Multiple Phase Shift Research Articles

Blind sequence estimation of MPSK signals using dynamically driven recurrent neural networks

This paper presents a novel blind sequence estimation of multiple phase shift keying (MPSK) signals approach using dynamically driven recurrent neural networks (DDRNN) with the continuous multi-threshold phase activation function (CMTPAF). With the consideration of the characteristics of MPSK signals, a CMTPAF is designed, the parameters of the CMTPAF are illustrated, and the two new concepts of accumulation points and repulsion points are proposed. The weight matrix of DDRNN-CMTPAF is constructed by utilizing the unitary signal space matrix obtained from singular value decomposition for the receiving signal matrix. It is important that the energy functions of synchronous and asynchronous modes in the designed DDRNN-CMTPAF are proposed and proved.

Widely Tunable Semiconductor Laser Based on Digital Concatenated Grating With Multiple Phase Shifts

In this paper, we proposed a widely tunable distributed Bragg reflector (DBR) laser based on digital concatenated grating with multiple phase shifts (MPS-DCG). The MPS-DCG can provide a comblike reflectivity spectrum with flat envelop covering over 100-nm wavelength range. Static characteristics of the MPS-DCG DBR laser, including the wavelength tuning range, output power, side-mode suppression ratio (SMSR), and L-I curves, are simulated using a time-domain traveling-wave model combined with a digital filter method. Tuning range of approximately 90 nm is obtained with good SMSR. The L-I curves show that the laser threshold current is around 30 mA.

Design of efficient full‐rate linear dispersion space‐time block codes over correlated fading channels

In this study, the authors present a method to design efficient full-rate linear dispersion space-time block codes (LD-STBCs) in correlated Rayleigh fading channels with simple detection at the receiver. The authors first derive a formula for the achievable capacity of an LD-STBC coded multi-input multiple-output (MIMO) system as a function of correlation at the transmitter and the receiver. Moreover, the authors compute closed-form bit-error rate equations for multiple phase shift keying (M-PSK) and multiple quadrature amplitude modulation (M-QAM) schemes. Then, the authors present a method to construct LD-STBCs over correlated Rayleigh fading MIMO channels. Finally, the authors design LD-STBCs for two and four transmit antennas. The designed LD-STBCs enjoy full-rate, minimum power fluctuation, simple structure, simple processing at the receiver. Moreover, the designed LD-STBCs for two transmit antennas provide better performance than Alamouti and LYC codes and the designed LD-STBCs for four transmit antennas provide better performance than TV codes at practical signal-to-noise ratios. Simulation results show that when the proposed LD-STBC for two transmit antennas is concatenated with an efficient outer channel encoder, it provides better performance than LYC code over correlated fading channels.

Multichannel Transmission Through a Gold Strip Plasmonic Waveguide Embedded in Cytop

In this paper, we experimentally characterize a low-loss polymer-based plasmonic waveguide and present its system-level performance for transmitting multiple on-off keying modulated channels (4 × 49 Gb/s). The same waveguide also exhibits the capability of transmitting multiple differential phase shift keying modulated channels (4 × 10 Gb/s). Signal transmission has been verified through bit-error-rate measurements. The plasmonic waveguide consists of a 3.6-mm-long, 5-μm-wide, and 35-nm-thick gold strip embedded in Cytop polymer and exhibits a total optical insertion loss of approximately 13 dB at a free-space optical wavelength of 1.55 μm.

Tunable acoustic bursts for customized tapered fiber Bragg structures

The inscription of customized fiber Bragg structures under acoustic excitation is proposed and demonstrated. By setting the proper acoustic excitation function, the desired spectrum of the grating can be achieved. In this paper, the effect of applying a burst acoustic wave during the process of Bragg grating inscription using the direct writing method through a phase mask is investigated. Among all the characteristics that can be changed due to a periodic defect insertion in the uniform Bragg structure, the control of phase is used to demonstrate this assertion. The results of numerical simulations are shown to be in excellent agreement with experiments. It can be further extended to generate multiple phase shifts in optical fiber and/or waveguides, if the defects are inserted at different positions, as is shown.

On the performance of selection cooperation with equal gain combining

In this study, the performances of selection cooperation are investigated in a scenario based on decode-and-forward and where equal gain combining (EGC) technique is adopted at the destination. Assuming that the channels suffer from independent non-identical Rayleigh fading, we first derive the cumulative distribution function, probability density function and moment generating function for the total instantaneous signal-to-noise ratio (SNR) at the destination after EGC. Then, these statistical functions are used to derive closed-form expressions for average SNR output, outage probability and average symbol error rate (SER) of selection cooperation. The results hold for arbitrary number of relays and refer to multiple-phase shift keying (M-PSK) modulations. Finally, simulations are carried out to verify the correctness of our theoretical analysis. A random network model is introduced to investigate the effect of relay number and path loss exponent on outage probability and average SER. In addition, based on this random network, the comparison between the performance of selection cooperation with EGC and that of selection cooperation with maximal ratio combining are performed.

Design of High Channel-Count Comb Filter Based on Digital Concatenated Grating With Multiple Phase Shifts (MPS-DCG)

The multiple phase shifts technique is introduced into digital concatenated grating to design fiber grating comb filters. Detailed analysis is given for the first time. We find that by increasing the channel multiplication factor and concatenated grating segment number, reflection spectrum can be broadened and channel density can be increased without increasing the sampling period. Comb filters covering the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> -band with different channel spacing (200, 100, and 50 GHz) are designed. An ultrahigh channel-count comb filter covering the <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">S</i> -, <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">C</i> -, and <i xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">L</i> -bands with 100 GHz channel spacing is also demonstrated. Simulation results indicate this technique is a promising method for designing ultrahigh channel-count comb filters.

Design of multi-channel optical code-division multiple-access encoders and decoders based on sampled fiber Bragg gratings

An encoding/decoding scheme of multi-channel optical code-division multiple-access (OCDMA) system using sampled fiber Bragg gratings (SFBGs) is proposed and numerically investigated. A multiple-phase-shift (MPS) technique based SFBG is first developed as a dense wavelength-division multiplexing (DWDM) device to accommodated multiple channels. The OCDMA scheme is achieved through phase coding/encoding on each individual channel of the SFBG and the auto correlative ratio for each user is larger than 14.3 dB. The whole system exhibits enhanced performance in terms of the capacity and security since the OCDMA technique is simultaneously implemented for all channels using the single SFBG.

Performance Analysis of Differential Modulation and Relay Selection with Detect-and-Forward Cooperative Relaying

This letter analyzes the performance of a multi-relay cooperative communication scheme with differential modulation and relay-selection (DM-RS). The scheme consists of a source, N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</sub> relays, and a destination, where the best relay is selected to forward the source node's signal with detect-and-forward (DetF) protocol. The capacity outage probability (COP) and symbol error rate (SER) of the scheme are investigated. In particular, a closed-form COP and an approximation at large signal-to-noise ratio (SNR) are derived. The COP approximation shows that the scheme can achieve a full diversity order of N <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">R</sub> +1. Furthermore, a closed-form SER approximation of the scheme with multiple phase shift keying (MPSK) modulation is derived. Simulation results confirm the presented mathematical analysis.

Surface Plasmon Resonance Phase Imaging Measurements of Patterned Monolayers and DNA Adsorption onto Microarrays

The optical technique of surface plasmon resonance phase imaging (SPR-PI) is implemented in a linear microarray format for real-time measurements of surface bioaffinity adsorption processes. SPR-PI measures the phase shift of p-polarized light incident at the SPR angle reflected from a gold thin film in an ATR Kretschmann geometry by creating an interference fringe image on the interface with a polarizer-quartz wedge depolarizer combination. The position of the fringe pattern in this image changes upon the adsorption of biomolecules to the gold thin film. By using a linear array of 500 μm biosensor element lines that are perpendicular to the interference fringe image, multiple bioaffinity adsorption measurements can be performed in real time. Two experiments were performed to characterize the sensitivity of the SPR-PI measurement technique: First, a ten line pattern of a self-assembled monolayer of 11-mercaptoundecamine (MUAM) was created via photopatterning to verify that multiple phase shifts could be measured simultaneously. A phase shift difference (Δφ) of Δφ = 182.08 ± 0.03° was observed for the 1.8 nm MUAM monolayer; this value agrees with the phase shift difference calculated from a combination of Fresnel equations and Jones matrices for the depolarizer. In a second demonstration experiment, the feasibility of SPR-PI for in situ bioaffinity adsorption measurements was confirmed by detecting the hybridization and adsorption of single stranded DNA (ssDNA) onto a six-component DNA line microarray patterned monolayer. Adsorption of a full DNA monolayer produced a phase shift difference of Δφ = 28.80 ± 0.03° at the SPR angle of incidence and the adsorption of the ssDNA was monitored in real time with the SPR-PI. These initial results suggest that SPR-PI should have a detection limit roughly 100 times lower than traditional intensity-based SPR imaging measurements.

Numerical study of three phase shifts and dual corrugation pitch modulated (CPM) DFB semiconductor lasers based on reconstruction equivalent chirp technology

A distributed feedback (DFB) semiconductor laser with three phase shifts based on reconstruction equivalent chirp (REC) technology is proposed and investigated numerically. With the combination of multiple phase shifts and corrugation pitch modulated (CPM) structure, we also propose a novel and more complex structure named dual CPM, which has a flatter light power distribution along the laser cavity compared with the true double phase shifts DFB laser diode (LD), while the P-I curves are nearly the same. The proposed dual CPM structure is also designed and analyzed based on REC technology. The simulation results show that, the DFB semiconductor laser with complex structure such as phase shifts, or even arbitrary variation of the grating period can be achieved equivalently and easily by changing the sampling structure. But its external characteristics are almost the same as those DFB lasers with true phase shifts, or true arbitrary variation of the grating period. The key advantage of the REC technology is that it varies only the sampling structure and keeps the seed grating (actual grating in sampling structure) period constant. So its fabrication needs only low-cost and standard holographic exposure technology. Therefore we believe this method can achieve the high-end and low-cost DFB LD for mass production.

Two-Transmitter Two-Receiver Cooperative MAC Protocol: Cross-Layer Design and Performance Analysis

Cooperative diversity is a promising and practical technique for realizing spatial diversity through a virtual antenna array formed by multiple distributed antennas of different nodes. In this paper, we propose and evaluate a novel cooperative cross-layer medium access control (CC-MAC) protocol, which combines space-time coding and adaptive modulation at the physical layer and employs truncated automatic repeat request (ARQ) at the data-link layer. The transmitter's partner is selected in the previous hop, and the receiver invites a partner to participate in data reception in the current hop, and in this situation, a two-transmitter two-receiver model is constructed. Because distributed space-time coding is applied at the transmitting set (transmitter and its partner), cooperative diversity and coding gain can be obtained. Based on the instantaneous channel state measured at the receiver, an adaptive modulation scheme is adopted to improve the link throughput at the physical layer. In addition, the truncated ARQ scheme is employed to further enhance the throughput performance at the data-link layer. Furthermore, under different system models with or without the truncated ARQ scheme, performances of the average packet error rate (PER) and symbol error rate (SER) with multiple phase shift keying (M-PSK) modulation and multiple quadrature amplitude modulation (M-QAM) over Rayleigh fading channel are analyzed. Simulation results verify the correctness of the performance analysis and show that CC-MAC can significantly improve system throughput and energy efficiency compared with other transmission schemes.

Multiple dual-wavelengths fiber ring laser utilizing a phase-only sampled fiber Bragg grating with multiple phase-shifts inserted

A simple technique to multiply the lasing wavelength in a semiconductor optical amplifier (SOA)-based fiber ring laser is proposed and demonstrated, which is based on the utilization of a multiple phase-shifts sampled fiber Bragg grating (FBG). Tunability for the wavelength spacing within all dual-wavelengths has also been demonstrated by changing the positions of phase-shifts. Moreover, more than 20 dual-wavelengths fiber lasers with a 3-dB linewidth of 0.017 nm and signal-to-noise ratio (SNR) of about 45 dB have been obtained.

Design of multi limb phase shifter

Plasma is a variable load. The impedance of the plasma varies over a wide range. This requires impedance matching with RF generator. The impedance of the generator is normally 50-Ohm. The impedance matching requires stub tuners and phase shifter. Multi limb phase shifter is one of the RF high power transmission line component that will be used for impedance matching. Multi limb phase shifter is a phase shifter where more than one arms are used for phase variation in a single stroke. This gives the advantage that with the same variation of length multiple phase shifts is achieved. Keeping the moving length small for one section makes the movement easier. Four limbs are being used here. The length of each limb is kept as 500 mm, so the overall length variation of 2000 mm is achieved. Here we present the design details of this Multi limb phase shifter. The Phase Shifter is of 9 3/16" size and is made up of ETP copper. The system is as per EIA standard and is of 50-Ohm type. The system will be motorized.

Efficient multiple phase shift patterns for dense 3D acquisition in structured light scanning

Although phase shifts (PS) are frequently used to acquire colored surfaces of static objects, especially when acquisition time is not critical, the periodic nature of relative (wrapped) PS maps makes it necessary to deal with the issue of phase unwrapping. Consequently, multiple phase shifts (MPS) have been widely used as an alternative, but this usually involves a large number of different PS maps to unwrap an absolute (unique) phase. In this paper we propose a new MPS method to unwrap a phase and accurately perform the dense 3D acquisition of neutral and colored objects using only two PS maps. Accuracy is reported including a quantitative and qualitative evaluation of the results.

Analysis for reflection peaks of multiple-phase-shift based sampled fiber Bragg gratings and application in high channel-count filter design

An analytical expression for calculating the reflection-peak wavelengths (RPWs) of a uniform sampled fiber Bragg grating (SFBG) with the multiple-phase-shift (MPS) technique is derived through Fourier transform of the index modulation. The new expression can accurately depict the RPWs incorporating various parameters such as the duty cycle and the DC index change. The effectiveness of the derived expression is further confirmed by comparing the RPWs estimated from the expression with the simulated reflective spectra using the piecewise uniform method. And the reflective spectrum has been well optimized by introducing the Gaussian apodization function to suppress the sidelobes without any wavelength shift on the RPWs. Then, a high-channel-count comb filter based on MPS is proposed by cascading two or more SFBGs with different Bragg periods but with the same RPWs. Noticeably, the RPWs of the new structured SFBG can also be accurately calculated through the expression. Furthermore, the number of spectral channels can be controlled by choosing gratings with specified difference Bragg periods.

Transmission spectra of coated phase shifted long-period fiber gratings

The transmission spectrum of the coated phase-shifted long-period fiber gratings (LPFGs) with single and multiple phase shifts is analyzed by the coupled-mode theory and the transfer matrix method, and the influences of the film parameters on the spectral characteristics are also studied. It is shown that these parameters will affect the LPFG filtering characteristics. The loss peak of transmission spectrum decreases with the increase of film thickness, and the peak position shifts with the film refractive index. Compared with the non-coated phase-shifted LPFG, the coated one has the similar desirable filtering characteristics, and it has a flexible ability to adjust the transmission properties.

Design of a broad spectrum multichannel optical filter based on FBG

To increase the channel number in the optic filter, the multiple-phase-shift (MPS) technology is adoped based on the multiple-reflection-spectrum-envelopes-concatenation (MRSEC) model which has a broadband flatness. The reflection spectra of the MPS digital concatenated sample gratings are simulated with transfer matrix method, the results show that wave band of the reflection spectrum is widened and the channel number is multiplied. What’s more, the spectrum flatness is improved with the increasing of refraction index change. Moreover, to improve the extinction ratio and peak value when MPS is adopted in concatenated SFBG, an available designing method based on the cascaded unit is put forward and the optimized results are obtained.

Flat-top and ultranarrow bandpass filter designed by sampled fiber Bragg grating with multiple equivalent phase shifts

We propose a novel approach to designing an optical filter with a flat-top and ultranarrow transmission band by using a sampled fiber Bragg grating (SFBG) having multiple equivalent phase shifts (EPSs). In the proposed approach, multiple EPSs are fabricated by adjusting several sampling periods of the SFBG. The obtained multiple EPSs are then arranged properly to get a flat-top transmission band in the narrow -1st reflection band of the SFBG, leading to the generation of a flat and ultranarrow transmission band. Filters with two or five EPSs are designed by simulation and experiment, with low ripples and ultranarrow 1 dB bandwidths observed in transmission bands.

Single and Multiple Phase Shifts Tilted Fiber Bragg Gratings

The spectral behavior of single and multiple phase shifts tilted fiber Bragg gratings has been experimentally investigated. To this aim, a simple and cost‐effective postprocessing technique based on local thermal treatment was used to create arbitrary phase shifts along the tilted grating structure. In particular, UV written tilted fiber Bragg gratings were treated by the electric arc discharge to erase the refractive index modulation in well‐defined regions. We demonstrate that these defects give rise to interference pattern for all modes, and thus defect states can be achieved within all the attenuation bands, enabling a simple wavelength independent spectral tailoring of this class of devices.