Differential Quadrature Phase Shift Keying Research Articles

Single-feeder fiber colorless wavelength-division-multiplexing passive optical network using differential quadrature phase-shift keying downstream and intensity remodulated upstream signals

Wavelength-division-multiplexing passive optical network (WDM-PON) has been considered as a promising next generation access network solution. A centralized light-wave colorless WDM-PON architec- ture based on a single feeder fiber. At the optical line terminal, differential quadrature phase shift keying (DQPSK) modulated signal at 10 Gbps is utilized for downstream transmission is proposed and demonstrated. At the optical line unit, part of the downstream signal is remodulated using an intensity modulated on/off keying technique for upstream transmission. Simulation results show that downstream and upstream signals achieved error-free transmission at 10-Gbps symmetric data rate with negligible power penalties. The proposed scheme exhibit improved tolerance to Rayleigh backscattering over 20 km standard single mode fiber. © 2013

Power distribution analysis for multiple modulation formats in an all-optical sampling wavelength division multiplexing system

An optimal power distribution analysis for an all-optical sampling orthagonal frequency division multiplexing (OFDM) scheme with multiple modulation formats including differential phase shift keyed (DPSK), differential quadrature phase shift keyed (DQPSK), and non-return-to-zero (NRZ) is proposed. The noise tolerances of different modulation formats are analyzed, and the optimal input power ratio between phase and intensity modulation formats for the best overall receiving performance is investigated under unchanged total input power. Moreover, this scheme can seamlessly coexist with the traditional WDM channel.

Transmission of 112 Gb/s dual-carrier DQPSK signal over 10 Gb/s-based WDM optical links

The 112Gb/s dual-carrier differential quadrature phase shift keying (DC-DQPSK) optical transceiver, which does not need digital signal processing and coherent detection, is proposed for cost-effective 100G transport solution. In this paper, we describe upgrade schemes of 10Gb/s-based WDM optical links by adopting 112Gb/s DC-DQPSK transceiver, while the dispersion of the optical links is compensated 100% at each span. Method of introducing the DC-DQPSK signal into single grid of 100GHz spaced WDM link is demonstrated. Performance sufficient for error-free operation after forward error correction is achieved over 640km standard single mode fiber (SSMF) link. In another method, we experimentally investigate the transmission performance with co-propagating 10.7Gb/s on-off-keying (OOK) signals over 1000km of SSMF when the dual carriers occupy two channel grids separately. Excellent tolerance to the nonlinearities impacted by the OOK signals and low optical signal-to-noise ratio requirement are verified to demonstrate superior transmission performance in 10Gb/s-based WDM links.

Reconfigurable crystal-based demodulator for both differential-phase-shift keying and differential-quadrature-phase-shift keying formats: principle, design and performance

A reconfigurable demodulator for both differential-phase-shift keying (DPSK) and differential-quadrature-phase-shift keying (DQPSK) formats is theoretically and experimentally presented. In this crystal-based demodulator, a rotatable quarter-wave plate is implemented to switch the operation of the device between DPSK and DQPSK modes. To mitigate polarisation-dependent-frequency shift (PDFS), the authors control uniformity of optical path length differences for the orthogonal polarisation states in the delay crystal, a liquid crystal phase-tuning retarder is used to improve the tuning time. The design and fabrication consideration of this device are also discussed. The packaged device has a low PDFS of within ±0.2 GHz over C-band, fast tuning time of 20.5 ms, error-free demodulation of optical transponder unit-3 DPSK and DQPSK signals can be achieved.

Field Trial of 112 Gb/s Dual-Carrier DQPSK Channel Upgrade in Installed 516 km of Fiber Link and ROADM

A field trial of 100GE signal transmission using dual-carrier differential quadrature phase shift keying (DC-DQPSK) based optical transceiver is demonstrated for 100 Gb/s metro area network. Neither high-end ADC/DSP nor fast optical polarization tracking is required in the DC-DQPSK based optical transceiver, which results in low electrical power consumption of ~ 35 W. The measured OSNR sensitivity of DC-DQPSK optical transceiver at the BER of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">- 3</sup> is 18.3 dB. After the transmission through 516 km of installed fiber and ROADM, an error-free transmission of 100GE signal over 106 hours with OTU4 framer and forward error correction (FEC) decoding proves feasibility of DC-DQPSK optical transceiver for 100G metro network applications.

A Dual-Channel 23-Gbps CMOS Transmitter/Receiver Chipset for 40-Gbps RZ-DQPSK and CS-RZ-DQPSK Optical Transmission

This paper describes a dual-channel 23 (20 to 27) Gbps chipset designed in a 40-nm CMOS process for 40 Gbps differential quadrature phase-shift keying (DQPSK) optical transmission. The transmitter has a 2-tap FIR filter and generates two channels of full-rate data. Data outputs exhibit 10 ps rise/fall times, 0.2 ps <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">rms</sub> RJ, 0.8 ps <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pp</sub> DJ, and a ±0.5 UI skew adjustment relative to the full-rate and half-rate clock outputs. The receiver has two 20-27-Gbps input channels, with each channel including a peaking filter, decision threshold adjustment, and 1-tap loop-unrolled DFE. It achieves a 7- mV <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">ppd</sub> input sensitivity and a 0.7-UI <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">pp</sub> high-frequency jitter tolerance. The transmitter and receiver dissipate 0.63 and 1.2 W, respectively.

Re-modulated technology of WDM-PON employing different DQPSK downstream signals

This paper proposes a kind of modulation architecture for wavelength-division-multiplexing passive optical network (WDMPON) employing optical differential quadrature phase shift keying (DQPSK) downstream signals and two different modulation formats of re-modulated upstream signals. At the optical line terminal (OLT), 10 Gbit/s signal is modulated with DQPSK. At the optical network unit (ONU), part of the downstream signal is re-modulated with on-off keying (OOK) or inverse-return-to-zero (IRZ). Simulation results show the impact on the system employing NRZ, RZ and carrier-suppressed return-to-zero (CSRZ). The analyses also reflect that the architecture can restrain chromatic dispersion and channel crosstalk, which makes it the best architecture of access network in the future.

Colorless all-optical sum and subtraction of phases for phase-shift keying signals based on a periodically poled lithium niobate waveguide

A colorless all-optical scheme performing the subtraction and addition of phases between phase-shift keying (PSK) signals exploiting cascaded sum and difference frequency generation in a periodically poled lithium niobate waveguide is introduced and experimentally demonstrated. The subtraction of phases of two 40 Gb/s differential quadrature PSK signals has been experimentally tested and performances have been analyzed in terms of bit error rate measurements.

Compact and Colorless PLC-Type 1-Bit Delay Line Interferometer for DQPSK Demodulator

A compact and colorless planar lightwave circuit (PLC) type 1-bit delay line interferometer for a differential quadrature phase-shift keying (DQPSK) demodulator is demonstrated by adopting wavelength insensitive couplers with narrow coupling waveguides and novel circuit arrangement suitable for integrated DQPSK receivers. The fabricated interferometer realizes a small chip size and practical properties in both entire C- and L-bands.

Optical Performance Monitoring Using Artificial Neural Networks Trained With Empirical Moments of Asynchronously Sampled Signal Amplitudes

We propose a low-cost technique for simultaneous and independent optical signal-to-noise ratio (OSNR), chromatic dispersion (CD), and polarization-mode dispersion (PMD) monitoring in 40/56-Gb/s return-to-zero differential quadrature phase-shift keying (RZ-DQPSK) and 40-Gb/s RZ-DPSK systems, using artificial neural networks (ANN) trained with empirical moments of asynchronously sampled signal amplitudes. The proposed technique employs an extremely simple hardware and digital signal processing to enable multi-impairment monitoring at different data rates and for various modulation formats without necessitating hardware changes. Simulation results demonstrate wide dynamic ranges and good monitoring accuracies.

Nonlinear Tolerance of 53.5-Gb/s Differential 6-ary PSK Surrounded by 10.7-Gb/s NRZ-OOK Neighbors in SMF and DSF Transmission Links

We demonstrate an optical transmission system based on a 53.5-Gb/s differential 6-ary phase-shift-keying (D6PSK) signal with copropagating 10.7-Gb/s nonreturn-to-zero (NRZ) on-off keying (OOK) channels over either 320-km-long single-mode fiber link with in-line dispersion compensation or 320-km-long dispersion-shifted fiber link, and compare its performances with that of a classical polarization-division-multiplexing differential quadrature phase-shift-keying (DQPSK)-based system. The results show that the nonlinear tolerance of the D6PSK signal outperforms that of the PDM-DQPSK signal in terms of the cross-phase modulation effect induced by the 10.7-Gb/s NRZ-OOK neighboring channels.

Novel 2N bit bipolar photonic digital-to-analog converter based on optical DQPSK modulation coupled with differential detection

A novel 2N bit bipolar photonic digital-to-analog converter (PDAC) scenario based on the optical differential quadrature phase shift keying (ODQPSK) modulation coupled with differential detection is proposed. Compared with other proposed schemes, this bipolar PDAC has a greater dynamic range and a larger noise margin with good scalabilities both in speed and resolution. We demonstrate a 4 bit PDAC in a proof-of-principle experiment at a sampling rate of 2.5 GS/s.

RZ-DQPSK Signal Amplitude Regeneration Using a Semiconductor Optical Amplifier

An all-optical return-to-zero differential quadrature phase-shift keying (RZ-DQPSK) signal regeneration scheme is experimentally demonstrated. Thanks to the gain saturation effect, common quantum-well semiconductor optical amplifiers have the ability to regenerate the amplitude distorted RZ-DQPSK signal, so amplitude noise can be reduced while phase information will not be distorted. A significant eye-opening improvement and a negative power penalty of about 1 dB can be achieved for an 80 Gb/s RZ-DQPSK signal.

High-speed addition/subtraction/complement/doubling of quaternary numbers using optical nonlinearities and DQPSK signals

We propose an innovative approach to implementing multiple arithmetic functions of quaternary numbers using optical nonlinearities and differential quadrature phase-shift keying (DQPSK) signals. By adopting 100 Gbit/s DQPSK signals (A, B) and exploiting nondegenerate four-wave mixing (FWM) for addition/subtraction and degenerate FWM for complement and doubling in a single highly nonlinear fiber, we demonstrate 50 Gbaud/s simultaneous quaternary addition (A+B), dual-directional subtraction (A-B, B-A), complement (-A, -B), and doubling (2B). Power penalties less than 4 dB (addition), 3 dB (dual-directional subtraction), 2 dB (complement), and 3.1 dB (doubling) are observed at a bit-error rate of 10(-9).

Parametric Amplification and Wavelength Conversion of Single- and Dual-Polarization DQPSK Signals

We demonstrate system experiments for polarization-independent parametric amplification and wavelength conversion of single-channel differential quadrature phase-shift keying (DQPSK) signals up to 112 Gbit/s. Dual-pump four-wave mixing in a highly nonlinear fiber is utilized to achieve up to 20 dB ON-OFF gain and conversion efficiency. The investigations are done in a polarization-dependent (straight) as well as in a polarization-independent (loop) configuration using single- and dual-polarization DQPSK. Particular attention is paid to the resulting optical signal-to-noise ratio penalties after the amplification. We ascribe this to pump-induced nonlinear phase noise. It is shown that this type of excess noise is increased for the loop configuration in comparison with the straight configuration due to Rayleigh backscattering and that it depends on the input polarization of the signal. Still, the penalty can be made negligible using high-quality pump sources.

Compensation of Nonlinear Phase Noise Using the Effective Negative Nonlinearity of a Nonlinear Amplifying Loop Mirror

The nonlinear amplifying loop mirror (NALM) has been explored for use as a nonlinear phase-shift compensator (NPSC). Operation conditions for a tunable effective negative nonlinearity are considered and the NALM parameter optimization is discussed for direct bit-error-ratio (BER) improvement by postcompensation after a nonlinear transmission line. In this configuration, the fundamental limits for NPSC are estimated for differential quadrature phase-shift keying (DQPSK) using a simplified model. Numerical simulations of a 20 Gb/s RZ-DQPSK transmission system confirmed the applicability of this model and showed a significant BER improvement in a realistic transmission line. Alternatively, the fiber launch power per span could be increased by 2 dB for the same BER.

Interactive Kalman Filtering for Differential and Gaussian Frequency Shift Keying Modulation with Application in Bluetooth

Some applications are constrained only to implement low cost receivers. In this case, designers are required to use less complex and non-expensive modulation techniques. Differential Quadrature Phase Shift Keying (DQPSK) and Gaussian Frequency Shift Keying (GFSK) can be non-coherently demodulated with simple algorithms. However, these types of demodulation are not robust and suffer from poor performance. This paper proposes a new method to enhance the performance of DQPSK and GFSK using Interactive Kalman Filtering (IKF) technique, in which a one Unscented Kalman Filter (UKF) and two Kalman Filters (KF) are coupled to optimize the demodulated signals. This method consists of simple but very effective algorithms without adding complexity to the demodulators comparing to other very complex methods. UKF is used in this method due to its superiority in approximating and estimating nonlinear systems and its ability to handle non-Gaussian noise environments. The proposed method has been validated by creating a MATLAB/SIMULINK Bluetooth system model, in which the IKF is integrated into the receiver, which implement both DQPSK and GFSK, and run simulation in Gaussian and Non-Gaussian noise environments. Results have shown the effectiveness of this method in optimizing the received signals, and that the UKF outperforms the Extended Kalman Filter (EKF).

Ultrafast Coherent Optical Transmission

This paper presents recent progress toward the realization of ultrahigh-speed coherent optical transmission with a single-channel bit rate of more than 1 Tbit/s using ultrashort pulse technology and an advanced modulation format. We first describe Tbit/s optical time-division multiplexing (OTDM) transmission employing differential binary or quadrature phase shift keying. We present our recent demonstrations of single-polarization 640-Gb/s differential phase-shift keying and 1.28-Tb/s differential quadrature phase-shift keying transmissions over 525 km, which employ an ultrafast optical Fourier transformation technique. We then focus on coherent optical transmission using quadrature amplitude modulation (QAM) with a multiplicity of 512 that enables us to achieve an ultrahigh spectral efficiency of more than 10 b/s/Hz. Finally, we demonstrate a novel ultrahigh-speed, spectrally efficient coherent pulse transmission combining OTDM and QAM. A 400 Gb/s, 32 RZ/QAM signal was successfully transmitted over 225 km on a single carrier at 10 Gsymbol/s × 4-OTDM.

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.

80-GB all-optical serial-to-parallel convertor for QPSK signal based on cascaded phase modulators and optical f ilters

An all-optical serial-to-parallel converter (SPC) utilizing two cascaded phase modulators and optical band-pass filters (OBPFs) is experimentally investigated and applied to demultiplex an 80-GBd optical time-division multiplexing (OTDM) return-to-zero (RZ) differential quadrature phase-shift keying (QPSK) signal. Two 40-GBd OTDM tributaries are error-free demultiplexed with a power penalty of approximately 4 dB in the worst case. With its advantages of compact structure, high speed, low power penalty, simultaneous two-tributary operation, and no assistance from a light source, the SPC has potential for use in future OTDM networks. However, the performance of the SPC still needs improvement.