Showing papers on "Phase noise published in 1986"
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TL;DR: The subject of phase noise in semiconductor lasers is reviewed in this paper, where Langevin forces, laser linewidth above threshold and below threshold, line structure due to relaxation oscillations, phase fluctuations, line narrowing by a passive cavity section and by external feedback, coherence collapse due to optical feedback, and the shot noise limits of several schemes of coherent optical communication are discussed.
Abstract: The subject of phase noise in semiconductor lasers is reviewed. The description of noise in lasers and those aspects of phase noise that are relevant to optical communications are emphasized. The topics covered include: Langevin forces; laser linewidth above threshold and below threshold; line structure due to relaxation oscillations; phase fluctuations; line narrowing by a passive cavity section and by external feedback; coherence collapse due to optical feedback; the shot noise limits of several schemes of coherent optical communication, and the linewidth required to approach these ideal limits.
330 citations
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TL;DR: In this article, measurements and calculations of interferometrically demodulated phase noise in an InGaAsP DFB laser were performed and the results led to a novel method of laser linewidth measurement.
Abstract: Measurements and calculations of interferometrically demodulated phase noise in an InGaAsP DFB laser are reported. The results led to a novel method of laser linewidth measurement. The effect of this noise on a DPSK coherent system is considered.
131 citations
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TL;DR: In this paper, a formalism for the analysis of laser phase noise effects on a general linear time-invariant optical system is presented for the autocovariance function of the instantaneous output intensity which are valid for any source coherence time as long as the source intensity fluctuations are assumed to be negligible.
Abstract: Performance of many optical circuits and systems, such as signal processing and sensing devices, is influenced by random fluctuations of the optical source emission field This paper outlines a formalism for the analysis of laser phase noise effects on a general linear time-invariant optical system Theoretical expressions are presented for the autocovariance function of the instantaneous output intensity which are valid for any source coherence time as long as the source intensity fluctuations are assumed to be negligible Applications of the results to some fiber-optic systems such as Mach-Zehnder and recirculating delay line devices also are demonstrated, both in the coherent and incoherent regimes Although the analysis is not limited just to fiber-optical systems, our attention is focused on fiber optics
131 citations
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TL;DR: In this article, the impact of laser phase noise on optical heterodyne communications receivers is analyzed in terms of the system signal-to-noise ratios and error rates, and the maximum permissible laser linewidth Δν is evaluated for each of these receivers and compared with previously published theoretical and experimental results.
Abstract: The impact of laser phase noise on optical heterodyne communications receivers is analyzed in terms of the system signal-to-noise ratios and error rates. An ASK receiver, three FSK receivers and a DPSK receiver are investigated. The maximum permissible laser linewidth Δν is evaluated for each of these receivers and compared with previously published theoretical and experimental results. It is shown that Δν depends on the system data rate R and on the modulation/demodulation technique chosen. For example, DPSK receivers require at least Δν ^ 0.7% of R while FSK receivers with postdetection frequency discrimination require at least Δν ^ 1.9% of R if the mark-space separation 2 fd is equal to R. At the same time, ASK receivers with envelope postdetection processing, and FSK receivers with large frequency deviation are much more tolerant to phase noise: they only require Av<9%ofR.
123 citations
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TL;DR: In this paper, the performance of the phase-locked loop subsystem is analyzed taking into account both shot noise and laser phase noise, and it is shown that for reliable phase locking (rms phase error less than 10°), heterodyne second-order loops require at least 6771 electrons/s per volt every hertz of the laser linewidth.
Abstract: An optical PSK heterodyne communications receiver is investigated. The receiver is based on the decision-directed phase-locked loop. The performance of the phase-locked loop subsystem is analyzed taking into account both shot noise and laser phase noise. It is shown that for reliable phase locking (rms phase error less than 10°), heterodyne second-order loops require at least 6771 electrons/s per volt every hertz of the laser linewidth. This number corresponds to the limit when the loop dumping factor η is infinitely large; if \eta = 0.7 , then the loop needs 10 157 electrons/(s . Hz). If the detector has a unity quantum efficiency and \lambda = 1.5 \mu m, the above quoted numberers give 0.9 pW/ kHz for \eta \rightarrow \infty and 1.35 pW/kHz for
u = 0.7 . The loop bandwidth required is also evaluated and found to be 155 \Delta
u , where \Delta
u is the laser linewidth. Finally, the linewidth permitted for PSK heterodyne recievers is evaluated and found to be 2.26 \cdot 10^{-3} R_{b} where R b is the system bit rate. For R_{b}=100 Mbit/s, this leads to \Delta
u kHz. Such and better linewidths have been demonstrated with laboratory external cavity lasers. For comparison, ASK and FSK heterodyne receivers are much more tolerant to phase noise,-they can tolerate \Delta
u up to 0.09 R b . At the same time, homodyne receivers impose much more stringent requirements on the laser linewidth ( \Delta
u ).
123 citations
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TL;DR: In this article, closed-form theoretical expressions for the autocovariance function, variance, and noise power spectral density of the instantaneous output intensity are presented for any optical biasing phase and any source coherence time.
Abstract: Dynamic range of many optical signal processing and sensing devices incorporating two-beam interferometers (such as Mach-Zehnder and Michelson interferometers) can be limited by random phase fluctuations of the optical source emission field. This paper is concerned with the intensity fluctuations, originating from the laser source phase noise, at the output of a two-beam interferometer. Closed-form theoretical expressions are presented for the autocovariance function, variance, and noise power spectral density of the instantaneous output intensity which are valid for any optical biasing phase and any source coherence time. Application of the results in the noise performance evaluation of optical devices incorporating two-beam interferometers will also be shown.
122 citations
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01 Jan 1986TL;DR: The characterization of frequency stability in the time domain and frequency domain are briefly defined and their relationships explained in this article, where techniques for making precise measurements of frequency fluctuations in oscillators, multipliers, dividers, amplifiers, and other components are discussed.
Abstract: The characterization of frequency stability in the time domain and frequency domain are briefly defined and their relationships explained. Techniques for making precise measurements of frequency fluctuations in oscillators, multipliers, dividers, amplifiers, and other components are discussed. Particular attention is given to methods of calibration which permit accuracies of 1 dB or better to be achieved when measuring in the frequency domain. Common pitfalls to avoid are also covered, and efficient time-domain techniques are explained.
111 citations
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TL;DR: In this paper, it was shown that phase noise due to the fundamental linewidth of the diode laser and not bias current noise determines the noise floor of most FMCW systems in the regimes away from (1/ f ) noise.
Abstract: Frequency ramped diode laser sensing and measurement systems suffer from a variety of limitations and noise sources. Nonlinearities in the frequency ramp produce unwanted sidebands in the frequency spectra of the system output and make accurate distance determination difficult in the frequency domain. Thermally induced drifts in the laser frequency prohibit long-term sensitive phase measurements even with a reference interferometer. It is shown that phase noise due to the fundamental linewidth of the diode laser and not bias current noise determines the noise floor of most FMCW systems in the regimes away from (1/ f ) noise. Time domain techniques suffer from low resolution because only a few data points can be taken during each frequency ramp and thus achieve poor averaging of the phase noise. The signal to noise ratio (SNR) of frequency ramped systems is shown to be lower (10-30 dB) than the theoretical prediction for an unmodulated heterodyne system, which was substantiated by showing that the minimum detectable phase is somewhat higher than that predicted by the idealized model.
73 citations
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TL;DR: The power penalty due to modal noise can be considerably reduced by suitable system modifications, e.g., by optimization of the decision threshold setting or by application of a low coherent light source operating with several spectral emission lines of low coherence and low partition noise.
Abstract: A review is given of the statistics of modal noise and of the expressions for the signal-to-noise ratio for the cases of a monochromatic and a nonmonochromatic light source including the effects of source frequency fluctuations. Using the results, a quantitative analysis is made of how modal noise degrades the bit-error-rate performance of a digital transmission link with multimode fiber. Plots of the bit-error rate versus the received optical power show the characteristic asymptotic behavior (BER floor); expressions are derived for the asymptotic BER. The power penalty due to modal noise can be considerably reduced by suitable system modifications, e.g., by optimization of the decision threshold setting or by application of a low coherent light source such as an LED or a laser diode operating with several spectral emission lines of low coherence and low partition noise.
66 citations
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TL;DR: In this paper, the upper frequency for loop-gap resonators intended for use in electron spin resonance spectroscopy was extended to the Q band (35 GHz) and a practical structure was described containing sample support, frequency tuning, and variable coupling.
Abstract: The upper frequency for loop‐gap resonators intended for use in electron‐spin‐resonance spectroscopy has been extended to Q band (35 GHz). A practical structure is described containing sample support, frequency tuning, and variable coupling. A typical sample volume is 39 nL. High‐energy densities (15 GW−1/2) were achieved. As found previously at X band, Q‐band loop‐gap resonators permit observation of the dispersion with minimal demodulation of phase noise originating in the klystron. Theoretical calculations of the resonant frequency, Q, and the filling factor are found to be in good agreement with experiment.
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TL;DR: In this paper, the effect of chirp and phase noise on the formation of solitons in optical fibres is examined. And the results show that the soliton are stable with respect to quite large effects of both chirps and phase noises.
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TL;DR: In this article, the amplitude and phase noise spectra of a laser oscillator were calculated using the quantum mechanical Langevin equations, where the external field spectra were shown to be different from the internal field spectrum.
Abstract: The amplitude and phase noise spectra of the internal and external fields of a laser oscillator are calculated using the quantum mechanical Langevin equations. The outgoing field spectra are demonstrated to be different from the internal field spectra. The outgoing photon flux \hat{N} from a laser oscillator operating at far above the threshold has a spectral density equal to the classical shot noise level, 2\langle\hat{N}\rangle . On the other hand, the internal photon number spectrum is Lorentzian, and the variance is equal to the average photon number, \langle\hat{N}\rangle . The difference stems from the quantum mechanical interference between the transmitted internal field and the reflected zero-point fluctuation at the output coupling mirror. The relation between the present analysis and the previous noise theory of a laser is also discussed.
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TL;DR: In this article, a method for the reduction of excess phase noise in coherence-multiplexed fiber sensors is described, which utilises diode laser frequency modulation to effect a frequency translation of the excess noise power.
Abstract: A method for the reduction of excess phase noise in coherence-multiplexed fibre sensors is described. The technique utilises diode laser frequency modulation to effect a frequency translation of the excess noise power. An improvement close to 40 dB in minimum detectable phase shift sensitivity is demonstrated using the technique.
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TL;DR: In this paper, an approximate method is developed for finding the stochastic solutions of equations of the Burgers and Khokhlov-Zabolotskaya type for diffraction of intense noise, taking into account the effects of the spatial and temporal statistics, the excitation of random waves by distributed sources, and the formation of steady state spectra.
Abstract: Experiments in statistical nonlinear acoustics are reviewed. Measurements of the average intensities of the harmonics of a narrow-band randomly modulated signal, the nonlinear transformation of broad aerodynamic-noise spectra, and different effects involving the interaction of regular and random waves (active suppression of noise by an intense signal, excess fading of a weak signal in noise fields, cascade-like broadening of spectra, formation of white noise, and other effects) are described. Theoretical explanations are given for the observed phenomena. An approximate method is developed for finding the stochastic solutions of equations of the Burgers and Khokhlov-Zabolotskaya type. Results on the diffraction of intense noise, taking into account the effects of the spatial and temporal statistics, the excitation of random waves by distributed sources, and the formation of steady-state spectra, are presented for the first time. The problems of the nonlinear transformation of the statistical characteristics of acoustic noise and other general questions are discussed.
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TL;DR: In this paper, a linear homodyne optical phase-locked-loop has been demonstrated using a semiconductor local oscillator laser and has been shown to exhibit good dynamic response to environmental influences.
Abstract: A linear homodyne optical phase-locked-loop has been demonstrated using a semiconductor local oscillator laser and has been shown to exhibit good dynamic response to environmental influences. The receiver phase noise in this experiment was dominated by Rayleigh backscatter from the fibre link.
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19 Aug 1986
TL;DR: In this paper, the phase noise content of a microwave signal source was measured using a phase detector and mixing means, and the output of the phase detector was used to measure the phase signal noise content.
Abstract: Apparatus for measuring the phase noise content of a microwave signal source (10) includes a microwave cavity (22) resonant at a fixed frequency, signal generating means (23) operable to generate a frequency representing the difference between the source frequency and that of the resonant cavity, and mixing means (20) for combining the outputs of the source and the signal generating means. The output from the resonant cavity (22) is applied to a phase detector (15) together with a portion of the output of the mixing means (20) and the output of the phase detector (15) represents the phase noise content of the output of the microwave source (10). The signal generating means (23) includes a voltage-controlled oscillator the frequency of which is controlled by an output from the phase detector means (15) so as to maintain the output of the mixing means (20) at the resonant frequency of the microwave cavity (22).
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TL;DR: An approximate, nonlinear Fokker-Planck-type equation is obtained which offers an improved model for two-dimensional nonequilibrium, bistable flows driven by exponentially correlated Gaussian noise and accurately predicts the renormalization of the phase-space statistical densities P(x,v) with correlation time.
Abstract: We obtain here an approximate, nonlinear Fokker-Planck-type equation which offers an improved model for two-dimensional nonequilibrium, bistable flows driven by exponentially correlated Gaussian noise. The new model accurately predicts the renormalization of the phase-space statistical densities P(x,v) with correlation time. The theory is tested for accuracy by both analog electronic and digital simulations of a damped oscillator with a bistable potential, driven by additive, colored noise. For large noise strengths, the improved theoretical scheme is applicable for small noise correlation times tau, but becomes increasingly better for small noise strengths where its accuracy extends even tolarge noise correlation times. The crossover to overdamped motion is also discussed.
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TL;DR: In this article, the authors describe the design and performance of an M ary frequency shift keyed (FSK) signaling and demodulation scheme for an optical communication system using semiconductor lasers and heterodyne detection.
Abstract: This paper describes the design and performance of an M ary frequency shift keyed (FSK) signaling and demodulation scheme for an optical communication system using semiconductor lasers and heterodyne detection. Frequency or phase noise in semiconductor lasers causes spectral spreading, producing a nonzero linewidth laser signal. This degrades communication performance when compared to a system using an ideal laser with zero linewidth. We present estimates of the bit error rate (BER) performance of M -ary frequency shift keying (FSK) with noncoherent demodulation in the presence of white Gaussian frequency noise and additive channel noise. This is typical of an optical system using semiconductor lasers and heterodyne detection. Estimates use the union-Chernoff bound with a simplified channel model to predict the effects of frequency noise. Two effects of frequency noise are identified: signal attenuation or suppression, and crosstalk. These cause an offset in the BER curve from the BER in the absence of frequency noise, and an error rate floor, respectively. The error rate floor is lower than previously predicted. When performance is not crosstalk limited, M -ary FSK is found to perform better than binary FSK with the same system bandwidth constraints, as would be predicted if ideal lasers are used. Theoretical results are compared with Monte Carlo simulations of the system.
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TL;DR: Subsequent measurement of individual oscillator short-term frequency stability show that oscillator output signal phase noise sideband levels below f = 1 KHz are a result of resonator instability rather than substaining stage transistor phase noise.
Abstract: Abstrad-The design and performance of a novel dual-crystal controlled VHF oscillator circuit exhibiting output signal phase noise sideband spectra substantially lower than that obtainable using conventional single resonator oscillators is described. The use of multiple (two) crystal resonators effects a 5-dB reduction in phase noise sideband level for carrier offset frequenciesf 5 1 KHz. The SC-cut crystal resonators are operated at high drive level (5-8 mW), and individual oscillator output signals are extracted through the resonators. At modulation rates in excess of the resonator loaded bandwidth, additional oscillator signal phase noise suppression occurs as a result of the resonator narrowband transmission responses. Also, because the buffer amplifier additive noise spectra are uncorrelated, signal frequency summation at the amplifier outputs effects a 3 dB reduction in output signal phase noise sideband level a t high (7 2 10 kHz) modulation rates. Phase noise sideband levels of 134 dBlHz at f = 100 Hz and 181 dB/Hz a t f 2 10 KHz have been demonstrated using 80 MHz prototype oscillators. Subsequent measurement of individual oscillator resonator short-term frequency stability show that oscillator output signal phase noise sideband levels below f = 1 KHz are a result of resonator instability rather than substaining stage transistor phase noise. In addition, the use of identically operated resonators is shown to provide a means for reduction in device output signal frequency instability due to mechanical stress by using resonators exhibiting equal and opposite acceleration frequency sensitivities.
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TL;DR: In this paper, the performance of coherent optical receivers is discussed, taking into account both noise sources: the phase noise of the laser transmitter and the laser local oscillator and by the shot noise due to the detectors employed in the receiver.
Abstract: The performance of coherent optical receivers is affected by the phase noise of the laser transmitter and the laser local oscillator and by the shot noise due to the detectors employed in the receiver. In this paper, the performance of coherent optical receivers is discussed, taking into account both noise sources. Further, the maximum permissible laser linewidth AP for coherent optical communications systems is reported. Both heterodyne and homodyne systems are considered. It is shown that the value of AP depends on the system bit rate Rb and on the modulation/demodulation technique employed: for heterodyne receivers with noncoherent postdetection processing [used in conjunction with amplitude-shift keying (ASK) or frequency-shift keying (FSK) modulation formats], Av_0.09 Rb; for heterodyne receivers with coherent postdetection processing [used in conjunction with the phase-shift keying (PSK) modulation format], Av< 2.26 X 10-3 Rb; and for PSK homodyne receivers, Av 3.1 X 10-4Rb. This paper presents the main results only; details of the mathematics involved have been published elsewhere. The purpose is to give a user a set of simple laser linewidth requirements without forcing him to analyze the research results scattered among several publications.
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20 May 1986
TL;DR: In this article, the probability distributions of group delay, Doppler shift, and bandwidth have been found, and for the two former it is a Student's t-distribution, which depends only on first and second moments of power profiles, not on the details of the distribution of scatterers.
Abstract: For high signal-to noise ratios the channel quality is limited by phase variations in frequency and space. The probability distributions of group delay, Doppler shift, and bandwidth have been found, and for the two former it is a Student's t-distribution. The probability distributions depend only on the first and second moments of power profiles, not on the details of the distribution of scatterers. Implications for signal transmission are discussed briefly.
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TL;DR: In this article, the amplitude and phase noise spectra of the internal and external fields of a negative resistance oscillator were derived using electrical circuit theory, and it was shown that the difference between external and internal fluctuations becomes important in the quantum domain where external noise sources are not negligible as they often are in the classical domain.
Abstract: The amplitude and phase noise spectra of the internal and external fields of a negative resistance oscillator are derived using electrical circuit theory. It is shown that the difference between internal and external fluctuations becomes important in the quantum domain ( h\omega > kT ) where external noise sources are not negligible as they often are in the classical domain ( h\omega ). Using established methods to describe quantum fluctuations in electrical circuits, we obtain results in full agreement with the more exact but less general direct quantum mechanical analysis of a Fabry-Perot laser in Part I.
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02 Jun 1986
TL;DR: In this article, a temperature-stabilized ultra-low noise GaAs FET oscillator, using a temperature stabilized dielectric resonator in the feedback circuit, was developed.
Abstract: A highly stabilized ultra-low noise GaAs FET oscillator, using a temperature stabilized dielectric resonator in the feedback circuit, has been developed. A key factor for achieving high stability and low noise is a very high loaded Q (8000) . The oscillator operates at 4 GHz with a power output of 11.5 dBm, a frequency temperature coefficient of +- 0.02 ppm/°C, and a SSB N/C ratio of -130 dBc/Hz and -146 dBc/Hz at 10 KHz and 100 KHz off carrier, respectively. The oscillator is varactor tunable over a 1500 KHz bandwidth.
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01 Oct 1986TL;DR: In this article, the phase noise of a GaAs FET oscillator was measured and numerical simulations of it were performed. But the results showed that simulations with a conventional noise model lead to unsatisfactory agreement with the experimental results.
Abstract: Measurements and numerical simulations of the phase noise of a GaAs FET oscillator are described. It is shown that simulations with a conventional noise model lead to unsatisfactory agreement with the experimental results. A significantly improved accuracy is obtained with an extended oscillator noise model, which includes a periodically driven noise source.
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TL;DR: In this article, the influence of the noise of the common oscillator in the dual-mixer time-difference (DMTD) measurement system is determined. But, it is shown that this influence will be eliminated when the time difference between the zero crossings of the beats approaches zero no matter what kind of power spectral density the common Oscillator signal provides.
Abstract: Formulae are presented for the determination of the influence of the noise of the common oscillator in the dual-mixer time-difference (DMTD) measurement system. It is shown that this influence will be eliminated when the time difference between the zero crossings of the beats approaches zero no matter what kind of power spectral density the common oscillator signal provides. The formulae to calculate the influence of the common oscillator for different kinds of power-law density are presented. A synthesizer used as the common oscillator is also discussed.
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02 Jun 1986
TL;DR: In this paper, the set up and performance of a 94 GHz second harmonic Gunn oscillator that is cavity stabilized at its fundamental frequency is described, with a quality factor of about 7000 and reduced the phase noise by nearly 40 dB.
Abstract: The set up and the performance of a 94 GHz second harmonic Gunn oscillator that is cavity stabilized at its fundamental frequency is described. The cavity has a quality factor of about 7000 and reduces the phase noise by nearly 40 dB. The oscillator generates an output power of 40 mW, sufficient to drive low noise balanced mixers, to synchronize Impatt oscillators or to operate as a reference source in coherent radar systems.
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18 Mar 1986
TL;DR: In this article, a first phase-locked loop was proposed to generate an output signal at a frequency within a first predetermined range including the plurality of assignable frequencies in a broadcast telephone system for communicating information signals over an assigned frequency channel.
Abstract: In a broadcast telephone system for communicating information signals over an assigned frequency channel, the combination of a synthesizer for generating a signal at the assigned frequency and a PROM storing a plurality of sets of first and second signals associated with different predetermined assignable frequencies The synthesizer includes a first phase-locked loop for generating an output signal at a frequency within a first predetermined range including the plurality of assignable frequencies in response to the combination of a first frequency reference signal having a predetermined frequency and a second reference frequency signal having a frequency within a second predetermined range and derived from a second phase-locked loop a second phase-locked loop for generating a third reference frequency signal within a third predetermined range in response to a combination of a first signal from the PROM associated with a given assignable frequency and a fourth frequency reference signal having a predetermined frequency; and a frequency divider coupled to the PROM for dividing the frequency of the output signal from the second phase-locked loop by an amount indicated by a second signal from the PROM associated with said given assignable frequency to provide the second reference signal to the first phase-locked loop The phase-locked loops each include a minimizing phase noise and electronic noise due to microphonics
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06 Jan 1986
TL;DR: In this paper, a coarse tuning circuit is serially connected between the resonant circuit and the input to the amplifier to minimize noise at the frequency of operation while optimizing the coarse tuning range.
Abstract: A low noise two port voltage controlled oscillator having a coarse tuning circuit serially connected to an inductor to form a resonant circuit. A fine tuning circuit is serially connected between the resonant circuit and the input to the amplifier. A large capacitance series silicon varactor minimizes noise at the frequency of operation while optimizing the coarse tuning range.
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TL;DR: In this paper, the phase and frequency noise of a semiconductor laser was defined and a Gaussian pdf was developed for the probability density function (pdf) of the laser output phase or frequency noise.
Abstract: A physical definition for the phase and frequency noise of a semiconductor laser is given, which can be applied in determining the performance of coherent optical communication systems. The definition allows a filtered Poisson model to be developed for the probability density function (pdf) of the laser output phase or frequency noise, based on evaluating the cumulants of the noise processes. A condition is derived to quantify under what laser and system conditions a Gaussian pdf is a good approximation. It is shown that the phase and frequency noise can increase significantly for bit rates approaching the relaxation oscillation frequency of the laser diode.