interference (MCI) laser, which realizes a quasi-continuous tuning range covering the C++ band. By packaging the laser chip, wavelength locker and thermoelectric cooler (TEC) into a transmitter optical subassembly (TOSA) box and designing a compact print circuit board (PCB), a nano-integrable tunable laser assembly (Nano-ITLA) based on the thermo-optically tuned MCI laser is demonstrated for the first time. The Nano-ITLA is 25.0 mm (L) × 15.6 mm (W) × 6.5 mm (H), and realizes 120 International Telecommunication Union (ITU)-grid switching over 48 nm and less than 3 W total power consumption. The side-mode suppression ratios (SMSRs) are higher than 46 dB, the fiber coupled output powers are greater than 16 dBm, and the Lorentzian linewidths are less than 150 kHz. High precision wavelength locking and temperature control system make the output frequency deviation of all channels from the ITU-grid less than ± 0.5 GHz and the wavelength drift less than ± 1 pm. The output power can be accurately controlled and stabilized at ± 0.1 dB through a closed-loop feedback. The no-light shutdown function realizes an extinction ratio higher than 40 dB during wavelength switching. The Nano-ITLA demonstrates excellent application potential in the coherent optical communications.

Low-latency wavelength-switched clock-synchronized intra-data center interconnects enabled by hollow core fiber.

Fast (nanoseconds) optical wavelength switching is emerging as a viable solution to scaling the size and capacity of intra-data center interconnection. A key enabling technology for such systems is low-jitter optical clock synchronization, which enables sub-nanosecond clock and data recovery for optically switched frames using low-cost methods such as clock phase caching. We propose and demonstrate real-time low-latency wavelength-switched clock-synchronized intra-data center interconnection at 51.2 GBd using a fast tunable laser (with ns scale switching time) and ultra-stable-latency hollow core fiber (HCF) for optically-switched data center networks. For wavelength-switched systems, we achieve a physical layer latency below 46 ns, consisting of 28 ns transceiver latency and a 18 ns inter-packet gap. Finally, we show that by exploiting the low chromatic dispersion and thermally-stable latency features of HCF, active clock phase tracking can be entirely eliminated.

Förster resonance energy transfer efficiency measurements on vinculin tension sensors at focal adhesions using a simple and cost-effective setup.

Forces inside cells play a fundamental role in tissue growth, affecting important processes such as cancer cell migration or tissue repair after injury. Förster resonance energy transfer (FRET)-based tension sensors are a remarkable tool for studying these forces and should be made easier to use. We prove that absolute FRET efficiency can be measured on a simple setup, an order of magnitude more cost-effective than a standard FRET microscopy setup, by applying it to vinculin tension sensors (VinTS) at the focal adhesions of live CHO-K1 cells. Our setup located at Université Paris-Saclay acquires donor and acceptor fluorescence in parallel on two low-cost CMOS cameras and uses two LEDs for rapid switching of the excitation wavelength at a reduced cost. The calibration required to extract FRET efficiency was achieved using a single construct (TSMod). FRET efficiencies were measured for VinTS and the tail-less control VinTL, lacking the actin-binding domain of vinculin. Measurements were confirmed on the same cell type using a more standard intensity-based setup located at Rutgers University. The average FRET efficiency of VinTS () over more than 10,000 focal adhesions is significantly lower () than that of VinTL (), our control that is insensitive to force, in agreement with the force exerted on vinculin at focal adhesions. Attachment of the CHO-K1 cells on fibronectin decreases FRET efficiency, thus increasing the force, compared with poly-lysine. FRET efficiency for the VinTL control is consistent with all measurements currently available in the literature, confirming the validity of our measurements and hence of our simpler setup. Force measurements, resolved spatially inside a cell, can be achieved using FRET-based tension sensors with a cost effective intensity-based setup. This will facilitate combining FRET with techniques for applying controlled forces such as optical tweezers.

Light-triggered “on-off” switchable dielectric constant in (Bi0.5Na0.5)0.94Ba0.06TiO3 lead-free ceramics

Light control of dielectric properties is very significant to develop photo-dielectric devices. Here, light-triggered “on-off” switchable dielectric constant (εr) was observed in (Bi0.5Na0.5)0.94Ba0.06TiO3 lead-free ferroelectric ceramics, exhibiting unconventional photo-dielectric effect (PDE). The effects of light switch period (2–165 min), light intensity (20–100 mW/cm2), and wavelength (450–940 nm) on PDE were studied in detail. Variation in εr exhibits remarkable switch effect with changing light on-off, while dielectric loss remains almost unchanged, and conductivity is still as low as 10−12 S/cm with excellent electrical insulation under light irradiation. The unconventional PDE exists in the high-frequency range ≥1 MHz and at the low-temperature of −100 °C. In addition to the thermal effect and light-induced change in domain behavior, it is believed that polarization of the trapped electron-hole pairs under an external electric field contributes to the increase in εr, and the low mobility of the pairs contributes to low dielectric loss and low photoconductivity. The results exhibit that dielectric constant of the lead-free ceramics can be regulated via light, whilst the ceramics keep excellent electrical insulation, endowing the lead-free ceramics potential applications in photo-dielectric devices.

A C-band widely tunable and switchable erbium-doped fiber laser based on a Sagnac-like loop embedded in Lyot filter

In this paper, a new type of widely tunable and switchable multi-wavelength erbium-doped fiber laser based on a Sagnac-like loop embedded in Lyot filter is proposed. The nonlinear polarization rotation effect is obtained by adjusting two polarization controllers (PCs). The polarization-dependent isolator and the Sagnac-like loop are used as the basic structure to realize the wide tuning and wavelength switching in C-band. Compared with the traditional Lyot filter, the Sagnac-like loop is used to replace the segment of polarization-maintaining fiber, and a more uniform comb spectrum can be obtained by this filter. The tunable and switchable wavelengths can be achieved by adjusting the PCs based on the nonlinear effect of the loop. The laser can emit single-, dual-, triple-, quad- and quintuple-wavelengths. The optical signal-to-noise ratios all exceed 43 dB. It can also be adjusted to partial wavelength intervals for quad-wavelength and quintuple-wavelength. The tuning range can reach the full range of the C-band, and the laser efficiency can reach the practical application standard. It can be applied to some precision instruments and equipment.

A 2 μm Dual-Wavelength Laser at Cryogenic Temperature with Balanced Simultaneous Emission

A Tm,Ho:YAP laser at cryogenic temperature is demonstrated for the first time with simultaneous emission at 2000 nm and 2119 nm. The feasibility of switching wavelength and achieving balanced output powers at two widely separated wavelengths has been confirmed by investigating the temperature dependence of the laser spectra. The optimal temperature for balanced output evidently diminishes as the pump power density increases, thereby manifesting a rate of change quantified at 1.19 K/W. At the optimal temperature of 43.1 K, the optical-to-optical conversion efficiency of the Tm,Ho:YAP simultaneous dual-wavelength laser (SDWL) with a pump power of 11.8 W is 12.7%, corresponding to a slope efficiency of 15.8%.

Determination of 21 polyphenols in fruits by high performance liquid chromatography

To establish a high performance liquid chromatography(HPLC) method for simultaneous determination of flavonoids(epicatechin, isoorientin, eriocitrin, hyperoside, narirutin, naringin, hesperidin, neohesperidin, quercetin, didymin, naringenin and hesperetin), phenolic acids(gallic acid, chlorogenic acid, caffeic acid, ferulic acid, sinapic acid and p-coumaric acid), terpenoids(limonin), stilbenes(piceatannol and resveratrol) in fruits. Add ethanol-water(4∶1, V/V) solution to the fruit pulp sample, ultrasonic extraction at 55 ℃ for 10 min, after centrifugation, the supernatant was dried and re-dissolved, and then eluted with ZORBAX Eclipse XDB-C_(18)(4.6 mm×100 mm, 3.5 μm) as chromatographic column, polyphenols are determined by HPLC under switching wavelength, and quantified by external standard method. The 21 polyphenols can be detected within 45 min and well separated from baseline, with linear correlation coefficients greater than 0.999, the detection limit of the method was 0.03-0.31 μg/g, and the limit of quantitation of the method was 0.09-1.03 μg/g. The intra-day precision was 0.5%-9.3%, the inter-day precision was 2.0%-9.6%. The recoveries of more than 90% polyphenols in the three fruits at three levels were between 80.0% and 119.8%. The relative standard deviation of spiked recoveries of three samples was less than 10.8%. The detection result of citrus, mango, blueberry, persimmon and other samples proved that the composition of polyphenols in different fruits was different. The method is sensitive, accurate and reproducible, and is suitable for the determination of polyphenols in fruits.

Rearrangeability and repackability of a multicast wavelength-space-wavelength elastic optical network

Elastic optical networks (EONs) have been introduced to meet the demands of the rapidly growing Internet. These networks can efficiently keep up with the emerging bandwidth-hungry and highly dynamic services, and can support multicast services using techniques like the path, tree or subtree methods. A multicast wavelength-space-wavelength (M-WSW) network is a switching node architecture for EONs, which adopts the subtree method to support multicast connections. An M-WSW network consists of three node stages in which wavelength, space and wavelength switches are used, respectively. A nonblocking M-WSW network guarantees that any connection between a free input and a free output can always be realized, and studying the nonblockingness of a network has attracted much attention from researchers. Sufficient conditions, in terms of the number of middle space switches, for an M-WSW network to be strict-sense nonblocking (SNB) or wide-sense nonblocking (WSNB) were examined in an earlier study. It is known that SNB networks usually incur a higher hardware cost, for instance, the number of middle space switches, compared to WSNB, rearrangeably nonblocking (RNB), or repackably nonblocking (RPNB) networks. This paper studies the rearrangeability and repackability of M-WSW networks, and derives the sufficient and necessary conditions for an M-WSW network to be RNB (or RPNB). The results show that the derived sufficient conditions for being RNB (or RPNB) require significantly fewer middle switches for SNB and WSNB networks, and the RPNB results require fewer middle switches than those for RNB in most cases.

Simultaneous Connections Routing in Wavelength–Space–Wavelength Elastic Optical Switches

In this paper, we investigate the three-stage, wavelength-space-wavelength switching fabric architecture for nodes in elastic optical networks. In general, this switching fabric has r input and output switches with wavelength-converting capabilities and one center-stage space switch that does not change the spectrum used by a connection. This architecture is most commonly denoted by the WSW1 (r, n, k) switching network. We focus on this switching fabric serving simultaneous connection routing. Such routing takes place mostly in synchronous packet networks, where packets for switching arrive at the inputs of a switching network at the same time. Until now, only switching fabrics with up to three inputs and outputs have been extensively investigated. Routing in switching fabrics of greater capacity is estimated based on routing in switches with two or three inputs and outputs. We now improve the results for the switching fabrics with four inputs and outputs and use these results to estimate routing in the switching fabric with an arbitrary number of inputs and outputs. We propose six routing algorithms based on matrix decomposition for simultaneous connection routing. For the proposed routing algorithms, we derive criteria under which they always succeed. The proposed routing algorithms allow the construction of nonblocking switching fabrics with a lower number of wavelength converters and the reduction of the overall switching fabric cost.

Multifaceted mirror array illuminator for fluorescence excitation-scanning spectral imaging microscopy.

Hyperspectral imaging (HSI) technologies offer great potential in fluorescence microscopy for multiplexed imaging, autofluorescence removal, and analysis of autofluorescent molecules. However, there are also associated trade-offs when implementing HSI in fluorescence microscopy systems, such as decreased acquisition speed, resolution, or field-of-view due to the need to acquire spectral information in addition to spatial information. The vast majority of HSI fluorescence microscopy systems provide spectral discrimination by filtering or dispersing the fluorescence emission, which may result in loss of emitted fluorescence signal due to optical filters, dispersive optics, or supporting optics, such as slits and collimators. Technologies that scan the fluorescence excitation spectrum may offer an approach to mitigate some of these trade-offs by decreasing the complexity of the emission light path. We describe the development of an optical technique for hyperspectral imaging fluorescence excitation-scanning (HIFEX) on a microscope system. The approach is based on the design of an array of wavelength-dependent light emitting diodes (LEDs) and a unique beam combining system that uses a multifurcated mirror. The system was modeled and optimized using optical ray trace simulations, and a prototype was built and coupled to an inverted microscope platform. The prototype system was calibrated, and initial feasibility testing was performed by imaging multilabel slide preparations. We present results from optical ray trace simulations, prototyping, calibration, and feasibility testing of the system. Results indicate that the system can discriminate between at least six fluorescent labels and autofluorescence and that the approach can provide decreased wavelength switching times, in comparison with mechanically tuned filters. We anticipate that LED-based HIFEX microscopy may provide improved performance for time-dependent and photosensitive assays.

(INVITED)Reconfigurable topology testbeds: A new approach to optical system experiments

Optical transmission systems provide high capacity, low latency and jitter, and high reliability for city-scale networks. Recirculating loop experiments have facilitated the study of signal propagation in long-haul optical transmission systems. However, they are unsuited for developing control and management software for city-scale optical networks with dozens or hundreds of reconfigurable optical add drop multiplexer (ROADM) units, diverse interconnection topologies, and dynamic traffic patterns. Large-scale testbeds can help, but may be inflexible and time- or cost-prohibitive. Reconfigurable testbeds such as COSMOS enable piece-wise emulation of a city-scale network by applying space and wavelength switching, dual-use software-defined networking (SDN) controllers, and comb sources, while digital twin models enable software emulation. Results from the development of a digital twin for COSMOS are presented for optical amplifiers and stimulated Raman scattering (SRS) including both analytical and machine learning (ML) models.

Blockchain-enhanced cross-ISP spectrum assignment framework in SDONs: SpectrumChain

Huge potentials of optical networks provide an excellent choice in meeting the exponential growth in bandwidth demand. In particular, Elastic Optical Networks (EONs), with its promising potentials in increased availability, failure resilience, load-balancing, and efficient resource allocations, are good candidates for the future high-speed networks. When EONs are augmented with the emerging Software Defined Networking (SDN) architecture, which decouples the data and control planes, an agile and synergistic combination emerges under a general term of Software Defined Optical Networking (SDON), albeit with operational challenges such optimal and efficient spectrum assignments. In this paper, we present a blockchain-enhanced QoS-concentrated cross-Internet Service Provider (ISP) spectrum assignment framework for SDONs, SpectrumChain (SC), to eliminate centralized mediators while coordinating QoS-based inter-ISP traffic. This study introduces a new blockchain use-case with reduced QoS signaling overhead while performing inter-ISP routing in SDONs. We also experience the proposed framework under Hop-by-Hop Wavelength Switching (HWS), Border-Node-Only Wavelength Switching (BWS), and No Wavelength Switching (NWS) scenarios to analyze its performance. Our extensive simulation results show that the SC framework can effectively handle the QoS-enabled inter-ISP routing in SDON architecture in terms of Flow Setup Time (FST), Messages Processed (MEP), Requests Serviced (RS), and Acceptance Ratio (AR) metrics under HWS, BWS, and NWS scenarios.