HDTV/Gigabit Ethernet over bidirectional WDM-PON based on injection-locked Fabry-Perot laser diodes

Bidirectional high definition television (HDTV)/Gigabit Ethernet over wavelength-division-multiplexing (WDM)-passive optical network (PON) based on injection-locked Fabry-Perot laser diodes (FP LDs) as transmitters were proposed and demonstrated. Injection-locked FP LDs, a particularly inexpensive option, are used to replace conventional distributed feedback (DFB) LDs. Services with 77 HDTV channels and 1 Gigabit Ethernet channel connection were successfully demonstrated over 40 km single-mode fiber (SMF) transport. Good performance of bit error rate (BER) and clear eye diagram were achieved in our proposed bidirectional WDM-PON.     

10 Gb/s TDM passive optical networks using four wavelengths multiplexed channels

We propose a new architecture for 10 Gb/s upstream traffic in TDM-PON using externally injection-locked Fabry-Perot laser diodes (FP-LDs) in each optical network unit (ONU). Four directly modulated 2.5 Gb/s FP-LDs were injection-locked by continuous wave (CW) carriers distributed from the optical line terminal (OLT). Hence, a total of 10 Gb/s upstream traffic can be achieved. Experimental results show negligible power penalty at a transmission of 25 km standard single mode fiber (SMF) without dispersion compensation. The performance of the injection-locked FP-LD is also studied.     

Utilization of four WDM channels with signal remodulation of OFDM-QAM for 10 Gb/s uplink passive optical networks

In this investigation, we experimentally investigate an extended reach (ER) time-division-multiplexed passive optical network (TDM-PON) using four wavelength-multiplexed channels to achieve 16 Gb/s downlink and 10 Gb/s uplink traffic. Each downlink signal uses the highly spectral efficient 4 Gb/s OFDM-QAM, and each uplink signal is generated by signal remodulating the downlink signal via a reflective semiconductor amplifier (RSOA) at 2.5 Gb/s non-return-to-zero (NRZ). In addition, the performance of the proposed ER TDM-PON has also been analyzed and discussed.     

Enhanced performance for 10 Gb/s long reach RSOA based WDM-PON by using power pre-emphasized OFDM signal

An extended reach 10 Gb/s wavelength division multiplexing passive optical networks (WDM-PONs) system based on reflective semiconductor optical amplifier (RSOA) is proposed by using power pre-emphasized orthogonal frequency division multiplexing (OFDM) signal. Experimental results show that the proposed technique can effectively enhance the system performance against the limited bandwidth and chirp induced fading effect from direct modulation of RSOA. The receiver sensitivity is improved by 5 dB at the limit of BER for forward error correction (FEC) code over the 60 km and 85 km fiber transmission without any dispersion compensation module.     

Upstream vertical cavity surface-emitting lasers for fault monitoring and localization in WDM passive optical networks

As wavelength division multiplexed passive optical networks (WDM-PONs) are expected to be first deployed to transport high capacity services to business customers, real-time knowledge of fiber/device faults and the location of such faults will be a necessity to guarantee reliability. Nonetheless, the added benefit of implementing fault monitoring capability should only incur minimal cost associated with upgrades to the network. In this work, we propose and experimentally demonstrate a fault monitoring and localization scheme based on a highly-sensitive and potentially low-cost monitor in conjunction with vertical cavity surface-emitting lasers (VCSELs). The VCSELs are used as upstream transmitters in the WDM-PON. The proposed scheme benefits from the high reflectivity of the top distributed Bragg reflector (DBR) mirror of optical injection-locked (OIL) VCSELs to reflect monitoring channels back to the central office for monitoring. Characterization of the fault monitor demonstrates high sensitivity, low bandwidth requirements, and potentially low output power. The added advantage of the proposed fault monitoring scheme incurs only a 0.5 dB penalty on the upstream transmissions on the existing infrastructure.     

Employing injection-locked Fabry–Perot laser diodes to improve bidirectional WDM–PON performances

We proposed and demonstrated a bidirectional wavelength-division-multiplexing (WDM)–passive optical network (PON) employing injection-locked Fabry–Perot laser diodes (FP LDs) at both transmitting sites, and adaptive filters at both receiving sites. Injection-locked FP LDs, a particularly inexpensive option, are used to replace the conventional distributed feedback (DFB) LDs in WDM–PON. Adaptive filters are attractive because they can track the variations and compensate the nonlinear distortions. Transmission performance over 20 km of a standard single-mode fiber (SMF) was investigated. Improved performance of bit error rate (BER), better and clear eye diagram were achieved in our proposed WDM–PON.     

基于注入锁定法布里-珀罗激光器的光学双稳态及光存储研究

研究基于注入锁定法布里-珀罗激光器的全光双稳态效应及其在全光存储中的应用. 进行了法布里-珀罗激光器的注入锁定的实验研究, 对注入锁定的法布里-珀罗激光器的输出功率特性进行实验分析, 得到了不同注入光波长失谐量对迟滞曲线的门限宽度和消光比的影响. 进一步, 通过对控制信号功率的合理设置, 实现了对10 Gb/s输入信号的2.5 GHz光存储验证了利用注入锁定法布里-珀罗激光器实现高速全光存储的可行性, 在高速光纤通信领域具有极大的应用价值.     

Characterization of Rayleigh backscattering performance of CS-SSB signal in carrier distributed passive optical network

Rayleigh backscattering (RB) is an intrinsic phenomenon when light propagating in fiber and its level is fixed by the fiber type and the network configuration used. Thus, RB noise would be one of the major impairments in a carrier distributed passive optical network (PON). Previously demonstrated carrier suppressed subcarrier-amplitude modulated phase shift keying (CSS-AMPSK) modulation may be useful to effectively mitigate the RB noise. However, this modulation is basically a carrier suppressed double sidebands modulation (CS-DSB) format, in which the same information is carried by the two sidebands with equal magnitude. This is not very power-efficient for PON. Here, we further extend our RB studies by using carrier suppressed single sideband non-return-to-zero (CS-SSB-NRZ) modulation. We experimentally characterize the CS-SSB-NRZ modulation when subjected to both contributions of RB: Carrier-RB and Signal-RB. Then, numerical simulations are performed, and the results are in good match with the experiment. Finally, upstream transmission experiment is performed showing the feasibility of using the CS-SSB-NRZ signal for the carrier distributed PON. The RB performance of the SSB-NRZ signals transmitted at different distances and driven at different radio-frequency (RF) f_s is also investigated.     

利用可调谐的混沌Fabry-Perot激光器实现波分复用无源光网络的断点检测

波分复用无源光网络具有支路多、节点密的特征,为精确定位各支路的断点,提出了一种基于可调谐混沌Fabry-Perot激光器的检测方法.将光反馈多纵模Fabry-Perot半导体激光器作为混沌光源,在改变反馈光光波模式的条件下输出波长可调谐的混沌激光.以探测光的波长标记各被测支路,将探测信号和携带延时信息的回波信号进行互相关运算,根据相关曲线峰值的位置即可完成定位.分析了可调谐混沌源的特性,并以1×4的波分复用无源光网络为例,进行了初步的实验验证,结果表明该方法可以精确定位光网络支路中连接点及断点的位置,空间分辨率达4 cm,且与探测距离无关.     

利用可调谐的混沌Fabry-Perot激光器实现波分复用无源光网络的断点检测

波分复用无源光网络具有支路多、节点密的特征,为精确定位各支路的断点,提出了一种基于可调谐混沌Fabry-Perot激光器的检测方法.将光反馈多纵模Fabry-Perot半导体激光器作为混沌光源,在改变反馈光光波模式的条件下输出波长可调谐的混沌激光.以探测光的波长标记各被测支路,将探测信号和携带延时信息的回波信号进行互相关运算,根据相关曲线峰值的位置即可完成定位.分析了可调谐混沌源的特性,并以1×4的波分复用无源光网络为例,进行了初步的实验验证,结果表明该方法可以精确定位光网络支路中连接点及断点的位置,空间分辨率达4 cm,且与探测距离无关.     

Design of wavelength adjustable lasers with photonic crystal based Fabry-Perot etalon for applications in optical network units of wavelength-division-multiplexed passive optical network systems

We propose a novel wavelength adjustable laser (WAL) with a photonic crystal based Fabry-Perot (FP) etalon. This laser will be a promising light source for optical network units (ONUs) of conventional wavelength-division-multiplexed passive optical network (WDM-PON) systems for up-stream transmission. It has the merits of a relatively simple fabrication and operation, wide process tolerance, low-cost, high side-mode suppression ratio, and wavelength-tunable characteristics. The optimization of the device structure and the implementation methods for this type of laser are discussed. Although the WALs in WDM-PON systems are not colorless, each laser can cover several wavelengths. Thus, the required number of different ONUs can be reduced. This approach may be necessary for 10 Gbps upstream transmission in next-generation optical access networks because the 10 Gbps data rate is difficult to achieve by using current colorless schemes.     

Chaos synchronization in injection-locked semiconductor lasers with optical feedback

Based on the rate equations, we have investigated three types of chaos synchronizations in injection-locked semiconductor lasers with optical feedback. Numerical simulation shows that the synchronization can be realized by the symmetric or asymmetric laser systems. Also, the influence of parameter mismatches on chaos synchronization is investigated, and the results imply that these two lasers can achieve good synchronization, with smaller tolerance of parameter mismatch existing.     

Characterization of phase modulated non-return-to-zero (PM-NRZ) format for DWDM long reach PONs

A technique which has been shown to be effective to mitigate the Rayleigh backscattering (RB) noise and potentially suited for use in the carrier distributed passive optical networks (PONs), uses a phase modulator (PM) at the reflective optical networking unit (RONU) to reshape the spectrum of the upstream non-return-to-zero (NRZ) signal, named PM-NRZ. Since the PM-NRZ signal has a much wider spectrum than the conventional NRZ signal, it would be very interesting to know its performance when applied to the multiple channels, or dense wavelength division multiplexed (DWDM) environment. Here, we, for the first time, show how close the neighboring channels can be located in the network by means of numerical simulations. We also provide solutions to reduce the crosstalk produced by neighboring PM-NRZ channels. Since in the WDM-PON system the distances between different ONUs and the head-end office vary, we also analyze the network performance when the powers of adjacent PM-NRZ signals change.     

Discretely tunable and multiwavelength erbium doped fibre lasers with Fabry-Perot etalon

Modern WDM telecommunication systems require stable and calibrated laser sources. In this paper, we present examples of such lasers based on erbium doped fibres, i.e., discretely tunable and multiwavelength ring lasers. For the first case, tuning is possible due to a tunable Bragg grating overlapping spectrally the third telecommunication window (1550 nm). When a Fabry-Perot etalon is inserted into the cavity, discrete tunable operation with appropriate spacing between operating wavelengths is possible. Different free spectral ranges (FSR) of applied etalons ensured operation at a wavelength spacing 0.4 nm, 0.8 nm or 1.6 nm, respectively. When an acoustooptical Bragg frequency shifter was inserted together with the Fabry-Perot etalon, the stable simultaneous multiwavelength operation covering the erbium doped gain range was achieved.     

光放大外腔式光纤法布里-珀罗干涉传感系统

提出了一种大幅度提高外腔式法布里珀罗干涉传感器干涉信号强度的方法 ,利用掺铒光纤放大自发辐射产生的光源代替一般宽带光源 ,同时由于掺铒光纤的放大作用可以放大干涉信号 ,将光纤法布里珀罗传感器的信号强度提高了 4个数量级 ,因而利用该方法可获得很强的信号和较高的信噪比。介绍了基于光放大的外腔式法布里珀罗干涉传感系统的结构、测量原理及实验。实验结果表明该传感器的应变精度为± 10 με,可满足实际应用的要求。该传感系统在大幅度提高传感器信号强度的同时并未提高系统的成本 ,因此有着较高的性价比和实用价值。     

Injection locked Fabry-Perot laser diodes for WDM passive optical network spare function

In this paper, a protection scheme for transmitters in wavelength-division-multiplexing passive optical network (WDM-PON) has been proposed and demonstrated. If any downstream transmitter encounters problems at the central office (CO), the interrupted communication can be restored immediately by injecting a Fabry-Perot laser diode (FP-LD) with the upstream lightwave corresponding to the failure transmitter. Compared with the conventional methods, this proposed architecture provides a cost-effective and reliable protection scheme employing a common FP-LD. In the experiment, a 1:36 protection capability was implemented with a 2.5 Gbit/s downstream transmission capability.     

光纤法布里-珀罗传感器串连复用的傅里叶变换解调方法初探

光纤法布里—珀罗传感器复用、特别是串连复用的解调十分困难。为解决这个问题,从光纤法布里—珀罗应变传感器的基本原理出发、在仅有两只传感器复用的基本条件下,深人分析了复用系统组合输出光强信号及其分布特性;研究了对其进行傅里叶变换的解调原理及具体实现方法,分析了因复用信号不满足傅里叶变换条件而在变换域产生的畸变,进行了计算机仿真解调。在此基础上,搭建了两只传感器的串连复用实验系统,并用此方法实现了两只复用传感器的解调,且传感器之间的相互影响小于5％。理论与实验表明,虽然传感器的复用信号不满足傅里叶变换的标准条件,且仿真与实验存在一定差异,但所提出的傅里叶变换方法,基本可用于光纤法布里—珀罗传感器的串连复用解调。     

外注入非制冷式FP半导体增益开关激光器产生低抖动光脉冲的实验研究

报道了低成本、非制冷法布里-玻罗腔半导体增益开光激光器稳定地产生超短脉冲的实验研究.通过使用外部连续光注入,增益开光激光器的脉冲抖动得到了有效的抑制.实验结果表,明当选择合适功率的连续光注入到非制冷半导体增益开关激光器腔内,可以稳定地产生脉宽26 ps、抖动低于400 fs、重复频率2.5 GHz的脉冲序列.     

Enhanced optical gain clamping for upstream packet based traffic on hybrid WDM/TDM-PON using fiber Bragg grating

In this paper, we propose a method to mitigate the temporal power transients arising from Erbium doped fiber amplifiers (EDFAs) on packeted/bursty scenario. The technique, applicable on hybrid WDM/TDM-PON for extended reach, is based on a low power clamping provided by a distributed feedback (DFB) laser and a fiber Bragg grating (FBG). An improvement in the data signal Q factor was achieved keeping the clamping control signal with a low power, accompanied by a maximum reduction in the gain excursion of 1.12 dB.