新型光接收系统架构：应用于超大容量低成本的短距光互连

大规模数据中心等新兴网络基础设施的部署急需超大容量低成本的短距光互连系统。传统的直调直检系统拥有简单的接收机结构,但只能检测信号的强度信息,这限制了其系统容量的进一步扩展。经典的相干传输系统能够调制解调高阶信号进而实现大容量传输,但收/发端都需要昂贵的窄线宽激光器和高复杂度的数字信号处理,这阻碍了其在短距光互连中的广泛应用。新型的直接检测光接收系统旨在结合直接检测和相干检测两者的优点,弥补二者之间的研究空白。因此,新型的光接收系统架构主要基于自相干检测。介绍了新型单偏振、双偏振、少模光接收系统架构。该类新型的光接收系统不需要本振激光器且能通过直接检测恢复光场信号,实现超大容量低成本的短距光互连。     

无源光网络中突发光发射机和接收机的设计

本文比较了无源光网络（ＰＯＮ）中突发工作方式的光发射机,接收机与传统的连续工作的光发射机,接收机的差别,分析了春特性,并给出了设计原理图,这些原理图同样适用于其它光纤计算机网络的光发射机,接收机。     

Complexities, error probabilities, and capacities of optical OOK-CDMA communication systems

The complexity in the hardware implementation of traditional optical code-division multiple-access correlation receivers with double optical hardlimiters is discussed. A comparison with the implementation of chip-level receivers is presented as well. In addition, the bit error probabilities and the throughput capacities for both chip-level and correlation systems (without hardlimiters) are derived and evaluated under code-correlation constraints equal to one and two. Our results reveal that chip-level receivers are much simpler and their performances are competitive with that of traditional correlation receivers with double optical hardlimiters. Further, the throughput capacity of chip-level systems can be increased by almost a factor of 3.4 when increasing the code-correlation constraint from one to two.     

Optical array receiver for communication through atmospheric turbulence

An optical array receiver concept is developed and analyzed. It is shown that for ground-based reception, the number of array elements can be increased without incurring performance degradation, provided the array telescope diameters exceed the coherence-length of the atmosphere. Maximum likelihood detection of turbulence-degraded signal fields is developed for the case of pulse-position modulated signals observed in the presence of background radiation. Performance of optical array receivers is compared to single-aperture receivers with diameters ranging from 4 to 8 m, both in the presence of turbulence and in a turbulence-free environment such as space. It is shown that in the absence of atmospheric turbulence, single-aperture receivers outperform receiver arrays when significant background radiation is present. However, it is also demonstrated that for ground-based reception of deep-space signals, the number of array elements can be as great as several thousand without incurring any performance degradation relative to a large single-aperture receiver.     

Analysis of the performance of time-spread optical code-division multiple access systems with integrate-and-dump receivers

The BER performance of asynchronous time-spread optical code-division multiple access (TS-OCDMA) systems employing integrate-and-dump receivers with partially coherent optical sources was analyzed. Monte-Carlo simulations of the system were performed to verify the validity of the model. Using the developed analytic model, the TS-OCDMA systems with integrate-and-dump receivers were compared with those employing optical thresholders. It was found that: (1) as the integration time (or gating time) increases, the systems with optical thresholders outperform those using integrate-and-dump receivers, (2) while the performance of both systems is improved as the optical sources become more incoherent, those with integrate-and-dump receivers benefit more, (3) when the systems are spectral-efficiency limited, the performance does not improve by using partially coherent sources.     

Gain-bandwidth-limited response in long-wavelength avalanche photodiodes

The gain-bandwidth(GB)-limited response of In0.53Ga0.47As/ InP heterostructure avalanche photodiodes (APD's) and related devices used in long-wavelength digital optical receivers is calculated. We find that these diodes, as currently designed, are useful at bit ratesB lsim 2Gbit/s when employed in conjunction with high-sensitivity optical receivers. Response at higher bit rates may be obtained depending on the details of device design. On the other hand, use of poor-quality receivers that require moderate-to-high values of optimum gain can significantly degrade the performance of heterostructure APD's at high bit rates due to GB limitations. We also show that APD receiver bandwidth can be expressed in terms of the sensitivity obtained using the receiver in conjunction with a p-i-n photodiode. It is found that the response speed of optimized receivers is lowest for an APD effective ionization rate ratio ofk = 0.5.     

Linear Direct-Detection Fiber-Optic Receiver Optimization in the Presence of Intersymbol Interference

A technique is developed for optimizing communication receivers by minimizing a Chernoff bound (CB) on the Bayes cost function. Being couched in terms of moment generating functions, the procedure is well suited to optical systems. Optimal CB receivers are derived and shown to coincide exactly with known minimum cost Bayes receivers for certain special cases of both electrical and optical communications for which closed form analytic solutions are possible. This provides endorsement for the method, which is then applied to more complex practical cases of linear optical fiber receivers in which both colored Gaussian noise and intersymbol interference play a part. The CB receivers are shown to offer some improvement compared with a zero forcing raised cosine equalizing receiver such as is commonly adopted, and all the evidence suggests that CB receivers achieve performance very close to the best possible with a linear receiver.     

Practical limitations on optical amplifier performance

Practical issues are considered to determine if significant improvements in the sensitivity, of 1.55-μm optical receivers can be realized through the use of semiconductor laser preamplifiers. It is found that practical problems related to realizable values of population inversion parameter, input coupling losses, external optical filter requirements, polarization effects, and source laser stability make it unlikely that optical preamplifiers can approach their optimum performance at data rates below several Gbit/s. The most promising application of optical preamplifiers will therefore be to increase the sensitivity of receivers in future fiber optic communication systems operating at multigigabit data rates.     

Active feedback lightwave receivers

This paper describes new p-i-n-FET lightwave receivers that achieve high sensitivity without signal integration, and dynamic ranges large enough that they cannot be saturated by present lightwave transmitters. IC versions can be realized inexpensively in standard fine-line NMOS, CMOS, or GaAs IC technologies, and thus are suitable for loop-plant, local-area-network, and data link applications, as well as long-haul transmission applications. These receivers also can readily be designed for bit-rates in excess of 1 Gbit/s for high-capacity systems. In addition, these receivers can be implemented on the same IC as other system functions, e.g., for single-chip lightwave regenerators and lightwave modems, and, eventually, for microprocessors with on-chip optical communications ports.     

FTTH光接收机功率放大器的设计与改进

在分析国内外FTTH光接收机应用前景和普通光接收机的功率放大器基础上,用MMIC替代通用放大模块,设计并经过优化改进找到了一款适合FTTH的CATV光接收机功率放大器.通过测试,性能指标完全符合要求,具有很好的实用价值.     

Microwave-bandwidth optical receiver systems

A theoretical and experimental evaluation of optical communications systems capable of microwave bandwidths is presented. The optical transmitter, modulator, and detection techniques are discussed with respect to both direct-detection and optical heterodyne receivers, and experiments in a nonlaboratory environment are described. At the high optical power levels or photon rates which are fundamentally necessary for gigahertz instantaneous bandwidths, it is found that signal-shot-noise limited operation may be obtained with new wideband photodetectors incorporating internal gain. Direct-detection receivers are thus generally superior to heterodyne receivers in these systems. A comparison is made of the relative merits of alternative systems and their dependence on various parameters such as information capacity, range, and background illumination.     

Performance of coherent optical receivers

Coherent optical communications, an area of research that shows great promise for future high-bandwidth and long-haul applications, is reviewed. Coherent optical receivers, which add light to the received signal as part of the detection process, have numerous advantages over direct-detection receivers, most notably increased sensitivity and increased selectivity, at the cost of increased complexity. The performance of coherent optical receivers under shot-noise-limited conditions is reviewed for a variety of modulation and demodulation formats. In addition, laser phase noise is discussed, and its effect on receiver performance is analyzed     

Bit error probability reduction in direct detection opticalreceivers using RZ coding

We analyze the bit error probability reduction for direct detection ON-OFF keying optical receivers using return-to-zero (RZ) coding instead of the nonreturn-to-zero (NRZ) format. For the same average optical power, RZ is shown to outperform NRZ, even when employing the same receiver bandwidth. Results are given for receivers whose noise variance is i) dominated by a signal-independent term (e.g., simple pin diode receivers), ii) dominated by a signal-dependent term (e.g., optically preamplified receivers), and iii) made up of two equally important contributions [e,g,, avalanche photodiode (APD) receivers]. Based on semianalytic simulations including intersymbol interference, we show that the achievable RZ sensitivity gain is typically less for dominating signal-independent noise than for dominating signal-dependent noise, where it amounts to about 3 dB. We also quantitatively discuss the influence of the optical pulse shape on the achievable RZ coding gain, and show that finite extinction ratios can significantly reduce that gain, especially when the RZ signals are produced by direct-modulation methods     

Optimal dimensioning of the WDM unidirectional ECOFRAME optical packet ring

To efficiently support the high rate and the high dynamicity of the traffic in metro networks, an optical packet-switched WDM ring, named ECOFRAME, is proposed. The key features of the proposed ring are optical transparency and statistical multiplexing of optical packets on parallel WDM channels. Such features can be exploited by properly allocating wavelengths and receivers. This paper aims to optimally dimension the unidirectional ECOFRAME rings. The dimensioning at minimum cost (i.e., for wavelengths and receivers) is modeled with an mixed-integer linear programming formulation. An heuristic algorithm is also proposed, and its performance is compared against the optimal solutions and bounds. When considering the receiver and wavelength cost, results indicate that trading the wavelengths for receivers allows cost saving of up to 75% with respect to WDM optical packet rings with a single dedicated wavelength per node (i.e., single receiver at each node).     

Heterodyne video distribution systems sharing transmitter and localoscillator lasers

The authors present theoretical and experimental results for coherent subcarrier multiplexed (SCM) systems using a novel architecture that shares both the transmitter and local oscillator (LO) laser among multiple optoelectronic receivers. The ability to share both lasers significantly reduces the cost and complexity compared to a multichannel coherent frequency division multiplexed (FDM) system. Experimental results confirm that the system performance can be greatly enhanced by inserting an inline optical amplifier so that many receivers can share one transmitter and LO laser. For example, with an amplifier chip gain of 24 dB, increasing the optical power at the input to the amplifier by 3 dB from -27.6 to -24.5 dBm, the number of receivers can be increased from 2 to 32     

Optical energy considerations for diode-clamped smart pixel opticalreceivers

We calculate the switching time as a function of optical energy for a single-stage smart pixel receiver. We find that operating the receivers dynamically using modelocked pulses is the most energy-efficient method of operation. We also show that the receivers no longer operate with constant optical input energy, like the symmetric self electro-optic effect device (S-SEED), but rather the product of the required optical energy and the switching time is constant, as a result of the introduction of electrical voltage gain     

Simulation performance of optimal and suboptimal nonsynchronizedreceivers

Two optimal receivers, along with their approximations derived for the optical on-off keying channel, are briefly described. These receivers make symbol decisions in the absence of synchronization. The various approximations to the optimal rules are derived. Computer simulations are presented that compare the performance of suboptimal receivers to that of jointly optimal receivers, as well as to receivers utilizing a separate synchronizer. It is observed that one of the approximations, which is rather simple to implement, performs as well as the significantly more complicated receiver that utilizes a separate, optimal, synchronizer. Further computer simulations show that the suboptimal receivers are quite robust to nonperfect knowledge of the received signal power     

A phototransistor with concentric electrodes on the Si substrate

A high-speed phototransistor with concentric lateral electrodes was fabricated on the Si substrate. The optical gain for continuous wave He-Ne laser excitation can be as high as 80. The pulse width in response to mode-locked laser pulses is 220 ps. A bandwidth of 1.7 GHz was observed for saturated unity-gain operation. The capability of being integrated is potentially useful in realizing high-speed optical receivers.     

大气光通信中应用最优选择分集

针对大气光通信中湍流对接收端误码率的影响,提出利用空间分集技术,通过对多发射器、多接收器最优选择来改善信噪比,降低误码率。仿真结果表明,当湍流较强时,多发射多接收比单发射单接收对系统的性能有更明显的改善。同时表明,在对数正态分布的光信道上,最优选择的效果与在瑞利衰落的无线信道上的效果基本相同。     

Analysis of optical amplifier noise in coherent opticalcommunication systems with optical image rejection receivers

A detailed theoretical analysis of optical amplifier noise in coherent optical communication systems with heterodyne receivers is presented. The analysis quantifies in particular how optical image rejection receiver configurations reduce the influence of optical amplifier noise on system performance. Two types of optical image rejection receivers are investigated: a novel, all-optical configuration and the conventional, microwave-based configuration. The analysis shows that local oscillator-spontaneous emission beat noise (LO-SP), signal-spontaneous emission beat noise (S-SP), and spontaneous-spontaneous beat noise (SP-SP) can all be reduced by 3 dB, thereby doubling the dynamic range of the optical amplifier. A 2.5-dB improvement in dynamic range has been demonstrated experimentally with the all-optical image rejection configuration. The implications of the increased dynamic range thus obtained are also discussed from a systems point of view