Wavelength Division Multiplexing Scheme Research Articles

All-optical reconfigurable optical neural network chip based on wavelength division multiplexing

Optical computing has become an important way to achieve low power consumption and high computation speed. Optical neural network (ONN) is one of the key branches of optical computing due to its wide range of applications. However, the integrated ONN schemes proposed in previous works have some disadvantages, such as fixed network structure, complex matrix-vector multiplication (MVM) unit, and few all-optical nonlinear activation function (NAF) methods. Moreover, for the most compact MVM schemes based on wavelength division multiplexing (WDM), it is infeasible to employ intrinsic nonlinear effects to implement NAF, which brings frequent O-E-O conversion in ONN chips. Besides, it is also hard to realize a reconfigurable ONN with coherent MVMs, while it is much easier to implement in WDM schemes. We propose for the first time an all-optical silicon-based ONN chip based on WDM by adopting a new adjustment mechanism: optical gradient force (OGF). The proposed scheme is reconfigurable with tunable layers, variable neurons per layer, and adjustable NAF curves. In the task of classification of the MNIST dataset, our chip can realize an accuracy of 85.13% with 4 full-connected layers and only 50 neurons in total. In addition, we analyze the influence of the OGF-based NAF under fabrication errors and propose a calibration method. Compared to the previous works, our scheme has the two-fold advantages of compactness and reconfiguration, and it paves the way for the all-optical ONN based on WDM and opens the path to unblocking the bottleneck of integrated large-dimension ONNs.

Design of a monolithic silicon-on-insulator resonator spiking neuron

Increasingly, artificial intelligent systems look to neuromorphic photonics for its speed and its low loss, high bandwidth interconnects. Silicon photonics has shown promise to enable the creation of large scale neural networks. Here, we propose a monolithic silicon opto-electronic resonator spiking neuron. Existing designs of photonic spiking neurons have difficulty scaling due to their dependence on certain nonlinear effects, materials, and devices. The design discussed here uses optical feedback from the transmission of a continuously pumped microring PN modulator to achieve excitable dynamics. It is cascadable, capable of operating at GHz speeds, and compatible with wavelength-division multiplexing schemes for linear weighting. It is a Class 2 excitable device via a subcritical Hopf bifurcation constructed from devices commonly found in many silicon photonic chip foundries.

Dense wavelength division multiplexing scheme based on effective distributed inline light fiber Raman amplifier configuration

Abstract This paper demonstrated the dense wavelength division multiplexing scheme based on effective distributed inline light fiber Raman amplifier configuration. Various forward/backward and bidirectional pumping power configurations are studied versus fiber reach. Output light signal power is demonstrated against fiber reach without Raman amplification technique. Output light signal power in the forward Raman amplification scheme is clarified with pumping power of both 500 mW and 700 mW in various fiber channel configurations. As well as output light signal power in the backward Raman amplification scheme with pumping power of both 500 mW and 700 mW in various fiber channel configurations. Amplification Raman gain parameter coefficient is demonstrated with various values of pumping power pump based on various fiber channel configurations. Backward amplification net parameter gain is studied for different single mode/true wave/freelight fibers channel configuration at different both pumping power values and fiber reach. As well as the forward amplification net parameter gain is clarified for different single mode/true wave/freelight fibers channel configuration at different both pumping power values and fiber reach.

Red InGaN Micro-LEDs on Silicon Substrates: Potential for Multicolor Display and Wavelength Division Multiplexing Visible Light Communication

Red micro light-emitting diodes (micro-LEDs) on silicon substrates are crucial for the realization of large-scale, high-quality, low-cost micro-LED displays, and are also beneficial for high-speed visible light communication (VLC). In this letter, micro-LEDs with different sizes were fabricated. The maximum light output power density of the 20 μm pixel can reach 3.36 W/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , which is 14 times higher than that of the largest pixel (150 μm). By adjusting the pixel size and injection current, a direct color shift from red to green can be observed. Moreover, multicolor emission with uniform brightness can be realized by adjusting duty cycle, which has broad application prospect in monolithic, multicolor displays. Despite the significant blue shift phenomenon, the peak wavelength of all pixels is still greater than 630 nm at the current density of 100 A/cm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> , which means that red light can be emitted in a large current density range to meet various application scenarios requiring different driving conditions. We have realized red, yellow and green micro-LED transmitters on Si substrate by changing the driving current density and modulation bandwidth up to 533.15 MHz is achieved when emitting green light. This is the report of red-emission micro-LEDs on Si substrates for visible light communication for the first time. And we proposed a proof-of-concept monolithic, multicolor wavelength division multiplexing scheme that achieved a total allowable transmission data rate of 2.35 Gbps. Such micro-LED is expected to be applied in multicolor displays, high-speed multi-channel VLC, color-tunable light sources, etc. In particular, due to its high integration and miniaturization, it is expected to be used in future practical application scenarios such as wearable communication devices and smartwatches.

Performance Analysis of the WDM Schemes for RoF System with Various Bit Rate

Communication that combines the methodologies of the two communications can be considered as communication fiber optic communication and can be used in communication systems and wireless. The integration of optical and wireless networks can function to increase mobility and capacity as well as reduce costs in access networks. Radio over fiber (RoF) can be a solution for many problems because it can control many base stations (BS) connected to a central station (CS) with an optical fiber. The high bit error rate (BER) and low Q factor value are caused by the Rof signal head received in low quality, so the receiver may not operate on high data speed networks. The solution to different signal problems and can be done with single mode fiber is the Wavelength Division Multiplexing (WDM) network. BER must be reduced to a guaranteed value, and the Q factor must be increased. WDM-RoF probes with different fiber lengths at various channel distances will be: simulated using Optisystem software, and the performance of the RoF receiver is measured and analyzed depending on the obtained BER, Q-factor value, and eye aperture height. The effects of degradation factors such as attenuation and dispersion are very limited with the addition of EDFA amplifier to Single Mode Fiber (SMF). The higher the bit rate of a communication system, the lower the performance of the system. In this study, analysis of the WDM-Rof system with bit rate variations was carried out to determine the bit rate value that still met the standard. From the simulation results, the Q-Factor and BER values at a bit rate of 11 Gbps do not meet the standards, i.e 4.50508 and 2.5390e-006.

A 40-Gbps fiber-FSO convergent transmission system employing OFCL-based WDM and external modulation technique

We have proposed and demonstrated a 40Gbps fiber-free space optics (FSO) convergent system based on external modulation and wavelength division multiplexing (WDM) technique. In this experiment, 4010×4 Gbps signal is successfully transmitted employing WDM scheme over 50 km single mode fiber plus 2.5 km FSO distance. Optical frequency comb lines (OFCL) are generated using a continuous wave laser diode, a radio frequency signal generator, a dual drive Mach Zehnder modulator, and an electrical attenuator. OFC lines, having a side mode suppression ratio (SMSR) value of ∼40 dB and flatness of ∼0.4 dB, are employed as broadband laser source in the presented convergent system. The performance of the fiber-FSO system is investigated theoretically for different weather conditions. Very low power penalty with low bit error rate (BER), clear eye diagrams, and standard Q-factor are achieved in the proposed system. The power penalty is restricted within 2.5 dB and 5.8 dB at a BER of 10−9 for 50 km SMF plus 2.5 km FSO distance in clear weather and 50-km SMF plus 0.4-km FSO distance in heavy fog condition respectively. Thus, the proposed WDM-convergent system is efficient enough for high data rate transmission along with low BER value of ∼10−9 and high Q-factor for different environmental scenarios.

High Resolution-Based Coherent Photonic Radar Sensor for Multiple Target Detections

The last decade witnessed remarkable growth in the number of global road accidents. To minimize road accidents, transportation systems need to become more intelligent. Multiple detection of target vehicles under adverse weather conditions is one of the primary challenges of autonomous vehicles. Photonic radar sensors may become the promising technology to detect multiple targets to realize autonomous vehicles. In this work, high-speed photonic radar is designed to detect multiple targets by incorporating a cost-effective wavelength division multiplexing (WDM) scheme. Numerical simulations of the proposed WDM-based photonic radar is demonstrated in terms of received power and signal to noise (SNR) ratio. The performance of the proposed photonic radar is also investigated under diverse weather conditions, particularly low, medium, and thick fog. The proposed photonic radar demonstrated a significant range resolution of 7 cm when the target was placed at 80 m distance from the photonic radar sensor-equipped vehicle. In addition to this, traditional microwave radar is demonstrated to prove the effectiveness of the proposed photonic radar.

Photonic dot-product engine for optical signal and information processing

In this paper, a novel 2 × 2 Mach–Zehnder-interferometer (MZI)-based dot-product calculator is proposed and analyzed in the silicon-on-insulator (SOI) platform. To calculate the dot product, a phase-shifted Bragg grating (PSBG) modulator is placed in each arm of the MZI for the phase modulation at the resonant wavelength, followed by a 3 dB 2 × 2 directional coupler (DC) as the output to convert the phase difference into the intensity distribution across bar and cross ports. Moreover, an electro-absorption modulator (EAM) is implemented between the PSBG and the DC to change the intensity of the passing light in both arms. Theoretical modeling shows that by adjusting the phase difference and absorption strength individually, multiplication of two input values can be achieved using the proposed design. Numerical analysis over 10 000 dot-product operations with 7 bit precision for input values reveals a mean squared error (MSE) of 2.67 × 10−5. By cascading multiple proposed designs operated at different wavelengths, vector-by-vector multiplication can be realized in parallel, leveraging the wavelength-division multiplexing (WDM) scheme and the Bragg reflection mechanism, with results superior to the current and prior MZI-based processors with coherent light sources. This design paves the way for large-scale optical information processing systems with high throughput.

Terabyte capacity-enabled (10 x 400 Gbps) Is-OWC system for long-haul communication by incorporating dual polarization quadrature phase shift key and mode division multiplexing scheme

Inter-satellite optical wireless communication (Is-OWC) links can become promising solutions to realize the next-generation high-speed communication services. The operation of Global Navigation Satellite Systems can be improved with the use of Is-OWC links through ranging and communication services. However, the key challenge in Inter-satellite link (ISL) is its effective range which is limited due to pointing errors. In this work, we propose to develop a high-capacity and long-reach Is-OWC link by incorporating hybrid mode division multiplexing (MDM) and wavelength division multiplexing (WDM) schemes to transmit ten independent channels over 40000kms Is-OWC link. Each channel is capable of carrying 400Gbps data which is encoded by the dual polarization quadrature phase shift key technique with required signal to noise ratio (SNR) and received power. The proposed Is-OWC link satisfies the enhanced communication within Geostationary Earth Orbit (GEO) and Low Earth Orbit (LEO) satellites. The proposed Is-OWC is further evaluated under the impact of space turbulences, particularly transmitter and receiver pointing errors. The result reported that the proposed Is-OWC link can transmit 4Tbps data over 16000kms with the transmitter pointing error of 2μrad and receiver pointing error of 1μrad.

Optical signal denoising through temporal passive amplification

Mitigating the stochastic noise introduced during the generation, transmission, and detection of temporal optical waveforms remains a significant challenge across many applications, including radio-frequency photonics, light-based telecommunications, spectroscopy, etc. The problem is particularly difficult for the weak-intensity signals often found in practice. Active amplification worsens the signal-to-noise ratio, whereas noise mitigation based on optical bandpass filtering attenuates further the waveform of interest. Additionally, current optical filtering approaches are not optimal for signal bandwidths narrower than just a few GHz. We propose a versatile concept for simultaneous amplification and noise mitigation of temporal waveforms, here successfully demonstrated on optical signals with bandwidths spanning several orders of magnitude, from the kHz to GHz scale. The concept is based on lossless temporal sampling of the incoming coherent waveform through Talbot processing. By reaching high gain factors (&gt;100), we show the recovery of ultra-weak optical signals, with power levels below the detector threshold, additionally buried under a much stronger noise background. The method is inherently self-tracking, a capability demonstrated by simultaneously denoising four data signals in a dense wavelength division multiplexing scheme.

Impact of Bandwidth on Range Resolution of Multiple Targets Using Photonic Radar

Futuristic transportation systems would be requiring more effective sensing system that are not only cost effective but also more efficient in sensing multiple targets while acquiring minimal area and utilizing low input power. To achieve that, frequency modulated continuous wave (FMCW) based Photonic Radar is proposed. For multiple targets detection, wavelength division multiplexing (WDM) scheme is used in conjugation with polarization division multiplexing (PDM) scheme. Impact of varying bandwidth is analyzed upon the performance of the proposed system using numerical simulations. The system is simulated for detecting and ranging over 100 meters by analyzing received echoes and verifying the range frequency with theoretically calculated values while effective operation is measured in terms of received power under varying level of attenuation up to 75 dB/Km under rain and fog conditions. Lastly, the system is replicated for range resolution with four varying operational bandwidths from 600 MHz to 4 GHz.

A 400-Gb/s WDM-PAM4 OWC system through the free-space transmission with a water\u2013air\u2013water link

A 400-Gb/s wavelength-division-multiplexing (WDM) four-level pulse amplitude modulation (PAM4) optical wireless communication (OWC) system through a 200-m free-space transmission with either an 8.8-m piped water–air–piped water link or a 6.5-m turbid water–air–turbid water link is successfully constructed. Incorporating PAM4 modulation with an 8-wavelength WDM scheme greatly increases the total transmission rate of the WDM-PAM4 OWC system to 400 Gb/s (50 Gb/s/λ × 8 λs). By adopting doublet lenses in free-space transmission, a laser beam reducer/expander and a reflective spatial light modulator (SLM) with an angle expander through the water–air–water link, good bit error rate performance and acceptable PAM4 eye diagrams are obtained. Using a reflective SLM with an angle expander not only adaptively adjusts the laser beam, but also effectively solves the oceanic engineering problems. This demonstrates WDM-PAM4 OWC system outperforms existing OWC systems through the free-space transmission with an air–water–air link because it can solve the practical engineering problems in actual oceanic environments.

Performance analysis of 1280 Gbps DWDM – FSO system employing advanced modulation schemes

In this work, we present a 1280 Gbps hybrid fiber + FSO system employing 32 channel dense wavelength division multiplexing (DWDM) and advanced modulation schemes. The system performance has been investigated by considering modified duobinary return-to-zero (MDRZ), duobinary return-to-zero (DRZ), and compressed spectrum return-to-zero (CSRZ) modulation formats under clear weather conditions. The effect of internal system parameters such as beam divergence, diameter of transmitter & receiver aperture has been analyzed in case of duobinary scheme as it outperforms the other two modulation formats. The performance of the proposed system has also been examined for different climatic turbulent conditions including rain, haze and fog weather conditions to predict the maximum range of transmission by employing duobinary modulation format. The received signal quality deteriorates below an unacceptable value in case of heavy fog, haze and rain weather conditions for the FSO range beyond 800 m, 1400 m and 1000 m respectively.

Cross-phase modulation compensation in multichannel system based on filter bank multicarrier modulation

Futuristic mobile data networks are expected to reach higher data rates per user to accommodate the specifications of emerging services, such as triple play and mobile applications. Researchers are carrying out their works to tackle the drawbacks of traditional orthogonal frequency-division multiplexing by designing new waveforms with high spectral efficiency and low out-of-band emissions. Among many others, filter bank multicarrier (FBMC) is an appealing candidate for beyond 5G that fulfills these constraints. Consequently, it is worth to shed light on the performance of FBMC in multichannel transmission system. The main contribution of our paper is to compensate fiber nonlinearity including self-phase modulation and cross-phase modulation effects using adaptive Volterra equalizer in longhaul FBMC system based on a 6 × 20 Gb / s in wavelength-division multiplexing scheme over 100 km × 30 spans of single-mode fiber (SMF). The impacts of channel spacing, bit rate, and fiber types on system performance are addressed. For a target of bit error rate = 10 − 3, the simulations show that this performance can be reached at −12 dBm of launch power when 5-taps third-order Volterra (TOV) equalizer is used for 12.5 GHz of channel spacing and an improvement of approximately 1 dB is obtained for 7 taps compared with the same equalizer with 3 taps. To further enhance the system performance, standard-SMF is replaced by a new class fiber called pure-silica-core fiber with large effective area, which exhibits a gain of almost 1.3 and 1 dB for 3 and 5 taps, respectively. The complexity burden of the TOV filter is also discussed.

A Cost-Efficient RGB Laser-Based Visible Light Communication System by Incorporating Hybrid Wavelength and Polarization Division Multiplexing Schemes

Visible light communication (VLC) has been proven a promising technology to counter the limitations of radio frequency (RF) communication technology such as high interference and high latency issues. VLC offers high bandwidth as well as immunity to interference from other electromagnetic spectrums. Due to these features, VLC can be an excellent solution for biomedical and healthcare applications for transmission of body sensor signals and other crucial patient information. In this work, a highly efficient VLC system is designed to transmit six channels, with each one carrying 10 Gbps of data, over a 500 m optical fiber link and a 200 cm VLC link. To make the VLC system cost effective, simple and efficient on-off keying (OOK) (non-return to zero) is used as the encoding scheme. Moreover, to further enhance the capacity and bandwidth of the proposed VLC system, hybrid wavelength division multiplexing (WDM) and polarization division multiplexing (PDM) schemes are incorporated by using red, green, and blue lasers. The reported results show the successful transmission of all channels (6 × 10 Gbps) over 500 m optical fiber and 200 cm of VLC link.

Cost-Efficient Hybrid WDM-MDM-Ro-FSO System for Broadband Services in Hospitals

The expansion of high-speed communication needs due to explosive growth of subscribers each year has led the researchers to design the next generation communication systems which can cope with the current growing demand. Millimeter waves, operated within the range of 30 GHz to 300 GHz, can become potential carrier for delivering large amount of data. However, in hospital scenarios, these radio waves are subjected to strict regulations due to direct impact on patients’ health as well as high interference with other medical devices which again imposes critical challenge on patients. Thus, it is a challenge for the researchers to provide communication/broadband services for transmission of such sensitive biomedical sensor data in hospitals locations. Radio over Free space (Ro-FSO) systems may become the attractive solution to deliver millimeter waves over free space link with high speed. Further, to expand the capacity of Ro-FSO systems, mode division multiplexing (MDM) plays a vital role in addition to wavelength division multiplexing (WDM) scheme. In this work, we have demonstrated the MDM-WDM scheme to deliver four channels with each one having the capacity of 10 Gbps up-converted to 40 GHz over FSO link which is suitable for providing broadband and communication services within the hospital premises. Moreover, the proposed WDM-MDM-Ro-FSO link is evaluated under different fog conditions.

WITHDRAWN: Fiber optics routing enhancement based heuristic searching technique

Optical network is the corner stone for the high data rate/throughput applications due to the wide bandwidth allowed in optical channel. Additionally, optical network tackled the delay problem since data is reformed into equivalent light and transmitted light speed to the destinations e.g. 3 × 10 8 m/h. Data can travel in optical domain over the light-path in high rate approaching to tens of Gigabits. Routing of data in optical domain is controlled by the wavelength division multiplexing (WDM) scheme in which allotting each wavelength at the ingress of optical fiber with its suitable bandwidth. Bandwidth of optical path is being optimized in order to utilize the fiber resources efficiently using Artificial Neural Network (ANN). In this paper Artificial Bee Colony (ABC) algorithm is used for optimizing the performance of ANN which is predicting the wavelength of the optical path.

Performance analysis of 320 Gbps DWDM—FSO System under the effect of different atmospheric conditions

The last decade has witnessed significant growth of optical communication systems due to low attenuation offered for longer distances with high capacities. Optical wireless communication such as Free space Optical (FSO) systems provide license free secure transmission with lower deployment cost to make it attractive solution for providing communication services in remote areas. However atmospheric turbulences can become major challenges for deploying the FSO systems as it affects its performance. In this work, we propose a 320 Gbps, 32 channel’s hybrid fiber + FSO system using cost efficient On OFF Key modulation by incorporating hybrid dense wavelength division multiplexing scheme. Each channel carries 10 Gbps data segregated by 100 GHz channel spacing. Also, the effect of variant climatic turbulence analyzed for non-return to zero and Return to zero system considering clear sky, light fog, moderate fog and dense fog conditions.

Rayleigh Backscattering Rejection in Single-Laser Homodyne Transceiver for UD-WDM Using λ-Shifting

With the aim of using a single laser per transceiver in single fiber splitter-based passive optical networks (PON) with coherent homodyne receivers, we apply wavelength shifting in an ultra-dense wavelength division multiplexing (UD-WDM) scheme. The studied architecture is based on a dual-parallel Mach-Zehnder Modulator (DP-MZM) operating in carrier-suppressed single-sideband (CS-SSB). In this configuration, a single laser feeds both the coherent homodyne receiver, and the transmitter, simplifying the wavelength management in the PON. The modulator carries out both data modulation and wavelength shifting. In this study, a bit rate of 4 Gb/s in QPSK is used to test several roll-off factors and channel spacing configurations. The results show that power budget gains of 18 dB are achievable with a channel spacing equal to only the symbol rate.

Effect of Temperature on Channel Compensation in Optical Camera Communication

General-purpose Complementary Metal Oxide Semiconductor (CMOS) sensors perform the image desegregation in three channels (red, green, and blue) as a result of a band-pass wavelength filtering carried out using Foveon or Bayer filters. This characteristic can be used in Optical Camera Communication (OCC) systems for increasing the links’ data rate by introducing Wavelength Division Multiplexing (WDM) or Color Shift Keying (CSK) modulation schemes. However, these techniques need a compensation stage to mitigate the cross-talk between channels introduced by the filters. This compensation is performed by a Channel State Information (CSI) estimation and a zero-forcing compensation scheme. The impact of the temperature effects of light-emitting diode (LED) emissions on the zero-forcing compensation scheme’s performance has not been analyzed in depth. This work presents a comprehensive methodology and experimental characterization of this impact for Foveon and Bayer-based image sensors, assuming that the CSI is estimated under temperature conditions different from the LED’s stationary temperature regime. Besides, Signal-to-Interference-plus-Noise Ratio (SINR) and Bit Error Rate (BER) performance metrics are presented in order to estimate the repercussion in an OCC link. The results reveal that the Foveon sensor obtains more unsatisfactory performance than the Bayer-based sensor. On the other hand, the blue band is the most penalized by the thermal effect.