Qun Zhang

Qun Zhang
Minnesota State University, Mankato | MSU · Department of Electrical & Computer Engineering Technology

Ph.D.

About

53
Publications
1,953
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304
Citations

Publications

Publications (53)
Article
Full-text available
Substrate integrated E-plane waveguide (SIEW) was invented recently to design E-plane waveguide devices on printed circuit board, which cannot be achieved by using the conventional substrate integrated waveguide (SIW). This paper is the first time to present an E-plane displaced SIEW junctions bandpass filter. The proposed design is shorter than th...
Article
We present a systematic study on PN junction phase shifters in silicon Mach-Zehnder modulators (MZMs) in both frequency and time domains, with an emphasis on their impact on MZMs' RF loss. The RF loss associated with PN phase shifters dominates the overall RF loss of a MZM's transmission line and determines a MZM's bandwidth. The RF loss is also ev...
Article
We reviewed recent breakthroughs on silicon photonic for 100Gbaud operation. Recent progress on high-speed Ge photodetector and carrier depletion modulator promises 100Gbaud optical transceivers with all-silicon material platform for commercial applications. We achieved high performance high-speed all-silicon photonics carrier-depletion Mach–Zehnde...
Article
We achieved high performance high speed silicon photonics carrier-depletion Mach-Zehnder modulation with commercial foundry by co-optimization of doping and device design assisted with an accurate electro-optical (EO) model. We demonstrated high performance IQ modulators operating at 85Gbaud 16QAM and 64Gbaud 64 QAM with extinction ratio of over 25...
Article
Pre-equalizer as high pass digital filter compensates for transmitter (Tx) frequency response to improve high baud rate transmission performances; however, it also increases the signal peak to average power ratio (PAPR) at the digital to analog converter (DAC). The increased PAPR induces performance penalty due to the reduced signal-to-noise-and-di...
Article
A second-order accurate finite-difference timedomain (FDTD) model is, for the first time, proposed for efficient and reliable modeling of depletion-mode traveling-wave silicon photonics (SiP) modulators. After reviewing small signal and firstorder large signal models for SiP modulators, we derive the second-order FDTD large-signal model for the sta...
Conference Paper
We achieved high performance silicon photonics carrier-depletion Mach-Zehnder modulation with a commercial foundry by optimizing doping and device design. We demonstrated IQ modulator operating at 85Gbaud 16QAM and 64Gbaud 64 QAM with >25dB extinction ratio.
Article
Substrate integrated waveguide (SIW) uses rows of plated through holes to emulate the intact vertical walls of a waveguide circuit. It succeeds in the design of H-plane circuits but not the E-plane circuits because an E-plane circuit requires longitudinal current on the vertical walls that is not supported by SIW. In this paper, a novel substrate i...
Article
Hardware‐software co‐design systems abound in diverse modern application areas such as automobile control, telecommunications, big data processing, and cloud computing. Existing works on reliability modeling of the co‐design systems have mostly assumed that hardware and software subsystems behave independently of each other. However, these two subs...
Article
Substrate integrated waveguide (SIW) is successful to design H-plane horn antenna but fails to design E-plane horn antenna. It is because the plated through holes in SIW only support vertical current but not longitudinal current, both of which are required by the E-plane horn antenna. In this paper, a novel substrate integrated E-plane waveguide (S...
Conference Paper
Time domain large signal model operating in block signal mode is proposed for traveling-wave silicon photonic (SiPh) modulators based on carrier depletion. The underlying theory, implantation algorithm details, and waveform level simulation results are summarized.
Article
As an application of the Internet of Things, smart home systems have received significant attentions in recent years due to their precedent advantages, eg, in ensuring efficient electricity transmission and integration with renewable energy. This paper proposes a hierarchical and combinatorial methodology for modeling and evaluating reliability of...
Article
Full-text available
A local error method based on an analytical scheme previously developed for the scalar optical fiber channel is applied to the second-order symmetrized split-step Fourier simulation of polarization multiplexed signal propagation through dispersion compensated optical fiber links. It is found that the global simulation accuracy for the vector propag...
Conference Paper
Polarization modulation is a technique to modulate digital information using different polarization of the electromagnetic wave. The existing waveform based modulation techniques are well developed and start approaching to their performance limits. Polarization modulation provides a new modulation dimension for wireless communications and can furth...
Conference Paper
A substrate integrated E-plane horn antenna is proposed in this paper. It is built on a printed circuit board. In order to provide paths for longitudinal current which are required by E-plane type of devices, two copper strips are laid at the middle layer of the antenna along the direction of propagation. Two rows of metal posts are arrayed along t...
Conference Paper
A novel substrate integrated E-plane waveguide is proposed. It is used to implement E-plane type of waveguide circuits on printed circuit boards which cannot be accomplished by the conventional substrate integrated waveguide. The new waveguide structure has two copper strips at the middle layer of the substrate. The strips follow the directions of...
Conference Paper
A local error method with semi-analytically pre-calculated step-sizes is proposed for the simulation of polarization multiplexing signal propagation through the single mode optical fiber. The method leads to efficient and reliable numerical performance.
Conference Paper
Simulation step-size optimization based on an analytical step-size selection rule is applied to the waveform level simulation of polarization multiplexed optical signal propagation through dispersion compensated optical fiber links over a large range of simulation accuracy level, chromatic dispersion, and differential group delay. Extensive numeric...
Article
An analytical step-size selection rule is proposed for the simulation of polarization multiplexed signal propagation through the single mode optical fiber. The method leads to approximately constant one step simulation error and high computational efficiency.
Article
A symmetrized split-step Fourier (SSSF) simulation model with global simulation accuracy control is extended to vector optical fiber multi-span propagation cases, which are applicable to the waveform level simulation of polarization multiplexed coherent optical communication systems. Using local error bound obtained from a scalar simulation package...
Conference Paper
For Nyquist signals generated via transmitter digital signal processing, optimal transceiver signal clipping levels are studied for different polarization coupling angles and different chromatic dispersion values in 43 Gb/s polarization multiplexing QPSK systems.
Conference Paper
A symmetric split-step Fourier (SSSF) simulation model with global simulation accuracy control was developed so that the prescribed global simulation accuracy can be automatically achieved for the waveform level simulation of optical signal propagation through a single mode fiber. Combined with the novel control of the one-step or local simulation...
Conference Paper
Using a Karhunen-Loève series expansion (KLSE) based quasi-analytical method for BER calculation, we investigate performance optimization for 44 Gb/s return-to-zero (RZ) partial DPSK (PDPSK) transceiver with reduced component bandwidth, where the optimization is done by pre-emphasizing the gain shape of electrical signal driving path in the transmi...
Article
Using the electrical engineering notation, we re-derive a formulation for a recently proposed parallel algorithm for the simulation of pulse propagation through a single mode optical fiber. The meaning of the change of variables in the original derivation has been explained, the performance of the re-derived parallel algorithm is probed when used i...
Article
Slot waveguides can provide high optical confinement in a nanoscale low-index layer. While a conventional waveguide has a Gaussian-like Eigenmode profile, the Eigenmode profile of a slot waveguide is quite non-Gaussian type, due to the large discontinuity of refractive indices and thus the transverse electric field component between the high and lo...
Article
We propose a technique to electronically postcompensate fiber nonlinearity in ≥40 Gbit/s long-haul WDM transmission systems. We have analyzed this technique for return-to-zero and carrier-suppressed return-to-zero modulation formats using two different dispersion maps. Our analysis shows that the proposed technique can increase the overall system m...
Article
Based on the computed exact probability density functions (PDFs), we analyze the conventional Gaussian approximation (GA) method and the thresholding-based bit error rate (BER) measurement method in back-to-back optical differential phase shift keying (DPSK) systems with balanced detection for the purpose of margin measurement in noise-loading expe...
Article
We present two new high efficiency right-angle slot waveguide bends based on a corner mirror and a triangular or square cavity. In contrast to previous devices, the nanophotonic slot regions in these bends are continuous, leading to more robust designs and the ability to create nanofluidic slot regions. The additional layer also leads to higher ben...
Conference Paper
By comparing with the exact optical communication system performance obtained using a quasi-analytical BER calculation method, we systematically analyze the accuracy of the Gaussian approximation (GA) method and the threshold-based margin measurement method for performance evaluation of on-off keying (OOK) optical amplifier systems. We reveal the i...
Conference Paper
After an introduction to the nonlinear fiber transmission and an optimal channel equalization scheme, recently proposed analytical step-size selection and scaling rules was verified to achieve comparable global simulation accuracy for split-step Fourier (SSF) simulations of optical pulse propagation through fiber with low simulation accuracy. Its a...
Article
Full-text available
Two right-angle bends for nanoscale slot waveguides with high bending efficiency based on a corner mirror and different resonant cavities are presented, one with a triangular cavity and the other with a square cavity. Through two-dimensional parametric scanning of the position of the mirror and the dimension of the cavity, a maximum bending efficie...
Article
Nanoscale slab slot waveguides provide for high optical confinement and have found abundant applications in silicon photonics. After developing an analytical mode solver for general asymmetric slot waveguides, the confinement performance of symmetric as well as asymmetric geometries was systematically analyzed and compared. For symmetric structures...
Article
In this short communication, we have explored and compared the performance of Alternate Phase Return-to-Zero (APRZ) modulation format on both strongly and weakly managed dispersion maps with varying path average dispersion values. Our findings show that, as opposed to 0 or 180 deg APRZ, 90 deg APRZ is more efficient for both strongly and weekly man...
Article
Analytical expressions involving both system parameters and step-size are proposed to represent the local simulation error for the symmetrized split-step Fourier (SSSF) simulation method. This analytical expression can be used for a step-size selection rule to achieve comparable local simulation accuracy for SSSF simulations. This can lead to compu...
Conference Paper
In this paper, we explain a graphical user interface (GUI) based computer modeling and design platform that has been developed to teach students about the current industry design practice in optical communications and to promote interactive learning in our senior/graduate level fiber optic communications course. We give an introduction to the quasi...
Article
In this paper, we propose to extend the Guassian approximation (GA) method for reliable system performance evaluation from the traditional optical on-off keying (OOK) systems to the emerging optical differential phase shift keying (DPSK) systems. The proposed method can be used to guide efficient numerical estimate as well as experimental measureme...
Conference Paper
Employing a rigorous KLSE based quasi-analytical method for the BER calculation, we optimize an 80 Gb/s NRZ-DPSK transceiver by pre-emphasizing the high frequency portion of the gain shape of electrical signal driving path.
Conference Paper
The back-to-back performance of optical RZ-DPSK and NRZ-DPSK formats was compared using KLSE method. The effect of unmatched optical bandpass filter was studied with/without the presence of the electrical low pass filter in the receiver.
Conference Paper
After developing a detailed model for DPSK transceivers, we present a covariance matrix based BER calculation method. We show that the transceiver imperfection and the linear fiber effects, such as chromatic dispersion and polarization mode dispersion, can be incorporated into our model and our BER calculation method. With the developed BER calcula...
Article
The feasibility of a 40 Gbit/s wavelength division multiplexed system using a power unbalanced polarization division multiplexing (PUPDM) scheme has been explored for metropolitan distances using the standard single mode fiber and erbium doped fiber amplifiers. PUPDM is a quaternary communication scheme in which two subchannels, each carrying 20 Gb...
Article
Full-text available
We describe a robust shooting algorithm to model backward-pumped Raman amplifiers. This algorithm uses a continuation method and a Jacobi weight in conjunction with the shooting algorithm. We compare this algorithm to the commonly used relaxation algorithm. We find that the shooting algorithm is more flexible, in that it can be applied to amplifier...
Article
An analytical expression involving both system parameters and step size is proposed to represent the local simulation error for the split-step Fourier simulation. Based on this result, scaling rules are derived to obtain comparable global accuracy for different system parameters. This is significant in enhancing computational efficiency in optical...
Conference Paper
Optical communication system design is a challenging task because there is no general analytical solution for the nonlinear and dispersive fiber channel. Although there has been progress in analytical channel models such as Volterra series model and other variants of the perturbation model, numerical simulations are still extensively used in channe...
Conference Paper
We describe a shooting algorithm for Raman amplifiers. Performance tests are done to compare the efficiency of two integration methods. Using a Jacobi weight and a continuation method yields more robust convergence of the algorithm.
Conference Paper
When the inline compensation is not slope matched, the CSRZ format has a greater tolerance to mismatch in the dispersion map than does the RZ format. This greater tolerance allows a larger fiber transmission bandwidth to be utilized and the number of WDM channels to be correspondingly increased.
Conference Paper
Next generation DWDM transport equipment must be designed to take advantage of the cost savings associated with both ultra-long haul transmission and high spectral efficiency. In addition, to support bandwidth-on-demand, and other differentiated services, high-speed data channels that can be shared efficiently and provisioned flexibly will be requi...
Article
Thesis (Ph. D.)--University of Virginia, 2001. Includes bibliographical references (160-166).
Article
We present a methodology for the design and optimization of multi-channel wavelength division multiplexed (WDM) fiber-optic systems. Multi-user systems are broadband and high power, some- times leading to severe linear and nonlinear degradation in the signal due to properties inherent in the fiber. Mastering these physical limitations of the fiber...

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