Study of all-optical XOR using Mach-Zehnder Interferometer and differential scheme

All-optical XOR functionality has been demonstrated experimentally using an integrated SOA-based Mach-Zehnder interferometer (SOA-MZI) at 20 and 40 Gb/s. The performance of the XOR results has been analyzed by solving the rate equation of the SOA numerically. The high-speed operation is limited by the carrier lifetime in the SOA. In order to solve the limitations imposed by carrier lifetime, a differential scheme for XOR operation has been experimentally investigated. This scheme is potentially capable of XOR operation to >100 Gb/s.     

Novel scheme for ultrafast all-optical XOR operation

A novel scheme for all-optical exclusive-OR (XOR) operating at 160 Gb/s is proposed and analyzed by means of numerical simulations. It consists of a Mach-Zehnder interferometer (MZI) where a semiconductor optical amplifier (SOA) is placed in each of its arms. This SOA-MZI setup is coupled to a delay interferometer, which acts as a signal regenerator. It is shown that error-free operation can be achieved at a data rate of 160 Gb/s, indicating that the proposed scheme is not limited by the SOA recovery time.     

All-optical multiple logic gates with XOR, NOR, OR, and NAND functions using parallel SOA-MZI structures: theory and experiment

The authors have proposed, simulated, and experimentally demonstrated all-optical multiple logic gates using two parallel semiconductor optical amplifier (SOA)-Mach-Zehnder interferometer (MZI) structures that enable simultaneous operations of various logic functions of XOR, NOR, OR, and NAND. The proposed scheme, which is optimized by adjusting the optical gain and phase differences in SOA-MZI structures with creative and systematic method, has great merits to achieve the reshaped output pulses with high extinction ratio and enable the high-speed operation at over 10 Gb/s through performance enhancement of SOAs. Its validity is confirmed through simulation and experiments at 2.5 and 10 Gb/s, respectively.     

All-optical logic XOR using differential scheme and Mach-Zehnder interferometer

All-optical Boolean XOR logic using a differential phase modulation scheme of the semiconductor optical amplifier-based Mach-Zehnder interferometer (SOA-MZI) proposed and experimentally demonstrated. The scheme is tested at 10 Gbit/s with full duty cycle operation. The proposed method is attractive because the speed of operation is not limited by the carrier recovery time of the SOA.     

改进型SOA-MZI全光异或门的加解密仿真研究

全光加密技术是解决目前光纤通信网的加解密速率瓶颈及物理层潜在的安全威胁的有力保证。针对现有全光异或加解密方案工作速率普遍较低的问题,在传统的SOA-MZI型全光异或门的基础上,利用两段色散互补的G.655单模光纤,并结合一个相位偏移器设计了一种改进型SOA-MZI全光异或方案,以该改进方案作为全光安全处理器在OptiSystem7.0仿真平台上搭建新的全光异或加解密方案,对输入信号比特速率分别为10Gb/s和40Gb/s的加解密方案进行了仿真实验验证。结果表明:基于改进型SOA-MIZ全光异或门的加解密方案可将全光异或加解密速率提高到40Gb/s,并且解密恢复出的明文数据的消光比约可以达到20dB,最大Q值约为25.7,加解密过程不会对通信系统引入额外误码。     

High-speed, all-optical XOR gates using semiconductor optical amplifiers in ultrafast nonlinear interferometers

We will review three recently-proposed high-speed, all-optical Exclusive OR (XOR) gates operating at 40 and 85?Gb/s, which were demonstrated using ultrafast nonlinear interferometers (UNIs) incorporating semiconductor optical amplifiers (SOAs). The first 40-Gb/s XOR gate was obtained using a dual UNI configuration. The second is a 40-Gb/s XOR gate without additional probe beam required, where the only inputs launched into the setup were data A and B. The XOR logic of data A and B is the sum of two components (A)B and(A)B , each of which was obtained from the output of UNI via cross-phase modulation (XPM) in SOAs. Furthermore, an 85-Gb/s XOR gate is, by far, the fastest XOR gate realized by SOAs, which was also demonstrated using a dual UNI structure. The operating speed of the XOR gate was enhanced by incorporating the recently proposed turbo-switch configuration. In addition, the SOA switching pulse energies of these XOR gates were lower than 100 fJ.     

基于非线性极化旋转技术的640G全光解复用

考虑超快载流子动态特性,文章通过仿真详细分析了基于半导体光放大器的非线性极化旋转效应实现640Gb/s到80Gb/s的解复用方案.结果表明:开关窗口的上升沿随时钟脉冲能量的变化不是很明显,而FWHM和下降沿则随时钟脉冲能量的增加而增加.此外,在相同条件下,当输入的时钟信号为TE模式时,输出的解复用信号具有最高的信道压制比.     

An 80-Gb/s optoelectronic delayed flip-flop IC using resonanttunneling diodes and uni-traveling-carrier photodiode

This paper describes an 80-Gb/s optoelectronic delayed flip-flop (D-FF) IC that uses resonant tunneling diodes (RTDs) and a uni-traveling-carrier photodiode (UTC-PD). A circuit design that considers the AC currents passing through RTDs and UTC-PD is key to boosting circuit operation speed. A monolithically fabricated IC operated at 80 Gb/s with a low power dissipation of 7.68 mW. The operation speed of 80 Gb/s is the highest among all reported flip-flops. To clarify the maximum operation speed, we analyze the factors limiting circuit speed. Although the bandwidth of UTC-PD limits the maximum speed of operation to 80 Gb/s at present, the circuit has the potential to offer 100-Gb/s-class operation     

High-Bit-Rate Dense SS-WDM PON Using SOA-Based Noise Reduction With a Novel Balanced Detection

The major drawback of incoherent broadband sources (BBSs) is their inherent intensity noise. Semiconductor optical amplifiers (SOAs) can be exploited at the transmitter to mitigate this noise. Optical filtering at the receiver, however, leads to the return of most of suppressed noise. Wider filtering at the receiver is the best known strategy to maintain performance gains, at the price of reduced spectral efficiency due to the tradeoff between noise cleaning and adjacent channel crosstalk. We introduce a novel balanced receiver for wavelength division multiplexing (WDM) systems that maintains greater noise cleaning and leaves spectral efficiency unchanged. Unlike standard receivers, our balanced scheme does not filter the desired signal. In this paper, we first demonstrate that the newly proposed receiver is equivalent to standard WDM receivers when no SOA for noise cleaning is present at the transmitter. Although a 2.9-dB power penalty is incurred, network capacity is unchanged, i.e., bit error rate (BER) floors due to intensity noise are the same. When SOAs are employed to mitigate severe intensity noise, we show that our receiver outperforms the wide filtering strategy by two orders of magnitude. Dense WDM capacity is demonstrated up to 10 Gb/s using a thermal source, a saturated SOA, and the balanced detection scheme. A BER of 10^-6 is achieved at 10 Gb/s; further improvement is possible using low overhead forward error correction or a better SOA design. This demonstrates the ability of spectrum-sliced wavelength division multiplexing (SS-WDM) passive optical networks (PONs) to operate at 10 Gb/s at good spectral efficiency. Error performance better than 10^-9 is achieved up to 8 Gb/s with 30-GHz optical channel bandwidth and 100-GHz spacing.     

基于SOA和改进M-Z干涉仪的光分组头提取方案

提出了一种基于半导体光放大器(SOA)和改进的马赫一曾德尔(M-Z)干涉仪的全光分组交换的分组头提取结构和方案.通过讨论SOA-改进的M-Z干涉仪参数对系统性能的影响,从而得到使性能优化的系统参数.数值分析和仿真结果表明,系统在分组头和净荷速率分别为2.5 Gb/s和40 Gb/s时,系统提取分组头的对比度达到15 dB以上.另外,该系统还具有结构简单、可扩展性好和易于集成的优点.     

10-Gb/s, 4-channel wavelength division multiplexing fibertransmission using semiconductor optical amplifier modules

A dense wavelength-division-multiplexing (WDM) transmission system with very-high-speed channels was investigated experimentally. A 10-Gb/s four-channel WDM optical transmission (total capacity of 40 Gb/s) over a 40-km dispersion-shifted fiber was achieved by using hybrid-integrated DFB-LD/driver modules for transmitters and two cascaded semiconductor optical amplifier (SOA) modules for receivers. The experiment confirmed that the SOA is applicable for WDM transmission systems with high bit rates because of its inherent wide bandwidth. The transmission capacity of 40 Gb/s, achieved using an intensity modulation/direct detection (IM/DD) scheme, is the highest ever reported. This technology will make possible ultralarge capacity (up to several-hundred gigabits per second) and long-haul transmission systems in the future     

适于异步光分组交换的反射式光分组头提取方案

基于半导体光放大器(SOA),提出了一种适于异步光分组交换的反射式全光分组头提取方案,它具有比特率透明、开关比(CR)大等特点,适于变长、全光分组交换。仿真了不同速率光分组头的提取效果,分析了系统参数对CR的影响。结果表明,当分组头脉冲速率分别为622Mb/s、2.5Gb/s及10Gb/s时,CR分别为25.46、25及21.7dB。CR随输入脉冲能量、小信号增益及SOA饱和能量的增大而增大,通过适当选取这些参数,可进一步提高系统性能。     

A Bidirectional WDM/TDM-PON Using DPSK Downstream Signals and a Narrowband AWG

We present an innovative architecture to realize a single feeder bidirectional amplified wavelength-division-multiplexing/time-division-multiplexing passive optical network based on modified nonreturn-to-zero differential phase-shift keying (DPSK) downstream signals at 20 Gb/s and a narrowband arrayed waveguide grating (AWG). The AWG plays at the same time the role of channel distributor, simultaneous demodulator for all DPSK channels, and eliminates the need for chromatic dispersion compensation. A saturated semiconductor optical amplifier (SOA) provides bidirectional amplification to compensate the splitter losses. The remodulated upstream signals are obtained at 1 Gb/s by means of a reflective SOA. Experimental results show error-free operation on both downstream and upstream signal.     

Optical Reshaping of 40-Gb/s NRZ and RZ Signals Without Wavelength Conversion

We experimentally demonstrate a scheme for all-optical reshaping at 40 Gb/s that is wavelength preserving and transparent to both nonreturn-to-zero and return-to-zero on-off keying signals. Eye-diagram reshaping is confirmed by means of bit-error rate versus threshold measurements on both modulation formats. The scheme is based on cross-gain compression in an semiconductor optical amplifier (SOA) and uses two SOAs that are not in interferometric configuration. Due to its working principle, this method is polarization-independent and suitable, in principle, for higher bit rates.     

基于级联半导体光放大器实现全光逻辑与门的改进方案

基于级联半导体光放大器(SOA)实现全光逻辑与门的方案中,第一级输出信号质量直接影响逻辑与运算结果.采用载流子恢复较慢的体材料半导体光放大器用于第一级转换,在10 Gbit/s以上得不到理想的转换结果,限制了该方案实现逻辑与门的速率.利用光纤延时干涉仪(DI)和第一级半导体光放大器级联可以改善第一级输出信号质量,从而有效提高第二级全光逻辑与门的实现速率.阐述了改进方案中延时干涉仪的作用,并进行了数值模拟.根据实验结果,采用载流子恢复较慢的半导体光放大器级联延时干涉仪能够实现高速归零(RZ)信号和非归零(NRZ)信号的反码,从而得到较高速率的全光逻辑与门.实验实现了20 Gbit/s的伪随机归零和非归零信号的全光逻辑与门,对40 Gbit/s的结果进行了分析和讨论.     

Cascadability Performance Evaluation of a New NRZ SOA-MZI Wavelength Converter

We evaluate the cascadability performance of a new semiconductor optical amplifier (SOA) Mach-Zehnder interferometer-based nonreturn-to-zero wavelength converter in a loop experiment. We use the bidirectional data injection control scheme with an additional continuous-wave signal to optimize the gains and phases imparted by the SOAs. The scheme has been shown to be capable of eight cascaded, error-free wavelength conversions at 10 Gb/s.     

Bidirectional Data Injection Operation of Hybrid Integrated SOA–MZI All-Optical Wavelength Converter

A bidirectional data signal input scheme of a semiconductor optical amplifier--Mach-Zehnder interferometer (SOA-MZI) wavelength converter was proposed and experimentally verified for a nonreturn-to-zero (NRZ)-format signal. Theoretical analyses reveal that it is possible to mitigate the patterning effect induced by cross-gain modulation (XGM) by utilizing the difference of the ratio between the XGM and cross-phase modulation on the injection directions of data signals. A hybrid integrated SOA-MZI all-optical wavelength converter, in which the coupling loss between the SOA and the silica waveguide was as small as 1 dB owing to a unique active alignment technique, was used for the experiment. We have verified the superior characteristics of the proposed operation scheme for the first time. Error-free wavelength-conversion operation for an NRZ signal at 40 Gb/s was confirmed     

All-optical XOR gate using semiconductor optical amplifiers without additional input beam

The novel design of an all-optical XOR gate by using cross-gain modulation of semiconductor optical amplifiers has been suggested and demonstrated successfully at 10 Gb/s. Boolean AB~ and A~B of the two input signals A and B have been obtained and combined to achieve the all-optical XOR gate. No additional input beam such as a clock signal or continuous wave light is used in this new design, which is required in other all-optical XOR gates.     

High-speed CMOS analog Viterbi detector for 4-PAM partial-responsesignaling

In this paper, a 1-Gb/s analog Viterbi detector based on a 4-PAM duobinary scheme is discussed with experimental results for a 0.25-μm CMOS implementation. This chip is the first analog integrated implementation of a reduced state sequence detector. Pipelining and parallel processing have been incorporated in this design for high-speed operation. Due to test equipment limitations, experimental results are given for 200-Mb/s operation while simulation results indicate a speed of 1 Gb/s. Power dissipation is 55 mW from a 2.5-V supply. The active area occupies 0.78 mm². Although a duobinary scheme has been the focus of this work for its application in optical links, this design can be readily modified or extended to other partial-response signaling schemes such as dicode and PR4     

Increasing input power dynamic range of SOA by shifting thetransparent wavelength of tunable optical filter

Gain-saturation-induced self-phase modulation (SPM) leading to pulse distortion in a semiconductor optical amplifier (SOA) is overcome by shifting a tunable optical filter (TOF). A recovered or broadened pulse can be obtained after filtering the amplified pulse in the SOA even if the short pulse is only 2-3 ps long. The input power dynamic range (IPDR) can be strongly increased by shifting the TOF and the direction of the shifted transparent wavelength is different for 10 Gb/s return-to-zero (RZ) or nonreturn-to-zero (NRZ) signals. The transparent wavelength of the TOF should be shifted to a longer wavelength for RZ signals and to a shorter for NRZ signals. 80-Gb/s optical time division multiplexing (OTDM) signal amplification in the SOA is demonstrated for the first time. We also demonstrate that a large IPDR for the 80-Gb/s OTDM signal can be obtained by shifting the TOF