Bidirectional WDM-PON architecture using a reflective filter and cyclic AWG

We proposed and demonstrated a bidirectional SCM-WDM PON using a reflective filter and cyclic AWG where up/downlink data could be provided using a single optical source. In the proposed scheme, the signal for downstream was modulated by a single CW laser diode and remodulated in the optical network unit as an upstream, the proposed WDM-PON scheme can offer the SCM signal for broadcasting service. In this paper, 1 Gb/s signals both for up- and downstream were demonstrated in 10 km bidirectional optical fiber link.     

Low cost architecture to integrate multiple PONs to a long reach spectrum sliced WDM network

A simple and cost effective long reach spectrum sliced WDM-PON architecture for 32 users is proposed in which multiple PONs are integrated which further increase utilization of bandwidth and network sharing between the users. It is a low cost network which uses LEDs as a broadband light emitting source and further increases equipment sharing between users. The feasibility of the architecture is analyzed using BER analysis. The architecture survives up to 150 + 20 km fiber length where BER values of each received channel are ≤10⁻⁹.     

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.     

Performance Degradation due to Cascaded Erbium-Doped Fiber Amplifier Power Transients in Wavelength Routed Optical Networking

We have investigated the fast power transient effect of the cascaded erbium-doped fiber amplifiers (EDFA) in wavelength routed optical networks. The bit error ratio (BER) degradation of surviving channel was measured at the different adding/dropping frequencies of the disturbed channels. The result show that, for low channel-adding/dropping frequency closed to EDFA transient rate, the transmission performances of the surviving channels are impaired severely.     

不同参数下GNSS软件接收机跟踪环性能分析

针对用户接收机实际跟踪卫星信号过程中跟踪环参数设置模糊性问题,着重分析了GNSS(Global Navigation Satellite System)接收机跟踪环路参数设计的范围,然后通过Matlab仿真环境对不同环路参数下信号跟踪效果进行了仿真,得出了接收机环路参数的经典取值（阻尼系数ζ=0.707,带宽BL=25 Hz）,最后通过软件接收机实验平台对实际采集到的卫星中频信号进行了跟踪验证,实验结果证明了跟踪环路参数选择的有效性。     

Performance Degradation due to Cascaded Erbium Doped Fiber Amplifier Power Transients in Wavelength Routed Optical Networking

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一种混合WDMA-OCDMA系统归一化吞吐量性能研究

理论分析了一种混合WDMA-OCDMA系统的归一化吞吐量性能.研究了光差拍噪声对系统归一化吞吐量性能的影响.提出了BCH信道编码的方案来改善系统性能.结果表明,当系统负载较轻时,归一化吞吐量略微下降;但当系统负载中等或较重时,归一化吞吐量明显提高.同时,BCH信道编码提高了WDMA-OCDMA系统的归一化吞吐量峰值.     

Metallic mesh properties and design of submillimeter filters

By using a Michelson interferometer in the asymmetric mode with helium cooled bolometer, we have measured with precision the complex transmittance and reflectance of metallic meshes in the wavelength region 0.7–4 at normal incidence. The important variations of the transmittance with the angle of incidence have been thoroughly investigated. Changes around the maximum transmittance are explained by the propagation of diffracted modes. Phase measurements show that a sharp dip appearing at _d with 1<_d/g<1.8 is related to the finite thickness of the mesh. From our measurements as well as other data precedently published it appears that there is a linear dependance between _d/g and the relative width of the slots of the mesh. All these deviations from classical models must absolutely be taken in account when designing high performances far infrared filters.     

Turbo码对快跳频光码分多址系统性能的改善

在考虑多用户干扰、色散效应和差拍噪声的情况下,分析了Turbo码对二进制脉冲位置调制(BPPM)的快跳频光码分多址(FFH OCDMA)系统性能的影响.在均匀交织器的情况下,用Turbo码的条件重量枚举函数得到了该系统的误码率的上界.数值模拟表明,Turbo码对FFH OCDMA系统的误码率性能有明显的改善,并且随着用户数的提高,Turbo码对误码率的改善程度也随之提高.也就是说,在一定的误码率性能要求下,Turbo编码的FFH OCDMA系统增加了同时使用的用户数.     

Transmission performance of 20 × 10 Gb/s WDM signals using cascaded optimized SOAs with OOK and DPSK modulation formats

We investigated 20 channels at 10 Gb/s wavelength division multiplexing (WDM) transmission over 1190 km single mode fiber and dispersion compensating fiber using cascaded inline semiconductor optical amplifier at a span of 70 km for RZ-DPSK (return zero differential phase-shift keying) modulation format by using same channel spacing, i.e. 100 GHz. We show for RZ-OOK (return zero on-off keying) format a transmission distance of up to 1050 km with Q factor more than 15 dB, without any power drops. We developed the SOA model for inline amplifier having minimum cross-talks and ASE (amplified spontaneous emission) noise power with sufficient gain. At optimal bias current of 400 mA, a high constant gain of 36.5 dB is obtained up to a saturation power of 21.36 mW. So reduction of cross-talk and distortion is possible by decreasing the bias current at appropriate amplification factor.The DPSK modulation format has less cross-talk as compared to OOK format for nonlinearities and saturation case. The impact of optical power received and Q factor at different distance for both RZ-OOK and RZ-DPSK modulation format has been illustrated. We have shown the optical spectrum and clear Eye diagram at the transmission distance of 1190 km in RZ-DPSK system and 1050 km in RZ-OOK systems.The bit error rate (BER) for all channels observed is less than 10⁻¹⁰ up to gain saturation for both DPSK and OOK systems. Finally, we investigated that the transmission distance decreases with a decrease in channel spacing of up to 20 GHz.     

Improved operation range of digital superconductive electronics by implementing passive phaseshifters

We implemented small superconducting loops containing a frozen single flux quantum in single flux quantum (SFQ) electronics. Such an element acts as a π-phaseshifter which is the missing complementary circuit element in SFQ electronics and can significantly improve the circuit reliability and robustness. We designed a four bit ripple counter including toggle flip-flops (TFF) with these π-phaseshifters. We analyzed the circuit stability by means of bit error rate (BER) measurements versus bias supply. The measured operation range of the counter in standard SFQ technique was ±14% and could be improved to ±24% for the new version utilizing π-phaseshifters. These results are a clear proof for a more robust circuit realization achieved without any additional power consumption. Furthermore, it supports the reduction of present power consumption in SFQ circuits by using smaller switching energy as well as the development of more complex circuits because of a reduced sensitivity against technological parameter spread.     

Investigations on power penalty at different spectral width using small signal analysis with higher-order dispersion

In this paper, a modified small signal analysis for power penalty at different spectral width of the light source has been investigated by incorporating the higher-order dispersion parameters. Further, we have analyzed the individual and combined effects of second- and third-order dispersion parameter on power penalty at different spectral line widths. The results have been reported over the range of 10-1000 km by considering the impact of individual and the combined higher-order dispersion terms. It has been observed that by reducing the spectral line width of the light source, the power required at the receiver can be minimized. The power penalty is further reduced if only third-order dispersion parameter is considered. Further, the transmitter distance can be maximized if the spectral width of the light reduces to 100 kHz.     

Performance analysis of source ranging by use of virtual receiver technique under different frequency bands

The traditional matched field processing localization need complicated computation to get the replica field and has high dependence on environment parameters and acoustic field model.To overcome the shortcoming,virtual receiver technique is used for source ranging.A virtual receiver is constructed by correlating the two signals of the guide source and the objective source received by a vertical line array.Then,the slope of the interference striation of the virtual field is estimated using relevant signal processing method.Combining with the waveguide invariant β,the range of the objective source is determined.Through the numerical simulations and data processing collected from the experiment carried out in the South China Sea in 2004,the virtual receiver technique for broadband source ranging under the slopebottom shallow water environment is discussed.As the frequency increases,the frequency bands should be broadened to obtain complete interference striation for good ranging results.In data processing,the receiving array spacing is too large to promise the orthogonality of the modes as the frequency increases and ranging results become worse.     

不同频段下利用虚拟接收方法的声源测距性能分析

考虑到传统的匹配场处理定位需要复杂的匹配声场计算,并对环境参数和声场模型有很高的依赖,为了克服这种缺点,采用虚拟接收方法对声源进行测距。首先对垂直阵接收到的引导声源和目标声源的信号进行相关处理,得到虚拟接收声场并估计虚拟接收声场干涉条纹的斜率,结合波导不变特征量β对目标声源进行测距。通过数值仿真和2004年南海实验数据处理,讨论了浅海斜坡海域环境中不同频段下利用虚拟接收方法对宽带声源测距的性能。随着频率升高,需要展宽频带以获得完整的干涉条纹和良好的测距结果。在实验数据处理中,选取频段较高的信号时,由于阵列间距偏大不能保证采样的简正波模式的正交归一特性,不能获得正确的测距结果。     

Enhanced performance analysis of optical CDMA communication system

Optical CDMA technique is required to meet the increased demand for high speed, large capacity communications in optical networks. OCDMA assures data access security and supports asynchronous burst data transmission. In this paper, improvement in optical CDMA has been done by implementing forward error correction technique and a distance of 100 km was achieved BER 10⁻¹⁹ at bit rate 3.75 Gbps with forward error correction in optical CDMA.     

Performance analysis of dispersion compensating optical FIR filters designed using a quasi-analytic synthesis approach

In this paper we investigate the performance of a quasi-analytic synthesis approach for dispersion compensating optical finite impulse response filters. It is shown by eye opening penalty and optical signal to noise ratio penalty calculations that with this method the filters dispersion can be adjusted reliably and with low effort to compensate for a specific amount of residual chromatic dispersion in optical transmission systems. The maximum attainable dispersion is then only limited by the filter order and the free spectral range rather then by optimization problems within the filter design.     

单纤双向WDM滤光片的研制

随着光纤接入网的发展 ,对光纤器件的价格、性能等方面提出了更严格的要求。尤其是当光纤线路紧张时 ,需要进行单纤双向传输。滤光片是关键元件 ,它分别要求 1310nm透过时要大于 98%、15 5 0nm反射时要大于 95 %以上 ,或者 1310nm反射时大于 95 %、15 5 0nm透过时大于 98%以上 ,并且带宽为± 40nm。由于滤光片尺寸较小 ,必须切割划片 ,所以对膜层的牢固度有很高的要求。经过膜系优化和大量的工艺实验 ,提供的样品完全满足用户的要求 ,现已定型批量生产。     

Simulation of Fiber to the Home at 10 Gbit/s using GE-PON architecture

In this paper, a fiber communication system is employed using Giga Ethernet Passive Optical Network (GE-PON) architecture. In this architecture an optical fiber is employed directly from a Central Office to the home. A 1:8 splitter is used as a PON element which establishes communication between a Central Office to different users. The architecture has been investigated for different lengths from a Central Office to the PON in terms of BER. For 10 Gbit/s system the plots between the BER and transmission distance are plotted and it are seen that as the distance increases beyond the 15 km the BER is increased very sharply. The results in the form of voice and data spectrum for different users of FTTH with GE-PON architecture are shown.