2.5 Gbit/s monolithic ICs for optical fiber transmitter and receiver in 0.35 μm CMOS process

2.5 Gbit/s monolithic integrated circuits （ICs） for optical fiber transmitter and receiver in 0.35 μm CMOS （complementary metal-oxide-semiconductor transistor） process are presented. The transmitter, which includes a 4： 1 multiplexer and a laser diode driver （LDD）, has four 622 Mbit/s random signals as its inputs and gets a 2.5 Gbit/s driving signal as its output; the receiver detects a 2.5 Gbit/s random signal and gets four 622 Mbit/s signals at the output. The main circuits include a trans-impedance amplifier （TIA）, a limiting amplifier, a clock and data recovery （CDR） unit, and a 1： 4 demultiplexer （DEMUX）. Test results prove the logic functions of the transmitter to be right, and the 10% to 90% rise and fall times of transmitter＇s output data eye diagram are 211.1 ps and 200 ps, respectively. The sensitivity of the receiver is measured to be better than 20 mV. The root mean square jitter of the DEMUX＇s output data is 15.6 ps and that of the clock after 1： 4 frequency dividing is 1.9 ps. Two chips are both applicable to 2.5 Gbit/s optical fiber communication systems.

Concept and Design of a Novel High-Bandwidth,High-Sensitivity Differential Receiver for Optical Interconnections

A novel high-bandwidth, high-sensitivity differential optical receiver without any additional cost compared to general optical receivers, is proposed for high-speed optical communications and interconnections. High bandwidth and high sensitivity are achieved through a fully differential transimpedance amplifier with balanced input loads and two photodetectors to convert the incident light into a pair of differential photogenerated currents,respectively. In addition,a corresponding 0.35μm standard CMOS optoelectronic integrated receiver with two 60μm × 30μm, 1. 483pF fingered p^＋/n- well/p-substrate photodiodes is also presented. The simulation results demonstrate that it achieves a 1.37GHz bandwidth and a 81.9dBΩ transimpedance gain,supporting data rates up to at least 2Gbit/s. The device consumes a core area of 0. 198mm^2 and the optical sensitivity is at least - 13dBm for a 10^-12 bit error rate under a 2^15 - 1 PRBS input signal.

A 10Gb/s GaAs PHEMT High Gain Preamplifier for Optical Receivers

A high gain cascade connected preamplifier for optical receivers is developed with 0.5μm GaAs PHEMT technology from the Nanjing Electronic Devices Institute. To begin with, the transimpedance amplifier has a -3dB bandwidth of 10GHz, with a small signal gain of around 9dB. The post-stage distributed amplifier （DA） has a -3dB bandwidth of close to 20GHz,with a small signal gain of around 12dB. As a whole,the cascade preamplifier has a measured small signal gain of 21.3dB and a transimpedance of 55.3dBΩ in a 50Ω system. With a higher signal-to-noise ratio than that of the TIA and a markedly improved waveform distortion compared with that of the DA, the measured output eye diagram for 10Gb/s NRZ pseudorandom binary sequence is clear and symmetric.

Relationship Between Noise Figure and Equivalent Input Noise Current Spectral Density for Optical Receiver Design

Based on the equivalent circuit model of a two-port optical receiver front-end,the relationship between the equivalent input noise current spectral density and the noise figure is analyzed. The derived relationship has universal validity for determining the equivalent input noise current spectral density for optical receiver designs, as verified by measuring a 155Mb/s high-impedance optical receiver front.end. Good agreement between calculated and simulated results has been achieved.

Electro-Optical Model of Soiling Effects on Photovoltaic Panels and Performance Implications

In this paper,a detailed model of a photovoltaic(PV)panel is used to study the accumulation of dust on solar panels.The presence of dust diminishes the incident light intensity penetrating the panel’s cover glass,as it increases the reflection of light by particles.This phenomenon,commonly known as the“soiling effect”,presents a significant challenge to PV systems on a global scale.Two basic models of the equivalent circuits of a solar cell can be found,namely the single-diode model and the two-diode models.The limitation of efficiency data in manufacturers’datasheets has encouraged us to develop an equivalent electrical model that is efficient under dust conditions,integrated with optical transmittance considerations to investigate the soiling effect.The proposed approach is based on the use of experimental current-voltage(I-V)characteristics with simulated data using MATLAB/Simulink.Our research outcomes underscores the feasibility of accurately quantifying the reduction in energy production resulting from soiling by assessing the optical transmittance of accumulated dust on the surface of PV glass.

A 0.5mV High Sensitivity 200Mbps CMOS Limiting Amplifier with RSSI for Optical Receivers

A 0. 5mV high sensitivity,200Mbps CMOS limiting amplifier （LA） with 72dB ultra wide dynamic range is described. A novel active DC offset cancellation loop is elaborately analyzed and designed to achieve this performance. Using a signal path, a received signal strength indicator （RSSI）, based on the piecewise-linear approximation, is realized with a ± 2dB logarithmic accuracy in a 60dB indicating range. The architecture of the LA and RSSI employed is determined by the optimal sensitivity and RSSI accuracy for a specified speed, gain, and power consumption. It consumes 60mW from a single 5V supply. The active area is 1.05mm^2 using standard 5V 0.6μm CMOS technology.

A 26-Gb/s CMOS optical receiver with a reference-less CDR in 65-nm CMOS

This paper presents a 26-Gb/s CMOS optical receiver that is fabricated in 65-nm technology. It consists of a tripleinductive transimpedance amplifier(TIA), direct current(DC) offset cancellation circuits, 3-stage gm-TIA variable-gain amplifiers(VGA), and a reference-less clock and data recovery(CDR) circuit with built-in equalization technique. The TIA/VGA frontend measurement results demonstrate 72-dB? transimpedance gain, 20.4-GHz-3-dB bandwidth, and 12-dB DC gain tuning range. The measurements of the VGA’s resistive networks also demonstrate its efficient capability of overcoming the voltage and temperature variations. The CDR adopts a full-rate topology with 12-dB imbedded equalization tuning range. Optical measurements of this chipset achieve a 10-12 BER at 26 Gb/s for a 2;-1 PRBS input with a-7.3-dBm input sensitivity. The measurement results with a 10-dB @ 13 GHz attenuator also demonstrate the effectiveness of the gain tuning capability and the built-in equalization. The entire system consumes 140 mW from a 1/1.2-V supply.

The 8×10 GHz Receiver Optical Subassembly Based on Silica Hybrid Integration Technology for Data Center Interconnection

An 8×10 GHz receiver optical sub-assembly （ROSA） consisting of an 8-channel arrayed waveguide grating （AWG） and an 8-channel PIN photodetector （PD） array is designed and fabricated based on silica hybrid integration technology. Multimode output waveguides in the silica AWG with 2% refractive index difference are used to obtain fiat-top spectra. The output waveguide facet is polished to 45° bevel to change the light propagation direction into the mesa-type PIN PD, which simplifies the packaging process. The experimentM results show that the single channel I dB bandwidth of AWG ranges from 2.12nm to 3.06nm, the ROSA responsivity ranges from 0.097 A/W to 0.158A/W, and the 3dB bandwidth is up to 11 GHz. It is promising to be applied in the eight-lane WDM transmission system in data center interconnection.

Design of Si-bipolar Monolithic Main Amplifier IC for Optical Fiber Receivers

A broadband amplifier with transadmittance and transimpedance stages is designed and two types of improved AGC amplifiers are developed on the base of theory study. Making use of the basic amplifier cells, a main amplifier IC for optical-fiber receivers is deliberated. By computer simulating the performances of the designed main amplifier meet the necessity of high gain and wide dynamic range . They are maximum voltage gain of 42 dB, the bandwidth of 730 MHz,the input signal( V p-p )range from 5 mV to 1 V,the output amplitude about 1 V, the dynamic range of 46 dB. The designed circuit containing no inductance and large capacitance will be convenient for realizing integration. A monolithic integrated design of 622 Mb/s main amplifier is completed.

Receiver Power Allocation and Transmitter Power Control Analysis for Multiple-Receiver Wireless Power Transfer Systems

As different power has its own receivers,this paper analyzes and designs a multiple-receiver wireless power transfer(WPT)system systematically.The equivalent circuit model of the system is established to analyze the key parameters including transmitter power,receiver power,transmission efficiency,and each receiver power allocation.A control circuit is proposed to achieve the maximum transmission efficiency and transmitter power control and arbitrary receiver power allocation ratios for different receivers.Through the proposed control circuit,receivers with different loads can allocate appropriate power according to its power demand,the transmitter power and system efficiency do not vary with the change of the number of receivers.Finally,this control circuit is validated using a 130-kHz WPT system with three receivers whose power received is 3:10:12,and the overall system efficiency can reach as high as 55.5%.

Optical transmitter module with hybrid integration of DFB laser diode and proton-exchanged LiNbO_(3)modulator chip

In this work,a hybrid integrated optical transmitter module was designed and fabricated.A proton-exchanged Mach–Zehnder lithium niobate(LiNbO_(3))modulator chip was chosen to enhance the output extinction ratio.A fiber was used to adjust the rotation of the polarization direction caused by the optical isolator.The whole optical path structure,including the laser chip,lens,fiber,and modulator chip,was simulated to achieve high optical output efficiency.After a series of process improvements,a module with an output extinction ratio of 34 dB and a bandwidth of 20.5 GHz(from 2 GHz)was obtained.The optical output efficiency of the whole module reached approximately 21%.The link performance of the module was also measured.

Switched-mode AGC circuits with internally created reset module for burst-mode unbalanced data optical receiver

This paper presents an innovative switched-mode auto gain control （AGC） circuit with internally created reset module for DC-10Mb/s burst-mode unbalanced （BMU） optical data transmission. Conventional AGC circuit is inappropriate for BMU data transmission because it is based on average level detection and requires considerable time to settle on a predefined gain. Therefore, we adopt a fast switched-mode AGC based on peak level detection. After the gain is adjusted, the peak level detectors need to re-detect the peak level of the input signal. Thus, we develop an internally created reset module. This AGC with reset module exhibits a fast operation and achieves an adjusted stable gain within one-bit, avoiding any bit loss up to 10Mb/s data rate. During power-up, the peak level detectors possibly hold an uncertain level resulting in the bit-errors. We propose a power-up reset circuit to solve this problem. Designed in a 0.5μm CMOS technology, the circuit achieves an optical sensitivity of better than -30dBm and a wide dynamic range of over 30dB with a power dissipation of only 30 mW from a 5V supply.

Optimizing Optical Attocells Positioning of Indoor Visible Light Communication System

Visible light communication(VLC),which is a prominent emerging solution that complements the radio frequency(RF)technology,exhibits the potential to meet the demands of fifth-generation(5G)and beyond technologies.The random movement of mobile terminals in the indoor environment is a challenge in the VLC system.The model of optical attocells has a critical role in the uniform distribution and the quality of communication links in terms of received power and signal-to-noise ratio(SNR).As such,the optical attocells positions were optimized in this study with a developed try and error(TE)algorithm.The optimized optical attocells were examined and compared with previous models.This novel approach had successfully increased minimum received power from−1.29 to−0.225 dBm,along with enhanced SNR performance by 2.06 dB.The bit error rate(BER)was reduced to 4.42×10−8 and 6.63×10−14 by utilizing OOK-NRZ and BPSK modulation techniques,respectively.The optimized attocells positions displayed better uniform distribution,as both received power and SNR performances improved by 0.45 and 0.026,respectively.As the results of the proposed model are optimal,it is suitable for standard office and room model applications.

Optical nonlinearity measurement of 4-(N-methyl,N-hydroxyethl)amino,4'-nitroazobenzene using a transmittance technique with a phase object(T-PO) with top-hat beams at 600-nm wavelength

The transmittance technique with a phase object（T-PO）,for measuring optical nonlinear coefficients is proposed with a top-hat beam.The sensitivity of the T-PO with a top-hat beam is a factor of 4 greater than that with a Gaussian beam.The validity of this method is verified by measuring the nonlinearity of a well-characterized liquid,CS 2 at 532-nm wavelength.The ease of use of this method has been proved by measuring a new compound 4-（N-methyl,N-hydroxyethyl）amino,4＇-nitroazobenzene（ANAB） at 600-nm wavelength,indicating that this method can be extended to the measurement of optical nonlinearities in a wide-band spectrum.

Transmittance Measurement of the Nonplanar Optical Based on Focal-Plane-Array Camera

Aiming to solve the problem that it is difficult to accurately measure UV cut-off transmittance of xenon quartz glass by using present spectrophotometer in China SG III project. Through the analysis, we believe that its reason was that the xenon quartz glass was nonplanar so the outgoing beam geometry from under-test was different from that from standard sample. A method of transmittance measurement based on focal-plane-array camera was proposed in this article. The effects of camera uniformity and spot sampling on transmittance measurement were analyzed theoretically. This method, which can reduce the effect of beam geometry on transmittance measurement and eliminate the cutting error occurring during light transmission by monitoring the completeness of incident beam in real-time, is verified from experiments. The random standard uncertainty of this method here is 0.035% or less. It is particularly useful in the transmittance measurement of nonplanar optical.

2.5 Gb/s Optical Transponder技术与设计

网络容量增长的同时也促进了光纤通信技术的发展,使得宽带传输和接入方式处于越来越重要的地位,如何有效地解决光纤干线上和大部分基于电缆局域网的信号转换成为亟待解决的问题,光收发器(opticaltransponder)很好地解决了宽带传输和接入的这一“瓶颈”问题。2.5 Gb/s是目前最流行的传输速率,其相应transponder用于SDH/Sonet OC-48/STM-16的光/电接口。文章介绍了2.5 Gb/s optical transponder的功能、结构等技术和相应的设计方案。

Effect of annealing treatment on the structural, optical, and electrical properties of Al-doped ZnO thin films

Highly conductive and transparent Al-doped ZnO （AZO） thin films were prepared from a zinc target containing Al （1.5 wt.%） by direct current （DC） and radio frequency （RF） reactive magnetron sputtering. The structural, optical, and electrical properties of AZO films as-deposited and submitted to annealing treatment （at 300 and 400℃, respectively） were characterized using various techniques. The experimental results show that the properties of AZO thin films can be further improved by annealing treatment. The crystallinity of ZnO films improves after annealing treatment. The transmittances of the AZO thin films prepared by DC and RF reactive magnetron sputtering are up to 80% and 85% in the visible region, respectively. The electrical resistivity of AZO thin films prepared by DC reactive magnetron sputtering can be as low as 8.06 x 10-4 Ωcm after annealing treatment. It was also found that AZO thin films prepared by RF reactive magnetron sputtering have better structural and optical properties than that prepared by DC reactive magnetron sputtering.

Porous block copolymer films with self-adjustable optical transmittance and passive radiative cooling

As an energy-free cooling technique,radiative cooling has garnered significant attention in the field of energy conservation.However,traditional radiative cooling films often possess static optical properties and their inherent opacity limits their applications in building such as windows.Therefore,there exists a requirement for passive radiative cooling films endowed with adjustable transmittance.Here we report the porous block copolymer films with self-adjustable optical transmittance and passive radiative cooling.In a result,the film exhibited a high solar reflectance(0.3-2.5μm)of 96.9%and a high infrared emittance(8-13μm)of 97.9%.Outdoor experiments demonstrated that the film surface temperature was 6.6℃lower than ambient temperature,with a cooling power of 104.8 W·m^(-2).In addition,the film’s transmittance can be regulated by altering the polarity of the post-processing solvent,providing an effective approach for regulating indoor light intensity and thermal balance,thereby enhancing the applicability of radiative cooling.

Electronic structure and optical properties of In-doped SrTiO3 by density function theory

The effect of In doping on the electronic structure and optical properties of SrTiO3 is investigated by the first-principles calculation of plane wave ultra-soft pseudo-potential based on the density function theory （DFT）. The calculated results reveal that due to the hole doping, the Fermi level shifts into valence bands （VBs） for SrTi1-x InxO3 with x = 0.125 and the system exhibits p-type degenerate semiconductor features. It is suggested according to the density of states （DOS） of SrTi0.875In0.125O3 that the band structure of p-type SrTIO3 can be described by a rigid band model. At the same time, the DOS shifts towards high energies and the optical band gap is broadened. The wide band gap, small transition probability and weak absorption due to the low partial density of states （PDOS） of impurity in the Fermi level result in the optical transparency of the film. The optical transmittance of In doped SrTiO3 is higher than 85% in a visible region, and the transmittance improves greatly. And the cut-off wavelength shifts into a blue-light region with the increase of In doping concentration.

Glycerol effects on optical,weight and geometrical properties of skin tissue

Complex study of glycerol effects on the skin tissue was performed.The change in optical,weight and geometrical parameters of the rat skin under the action of the glycerol solutions was studied ex vivo.Possible mechanisms of the skin optical clearing under the action of glycerol solutions of different concentrations were discussed.The results can be helpful for refinement of models developed to evaluate the effective diffusion coefficients of glycerol in tissues.