高非线性光纤中并行交叉相位调制的偏振膜色散监测方法

利用信号光和插入的连续泵浦光之间产生的交叉相位调制（XPM）效应,提出了一种基于并联的XPM效应来监测光相位调制信号的一阶偏振模色散（PMD）的新技术。泵浦光的光谱会随着信号光中PMD和色散（CD）的变化而发生变化,所以导致泵浦光的光功率发生变化,在并联的一个支路中抑制PMD的影响,利用并联的两路同一波段泵浦光功率的差值来进行监测。仿真结果显示,新的技术可以实现对40 Gb/s非归零差分四相移相键控（NRZ-DQPSK）光信号从0~20 ps的监测。在20 ps的监测范围内,新技术的动态范围大于3 dB,可以用来进行准确的监测。对信号速率、色散、泵浦光功率和滤波器带宽对新技术的影响做了详细的研究。     

WDM PON using 10-Gb/s DPSK downstream and re-modulated 10-Gb/s OOK upstream based on SOA

A signal remodulation scheme of 10-Gb/s differential phase-shift keying(DPSK) downstream and 10-Gb/s on-off keying(OOK) upstream using a semiconductor optical amplifier(SOA) and a Mach-Zehnder intensity modulator(MZ-IM) at the optical networking unit(ONU) side for wavelength division multiplexed passive optical network(WDM PON) is proposed.Simulation results indicate that error-free operation can be achieved in a 20-km transmission,and the receiver sensitivity of return-to-zero differential phase-shift keying(RZ-DPSK) is higher than nonreturn-to-zero differential phase-shift keying(NRZ-DPSK) in the proposed scheme.     

NRZ-DPSK and RZ-DPSK Signals Signed Chromatic Dispersion Monitoring Using Asynchronous Delay-Tap Sampling

In this paper, we demonstrated a signed chromatic dispersion (CD) monitoring method of 10 GHz nonreturn-to-zero differential phase-shift keying (NRZ-DPSK) and return-to-zero differential phase-shift keying (RZ-DPSK) signals by using asynchronous delay-tap sampling and an imperfect tuned delay interferometer. This method could monitor not only the value but also the polarity of residual CD. The demodulated signals show amplitude shoulders on the rising edge or the trailing edge with CD accumulation. Delay-tap sampling scatter plots could reflect this signal distortion by a unique characteristic and realize the signed CD monitoring. The monitoring range can be up to plusmn400 and plusmn720 ps/nm for NRZ-DPSK and RZ-DPSK signals, respectively. Simulation and experimental results are also proposed.     

In-line performance monitoring for RZ-DPSK signals using asynchronous amplitude histogram evaluation

The asynchronous amplitude histogram evaluation technique has been applied to in-line performance monitoring for return-to-zero differential phase-shift keying (RZ-DPSK) signals. The principle of operation was studied by simulation and experiment. It has been demonstrated that residual dispersion and signal optical signal-to-noise ratio can be obtained by Gaussian curve fitting of only one peak in the amplitude histogram of the RZ-DPSK signal.     

111-Gb/s Transmission Over 1040-km Field-Deployed Fiber With 10G/40G Neighbors

We demonstrate transmission of a 111-Gb/s coherent polarization-multiplexed return-to-zero differential quadrature phase-shift keying signal over 1040-km field-deployed fiber together with different types of neighboring channels, and with a cascade of 50-GHz reconfigerable optical add-drop multiplexers. Our transmission experiment proves the feasibility of transmitting a 111-Gb/s phase-modulated channel with 10 times 10.7-Gb/s on-off keying neighboring channels on a 50-GHz grid, despite the presence of strong cross-phase modulation.     

Optical Performance Monitoring of Phase-Modulated Signals Using Asynchronous Amplitude Histogram Analysis

As optical networks continue to grow towards high capacity and high flexibility, new transmission technologies are being introduced. In order to maintain the quality of signal and control over network in the transparent domains, optical performance monitoring (OPM) systems are becoming a necessity. Phase modulation formats emerge as the solution of choice in transparent domains because of their sensitivity, spectral efficiency, and resilience to optical impairments. In this paper, we demonstrate a flexible OPM method for phase-modulated signals using asynchronous amplitude histogram analysis. We show numerically and experimentally the monitoring of optical signal-to-noise ratio (OSNR), chromatic dispersion (CD), and polarization-mode dispersion (PMD) for differential phase-shift keying (DPSK) and differential quadrature phase-shift keying (DQPSK) signals. The OSNR can be measured within range of 20-35 dB and accumulated chromatic dispersion between 600 and 600 ps/nm. The asynchronous amplitude histogram monitoring method is proved to be a precise and versatile monitoring tool for high-capacity optical networks.     

Amplitude Regeneration of RZ-DPSK Signals in Single-Pump Fiber-Optic Parametric Amplifiers

The input power tolerance of a single-pump fiber-optic parametric amplifier (FOPA) is experimentally shown to be enhanced for return-to-zero differential phase-shift keying (RZ-DPSK) modulation compared to RZ on–off keying modulation at 40 Gb/s. The improved nonlinear tolerance is exploited to demonstrate amplitude regeneration of a distorted RZ-DPSK signal in a gain-saturated FOPA. An optical signal-to-noise ratio penalty of 3.5 dB after amplitude distortion is shown to be reduced to 0.2 dB after the FOPA, thus clearly demonstrating the regenerative nature of saturated FOPAs for RZ-DPSK modulation.      

Experimental Investigation of Delay-Tap Sampling Technique for Online Monitoring of RZ-DQPSK Signals

We experimentally demonstrate optical performance monitoring of 20-Gb/s return-to-zero differential quadrature phase-shift keying signals using an asynchronous delay-tap sampling technique. This method allows online monitoring of accumulated chromatic dispersion in the range from $-$600 to $+$600 ps/nm. We also show evaluation of optical signal-to-noise ratio at a level of 6.7 dB and monitor operation at input power of $-$ 16 dBm.      

Novel Optical Vector Signal Generation With Carrier Suppression and Frequency Multiplication Based on a Single-Electrode Mach–Zehnder Modulator

This investigation presents a novel modulation approach for generating optical vector signals using frequency multiplication based on double sideband with carrier suppression. A single-electrode Mach–Zehnder modulator is biased at null point with a driving signal consisting of a 10-GHz sinusoidal signal and a 5-GHz sinusoidal signal modulated with 1.25-Gb/s on–off keying, 1.25-Gb/s binary phase-shift keying data, or 625-MSym/s quadruple phase-shift keying data. After square-law photodetection, a 1.25-Gb/s radio-frequency signal at a sum frequency of 15 GHz is generated. After transmission over 50-km single-mode fiber, the power penalty of all three modulation formats is under 0.2 dB.      

Converged Wireless and Wireline Access System Based on Optical Phase Modulation for Both Radio-Over-Fiber and Baseband Signals

We propose and experimentally investigate a scheme for transmitting a phase-modulated radio-over-fiber (RoF) signal along an existing fiber infrastructure without degradation of the existing baseband signal. Optical phase encoding of both signals, namely a baseband 21.4-Gb/s nonreturn-to-zero differential quaternary phase-shift keyed signal and a 5.25-GHz RoF carrying 1.25 Gb/s, enables the use of identical optical receiver structures. The experimental results show that both receivers achieve error-free operation after 80-km standard single-mode fiber transmission. The proposed scheme has potential applications for converged wireless and wireline optical access networks.      

A Multicast WDM-PON Architecture Using DPSK/NRZ Orthogonal Modulation

We propose a novel scheme to overlay multicast data on a wavelength-division-multiplexed passive optical network (WDM-PON) with point-to-point data delivery. The differential phase-shift keying multicast signal is superimposed onto all point-to-point nonreturn-to-zero (NRZ) signals. By adjusting the extinction ratios of the individual NRZ point-to-point signals, multicast can be realized and only the designated optical network units can properly receive the multicast data. We successfully demonstrated the proposed WDM-PON with 10-Gb/s downstream point-to-point signals and 10-Gb/s multicast signals.      

Rayleigh Backscattering Noise-Eliminated 115-km Long-Reach Bidirectional Centralized WDM-PON With 10-Gb/s DPSK Downstream and Remodulated 2.5-Gb/s OCS-SCM Upstream Signal

We propose a novel scheme of Rayleigh backscattering noise-eliminated, long-reach, single-fiber, full-duplex, centralized wavelength-division multiplexed passive optical network with differential quadrature phase-shift keying (DPSK) downstream and remodulated upstream using an optical carrier-suppressed subcarrier-modulation (OCS-SCM) technique and optical interleaver. The error-free transmissions of 10-Gb/s downstream and 2.5-Gb/s upstream signals are experimentally demonstrated over 115-km single-fiber bidirectional SMF-28 with less than 0.5 and 1.9 dB power penalties, respectively.      

A comparative study of DPSK and OOK WDM transmission over transoceanic distances and their performance degradations due to nonlinear phase noise

We have compared experimentally the transmission performance of return-to-zero differential phase-shift keying (RZ-DPSK) with RZ-ON-OFF keying (OOK), nonreturn-to-zero differential phase-shift keying (NRZ-DPSK), and NRZ-OOK for 100/spl times/10-Gb/s transmission with a spectral efficiency of 0.22 b/s/Hz over transoceanic distances. The Q degradation of the RZ-DPSK after transmission over 9180 km was 3 dB greater than that of RZ-OOK. The experimental results clearly showed the major cause of degradation for DPSK is not cross-phase modulation but self-phase modulation. The calculated nonlinear phase noise, i.e., the Gordon-Mollenauer effect, agreed with the experimental results. A distributed-Raman-amplifier assisted erbium-doped-fiber-amplified transmission line acted well in reducing the nonlinear phase noise.     

Full-Duplex Radio-Over-Fiber System Using Phase-Modulated Downlink and Intensity-Modulated Uplink

We propose and demonstrate a full-duplex radio- over-fiber system employing a phase-modulated downlink and an intensity-modulated uplink over a single optical carrier. Each downlink and uplink is encoded with 200-Mb/s 16-quadrature amplitude modulation and a 100-Mb/s quadrature phase-shift keying signal carried in the 6-GHz band, respectively. The demonstration results show that the constraints on modulation index of the downlink signal as well as power budget of uplink signal can be relaxed thanks to the constant intensity of the phase-modulated downlink signal. The results also show the good error vector magnitude performance in both downlink and uplink signals after transmission over a 25-km fiber link. The effect of phase modulation to intensity modulation conversion of the downlink signal is also measured and evaluated for the scalability of the proposed technique.      

Investigation of Dispersion Compensation in 2.5 Gbit/s OOK Label and 40 Gbit/s RZ-DPSK Payload Optical Label Switching System Based on Optical Carrier Suppression and Separation

Three dispersion compensation schemes of an optical label switching transmission system were investigated, which employs 40 Ghit/s return zero differential phase-shift keying(RZ-DPSK) payload labeled with 2.5 Gbit/s on-off keying(OOK) signal based on the optical carrier suppression and separation(OCSS) technique. In the system, proposed are the receiver sensitivity of payload and label, achieving -32.4 dBm and -38. 5 dBm, respectively. Using the optimal dispersion compensation scheme, after transmitted over 160 km and 320 km SMF respectively, the label can be recovered without power penalty, while the payload can be recovered with less than 2 dB and 5 dB penalty, respectively.     

WDM transmission at 6-Tbit/s capacity over transatlantic distance, using 42.7-Gb/s differential phase-shift keying without pulse carver

We report the transmission of a record 6 Tbit/s capacity over 6120 km distance, involving channels modulated at 42.7-Gb/s bit-rate with differential phase-shift keying (DPSK). The performance is found similar to DPSK with subsequent pulse carving, namely RZ-DPSK.     

Wavelength Conversion Based on Copolarized Pumps Generated by Optical Carrier Suppression

Polarization-insensitive wavelength conversion based on four-wave mixing for 112-Gb/s polarization- multiplexed return-to-zero quadrature phase-shift keying signals (PolMux-RZ-QPSK) with digital coherent detection is experimentally demonstrated. The dual-pumps always have the same polarization direction and fixed frequency spacing because they are generated by the optical carrier suppression technique. The conversion efficiency at different pumping powers and signal wavelengths has also been investigated. A tuning range of a signal wavelength of wider than 18 nm is realized with the same conversion efficiency in this proposed architecture. There is no obvious optical signal-to-noise ratio penalty for the converted 112-Gb/s PolMux-RZ-QPSK signals.      

Optimization of Key Parameters in 622-Mb/s Amplitude Shift Keying Labeled 40-Gb/s Return to Zero Differential Phase Shift Keying Optical Switching Network

Optimized are the label extinction ratio and dispersion compensation of an optical label switching transmission system, which employs 40-Gb/s return to zero differential phase shift keying（RZ-DPSK） payload labeled with 622-Mb/s amplitude shift keying（ASK） control data. In our scheme, the receiver sensitivities of payload and label achieves -27.8 dBm and -33.5 dBm, respectively. After transmitted over 40 km, 60 km and 80 km single mode fiber（SMF）（with dispersion compensation） respectively, the payload can be recovered with no power penalty, while the label can be recovered with less than 2 dB penalty.     

1.14 b/s/Hz spectrally efficient 50/spl times/85.4-Gb/s transmission over 300 km using copolarized RZ-DQPSK signals

1.14 b/s/Hz spectrally efficient 50/spl times/85.4-Gb/s copolarized return-to-zero differential quaternary phase-shift keying (RZ-DQPSK) signals have been transmitted over 300 km of nonzero dispersion-shifted fiber (NZ-DSF), using optical prefiltering and conventional C-band erbium-doped fiber amplifier (EDFA) repeaters. In this study, in order to enhance the spectral efficiency, the impact of optical prefiltering on the RZ-DQPSK signal was experimentally investigated in comparison to the DQPSK signal, and we found that the RZ-DQPSK signal had better sensitivity with almost the same nonlinear tolerance than the DQPSK signal even with 65-GHz bandwidth optical prefiltering.     

A WDM Passive Optical Network With Polarization-Assisted Multicast Overlay Control

We propose a novel wavelength-division-multiplexed passive optical network which supports simultaneous delivery of 10-Gb/s point-to-point downstream and upstream data as well as 10-Gb/s downstream multicast data. The multicast overlay control is achieved by a polarization-assisted scheme at the optical line terminal (OLT). A separate lightpath is provided for the downstream multicast differential phase-shift keying (DPSK) data without additional light sources. The upstream amplitude-shift keying signal at the optical network unit is superimposed onto the received multicast DPSK signal before being transmitted back to the OLT.