10 Gbit/s low-power bit synchroniser with automatic retiming phase alignment

A 10 Gbit/s bit-synchroniser circuit has been fabricated using an enhancement/depletion 0.3 mu m recessed-gate AlGaAs/GaAs/AlGaAs quantum well FET process. The differential gain of the exclusive-or phase comparator circuit is measured to be 371 mV/rad. The phase margins for monotonous phase comparison are -54/+21 degrees relative to the 'in bit cell centre' position of the negative going clock edge. The chip has a power dissipation of 160 mW when using a supply voltage of 1.90 V.<>     

High-speed optical receiver with soft decision ISI cancellation

A receiver with soft decision intersymbol interference (ISI) cancellation (SDIC) is presented to deal with ISI in high-speed lightwave systems. The analytical and simulation results show that the transmission distance can be doubled with SDIC. In addition, the receiver with SDIC allows the ISI cancellation circuit to operate with a processing and propagation delay much longer than 1-b period. Therefore, it is very promising in very-high-bit-rate optical systems     

基于延时自零差光相干接收机的激光器相位噪声测试系统

在相干光通信系统中,激光器相位噪声是影响接收机灵敏度的重要因素。针对相干光通信中的激光光源相位噪声测试提出并研究了表征激光器相位噪声的3个关键指标,分别是电场的功率谱密度、相位误差方差和FM噪声谱线,建立了基于延时自零差相干接收技术的窄线宽激光器相位噪声测试系统,实现了系统仿真,并对一窄线宽激光器进行了相位噪声测试,相比传统的自外差线宽测量技术,此方法在满足测试分辨率要求的同时能够更全面表征激光器相位噪声特性。     

水下无线光自动对准系统的设计与实现

水下无线光通信(UOWC)具有保密性好、容量大、传输速度快等优点,可应用于水下信息传输、资源勘查等领域,通信链路的快速建立和持续稳定是水下无线光通信实际应用的基本条件。在平台扰动和海水信道杂质干扰的条件下,如何实现远距离的快速对准是水下无线光通信必须解决的问题。针对水下无线光通信过程中系统发射端和接收端之间的链路由于干扰问题引起底层平台不断移动而无法对准的问题,搭建了一个基于激光二极管(LD)的水下无线光自动对准系统,该系统具有自动对准控制的特点,即系统在底层平台移动的情况下,依然可以实现链路的对准。     

Passive alignment optical subassemblies for military/aerospacefiber-optic transmitter/receiver modules

Under the DARPA sponsored Avionics Optoelectronic Module Technology program, new passive alignment carrier (PAC) optical subassemblies (LED-PAC and PIN-PAC) ruggedized for military/aerospace avionics fiber-optic transmitter and receiver applications have been developed, LED-PAC and PIN-PAC silicon micro-optical bench substrates were fabricated together on a 5 in diameter silicon wafer via multistage photolithography, thin-film, and substrate processing. Alignment v-grooves designed for passive optical alignment of 100/140 μm multimode optical fiber to the optoelectronic devices were terminated by solder locking the fiber to the silicon PAC substrates. The LED-PAC comprising a surface emitting LED die-bonded onto a novel precision molded AM submount passively mounted onto the silicon microbench achieves the required high coupling efficiency to 100/140 μm multimode optical fiber to meet stringent avionics transmitter output power requirements. The 100/130 μm multimode optical fiber-pigtailed PIN-PAC with a refractive lens etched into the p-i-n photodiode backside surface exhibited responsivities greater than 0.8 A/W at 1.3 μm wavelength. The LED-PAC and PIN-PAC optical subassemblies integrated with Boeing ARINC 636 (FDDI) transmitter and receiver thick film multichip (MCM-C) circuitry are capable of meeting both ARINC 636 and FDDI physical layer requirements     

Optimum optical power splitting ratio of decision drivenphase-locked loop in BPSK optical homodyne receiver

In a BPSK optical homodyne receiver that utilizes a decision-driven phase-locked loop, the splitting ratio of the received power and that of the local oscillator power are very important parameters in achieving high receiver sensitivity. This paper determines the optimum setting of these parameters considering the influence of the relative intensity noise of the local oscillator and the thermal noise of the preamplifier. The optimum splitting ratio of the local oscillator power to the Q-arm is found to be 0.5. The splitting ratio of the received power to Q-arm is obtained as a function of laser linewidth. The optimum setting of the received power and the local oscillator power Is independent of the relative intensity noise of the local oscillator, the thermal noise of the preamplifier and the bit rate, At the optimum splitting ratios, required beat linewidth is obtained as 1.3×10 ^-3/T_b(τ/T_b≪1) and 2.99×10 ^-3/τ(τ/T_b≫1), where T_b is the bit duration and τ is the loop propagation delay time. We show that the total power penalty of 0.8 dB from the shot noise limit can be realized with the relative intensity noise of -170 dB/Hz and equivalent input noise current of 10 pA/√(Hz), even if an imperfect balanced receiver is utilized; quantum efficiency ratio of the twin-photodetector is 0.96, propagation time difference T/T_b is 0.01. To confirm the theoretical model, a BPSK homodyne detection experiment is performed and good agreement is found between theoretical and experimental results     

DAML相干光接收机的冷启动

DAML (辅助判决式最大似然)相位估计相干光接收机已成为光通信领域未来考虑试验的相干接收方式之一。文章对DAML相干光接收机的启动进行了研究,在此基础上提出了一种冷启动方案。仿真验证了该方案的可行性,同时,对该方案进行了优化。仿真表明,当M次幂算法与DAML算法参数均取最优值时,冷启动方案性能达到最佳。     

Improving upstream transmission performance using a receiver with decision threshold level adjustment in a loopback WDM-PON

We have experimentally demonstrated that the use of an optical receiver with decision threshold level adjustment (DTLA) improved the performance of an upstream transmission in reflective semiconductor optical amplifier (RSOA)-based loopback wavelength division multiplexing-passive optical network (WDM-PON). Even though the extinction ratio (ER) of the downstream signal was as much as 9 dB and the injection power into the RSOA at the optical network unit was about ?24 dBm, we successfully obtained error-free transmission results for the upstream signal through careful control of the decision threshold value in the optical receiver located at optical line terminal (OLT). Using an optical receiver with DTLA for upstream signal detection overcame significant obstacles related to the injection power into the RSOA and the ER of the downstream signal, which were previously considered limitations of the wavelength remodulation scheme. This technique is expected to provide flexibility for the optical link design in the practical deployment of a WDM-PON.     

Integrated optical receiver with beam localisation

The performance of optical receivers is degraded by misalignment and defocusing of the incident light beam on a detector. The presented integrated optical receiver solves the alignment and defocusing problem using optoelectronic light beam localisation. A demonstrator is realised in a standard CMOS technology     

An electron image projector with automatic alignment

An electron image projector for silicon device processing is described which uses an air-cored solenoid and a caesium iodide photocathode. The alignment method is based on the X-rays which are generated when high-voltage electrons strike matter. Phase sensitive detection is used to convert the off balance to a linear signal which is then fed back into analog electronics. Results are presented showing a marker pattern automatically aligned to an accuracy of 0.1 µm.     

Coherent optical receiver for 680 Mbit/s using phase diversity

A coherent optical receiver using a multiport optical coupler to provide phase diversity is described. By this means, only homodyne bandwidth is required in the signal processing, but with tolerances on the frequency tracking typical of heterodyne systems. Measured sensitivities with limited local-oscillator power are ?47.5 dBm at 320 Mbit/s and ?42 dBm at 680 Mbit/s. The results at the higher bit rate are strongly influenced by limited receiver module bandwidth.     

基于科斯塔斯锁相环的光学零差相干接收技术

零差相干光通信能够实现极高的通信速率和接近量子极限的灵敏度,是新一代空间通信领域极具潜力的通信体制。以窄线宽激光器作为本振源,结合90°光学混频技术和科斯塔斯光学锁相环技术,实现了信号光的零差相干接收。试验结果表明,信号光和本振光经过90°光学混频后I、Q两路信号相位差保持90°,科斯塔斯光学锁相环可以长时间实现信号光和本振光之间的相位锁定,接收速率为2Gbps的二进制相移键控(BPSK)信号,试验结果表明,该接收机能够很好地实现基带信号解调。     

Integrated PINFET optical receiver with high-frequency InP-MISFET

Monolithic integration of an InGaAsP PIN photodiode with an n-channel enhancement InP-MISFET is reported. Photo-current amplification characteristics at 1000 Mbit/s have been achieved.     

Four-port homodyne receiver for optical fibre communications comprising phase and polarisation diversities

A new four-port homodyne receiver for optical fibre communications is proposed and studied experimentally. It comprises phase-and polarisation-diversity schemes, removing the need for phase locking and polarisation control. The bit-error-rate measurement is also reported.     

Bayes error probability with inaccurate decision threshold

In a binary detection problem, the author derives an expression for the excess error probability caused by inaccurate setting of the threshold.<>     

Direct-detection optical CDMA receiver with interference estimation and double optical hardlimiters

This paper proposes a new channel interference cancellation technique using interference estimation and double optical hardlimiters (DHLs) for direct-detection optical code-division multiple-access systems. In the proposed system, when the output of the DHL is "0", the proposed system outputs "0". When the output of the DHL is "1", the proposed system reconstructs the interference and estimates whether the output "1" is owing to the interference or the transmitted signal. It is shown that the proposed system is effective to reduce the effects of the channel interference. Moreover, it is shown that the proposed system can improve the error floor of the systems with DHL.     

Effect of external cavity semiconductor laser phase noise on a DPSKheterodyne optical receiver

The effect of an external cavity semiconductor laser on the performance of a DPSK heterodyne optical system is evaluated. The actual shape of the frequency fluctuation spectral density of the optical source is taken into account, and a comparison with a PSK coherent heterodyne system is carried out     

Stabilisation of heterodyne receiver sensitivity with automatic polarisation control system

A low-insertion-loss automatic optical fibre polarisation control system with low driving voltage and low monitoring power has achieved stabilisation of the receiver sensitivity within the fluctuation range of less than 0.4 dB in an optical FSK heterodyne 280 Mbit/s, 141 km transmission experiment.