Search

The paper discusses options for using semiconductor optical amplifiers in the radio-over-fiber systems. The theoretical evaluation of the optical parameters of the amplifier, modulator and detector implemented on the basis of the semiconductor optical amplifier, as well as estimates of the parameters of the device using a semiconductor optical amplifier as a multifunctional optical device power modulator detector.

In this paper a micro-integrated laser-amplifier for a wavelength of 1180nm is presented. The modules can amplify laser emission from any source, which is coupled into the polarization-maintaining input fiber of the module, to an optical power > 1W. Thereby, the spectral properties of the seed source are maintained. The output of the module is free space allowing easy access to the emitted beam. The footprint of the module is only 47mm • 34 mm. The article discusses the utilized amplifiers, preceding bench top experiments and gives a detailed experimental characterization of the amplifier module.

The proliferation of a Colorless and Directionless and Contentionless (CD and C) architecture in metro core networks is rising up ever-greater demands on optical amplifiers to be smaller and higher integration. we overview recent advances in optical amplifier technologies, multiple EDFA arrays for compensating loss of a multicast switch and switchable gain EDFAs supporting a wide range of fiber-span loss distributions in the network and focus on the embedded passive component and pump laser in the amplifiers. We will also focus on the pluggable small form factor EDFA amplifies optical signals to enable long Hybrid Fiber Coaxial (HFC) links and amplifier for CFP-DCO/CFP2-ACO transceiver. Finally, we will discuss the feasibility of L-band amplifier and distribution Raman amplifier in a short-haul systems to realize a requisite optical signal to noise ratio (OSNR) to support high bit rate transmission beyond 100G and high capacity transmission.

The lock-in amplifier is recovered by phase sensitive detection technique for the weak signal submerged in the noise background. This design is based on the TI ultra low power LM358, INA129, OPA227, OP07 and other chips as the core design and production of the lock-in amplifier. Signal generator by 10m ohms /1K ohm resistance points pressure network 10 mu V ~ 1mV adjustable sine wave signal s (T). The concomitant interference signal together through the AC amplifier and band-pass filter signal x (T), on the other hand reference signal R (T) driven by square wave phase shift etc. steps to get the signal R (T), two signals and by phase sensitive detector are a DC full wave, again through its low pass filter and a DC amplifier to be measured signal more accurate detection, the final circuit through the AD conversion and the use of single-chip will display the output.

A high power single-frequency fiber amplifier with linear polarization is demonstrated based on the master oscillator power amplifier configuration, consisting of a single-frequency seed laser at 1064.1 nm and three-stage amplifiers. To suppress stimulated Brillouin scattering, a short piece of polarization-maintaining active fiber with large core diameter of 25 μm and high pump absorption coefficient is adopted in the main amplifier. Besides, step-distributed longitudinal strain is intentionally imposed on the active fiber to broaden the effective SBS gain spectrum and correspondingly improve the SBS threshold. As a result, a pump-limited single-frequency output of 414 W is obtained with no sign of SBS and mode instability, experimentally showing that the SBS threshold is improved by at least two times through introducing extra strain.. The slope efficiency of the main amplifier is about 80 %. The polarization degree is better than 98 % at all the power levels. To the best of our knowledge, this is the highest output power of single-frequency polarization-maintained fiber amplifier based on all-fiber structure.

An improved sense amplifier with speed-up pre-charge scheme is introduced in this paper. What’s more, in order to avoid unexpected fatal damage while reading operation, clamp voltage is adopted. Distinguished with the conventional current sense amplifier, the proposed sense amplifier shortens not only the read access time by reducing the charging time due to parasite capacitor of storage cells but also the delay time because of the RC delay on wire by using two branches of pre-charge circuit at the both ends of bit lines. The simulation result taken in SMIC 28nm process shows that, with 1Kb PCM array, the proposed sense amplifier can efficiently reduce the access time from 33.7ns to 16.5ns.

The focal plane of the X-ray Integral Field Unit (X-IFU) instrument of the Athena observatory is composed of about 4000 micro-calorimeters. These sensors, based on superconducting Transition Edge Sensors, are read out through a frequency multiplexer and a base-band feedback to linearize SQUIDs. However, the loop gain of this feedback is lower than 10 in the modulated TES signal bandwidth, which is not enough to fix the gain of the full readout chain. Calibration of the instrument is planned to be done at a time scale larger than a dozen minutes and the challenging energy resolution goal of 2.5 eV at 6 keV will probably require a gain stability larger than 10 -4 over a long duration. A large part of this gain is provided by a Low-Noise Amplifier (LNA) in the Warm Front-End Electronics (WFEE). To reach such gain stability over more than a dozen minutes, this non-cooled amplifier has to cope with the temperature and supply voltage variations. Moreover, mainly for noise reasons, common large loop gain with feedback can not be used. We propose a new amplifier topology using diodes as loads of a differential amplifier to provide a fixed voltage gain, independent of the temperature and of the bias fluctuations. This amplifier is designed using a 350 nm SiGe BiCMOS technology and is part of an integrated circuit developed for the WFEE. Our simulations provide the expected gain drift and noise performances of such structure. Comparison with standard resistive loaded differential pair clearly shows the advantages of the proposed amplifier topology with a gain drift decreasing by more than an order of magnitude. Performances of this diode loaded amplifier are discussed in the context of the X-IFU requirements.

We present experimental results on a three-section master oscillator power amplifier at 1.57 μm to be applied in an integrated path differential absorption LIDAR system for column-averaged atmospheric CO 2 measurements. The application requires high power and good beam quality together with spectral purity and modulation capacity to be used in a random modulation CW LIDAR system. The device consists of a distributed feedback laser acting as master oscillator, a bent modulator section and a tapered optical amplifier section with a tilted front facet to avoid coupled cavity effects. The modulator section acts as an absorber or amplifier when driven at zero or positive bias. Devices with different geometries and epitaxial structures were fabricated and characterized, presenting CW output powers higher than 350 mW and stable single mode emission. At the frequency required by the application (12.5 MHz) a high optical modulation amplitude and extinction ratio were achieved.

This work is novel in that it explains the modeling and simulation of a thulium-doped fiber amplifier (TDFA) in a reconfigurable wavelength division multiplexing (WDM) system operating at 2 μm. We use the optical gain-clamping technique in order to control gain amplification and eliminate deleterious channel power fluctuations resulting from input power variation at the TDFA. The investigated system consists of 12 channels with -4 dBm total input power. Simulation results indicate that approximately1.5dB power excursion is produced after dropping 11 channels in unclamped-gain amplifier, and only 0.005 dB in a clamped-gain amplifier. Additionally, a clamped configuration brings the power excursion from 4.2 dB to under 0.08 dB, after adding 11 channels to the investigated system. Hence, optical gainclamping is a simple and robust technique for controlling the power transient in amplifiers at 2 μm.

The paper presents the lumped model of high speed amplifier useful for frequency and time domain (also large signal) simulation. Model is constructed on the basis of two-domain device measurements, namely small signal frequency parameters and time response to the input step of varying amplitude. Rational approximation of frequency domain data leads to small signal model composed of RLC subcircuits and controlled sources. Next, the model is complimented with the nonlinearities identified from time-domain measurements, including those taken for large input signals. Final amplifier model implemented in SPICE simulator is shown to correctly render the behavior of the device over the wide variety of operating conditions.

In this paper, we demonstrate an ytterbium-doped all-fiber master-oscillator power amplifier (MOPA) system which uses a narrow-linewidth seed source, generating narrow-linewidth and high power continuous-wave output power at 1064nm. Our MOPA configuration system consist of three amplifier stages. We use single-mode Yb-doped fiber as the gain fiber in the first and second pre-amplifier stages, so it can keep good beam quality before entering the main amplifier stage. In order to raise the threshold of nonlinear effects, such as SBS and SRS, and to relieve heat effect, our high power system choose large mode area (LMA) fiber as the gain fiber in the main amplifier stage. For the sake of suppressing high-order modes in LMA fiber, we design novel watering cooling plates of different sizes, and using them in our main amplifier stage. By optimizing its structure, we get very good laser beam pattern on CCD at high power output. The beam quality factor (M 2 ) was about 1.4 at 1.31 kW.

The noise of photoconductive detector is so weak that the PAR 124A lock-amplifier is main test facility despite of discontinuation by long-gone manufacturer for decades. The paper uses 124A and 7124 lock-in amplifier system to test noise and response signal of several photoconductive detectors while use the SR830 internal oscillator and thermal noise of pure resistance as standard signal and noise source respectively. The results indicate that the data of two test system can fit each other except the background noise. The 124A lock-in amplifier with 116 transformer is 0.2nV/√Hz and 7124 lock-in amplifier with 5184 preamplifier is 0.8 nV/√Hz at 1kHz. The impedance of 116 transformer is small and the impedance of 5184 preamplifier is 5MΩ, so the signal of 116 transformer will decay and the 5184 preamplifier won’t in case of testing the performance of photoconductive detector with larger source resistance. Finally we suggest to use 7124 lock-in amplifier system in case of testing photoconductive detector with larger source resistance and use 124A lock-in amplifier system prior to 7124 lock-in amplifier system in case of testing photoconductive detector with small source resistance.

Due to its better performance, high fiability and large power capability, balanced amplifier is one of the most popular designs used in narrow band applications. However, with a balanced amplifier in class A operation, the band-pass is still narrow with classical coupler [1]. In this paper, we propose a new method for widen the band-pass and linearity of the amplifier, by using two Lange couplers and by adding two drivers, so that small signal could be amplified [2], [3], [4], [5]. The proposed amplifier works in the 0.9 – 2.4 GHz band, with good performances. We also propose an A class X-band amplifier, with Wilkinson power divider used as a combiner and divider. The amplifier will operate at 9,5 GHz with Continuous Wave (C.W). The two methods were validated by simulating the balanced amplifier with Lange coupler and the balanced amplifier with Wilkinson power divider, in class A operation.

The paper presents the lumped model of RF amplifier for the generic SPICE circuit simulator. Model is constructed on the basis of measured s-parameter data set of the amplifier. Data – transformed to admittance (y) domain - is approximated by rational functions, which later are synthesized as RLC (sub)circuits. Final amplifier model - obtained by representing Y matrix of two-port circuit by the set of passive components and controlled voltage/current sources – is shown to be equivalent to the original s-based model and may be used in any generic circuit simulator.

Investigation of optical back propagation performances under some practical impairments such as non-ideal optical phase conjugation and non-ideal amplifier noise is presented. The results can also be used to determine the optimum operating system parameters under non-ideal conditions.

We present the preliminary results of the design and test activities for a DC cryogenic low noise amplifier for the SAFARI imaging spectrometer, planned to be onboard the SPICA mission, necessary not only to drive, as usual, the voltage signal produced by the SQuID but also to boost such signals over about 7 meter of path towards the warm feedback electronics. This development has been done in the framework of the mission preparation studies, within the European Consortium for the development of the SAFARI instrument. The actual configuration of the SAFARI focal plane assembly (FPA), indeed, foresees a long distance to the warm back end electronics. It is therefore mandatory to boost the faint electric signal coming from the SQuID device by keeping under control both power dissipation and noise: this is the main role of the designed Cryogenic Low Noise Amplifier (LNA). Working at 136K, it has a differential input gain-stage, and a differential balanced voltage buffer output stage, running at few mW target overall power. At present the design is based on the use of Heterojunction Si:Ge transistors, the required bandwidth is DC-4MHz and the required noise lower than 1 nV/rtHz.

A wideband and compact solid state power amplifier MMIC is simulated around 220 GHz. It utilizes 6 μm emitter length common base HBTs from a 250 nm InP HBT technology. Specific power cells and power combiners are simulated in order to minimize the width of the die, which must not exceed 300 μm to avoid multimode propagation in the substrate. Four stages are implemented over a total area of the (275x1840) μm 2 . Simulations of this power amplifier indicate a minimum output power of 14 dBm associated with 16 dB of power gain from 213 GHz to 240 GHz.

Fully integrated semiconductor master-oscillator power-amplifiers (MOPA) with a tapered power amplifier are attractive sources for applications requiring high brightness. The geometrical design of the tapered amplifier is crucial to achieve the required power and beam quality. In this work we investigate by numerical simulation the role of the geometrical design in the beam quality and in the maximum achievable power. The simulations were performed with a Quasi-3D model which solves the complete steady-state semiconductor and thermal equations combined with a beam propagation method. The results indicate that large devices with wide taper angles produce higher power with better beam quality than smaller area designs, but at expenses of a higher injection current and lower conversion efficiency.

Pre-amplifier between the frontend and main power amplifier is the key unit of high power laser divers. The recent progresses on the off-axis quadruple pass amplifier are presented, which include the beam path design, parasitic oscillation research and experimental results. A single longitudinal mode, temporally shaped laser pulse with 5ns pulse duration at 1053nm is injected into a Nd: Glass regenerative amplifier, which can provide a 12mJ energy output with 0.5% long term energy stability. The quadruple pass amplifier is designed as an off-axis pattern. With 1.3mJ energy injection, amplified pulse with 16.5J can be achieved, and the measured output energy stability of the amplifier is 7.3% (PV) at this output energy level, corresponding to a 21 shot result. The total gain of the amplifier is more than 10,000. The parasitic oscillation was analyzed and discussed, and the parasitic mode and pencil beam are neither observed in the experiment.

The issue of temporal pulse distortion occurring during amplification process in a 2-stage, fiber amplifier, operating in the eye-safe spectral region, is discussed. The amplifier was built in a Master Oscillator Power Amplifier (MOPA) configuration and seeded by a distributed feedback (DFB) laser providing nanosecond pulses at a repetition rate of 20 kHz. It operated at a wavelength of 1549.13 nm and generated over 200 mW of output power with a slope efficiency of up to 28%. The comparison between the calculated and measured results on saturation-induced pulse shape deformation, for ~300-ns pulses, is presented. The analyzed pulse shapes embraced rectangle, Gaussian, triangle and "M" letter.

Broadband, continuous-wave, electromagnetic induction sensors have been shown to perform well, but they usually use power inefficiently because of the power wasted in the linear amplifier used to drive the coils. Generally, much more power is dissipated in the power amplifier than in the coil in these systems. Methods for reducing this power are investigated using both linear and switched-mode amplifiers. Significant reductions in power dissipated by the linear amplifier are achieved by optimizing the signal used to drive the coil. Much greater reductions are achieved with the switched-mode amplifier using an optimized signal that has most of its energy in the desired frequencies for the sensor. Both of these techniques are shown to perform well in a prototype system.

This paper discusses a capacitor transimpedance amplifier (CTIA) designed for an infrared readout circuit. The CTIA has better gain control, high dynamic range, a stability bias point and low impedance. It applies a short-wave detector and small current source because input impedance is very small in an amplifier feedback mechanism. This research on a capacitor transimpedance amplifier (CTIA) is designed for an infrared readout circuit. It is designed, simulated and laid out using the TSMC 0.35um 2P4M CMOS 5V process. The clock rate operates at 3MHz. Layout area is 30umX30um and the array size is 20X16. The simulation current sets 0.01nA~1.3nA. The output swing is 2.8V and power consumption is 10.1 mW according to the measurement results.

We describe the design and optimization of low-noise, single-stage output amplifiers for p-channel charge-coupled devices (CCDs) used for scientific applications in astronomy and other fields. The CCDs are fabricated on highresistivity, 4000-5000 Ω-cm, n-type silicon substrates. Single-stage amplifiers with different output structure designs and technologies have been characterized. The standard output amplifier is designed with an n+ polysilicon gate that has a metal connection to the sense node. In an effort to lower the output amplifier readout noise by minimizing the capacitance seen at the sense node, buried-contact technology has been investigated. In this case, the output transistor has a p+ polysilicon gate that connects directly to the p+ sense node. Output structures with buried-contact areas as small as 2 μm × 2 μm are characterized. In addition, the geometry of the source-follower transistor was varied, and we report test results on the conversion gain and noise of the various amplifier structures. By use of buried-contact technology, better amplifier geometry, optimization of the amplifier biases and improvements in the test electronics design, we obtain a 45% reduction in noise, corresponding to 1.7 e- rms at 70 kpixels/sec.

Based on the technique of master oscillator power amplifier (MOPA), a two-stage ytterbium-doped fiber amplifier (YDFA) with all-fiber structure is theoretically simulated. The seed signal operating at the wavelength of 1064 nm has the characteristic of high repetition rate (10 MHz), ultrashort pulse duration (10 ps), low signal power input (20μW) and single longitudinal mode. The gain (and amplification stimulation emission power) is calculated at the different pump powers and gain fiber lengths of YDFA pumped by 975 nm. In addition, the amplifications at the different signal power inputs (1-25μW) are also simulated. The numerical results can be used to optimize the YDFA.

A low noise and relatively high dynamic range CMOS active pixel sensor (APS) using a variable-gain column amplifier is presented and analyzed. On this signal path there are a pixel source follower, a switched-capacitor, noise-cancelling, variable-gain amplifier, and a correlated double sample (CDS) circuit in each column. The using of high gain for the column amplifier reduces input-referred random noise, but it may reduce the dynamic range of this device at meanwhile. In this paper, we present a detail analysis for the noise and the dynamic range with the variable gain of the column amplifier. It is revealed that the total random read noise can be analyzed in three parts: the first part is from the pixel circuit, including the pixel-related fixed-pattern noise, reset noise and pixel source follower amplifier noise; the second part is from the column circuit, including the column-related fixed-pattern noise and the column amplifier noise; and the third part is from the output amplifier in the chip-level circuit. The analysis suggests that the noise components from the pixel and column can be significantly cancelled by the double-stage column noise canceller, and the noise components from the output amplifier in the chip-level circuit, are the major noise source and can be greatly reduced if the signal is amplified before this noise is added. Both the analysis and measured result indicate that we can achieve a low input-referred noise and keep a relatively high dynamic gain by choosing a proper column amplifier gain.

This paper considers driving an Ionic Polymer-Metal Composite (IPMC) actuator using a Pulse Width Modulation (PWM) amplifier, in order to shed light on the characteristics of PWM driving of IPMCs. Generally, it is said that an efficiency of a PWM amplifier is higher than that of a linear amplifier. However, high current flows across the IPMC in the use of a PWM amplifier, and it is supposed to become the power consumption high. We solve this problem by putting an inductor between the PWM amplifier and the IPMC. The simulation and the experiment results demonstrate the effectiveness of the proposed method.

A single-frequency master-oscillator fiber power-amplifier operating at 1991 nm was demonstrated. The seeding laser was a diode-pumped, high efficient, single-longitudinal-mode Tm:YAP laser with a coupled-cavity configuration. 721 mW single-frequency output power was obtained at 1991 nm, the slope efficiency was 46%. The power amplifier was a diode-pumped Tm-doped fiber. 8.6 W single frequency output power was obtained from the amplifier. The maximum output power was limited by the low coupling efficiency of the seeding signal into the fiber core. The strength of ASE in the fiber amplifier with respect to the power of input signal was studied experimentally. High power single-frequency lasers at 2 μm optical region have potential applications on eye-safe coherent lidar and optical remote sensing.

Pre-amplifier circuit is critical for the noise performance of the high speed CCD camera. Its main functions are amplification and impedance transform. The high speed and low noise pre-amplifier of CCD camera is discussed and designed in this paper. The high speed and low noise operational amplifier OPA842 is adopted as the main part. The gain-set resistors for the amplifier are designed optimally. The different precision gain-set resistors are swept using Monte Carlo method. CCD video signal which has high DC offset voltage is AC coupled to the amplifier. The output signal of the amplifier is source terminated using 50 ohms matching resistor so as to transmit the video signal through coaxial cable. When the circuit works in high speed, the PCB will have important effect to circuit performance and can even cause the amplifier unstable due to the parasitic problem of PCB. So the parasitic model of the PCB is established and the PCB layout design issues are also presented. The design result shows that the pre-amplifier can be used in the camera whose pixel rate could be up to 40 MHz and its input referred noise density is about 3 nV/Hz1/2.

By using Digital Lock-in Amplifier LI5640, the intensity distribution of LED is measured, meanwhile compared with two other common measuring methods with the internal modulation. The structure of the research system, the transmitter module, the optical receiving module, the research light path and Digital Lock-in Amplifier LI5640 are all introduced and the analysis based on research results is given. It's proved that the Lock-in Amplifier is superior for weak light signal detecting; also this research system can be the reference of correlative research designs.

In this paper, a novel technique to set the coupling constant between cells of a coupled resonator optical waveguide (CROW) device, in order to tailor the filter response, is presented. It is known that using the same K value for all the couplers produces filtering responses with significant side-lobes for the side-coupled integrated spaced sequence of resonators (SCISSOR) or significant ripples in the pass-band for the direct coupled microrings (CROW). It is also known that the side-lobes/ripples can be reduced, and the pass/reject bands can be made wider, by apodizing the K value of each individual coupler in the structure, starting from a nominal K value (either increasing or decreasing it). This technique consists on changing the effective length of the coupling section by applying a longitudinal offset between the resonators. On the contrary, the conventional techniques are based in the transversal change of the distance between the ring resonators, in steps that are commonly below the current fabrication resolution step (nm scale), leading to strong restrictions in the designs. The technique has been experimentally demonstrated employing a racetrack ring resonator geometry. The proposed longitudinal offset technique allows a more precise control of the coupling and presents an increased robustness against the fabrication limitations, since the needed resolution step is two orders of magnitude higher. Both techniques are compared in terms of the transmission response of CROW devices, under finite fabrication resolution steps. The offset technique presented is sufficient by itself for apodization, and optimized CROW's can be produced with a fixed distance between the rings, solely by changing the offsets.

The presented paper describes a 10 Gbps optical receiver. The transimpedance amplifier (TIA) is realized in standard 0.35 μm SiGe BiCMOS technology. The main novelty of the presented design - investigated in the European Community project HELIOS - is the hybrid connection of the optical detector. The used Germanium photodetector will be directly mounted onto the receiver. A model of the relevant parasitics of the photodetector itself and the novel connection elements (micropads, metal vias and metal lines) is described. Based on this photodetector model an optical receiver circuit was optimized for maximum sensitivity at data rates in the range of 10 Gbps. The design combines a TIA and two limiting amplifier stages followed by a 50 Ω CML-style logic-level output driver. To minimize power supply noise and substrate noise, a fully differential design is used. A dummy TIA provides a symmetrical input signal reference and a control loop is used to compensate the offset levels. The TIA is built around a common-emitter stage and features a feedback resistor of 4.2 Ω. The total transimpedance of the complete receiver chain is in the range of 275 kΩ. The value of the active feedback resistor can be reduced via an external control voltage to adapt the design to different overall gain requirements. The two limiting amplifier stages are realized as differential amplifiers with voltage followers. The output buffer is implemented with cascode differential amplifiers. The output buffer is capable of driving a differential 50Ω output with a calculated output swing of 800mVp-p. Simulations show an overall bandwidth of 7.2 GHz. The lower cutoff frequency is below 60 kHz. The equivalent input noise current is 408 nA. With an estimated total photodiode responsivity of 0.5 A/W this allows a sensitivity of around - 23.1 dBm (BER = 10-9). The device operates from a single 3.3 V power supply and the TIAs and the limiting amplifier consume 32 mA.

The pump beam generation line of an optical parametric chirped pulse amplifier (OPCPA) system providing few-cycle pulses with energy in the millijoule range at repetition rates up to 10 kHz is presented. The overall design of the system is briefly discussed including stretching-compressing and parametric amplification. The main emphasis is on the requirements on the pump beam for successful pumping of a parametric amplifier. Aspects of the design of the multistage hybrid amplifier line are detailed and performances of each stage are presented.

In Chapter 5 we saw that the front-end plays a major role in determining the noise performance of a receiver. In this chapter, we will explore four principal types of front-end designs that are used in optical receivers. We will review the use of bipolar and field-effect transistors in front-end amplifiers and we will examine representative examples of receiver front-ends using p-i-n photodiodes and APDs. 6.1 Front-End Architectures An optical receiver's front-end design can usually be grouped into one of four basic configurations: 1) resistor termination with a low-impedance voltage amplifier, 3) high-impedance amplifier, 4) transimpedance amplifier, and 5) noise-matched or resonant amplifier. Any of the configurations can be built using contemporary electronic devices such as operational amplifiers, bipolar junction transistors, field-effect transistors, or high electron mobility transistors. The receiver performance that is achieved will depend on the devices and design techniques used. The names typically used to describe these four configurations can be somewhat misleading. Fundamentally, the front-end of an optical receiver responds to an optical signal by generating a photocurrent with a photodetector. The photocurrent is then converted to a voltage. Electronic signal processing stages process the recovered voltage to extract the desired information. The dimensions of the transfer function associated with the front-end will consequently be volts per amp or ohms. Thus the transfer functions of virtually all optical receivers are actually transimpedance in nature. 6.1.1 Low Impedance Voltage Amplifier A simple optical receiver front-end is illustrated in Fig. 6.1. It consists of a photodetector, a load resistor, and a low input-impedance voltage amplifier.

We report high power phase locked fiber amplifier array using the Self-Synchronous Locking of Optical Coherence by Single-detector Electronic-frequency Tagging technique. We report the first experimental results for a five element amplifier array with a total locked power of more than 725-W. We will report on experimental measurements of the phase fluctuations versus time when the control loop is closed. The rms phase error was measured to be λ/60. Recent results will be reported. To the best of the authors' knowledge this is the highest fiber laser power to be coherently combined.

A 1.25-2.5Gb/s burst-mode limiting amplifier for gigabit passive optical networks (GPON) is presented in this paper. It supports both PIN-PD and APD diodes. A response time of 5 ns and sensitivity of 4 mVpp is achieved by introducing a modified amplified stage with active feedback and negative Miller capacitance compensation techniques. This circuit operates with a supply voltage 3 V and it is fabricated in 180 nm CMOS technology. The influence of the parasitic layout elements and their effects on the performance of the limiting amplifier will be illustrated using RC and RLC parasitic extraction and simulation results.

We report on the fiber-based amplification of a commercially packaged, fiber-pigtailed-pulsed diode laser operating at wavelength of 1064nm (bandwidth 0.45nm). The cascaded Yb-doped fiber amplifier can operate safely by using cascaded Wavelength division multiplexing (WDM) in each single-mode amplification stage. The total isolation of cascaded WDM can protect the laser diodes from destroyed by feedback of optical power. At repetition rate of 50kHz, pulse duration of 20ns, and average power of 0.5mW, output power up to 1.05W And peak power up to 1.05kW are obtained, with a high signal to noise ratio of 20dB. The whole system is a good choice for a preamplifier of high-power short-pulse amplification. The aim of the experiment is to study the design of preamplifier for high-power short-pulse amplifier via cascaded fiber-based amplifier.

We report on recent advances in the development of a 1064 nm pulsed master oscillator fiber power amplifier (MOFPA) with integrated modulators enabling programmable temporal pulse shapes and its employment in a tandem photonic amplifier. The MOFPA amplifier chain is seeded by a laser diode operated in the CW regime, yielding very stable spectral characteristics that are independent of the pulse repetition rate and pulse shape. The use of 3 GHz integrated LiNbO3 electro-optic modulators in conjunction with high speed digital electronics results in an excellent pulse shaping capability, a fine pulse amplitude stability and high repetition rate operation (100 kHz-1MHz) with fast rise times (

Simplicity and low parts count are key virtues to this high voltage amplifier. Optoisolators replace complex high voltage transistor biasing schemes. This amplifier employs only 2 optoisolators, 16 high voltage mosfets transistors, 2 low voltage ones, 6 linear IC's and a score of passive components. Yet it can amplify opamp signals to 5 kV peak-to-peak from DC to sine waves up to 20 kHz. Resistor feedback guarantees the fidelity of the signal. It can source and sink 10 mA of output current. This amplifier was conceived to power ion traps for biological whole cell mass measurements. It is a versatile tool for a variety of applications.

The performance of a novel current-steering logic sense amplifier is verified through simulations in 0.35 μm CMOS technology. Because the reading time affects destructively the MRAM cell by thermal dissipation and it also affects the consumption of power, a new sense amplifier is proposed, one that operates at high frequency, that has a reading time of the order of ns and a low power consumption. This sense amplifier uses the differential charge of the bit line capacity where the MTJ resistance determines the gain of the amplifying. The differential amplifying starts when the bit line voltage reaches a certain threshold. In this way we increase the sensitivity of the device and the two values of the MTJ resistance will be distinguished in a much shorter time. The output voltage will be stored in a latch structure as the maximum I minimum voltage level (VDD or gnd).© (2007) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Built on the maser oscillator power amplifier configuration including a single mode erbium-doped fiber laser used as the signal source and a large-mode-area Erbium/Ytterbium double-clad fiber used as the gain medium, the polarization states of the signal light and the amplified signal light are experimentally investigated. The results show that the polarization degree of the output of the amplifier is low without taking any polarization control measure; after inserting a polarizer in the loop of the signal source, the degree of polarization is improved evidently and the stability of the polarization state becomes better, whether for continuous wave operation or for mode-locked operation. The mode-locked operation had a little lower polarization degree and a better PS's stability than the continuous wave operation of the output of the amplifier. When introducing a polarizer in the loop of the signal, the instability of the polarization state of the output of amplifier is mainly caused by the polarization parameter azimuth. So, the combination use of a polarizer and a polarization controller is supposed to improve the polarization degree and the stability of the output of the amplifier, furthermore, polarization-maintaining gain fiber is recommended to be used to avoid the random perturbation of the environment. This work offers an important experimental basis for the control of the PS in the laser beam coherent combination.© (2007) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Architectures are discussed in which power amplifiers are able to vary their performance characteristics in response to changing output power levels, frequencies, load impedance levels and linearity constraints. Necessary elements for implementation of such systems are reviewed, including sensors to detect changes in the external environment, actuators to adapt the amplifier characteristics, and algorithms to implement the associated control functions. An example is described of a power amplifier for cell phone applications that measures the load impedance provided by the antenna and varies its output impedance match accordingly, in order to preserve output power, efficiency and linearity as the external antenna is handled. The system automatically provides output tuning for a 1W linear amplifier, and can accommodate output standing wave ratios up to 8:1. It improves output power and efficiency by x2 in representative mismatch scenarios. The insertion loss of the system is comfortably low at 0.5dB.

All-optical wavelength conversion using cross-gain modulation in a semiconductor optical amplifier is one of the simplest and most common techniques to perform such operation. However, the finite gain recovery time of the amplifier causes severe distortion and pattern dependence at high bit-rates. The present work shows that it is possible to reduce the pattern dependence of the output converted signal using a fiber Bragg grating operating on its transmission edge. A wavelength converter using the non-linear effect of cross-gain modulation in a semiconductor optical amplifier can be assembled in the co-propagating and counter-propagating modes. The advantage of the counter-propagating mode is the possibility of an assembly without an optical filter in the output of the converter to filter the input signal, however this scheme introduces crosstalk in WDM systems, due to the residual facets reflectivity of the semiconductor optical amplifier. In this paper we analyze by simulation using commercial software, the improvement in the frequency response of a wavelength converter based on cross gain modulation in semiconductor optical amplifier in the counter-propagating mode using a fiber Bragg grating. The simulation results show that, with the fiber Bragg grating in the output of the converter, the pattern dependence of the converted signal is reduced. This paper also shows the advantages and disadvantages of the counter-propagating mode.

This work presents the idea of the conversion of the optoelectronic system into the functional electric model on the example of fiber amplifier. The functional model is formulated in a long line of lumped constants form. It is dedicated for electrical simulators like SPICE (Simulation Program for Integrated Circuit Emphasis). It can be widely used in design and analysis of fiber transmission lines, whose optical fiber amplifier is one of the most important parts. This model together with previous showed analysis enables qualification time life of ions in excited state in working amplifier.

A simple method of broadband distributed Raman amplifier is presented based on Chirped Fiber Bragg Grating Filter. C+L band gain flattened distributed fiber Raman amplifier with bandwidth of 50nm (1520nm~1570nm) and 15 dB averaged gain and ± 0.6dB gain ripple using single pump has been demonstrated. Compared to design methods of other existing Raman amplifier, our method has a substantial improvement in simplifying system.

Ultimate spectral efficiency of information transmission of erbium-doped fiber amplifiers and lumped amplifier chains is considered on the basis of the number-state model for linear communication channel. For single amplifier the efficiency is about 12-14 bit⋅s-1Hz-1 at 1 μW⋅GHz-1 input signal power density depending on pumping conditions. For long-haul communication lines it approximates 7-14 bit⋅s-1 Hz-1 for spectral density of input signal power of 1-100 μW⋅GHz-1.© (2006) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

The Log Amplifier described in this paper is designed for hearing aids (HA) application. It works on a low single-supply voltage (1.3V). The input signal varies between 0.01mV and 100mV. To give enough compensation to the hearing impairment, the amplifier provides a very large gain. The output swing is limited because of the low supply voltage and the large gain. Therefore, the logarithmic amplifier introduced into the design of HA to compress input signal so that the output distortion can be avoid. Another factor we use it here is that the amplifier has enough sensitivity and gain to deal with the compressed input signal without getting extra distortion coursed by the pre-process on input signal. The short channel CMOS devices play an important role in reduction of the supply voltage. DONG-BU ANAM 0.18 μm process is selected.

This paper addresses the optimization of power at the circuit level in the main blocks of CMOS APS image sensors. A pixel bias current of zero during the readout period is shown to reduce the static power and enhance the settling time of the pixel. A balanced operational transconductance amplifier (OTA) has been demonstrated to be a better candidate as an amplifier when employed in a correlated double sampling (CDS) circuit or as a comparator in an analog-to-digital (A/D) converter, as compared to a Miller two-stage amplifier. Using common-mode feedback (CMFB) in an OTA can further reduce the quiescent power of the amplifier. The low power capability of a CMFB OTA is discussed in this paper by performing a comparison with a conventional OTA using a 0.18 μm technology.

This work presents a functional model of an optical amplifier, which uses the active fiber doped with erbium called EDFA (eng: Erbium Doped Fiber Amplifier).The amplification obtained takes place entirely in optical domain without conversion to electric signals, how this happens in case of amplifiers SOA. However, with regard to the environment, in which works the optical amplifier (transmitters and receiver sets), it is useful to analyze suitable amplifier model in electric domain. For executing such model, it was proposed the delimitation of fiber parameters taking into account the threshold effects of amplification.

Since a switched-capacitor sample-and-hold amplifier (SHA) has a feedback loop outside its op-amp, an op-amp with positive feedback technique (PFT) can be adopted to enhance the DC-gain of the op-amp. This paper proposes a positive feedback amplifier with dramatically increased DC-gain of 127-dB and reports that a SHA adopting proposed amplifier is stable by feedback operation. Measurement results demonstrated stable operation with spurious free dynamic range (SFDR) of 70-dB.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A detailed description of a read-out amplifier for high frequency MEMS resonators is done. Both read-out requirements and circuit architecture are presented. The architecture of the system is mainly based on three blocks: a trans-impedance amplifier, followed by a three-stage voltage-to-voltage amplifier, and finally by an output buffer amplifier. Physical design is based on AMS 0,35 μm technology. Also, simulation and fabrication results are presented and analyzed. Simulation results show an AC transimpedance gain of 70 dBΩ and a cut-off frequency of 400 MHz, for a band-pass bandwidth over 350 MHz. The fabricated amplifier has an input noise current spectral density of 11 pA/(Hz)1/2, a power dissipation of 200 mW, and occupies an active area of 600 μm * 450μm. Integration of read-out circuit with MEMS resonator has been designed and implemented, by properly connection of MEMS signals to the amplifier, in order to enable characterization of a set of MEMS resonators. Integration analysis will allow future extraction of electrical parameters of the resonator.© (2005) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.