Demultiplexing Scheme Research Articles

Demodulation Performance Comparison of High-Speed Coherent Nyquist Pulse Signal with Analog and Digital Demultiplexing Schemes

We compare the demodulation performance of an analog OTDM demultiplexing scheme and digitized OTDM demultiplexing with an ultrahigh-speed digital signal processor in a single-channel OTDM coherent Nyquist pulse transmission. We evaluated the demodulation performance for 40, 80, and 160 Gbaud OTDM signals with a baseline rate of 10 Gbaud. As a result, we clarified that the analog scheme performs significantly better since the bandwidth for handling the demultiplexed signal is as narrow as 10 GHz regardless of the symbol rate. This enables us to use a low-speed A/D converter (ADC) with a large effective number of bits (ENOB). On the other hand, in the digital scheme, the higher the symbol rate becomes, the more bandwidth the receiver requires. Therefore, it is necessary to use an ultrahigh-speed ADC with a low ENOB for a 160 Gbaud signal. We measured the ENOB of the ultrahigh-speed ADC used in the digital scheme and showed that the measured ENOB was approximately 1.5 bits lower than that of the low-speed ADC used in the analog scheme. This 1.5-bit decrease causes a large degradation in the demodulation performance obtained with the digital demultiplexing scheme.

Multi-Orbital-Angular-Momentum-Mode Vortex Wave Multiplexing and Demultiplexing with Shared-Aperture Reflective Metasurfaces

As an alternative degree of freedom for wireless communications, orbital angular momentum (OAM) multiplexing and demultiplexing can be applied to achieve higher communication capacity. Metasurface has advanced ability to manipulate electromagnetic (EM) waves, and has gradually become an enabling EM technology for future wireless communications. It is meaningful and useful to combine the advantages of OAM and metasurfaces. Here we propose a multi-OAM-mode vortex wave multiplexing and demultiplexing scheme based on shared-aperture reflective metasurface. The specifically designed reflective metasurface can realize the corresponding OAM-mode modulations and demodulations of different incident carrier waves in the corresponding data channels. By modulating multiple data channels on multiple OAM modes, the multiplication of the communication capacity could be achieved. A prototype operating at microwave frequencies is designed, simulated, and fabricated for proof-of-concept illustration. To validate the OAM multiplexing and demultiplexing scheme, we conduct dual-channel OAM-mode transmission experiments, in which two shared-aperture reflective metasurfaces are adopted as the transmitter and receiver, respectively. This work paves the way for the metasurface-based OAM communication applications in future wireless communication technologies.

All-fiber few-mode optical coherence tomography using a modally-specific photonic lantern.

Optical coherence tomography (OCT) was recently performed using a few-mode (FM) fiber to increase contrast or improve resolution using a sequential time-domain demultiplexing scheme isolating the different interferometric signals of the mode-coupled backscattered light. Here, we present an all-fiber FM-OCT system based on a parallel modal demultiplexing scheme exploiting a novel modally-specific photonic lantern (MSPL). The MSPL allows for maximal fringe visibility for each fiber propagation mode in an all-fiber assembly which provides the robustness required for clinical applications. The custom-built MSPL was designed for OCT at 930 nm and is wavelength-independent over the broad OCT spectrum. We further present a comprehensive coupling model for the interpretation of FM-OCT images using the first two propagation modes of a few-mode fiber, validate its predictions, and demonstrate the technique using in vitro microbead phantoms and ex vivo biological samples.

A Novel Demultiplexing Scheme for Vortex Beams in Radio Communication Systems

The orbital angular momentum (OAM) based communication is a promising technology in the wireless communication system for its improving spectrum efficiency. However, for the OAM demultiplexing, it requires a very large aperture size in the receiving end due to the OAM beam divergence and the amplitude null in the beam center, which restricts the full development of OAM based communication. In this paper, we propose a novel partial arc sampling receiving (PASR) scheme based on the augmented dynamic mode decomposition (ADMD) to solve this issue. We explore the use of the phase delay coordinates in the conventional DMD to sort the arbitrary OAM modes with arc sampling receiving. Simulation results demonstrate the accuracy and robustness of the proposed approach in sorting both integral and fractional OAM modes with the PASR scheme. Our work offers a practical approach for demultiplexing OAM beams in radio communication systems with fewer receiving devices, especially for the long-distance transmission case.

Achieving the Ultimate Quantum Timing Resolution

Accurate time-delay measurement is at the core of many modern technologies. We present a temporal-mode demultiplexing scheme that achieves the ultimate quantum precision for the simultaneous estimation of the temporal centroid, the time offset, and the relative intensities of an incoherent mixture of ultrashort pulses at the single-photon level. We experimentally resolve temporal separations 10 times smaller than the pulse duration, as well as imbalanced intensities differing by a factor of 102. This represents an improvement of more than an order of magnitude over the best standard methods based on intensity detection.Received 3 September 2020Accepted 12 November 2020DOI:https://doi.org/10.1103/PRXQuantum.2.010301Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.Published by the American Physical SocietyPhysics Subject Headings (PhySH)Research AreasNonlinear opticsPhotonicsQuantum metrologyQuantum opticsQuantum parameter estimationAtomic, Molecular & OpticalQuantum Information

A PDM-based 128-Gb/s PAM4 fibre-FSO convergent system with OBPFs for polarisation de-multiplexing

A polarisation-division-multiplexing (PDM)-based four-level pulse amplitude modulation (PAM4) fibre-free-space optical (FSO) convergent system with optical band-pass filters (OBPFs) for polarisation de-multiplexing is feasibly demonstrated for the first time. In a PDM scenario with PAM4 modulation, the transmission capacity of fibre-FSO convergent systems is enhanced four times with an aggregate channel capacity of 128 Gb/s (64 Gb/s PAM4/polarisation × 2 polarisations). With an OBPF, polarisation-tracking free de-multiplexing is attained by eliminating other optical carrier with orthogonal polarisation. An OBPF is a simple polarisation de-multiplexing scheme in which the polarisation-orthogonal carrier can be effectively de-multiplexed and the cross-polarisation interference can be nearly eliminated. Compared with traditional PDM-based fibre-FSO convergent systems with sophisticated polarisation-tracking mechanism and elaborate digital signal processing (DSP) approach, it reveals a noteworthy one with the advantage of simplicity. Through 25 km single-mode fibre transport and 500 m FSO link, sufficiently low bit error rate and qualified PAM4 eye diagrams are attained. This proposed polarisation-tracking free PDM-based fibre-FSO convergent system is notable because it not only incorporates the fibre backbone and optical wireless feeder, but it also simplifies the framework since complicated polarisation-tracking mechanism and DSP approach are not involved.

Dispersion immune polarization demultiplexing scheme based on extended Kalman filter for Stokes vector Kramers–Kronig receiver

A dispersion immune and dynamic polarization recovery scheme based on extended Kalman filter (EKF) is proposed for Stokes vector Kramers–Kronig (SVKK) receiver. In the transmitter, a carrier is aligned at the edge of the data-carrying signal spectrum in one of the two polarizations. In the receiver, the signal detection is implemented based on Stokes vector receiver (SVR). The proposed dynamic polarization demultiplexing scheme is transparent to modulation formats and can track dynamic polarization rotation up to 30 Mrad/s. Furthermore, the proposed scheme is immune to chromatic dispersion.

Polarization demultiplexing scheme for probabilistic shaping Stokes vector direct detection system using extended Kalman filter

A polarization demultiplexing (PolDemux) scheme using extended Kalman filter (EKF) is proposed to work in probabilistic shaping Stokes vector direct detection (PS SV-DD) system which has a good performance in the rotation of state of polarization (RSOP) compensation with lower optical signal to noise ratio (OSNR) requirement. As the ideal constellation points for the probabilistically shaped (PS) signal quite distinguished from the uniformly distributed signal in Stokes space, the algorithm of PolDemux will be somewhat different. To handle this problem, we propose a PolDemux scheme which can be suitable for both uniformly distributed quadrature amplitude modulation (QAM) signal and PS QAM signal. A 28GBaud Nyquist PS SV-DD system is constructed for performance evaluations. Different PolDemux algorithms are implemented for comparisons. Four different PS 16-QAM signals with different probability distributions and a PS 64-QAM signal with the entropy of 4bit/symbol are used to check the performances in the PS SV-DD system. The simulation results verify that the proposed scheme has the capability of RSOP tracking speed up to 41Mrad/s. Moreover, the proposed scheme performs better comparing with other algorithms, no matter what RSOP impairment model is chosen, either the model with 2 parameters or a universal model with 3 parameters compared with other PolDemux algorithms.

Mode sorter designed for (de)multiplexing vector vortex modes

Mode-division multiplexing is significant in optical communications, and a vector vortex beams (VVBs) set is one of the candidates of the orthogonal set. Although a basic (de)multiplexing scheme has been promoted, there is still a great potential to enable more VVBs with high efficiency. In this work, we promote a vector vortex mode sorter based on a Sagnac interferometer and Q-plate to solve the problem. The Sagnac interferometer acts as a sorter according to |ℓ|, and the Q-plate takes an effect on the shift of indices m. Since our scheme is achieved by the coupling between polarization and orbital angular momentum, it is also suitable for realizing single-photon multi-qubit encoding in quantum information and quantum communications.

Nyquist OTDM signal demultiplexing utilizing a single IQ modulator

This paper investigates a novel demultiplexing scheme for Nyquist optical time-division multiplexed (N-OTDM) signal using a single commercially-available IQ modulator. With only a free-run LO cascaded with a RF-driven IQ modulator at the receiver side, the proposed scheme enables N-OTDM signal demultiplexing with extremely simple structure. The feasibility and detailed influence mechanism on demultiplexing performance are firstly investigated through numerical simulation, which indicates that the insufficient suppressed high-order sideband of the generated comb from the IQ modulator is the main limiting factor that degrades the demultiplexing performance. In addition, this scheme is also experimentally demonstrated in a 160 GBaud to 40 GBaud N-OTDM demultiplexing experiment. Experimental results show that about 6.8 dB required-OSNR improvement (@BER=1E-4) is observed compared with Gaussian sampling with the same pulse-width.

Joint Scheme of Dynamic Polarization Demultiplexing and PMD Compensation Up To Second Order for Flexible Receivers

Polarization division multiplexing (PDM) doubles the bitrate of flexible transponders, whereas the joint effects of fast state of polarization (SOP) rotations, first-order polarization mode dispersion (PMD), and second-order PMD (SOPMD) would severely degrade the system performance. In this paper, we propose and experimentally validate a novel dynamic polarization demultiplexing scheme using extended Kalman filter (EKF) in digital signal processing of flexible receivers. The idea comes from two-stage PMD compensator in optical domain to perform SOP tracking and equalization of first-order PMD and SOPMD. After parameters optimization of EKF, the scheme can track up SOP rotations more than 35 times and 50 times faster than that of constant modulus algorithm (CMA) and CMA/multiple modulus algorithm (MMA), respectively. More importantly, when SOP keeps a fast rotation of 1.00, 10.00, or 20.02 Mrad/s, the system tolerances of first-order PMD and SOPMD that the joint scheme achieves are 28.57 ps and 793 ps2 for 28 GBaud PDM-QPSK at optical signal-to-noise rate (OSNR) of 17 dB, and 50 ps and 4836 ps2 for 10 GBaud PDM-16 quadratic-amplitude modulation (QAM) at OSNR of 23 dB, respectively. In addition, the proposed scheme has a fast convergence speed of about 50 symbols (equal to 5 ns). The calculation complexities of each symbol that the proposed scheme consumes are just about 44% of CMA for PDM-QPSK, and 31% of CMA/MMA for PDM-16 QAM.

Simplified demultiplexing scheme for two PDM-IM/DD systems utilizing a single Stokes analyzer over 25-km SMF

We propose a four-linear state of polarization multiplexed intensity modulation and direct detection (IM/DD) scheme based on two orthogonal polarization division multiplexing (PDM) on-off keying systems. We also experimentally demonstrate a simple demultiplexing algorithm for this scheme by utilizing only a single Stokes analyzer. At the rate of 4×10 Gbit/s, the experimental results show that the power penalty of the proposed scheme is about 1.5dB, compared to the single PDM-IM/DD for back-to-back (B2B) transmission. Compared to B2B, just about 1.7dB power penalty is required after 25km Corning LEAF optical fiber transmission. Meanwhile, the performance of the polarization tracking is evaluated, and the results show that the BER fluctuation is less than 0.5dB with a polarization scrambling rate up to 708.75deg/s.

A Highly Flexible Polarization Demultiplexing Scheme for Short-Reach Transmission

We propose and experimentally demonstrate an effective and highly flexible polarization demultiplexing scheme based on a Stokes analyzer, which could be also applied to the nonorthogonal polarization division multiplexing (NPDM) schemes. Compared with the conventional direct detection, the proposed method has better tolerance to the polarization-dependent loss. Furthermore, such an approach can significantly enhance system flexibility without increasing cost and complexity since the transmitted signals are not required to maintain strict orthogonality, and no additional polarization-tracking feedback circuit is needed. Experimental results show that any polarization multiplexing degree that is larger than 23° can be adaptively demultiplexed after 10-km transmission using optical orthogonality monitoring and digital-signal-processing (DSP) algorithms.

Design of ternary Multiplexer and De-multiplexer circuit with optical nonlinear material (OPNLM) based switch

Multiplexer and De-multiplexer operation play a very important role in all-optical computation, communication and control. Considerable number of multiplexing – de-multiplexing scheme in digital optical processing have already been reported. A design of all-optical ternary Multiplexer De-multiplexer circuit with optical nonlinear material (OPNLM) based switch is proposed and described in this paper. Different logic states have been represented by different polarization states of light. Logical simulation is also included here. This circuit will be useful in future all-optical multi-valued logic based computing and information processing system.

A multiple-input-multiple-output visible light communication system based on VCSELs and spatial light modulators

A multiple-input-multiple-output (MIMO) visible light communication (VLC) system employing vertical cavity surface emitting laser (VCSEL) and spatial light modulators (SLMs) with 16-quadrature amplitude modulation (QAM)-orthogonal frequency-division multiplexing (OFDM) modulating signal is proposed and experimentally demonstrated. The transmission capacity of system is significantly increased by space-division demultiplexing scheme. With the assistance of low noise amplifier (LNA) and data comparator, good bit error rate (BER) performance, clear constellation map, and clear eye diagram are achieved for each optical channel. Such a MIMO VLC system would be attractive for providing services including data and telecommunication services. Our proposed system is suitably applicable to the lightwave communication system in wireless transmission.

A combined scheme of polarization mode dispersion compensation and polarization de-multiplexing in a polarization division multiplexing system with direct detection

A model of polarization mode dispersion (PMD) and state of polarization (SOP) variation induced coherent crosstalk is established in a polarization division multiplexing system. The properties of radio frequency power of one channel in the presence of PMD are investigated. A combined scheme of PMD compensation and polarization de-multiplexing in optical domain is proposed, which is based on monitoring of the feedback signal of RF power. A modified particle swarm optimization algorithm is also used for the adaptive polarization control. The validity of the PMD compensation and polarization de-multiplexing scheme proposed here is demonstrated in a 112Gb/s-PDM-DQPSK simulation system. Results show that the PMD tolerance of the transmission system is increased by 20 ps with 1 dB OSNR margin and the channel separation is accomplished as well.

Ridge Substrate Integrated Waveguide (RSIW) Dual-Band Hybrid Ring Coupler

A novel dual-band ring coupler is proposed in Ridge Substrate Integrated Waveguide (RSIW) technology. The structure is based on two concentric rings with the outer ring loaded by a low insertion loss de-multiplexing scheme allowing independent dual band operation. The RSIW ensures a wide-band fundamental mode operation covering both frequency bands while providing a compact design. A C/K band coupler is experimentally verified showing coupling bandwidths of 6.9% and 14.6% centered at 7.25 and 20.5 GHz, respectively.

Half baudrate electrical clock based demultiplexing scheme for OTDM-DQPSK signal using SOA and optical f ilter

A demultiplexing scheme based on semiconductor optical amplifier (SOA) and optical filter for optical time division multiplexing differential quadrature phase shift keying (OTDM-DQPSK) system is proposed and investigated experimentally. With only a common half baudrate electrical clock modulated 33% duty cycle return-to-zero (RZ-33) optical clock signal as pump, this scheme is cost-effective, energy-efficient, and integration-potential. A proof-of-concept experiment is carried out for the demultiplexing of a 2 \times 40-GBd OTDM-DQPSK signal. Error-free performance is demonstrated, and the average power penalty for both channels is about 3 dB.

A subcarrier demultiplexing scheme based on a coefficient-switchable microwave photonic filter in radio-over-fiber systems

A flexible method for subcarrier demultiplexing in radio-over-fiber (RoF) systems is proposed and experimentally demonstrated. The subcarrier demultiplexer is realized by a coefficient-switchable microwave photonic filter, which is based on biasing Mach–Zehnder modulator (MZM) at different transmission slopes. The 2.4 GHz and 2.7 GHz subcarrier signals both modulated with 100 Mbps on-off keying (OOK) data are transmitted and demultiplexed in the RoF system. The experimental result shows that each of the two subcarriers can be individually selected out with the other one well depressed. The proposed subcarrier demultiplexing scheme is simple, feasible, cost-effective and has good potential applications in the multiplexed RoF systems.

Data driver architecture and driving scheme of AMOLED microdisplay for mobile projectors

For a mobile projector application that can be embedded in a cellular phone, a 6-bit data driver integrated in a 0.4-inch diagonal VGA AMOLED on silicon substrate is proposed. The proposed data driver has a couple of features tailored for a microdisplay application: To be integrated with a very fine pixel pitch of 4.2 ¿m, the data driver uses a 33-degree demultiplexing scheme, thereby taking circuit area within the peripheral height of 810 ¿m. In addition, the separate gamma correction is provided to resolve the color shift problem due to the transmittance mismatch of red, green, and blue color filters. In spite of the separate gamma correction involved, the height of the data driver is not increased, because it is realized by making use of a time sharing method synchronized with the 33-degree demultiplexing.