Line Amplifiers Research Articles

Experimental and Theoretical Study of Polarization Dependent Loss in a Optical Recirculation Loop

An investigation of Polarization Dependent Loss (PDL) behavior is performed in an Recirculation Loop (RCL) experimental apparatus. The RCL allows to simulate the transmission for several links of fiber with only one line amplifier, some filters and devices for tests and a fiber coil, with a very lesser cost. The PDL statistical nature turns its accumulated contribution in the RCL different from the sum of each different elements contributions, therefore the alignment of the elements with PDL changes, depending on the ambient conditions as tensions and temperature. Theoretical analyses are also performed using the Jones and Mueller matrix approach to represent each element in the loop. The PDL in the devices must be characterized correctly, with the objective to foresee the impact in the performance of the new generations of systems DWDM. Experimental errors are considered in the theoretical results and compared with experimental ones. A 7% depolarization most likely due to optical amplifier amplified spontaneous emission is identified in the experimental apparatus.

Evaluating SOA Nonlinearity Effects by High-Order Susceptibility on Constant Envelope Signals in WDM Systems

Nonlinearity effects, arising within a semiconductor optical amplifier (SOA), have been deeply investigated with particular interest for exploiting them in wavelength conversion. This application shrinks the research area to a precise scenario: a strong pump signal travels through the active medium simultaneously with a modulated signal to be converted. In this case, it is possible to neglect the spectral distribution of the optical power and phase relationship between propagating signals. SOAs have been also studied as line amplifiers for wavelength-division multiplexing (WDM) phase-modulated signals. Aim of this paper is to extend the propagation model in an SOA, in order to simulate nonlinearities occurring in the amplification of a WDM comb signal evaluating-wave mixing on constant envelope modulation schemes (differential phase-shift keying). This can be carried out due to an enhanced analytical model based on the optical field and medium interaction, overcoming the wide-used rate equation approach, which is based on the overall photons density.

Dispersion compensation of <inline-formula><math altimg="none" display="inline" overflow="scroll"><mrow><mn>2</mn><mtext>-</mtext><mo>×</mo><mn>10</mn><mtext>-</mtext><mi>Gb</mi><mo>∕</mo><mi mathvariant="normal">s</mi></mrow></math></inline-formula>, 1000-km long-haul fiber using only chirped fiber Bragg gratings

The impact of cascaded CFBGs delay ripple for dispersion compensation has been analyzed. The experimental results show that the overall penalty was proportional either to the number or to the square root of the number of CFBGs employed along the link. The delay ripple of the overall CFBGs fluctuates, and the overall CFBGs reflectivity was not simply additive but was related to the placement of the CFBG and line amplifier gain. For the first time, the experimental results of dispersion compensation for a 2-×10-Gb/s, 1000-km WDM system using self-made CFBGs with less than 1-dB power penalty for each channel have been achieved.

Characteristics of low noise hybrid fiber amplifier

The characteristics of hybrid fiber amplifier (HFA) are investigated. HFA is composed of three stages: short-length EDFA pre-stage, DCF Raman amplifier, and power boosting EDFA. HFA has low noise figure, high output power, and also wide input power dynamic range. Gain control method of HFA is presented experimentally, and the transient gain excursion is suppressed to less than 0.5dB at 3dB channel add-drop. HFA can be used as line amplifier in optical transmission link even combined with distributed Raman amplifier due to wide input power dynamic range. The transmission performance of HFA is better than EDFA by more than 1.0dB of Q-factor in 720km SMF transmission.

Noise and distortions limitations in the design of HFC CATV systems

The paper deals with HFC CATV systems. System parameters determinative in obtaining the desired carrier-to-noise ratio (CNR) and acceptable nonlinear distortions are considered. Formulae for the gain and the maximum number of RF amplifiers in the longest coaxial trunk line are developed. A mathematical model of the optical channel is suggested that makes it possible for the signal minimum level at the optical receiver input to be calculated if the value of CNR and the number of TV channels transmitted are known. Analytical expressions to determine the RF signal voltage in the input and output of the optical line are given that take into consideration the nonlinear distortions in the laser transmitter, the number of TV channels and the losses within the optical fiber and passive elements. Experimental results are given to illustrate the application of the formulae in the design of a HFS system section.

A low-power SRAM using hierarchical bit line and local sense amplifiers

This paper proposes a low power SRAM using hierarchical bit line and local sense amplifiers (HBLSA-SRAM). It reduces both capacitance and write swing voltage of bit lines by using the hierarchical bit line composed of a bit line and sub-bit lines with local sense amplifiers. The HBLSA-SRAM reduces the write power consumption in bit lines without noise margin degradation by applying a low swing signal to the high capacitive bit line and by applying a full swing signal to the low capacitive sub-bit line. The HBLSA-SRAM reduces the swing voltage of bit lines to V/sub DD//10 for both read and write. It saves 34% of the write power compared to the conventional SRAM. An SRAM chip with 8 K/spl times/32 bits is fabricated in a 0.25-/spl mu/m CMOS process. It consumes 26 mW read power and 28 mW write power at 200 MHz with 2.5 V.

System Analysis of Power Transients in Advanced WDM Networks

This paper considers dynamical transient effects in the physical layer of an optical circuit-switched wavelength-division-multiplexed network. These transients of the average transmission power have millisecond time scales. Instead of studying detailed nonlinear dynamics of the network elements, such as optical line amplifiers, a linearized model of the dynamics around a given steady state is considered. System-level analysis in this paper uses modern control theory methods and handles nonlinearity as uncertainty. The analysis translates requirements on the network performance into the requirements to the network elements. These requirements involve a few gross measures of performance for network elements and do not depend on the circuit switching state. One such performance measure is the worst amplification gain for all harmonic disturbances of the average transmission power. Another is cross-coupling of the wavelength channel power variations. The derived requirements guarantee system-level performance for all network configurations and can be used for specifying optical components and subsystems.

A WATT‐level 2.3‐GHz GaAs MESFET power amplifier with gap‐coupled microstrip‐line matching topology

AbstractA one‐stage hybrid power amplifier integrated with gap‐coupled microstrip lines for impedance matching is demonstrated in this work. The gap‐coupled microstrip line amplifier module realized here can provide 15‐dB power gain, 33.5‐dBm output power, and 42% power‐added efficiency (PAE) at 2.3 GHz. The demonstrated topology is suitable in monolithic IC technology, especially in the millimeter‐wave frequency because the gap‐coupled microstrip lines can be easily compacted into small size. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 346–348, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20137

Design optimisation of SOA-integrated DFB laser wavelength converter

Design optimisation of a distributed feedback laser wavelength converter integrated with semiconductor optical amplifiers in line was performed. It was found that, by increasing the SOA length on the output side, both the conversion efficiency and the optical signal-to-noise ratio could be increased. With an increase in SOA length on the input side, the conversion efficiency improves at the cost of the OSNR. Guidelines for designing DFB lasers with respect to the grating coupling coefficient and the length were also derived. The results indicate that the integration of SOAs significantly improves both the conversion efficiency and the optical S/N ratio.

Optimal allocation of amplifiers in a dispersion-managed line for a wavelength-division-multiplexed soliton transmission system

Optimal allocation of amplifiers in a dispersion-managed line is theoretically derived by means of minimizing the collision-induced frequency shift in a two-channel wavelength-division-multiplexed soliton transmission system. Almost complete cancellation of the frequency shift can be obtained for such a system with any strength of dispersion management.

Active narrowband magnetostatic wave filter

An active passband microwave filter consisting of a magnetostatic wave (MSW) delay line and microwave amplifier has been developed and tested. A narrow passband of 120 kHz was obtained at the S/C-band corresponding to a quality factor Q of ~40000. The frequency response characteristics are presented.

Internal valve leakage detection using an acoustic emission measurement system

A detailed experimental study was conducted to determine the lowest detectable compressed air leakage rate through an industrial control valve that can be reliably detected using an acoustic emission (AE) technique. Through-valve leakage was deliberately introduced into a 25.4 mm (1 in.) hard-seat globe type control valve under controlled conditions. This was achieved by carefully adjusting the control signal, 4-20 mA d.c., to the valve positioner which, in turn, varied the clearance between the valve plug and seat. Two AE sensors together with the state-of-the-art data acquisition and processing systems were used to monitor a wide range of leakage rates under different working conditions. The effects of the background noise on the measured AE signal were considerably reduced by using the real-time programmable filters that were part of the AE measurement system. This was carried out to produce more reliable and consistent results. The sensitivity of the AE sensors was improved by using line amplifiers with variable gain. The frequency spectrum analysis of the AE signal indicated that leak-related frequency components can be clearly distinguished from those produced due to background noise. Furthermore, it was evident that the selected leak-related frequency components increased in their amplitude as the leakage rate was increased. The paper concludes by illustrating that AE can be used reliably to detect the onset of air leakage through control valves at a differential pressure that could be as low as 110.3 kPa (1.103 bar) and in a noisy industrial environment.

Optimum configuration for cascaded fiber amplifiers in attenuation limited transmission systems

Fiber amplifiers play an important part in optical transmission systems to overcome the impact of attenuation. Together with the transmitter and receiver the positions of amplifiers on the optical path as well as the design of the amplifiers itself determine the bit error probability of the digital communication link. We present a simple method how to derive the optimum configuration for an optical transmission link with cascaded fiber amplifiers for an attenuation limited system. The bit error probability is calculated in dependence of the positions of the line amplifiers and the lengths of the doped fibers for systems with and without booster and optical preamplifier. In a first step we search the optimum configuration by numerical minimization of the bit error probability for a given transmission length, transmitter power and optical receiver. We have found a very simple rule how to determine the lengths of the transmission fibers and the doped fibers of the amplifiers for the minimum bit error probability when the length of the first transmission fiber is given. Therefore, the search for the optimum configuration reduces to the search of the appropriate length of the first transmission fiber which results in an enormous reduction of computing effort. We have investigated the effect on the bit error probability when one deviates from the optimum configuration. For the case, when the transmission length is reduced me have found that the bit error probability decreases always, when the lengths of the single transmission fibers are cut.

Quantum noise reduction in quasi-phase-matched optical parametric amplification

We present a calculation of quantum noise for parametric amplification in periodically inverted nonlinear media. An analytical expression is obtained for the noise figure of the amplifier. We show that such optical parametric amplifiers run in a phase-sensitive configuration can achieve noiseless amplification and squeezing, thus constituting a promising way for the integration of noiseless optical amplifiers in a communication line.

Optical Phase Division Multiplexed Transmission for Satellite Earth Station Signal Distribution

The optical phase division multiplexed duplex transmission for satellite multicarrier spectrum to and from earth station is described and investigated. The optical transmission bandwidth for uplink and downlink carriers are analysed as a function of number of carriers and phase deviations. Analytic expressions for channel CNR are derived and the results of computation are given with and without optical line amplifiers. It is seen that the scheme has great potential for multicarrier transmission.

Sound mixer with band separation

In a mixer there is a plurality of preamplifiers (10) followed by a plurality of tone control groups (11) connected to a plurality of voltage followers (12) to which a series of active filters (13,14,15) is connected, for selecting frequency bands of signals. Then a plurality of adders (50,60,70) is connected to the seried of filters for mixing the signals in each frequency band selected by the filters and for sending the mixed signal to a plurality of line amplifiers and final amplifiers, with which loudspeakers are connected. The preamplifiers, the tone control groups, the voltage followers, the series of filters, the adders, the line and power amplifiers and the loudspeakers are connected so as to form a plurality of circuits, all of them equal to each other.

Use of optical amplifiers to increase distribution capacity of optical analogue video systems

Optical amplifiers can be used to increase the distribution of analogue video signals over a passive optical network. The paper analyses the gains in system loss budget that can be obtained from the positioning of optical amplifiers either as transmitter power amplifiers, line amplifiers or receiver preamplifiers in a distribution network. Both AM and FM subcarrier multiplexed (SCM) video systems are considered within the constraints of operating with safe optical power levels on optical lines in the network. It is shown that under such conditions optical amplifiers can give significant advantages in the loss budget for FM SCM systems, but have limited application within AM SCM systems.

Denver Unit Well Surveillance and Pump-Off Control System

This paper describes a prototype system that demonstrates the technicalfeasibility of installing and operating an on-line, computer-based wellsurveillance and control system. This system provides a much higher levelof surveillance and control than possible with conventional equipment.Expansion of the system will include all wells and facilities in the DenverUnit of Wasson Field. Introduction Approval was obtained in Oct. 1974 to install a pilotcomputer production control (CPC) system to serve abattery (Battery 3) of the Denver Unit, Wasson Field.The test battery area contained 76 beam pumped wells, four satellite separation and test facilities, andtreating and storage facilities in the battery. The pump-off control portion of the system, whichmonitors and controls the individual wells, becameoperational in June 1976. Automatic well testing becameoperational in Feb. 1977. The system basically consistsof a small wellhead remote unit at each well, a largerremote unit at each satellite, and the battery. Thewellhead remote units take signals from the load andposition transducers on the pumping units and transmit position transducers on the pumping units and transmit the data to the pump-off control (POC) computer locatedin the production office at Denver City, TX. The largerbattery and satellite remote units communicate with adisc-based field computer located in the production office(see Fig.1). About 94,000 ft of six-pair cable was installed toconnect the wells, satellites, battery, and productionoffice. Microwave communication links the productionoffice with Shell computers located in Houston.Few problems have been encountered with this fieldcommunications network. Supervisory hardware, whichincludes all remote and computer interface units, alsohas performed satisfactorily. The first line amplifiers(repeaters) furnished by the hardware manufacturer wereunsatisfactory and had to be redesigned. The POCcomputer, which is a new model, had many problems earlier;however, recent changes seem to have improved itsreliability, Early problems also were experienced with loadcell transducers. The cables were constructed so that asmall strain on the cable caused it to tear out of the loadcell. This problem has been reduced substantially byusing a better method for connecting the cable to theload cell. Thus, the cable fails instead of damaging theload cell. The pump-off control technique has proven a reliablemethod for determining when a well is pumped off.The computer uses data from a well to calculate energy inputto the rod string during a certain portion of the stroke.When the energy drops below a specified limit, the well isconsidered pumped off. A limit can be set so that the wellshuts down for any degree of pump-off. The POC programalso checks for abnormal load conditions and eithershuts the well down or alerts the operator. To enhancewell surveillance, a sucker-rod diagnostic program wasimplemented in the field computer. Data can be transferredon request from the POC computer to the field computer foranalysis. Results normally are returned to the operator ina few seconds. From the results, the operator can determinehow the pump is performing and also detect any abnormal conditions that might be occurring in the well. The"on-line" combination of POC, automatic well testing, andsucker-rod diagnostics gives the field a powerful surveillancetool. JPT P. 1319

Measurements of primary spectra from a kilocurie 60Co unit and a 6 MeV linear accelerator.

Spectral measurements have been made of gamma radiation from a T.E.M. Stabilatron kilocurie cobalt 60 unit and of roentgen radiation from a Varian Clinac 6 MeV linear accelerator with a NaI crystal spectrometer, both units normally used by us for radiation therapy. The high photon flux density from these two types of radiation sources, especially the pulsating radiation from the accelerator, necessitates a reduction in the intensity. This is performed by spreading in A1 foil (SCRIMGER & CORMACK 1963, BENTLEY et coll. 1967, LOFROTH 1970), which reduces both intensity and energy, and by collimation. Multiple counts are reduced by means of a dual delay line amplifier (CHASE & SVELTO 1961 ) . A response matrix (SAM et coll. 1968) for the detector was constructed from the monoenergetic gamma ray source spectra and applied to obtain the gamma ray and roentgen spectra from the measured pulse height distribution. An iterative unfolding procedure ( SKARSGARD et coll. 1961 ) solved the matrix equation:

A Pulse Shape Analyzer for Phoswich Detectors

An electronic technique for separating the signals from a phoswich detector is discussed. The preamp output signal is amplified by two double delay line amplifiers operating in parallel. The time difference between the crossover points of the two amplifier output signals is measured. This time difference is a function of the detector pulse shape. For small pulses, this technique has less time jitter than the more usual leading edge/crossover measurement. It is also less sensitive to control misadjustments. An instrument based on this principle is described.