Centralized light-wave WDM-PON employing DQPSK downstream and 00K remodulated upstream signals

A novel architecture for wavelength-division-multiplexing passive optical network (WDM-PON) with centralized light-wave is proposed and demonstrated. At the optical line terminal (OLT) session of this architecture, optical differential quadrature phase shift keying (DQPSK) modulated signal with constant-intensity at 10 Gbit/s is utilized for downstream transmission. At the optical network unit (ONU), part of the downstream optical power is remodulated with on-off keying (OOK) intensity modulation at 10 Gbit/s for upstream without additional laser. Simulation results show that the power penalties of the downstream for 20 km single-mode fiber (SMF) transmission and multi-channels are negligible. While for the upstream, the power penalties are obvious. The simulation results and analysis also reflect that by reducing the launch power of DQPSK transmitters, power penalties can be reduced, although the transmission distance is limited.     

Simple and spectrally-efficient design of high capacity hybrid WDM/TDM-PON with improved receiver sensitivity

A simple design of hybrid wavelength division multiplexed/time division multiplexed passive optical network （WDM/ TDM-PON） is demonstrated for the high capacity next generation access （NGA） network, having advantages of both WDM and TDM based PON techniques. A 10 Gbit/s differential quadrature phase shift keying （DQPSK） data signal is used at optical line terminal （OLT） for downstream, whereas a 2.5 Gbit/s inverse return-to-zero （IRZ） data signal with high extinction ratio is used for upstream signal by intensity re-modulation of downstream signal, no additional laser is used at optical network unit （ONU）. Simulation results verify that aggregated 100 Gbit/s downstream transmissions of 10 DQPSK channels and aggregated 25 Gbit/s upstream transmission of 10 IRZ channels, using spectrally-efficient 50 GHz channel spacing, can be successfully achieved over a distance of 20 km with less than 1 dB transmission power penalties and improved receiver sensitivity.     

Colorless ONU implementation for WDM-PON using direct-detection optical OFDM

A novel architecture for the colorless optical network unit (ONU) is proposed and experimentally demonstrated with direct-detection optical orthogonal frequency division multiplexing (DDO-OFDM). In this architecture, polarization-division multiplexing is used to reduce the cost at ONU. In optical line terminal (OLT), quadrature amplitude modulation (QAM) intensity-modulated OFDM signal with x-polarization at 10 Gbit/s is transmitted as downstream. At each ONU, the optical OFDM signal is demodulated with direct detection, and y-polarization signal is modulated for upstream on-off keying (OOK) data at 5 Gbit/s. Simulation results show that the power penalty is negligible for both optical OFDM downstream and the on-off keying upstream signals after over 50 km single-mode fiber (SMF) transmission.     

A WDM-PON with DPSK modulated downstream and OOK modulated upstream signals based on symmetric 10 Gbit/s wavelength reused bidirectional reflective SOA

We investigate a wavelength-division-multiplexing passive optical network (WDM-PON) with centralized lightwave and direct detection. The system is demonstrated for symmetric 10 Gbit/s differential phase-shift keying (DPSK) downstream signals and on-off keying (OOK) upstream signals, respectively. A wavelength reused scheme is employed to carry the upstream data by using a reflective semiconductor optical amplifier (RSOA) as an intensity modulator at the optical network unit (ONU). The constant-intensity property of the DPSK modulation format can keep high extinction ratio (ER) of downstream signal and reduce the crosstalk to the upstream signal. The bit error rate (BER) performance of our scheme shows that the proposed 10 Gbit/s symmetric WDM-PON can achieve error free transmission over 25-km-long fiber transmission with low power penalty.     

多跳相干探测光谱幅度码标记交换系统传输特性分析

提出了一种基于标记栈技术的两跳相干探测光谱幅度码(SAC)标记交换系统.利用仿真软件,搭建了包含两个转发节点、两个156 Mb/s光谱幅度码标记、与40 Gb/s差分正交相移键控(DQPSK)净荷的光标记交换系统.利用接收光功率与光信噪比(OSNR)分析系统传输性能,并得到结论:经两个节点传输后,标记与净荷产生的功率代价与OSNR代价均未超过3 dB.     

A novel duplex WDM-PON with DPSK modulated downstream and re-modulation of the downlink signal for OOK upstream

We experimentally demonstrate and analyze a 10 Gbit/s full duplex wavelength division multiplexing passive optical network (WDM-PON) system. A non-return-to-zero differential phase shift keying (NRZ-DPSK) modulation technique is first utilized for downlink direction, and then the downlink signal is re-modulated for the uplink direction using intensity modulation technique of on-off keying (OOK) with a data rate of 10 Gbit/s per channel. An effective colorless WDM-PON full duplex transmission system is achieved for the data rate of 10 Gbit/s per channel with a channel spacing of 60 GHz over the distance of 25 km with low power penalty.     

Optical design and analysis of CWDM upstream TWDM PON for NG-PON2

For passively reach-extended next-generation passive optical networks (NG-PONs), we propose an asymmetric hybrid PON architecture and wavelength plan for using eight 2.5 Gbit/s coarse wavelength division multiplexing (CWDM) in the upstream direction and eight 10 Gbit/s dense wavelength division multiplexing (DWDM) in the downstream direction, called Cu-TWDM PON. The power budget feasibilities, the optical path losses, and the dispersion power penalties in the CWDM upstream wavelengths are precisely investigated in terms of related specifications required to enhance the network coverage to over 40 km with single-mode fibers (SMFs) based on ITU-T G.652.A and B and Corning’s SMF-28e, as the worst-case and the practical-case feasibilities, respectively. We also report on 10 Gbit/s and 2.5 Gbit/s transmission experiments up to 60 km for the downstream and upstream links. Based on the analyses and experimental results, we provide guidelines for the physical media dependent layer specification of Cu-TWDM PON for NG-PON applications.     

Centralized Lightwave WDM-PON Employing 16-QAM Intensity Modulated OFDM Downstream and OOK Modulated Upstream Signals

We have proposed and experimentally demonstrated a novel architecture for orthogonal frequency-division- multiplexing (OFDM) wavelength-division-multiplexing passive optical network with centralized lightwave. In this architecture, 16 quadrature amplitude modulation intensity-modulated OFDM signals at 10 Gb/s are utilized for downstream transmission. A wavelength-reuse scheme is employed to carry the upstream data to reduce the cost at optical network unit. By using one intensity modulator, the downstream signal is remodulated for upstream on–off keying (OOK) data at 2.5 Gb/s based on its return-to-zero shape waveform. We have also studied the fading effect caused by double-sideband (DSB) downstream signals. Measurement results show that 2.5-dB power penalty is caused by the fading effect. The fading effect can be removed when the DSB OFDM downstream signals are converted to single sideband (SSB) after vestigial filtering. The power penalty is negligible for both SSB OFDM downstream and the remodulated OOK upstream signals after over 25-km standard single-mode-fiber transmission.      

A Novel Scheme for Seamless Integration of ROF With Centralized Lightwave OFDM-WDM-PON System

We have experimentally demonstrated a novel transmission system for seamless integration of ROF with centralized lightwave OFDM-WDM-PON based on an integrated external modulator. At the one of two arms of the integrated external modulator, the optical carrier suppression (OCS) is realized to generate 40–GHz optical millimeter-wave (mm-wave) and up-converted baseband data signal as wireless signal. In another arm of the integrated external modulator, 16 quadrature amplitude modulation intensity-modulated OFDM signals at 10 Gbit/s are used for downstream transmission as wired signal based on double sideband modulation. By using one intensity modulator (IM), the downstream RF OFDM signal is remodulated for upstream on–off keying (OOK) data at 2.5 Gbit/s because of its downstream RZ shape waveform. The 10-Gbit/s wired signal, 2.5-Gbit/s wireless signal, and 2.5-Gbit/s upstream signal have been transmitted over 20-km single mode fiber (SMF) successfully.      

Study of dual-polarization OQAM-OFDM PON with direct detection

An offset quadrature amplitude modulation orthogonal frequency-division multiplexing (OQAM-OFDM) passive optical network (PON) architecture with direct detection is brought up to increase the transmission range and improve the system performance. In optical line terminal (OLT), OQAM-OFDM signals at 40 Gbit/s are transmitted as downstream. At each optical network unit (ONU), the optical OQAM-OFDM signal is demodulated with direct detection. The results show that the transmission distance can exceed 20 km with negligible penalty under the experimental conditions.     

An AWG-based 10 Gbit/s colorless WDM-PON system using a chirp-managed directly modulated laser

We propose an arrayed waveguide grating(AWG)-based 10 Gbit/s per channel full duplex wavelength division multiplexing passive optical network(WDM-PON).A chirp managed directly modulated laser with return-to-zero(RZ) differential phase shift keying(DPSK) modulation technique is utilized for downlink(DL) direction,and then the downlink signal is re-modulated for the uplink(UL) direction using intensity modulation technique with the data rate of 10 Gbit/s per channel.A successful WDM-PON transmission operation with the data rate of 10 Gbit/s per channel over a distance of 25 km without any optical amplification or dispersion compensation is demonstrated with low power penalty.     

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.      

Rayleigh backscattering minimization in single fiber colorless WDM-PON using intensity remodulation technique

The performance of colorless wavelength-division multiplexed passive optical network(WDM-PON) systems suffers from the transmission impairments mainly due to Rayleigh backscattering(RB).In this paper,we propose and demonstrate a single fiber colorless WDM-PON which enhances the tolerance to RB induced noise.The high extinction ratio in both return-to-zero(RZ)-shaped differential phase shift keying(DPSK) downstream(DS) data signal and intensity-remodulated upstream(US) data signal helps to improve the tolerance to RB induced noise.Simulation results show that downstream and upstream signals can achieve error-free performance at 10 Gbit/s with negligible penalty and improve the tolerance to RB induced noise over 25 km standard single-mode fiber.     

Single fiber colorless symmetric WDM-PON architecture using time interleaved remodulation technique for mitigating Rayleigh backscattering resilience

A time interleaved differential phase shift keying (DPSK) remodulation technique is proposed to mitigate the effect of Rayleigh backscattering (RBS)-induced noise in a single fiber colorless wavelength-division-multiplexing passive optical network (WDM-PON). In order to achieve a cost effective optical network unit (ONU) solution without dedicated laser sources for upstream signals to provide optimum symmetric capacity in a colorless WDM-PON, remodulation becomes the core attraction. Also as the performance of colorless WDM-PON systems suffers from the transmission impairments due to RBS, it is mitigated by using this remodulation scheme. Simulation results show that downstream and upstream signals achieve the error-free performance at 10 Gbit/s with negligible penalty, and enhance the tolerance to RBS-induced noise over a 25 km single-mode fiber.     

Transmission Performance Comparison of Direction Detection‐Based 100‐Gb/s Modulation Formats for Metro Area Optical Networks

Transmission performances of direct detection‐based 100‐Gb/s modulation formats are investigated and compared for metro area optical networks. The effects of optical signal‐to‐noise ratio sensitivity, chromatic dispersion, cross‐channel nonlinearity, and transmission distance on the performance of differential 8‐ary phase‐shift keying (D8PSK), differential phase‐shift keying plus three‐level amplitude‐shift keying (DPSK+3ASK), and dual‐carrier differential quaternary phase‐shift keying (DC‐DQPSK) are evaluated. The performance of coherent dual‐polarization quadrature phase‐shift keying (DP‐QPSK) with block phase estimation and coherent DP‐QPSK with digital differential detection are also presented for reference. According to our analysis, all three direct detection modulation formats could transmit a 100‐Gb/s signal over several hundred kilometers of a single‐mode fiber link. The results also show that DC‐DQPSK outperforms D8PSK and DPSK+3ASK, and the performance of DC‐DQPSK is comparable to that of coherent DP‐QPSK with digital differential detection. The maximum transmission distance of DC‐DQPSK is over 1,000 km, which is enough distance for metro applications.     

改进型双二进制归零码信号在标记交换系统中的新应用

提出以改进型双二进制归零码(MD-RZ)信号作为标记,分别采用差分相移键控非归零码(NRZ-DPSK)信号和差分正交相移键控非归零码(NRZ-DQPSK)信号作为载荷进行正交调制的新方案.然后提出了一种从标记信号中提取和恢复时钟的简单方案.比较了背对背系统中2.5 Gbit/s的MD-RZ标记叠加到10 Gbit/s的NRZ-DPSK载荷和20 Gbit/s的NRZ-DQPSK载荷上的频谱特性,证明了MD-RZ标记占空比越大,光分组信号的频带利用率越高.采用传统的二进制强度调制-直接检测(IM-DD)系统的接收机检测得到了背对背系统中不同占空比的2.5 Gbit/s MD-RZ标记的眼图.结果表明,若采用色散补偿技术,两种光分组信号中的MD-RZ标记能够在长距离传输时克服接收端眼图的失真;当入纤功率值高于18 dBm时,占空比取值越大,MD-RZ标记的眼开度代价具有越高的传输鲁棒性.     

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.     

Wavelength re-generation and re-modulation using optical phase lock loop techniques for 100-Gb/s DQPSK up-stream transmission in DWDM passive optical networks

We demonstrate, by partial experiment and simulation, a re-modulation scheme of the lightwave carrier imbedded in a downstream optical signals under differential quadrature phase shift keying (DQPSK) modulation format for upstream transmission over passive optical networks (PONs) at a bit rate of 100 Gb/s. The recovery of the optical carrier with the precise wavelength is implemented using an injection laser incorporating an optical phase locked loop (OPLL). In the computer simulation, the OPLL is implemented by a Simulink model consisting of interconnected system blocks following exactly the physical phenomena of the hardware structures. This model is then integrated with DQPSK modulation formats for up- and down-transmissions in PONs. Pulse shaping of Non-Return-to-Zero and Return-to-Zero (RZ) of 50% duty cycle and 67% duty cycle are used, respectively. Dispersion tolerance of 25 ps/nm with a bit error rate (BER) of 10⁻⁹ is achieved for both down- and upstream transmissions over fully dispersion compensated 80- km standard SMF and 1.5- km SSMF equivalent dispersion with carrier suppressed RZ pulse shaping (CS-RZ 67%). The contribution to BER by the timing synchronization error at the sampling of the optical network unit for re-modulation and related power penalty of these modulation formats is also investigated. It is noted that using the optical phase locking technique it is possible to remove any cross talks which may be generated from nonlinear effects such as cross-phase modulation, self-phase modulation, and four wave mixing.     

Dispersion-free single-mode fibre transmission experiments up to 1.6 Gbit/s

Long-span single-mode fibre transmission experiments at 1.3 ?m have been refined toward higher digit rate and longer fibre span. Error-rate against receiving optical level characteristics showed that optical power penalties at 100 Mbit/s, 1.2 Gbit/s and 1.6 Gbit/s are negligible, even after 30 km, 23 km and 13 km fibre transmission, respectively.     

A novel orthogonal modulation format of D8PSK/ASK with differential bi-phase encoding and its application in a label switching optical network

The principle of a novel orthogonal modulation format of differential 8-level phase-shift keying amplitude-shift keying (D8PSK/ASK) with differential bi-phase encoding (DBC) is introduced. Based on it, an optical labeling scheme, in which the payload is 100 Gbit/s D8PSK signal and the label is 10 Gbit/s DBC-ASK signal, is proposed and simulated. The results are compared with other current schemes, and the effects of transmission range, modulation extinction ratio (ER) and received power on system performance are analyzed, respectively. The results show that the spectrum efficiency and bit error rate (BER) are improved greatly, and when the modulation ER is increased to 11 dB, the balanced performance between the payload and label is achieved.