Phase Noise Measurement Techniques Research Articles

All-fiber transient phase noise characterization of polarization maintaining Yb-doped fiber amplifiers

We demonstrated an all-fiber phase noise measurement technique to detect transient phase variation of polarization maintaining Yb-doped fiber amplifier based on active phase locking of an optical heterodyne detection system. The root mean square, power spectral density, and drift velocity in the phase noise were analyzed for both core-pumped single clad fiber amplifier and clad-pumped double-clad fiber amplifier. The phase noise was further analyzed in terms of the seed laser power, amplifier output power, and fiber optic component configurations. The phase drift velocity measurements at various amplifier output powers indicated the optical phase were closely related to the temperature variations.

Highly-Sensitive Phase and Frequency Noise Measurement Technique Using Bayesian Filtering

Spectral purity of laser sources is typically investigated using phase or frequency noise measurements, which require extraction of the optical phase. This is a challenging task if the signal-to-noise-ratio (SNR) of the spectral line or the linewidth-to-noise-ratio (LNR) are not sufficiently high. In this letter, we present a statistically optimal method for optical phase noise measurement that relies on coherent detection and Bayesian filtering. The proposed method offers a record sensitivity, as the optical phase is measured at a signal power of -75 dBm (SNR of -11 dB in 1.1 GHz receiver bandwidth). Practically, this means that the phase noise measurements are, up to a high-degree, not limited by the measurement noise floor. This allows measurements down to -200 dB rad 2 /Hz and up to 10 GHz, which is useful when measuring the Schawlow-Townes (quantum noise limited) laser linewidth. Finally, the estimated optical phase is highly accurate allowing for quantum limited signal demodulation. The method thus holds the potential to become a reference measurement tool.

Investigation Into the Phase Noise of Modulated Grating Y-Branch Lasers

Theoretical and experimental investigations of the phase noise of modulated grating Y-branch (MGY) lasers are presented, mainly focusing on influence of the additive Vernier effect. A comprehensive simulation model based on transmission line model is developed, taking into account the spontaneous emission noise in the active section, the carrier shot noise in the passive sections, the 1/f noise for the injection currents and the detuned-loading effect induced by the grating reflectors. The phase noise characteristics of the MGY laser and the SGDBR laser are simulated, and compared to find the difference between the additive and multiplicative Vernier effects. The results clearly indicate that the MGY laser exhibits more serious phase noise due to using the additive Vernier effect. It has been found that different super-mode selection methods lead to different reflection characteristics, which play an important role in determining the phase noise. Finally, the phase noise of the MGY laser and the SGDBR laser are measured by using a coherent phase noise measurement technique, the experimental results turn out to be in agreement with the simulations.

Phase Noise Measurement and Testing with Delta-Sigma TDC

This paper describes a phase noise measurement and testing technique for a clock using a delta-sigma time-to-digital converter (TDC) and verifies its effectiveness with MATLAB simulations. The proposed technique can be implemented with relatively small circuitry, based on the following: (i) The clock under test (CUT) is a repetitive signal. (ii) The time resolution with CUT and a reference clock can be finer with longer measurement time with the delta-sigma TDC. (iii) The phase noise power spectrum can be calculated from the delta-sigma TDC output data using FFT. High performance spectrum analyzers with long measurement time (several ten seconds order due to average of several-time phase measurement results), which are very costly in mass production testing, are not be needed for phase noise measurement with the proposed technique. Our simulation used the input clock of 1 MHz in several phase fluctuation cases, and we observed that the phase fluctuation spectrum at the expected frequency from TDC output power spectrum obtained by FFT. We also investigated the amount of phase fluctuation with our theoretical calculation, which agrees with the simulation results.

Getting Its Measure: Oscillator Phase Noise Measurement Techniques and Limitations

Accurate measurement of phase noise is one of the most difficult measurements in all of electrical engineering. The biggest challenge is the huge dynamic range required in most phase noise measurements. There are several methods to measure phase noise, and the right one must be chosen to make the necessary measurements. To make a proper selection from the various methods, it is necessary to know and appreciate the weaknesses and strengths of each of the different techniques because none of these methods is perfect for every situation. This article focuses on key phase noise measurement techniques for oscillators and reviews their advantages and disadvantages.

Dual correlated pumping scheme for phase noise preservation in all-optical wavelength conversion

We study the effect of transfer of phase noise in different four wave mixing schemes using a coherent phase noise measurement technique. The nature of phase noise transfer from the pump to the generated wavelengths is shown to be independent of the type of phase noise (1 / f or white noise frequency components). We then propose a novel scheme using dual correlated pumps to prevent the increase in phase noise in the conjugate wavelengths. The proposed scheme is experimentally verified by the all-optical wavelength conversion of a DQPSK signal at 10.7 GBaud.

Phase-Noise Measurement System for the Terahertz-Band

We present phase-noise measurements in support of terahertz electronics. By combining even-harmonic mixers with a 2.5 GHz frequency comb, we achieve a phase-noise measurement system in waveguide (WR1.5) by use of cross-spectral and digital phase-noise measurement techniques. At 670 GHz an upper bound of this system's noise floor is found to be -20, -40, and -60 dBc/Hz at 1, 100, and 10000 Hz offsets, respectively. In addition, a commercial, low-phase-noise, 670 GHz source is measured at offset frequencies from 0.1 Hz to 1 MHz.

Phase noise measurement of a narrow linewidth CW laser using delay line approaches

Two different laser phase noise measurement techniques are compared. One of these two techniques is based on a conventional and low-cost delay line system, which is usually set up for the linewidth measurement of semiconductor lasers. The results obtained with both techniques on a high-spectral-purity laser agree well and confirm the interest of the low-cost technique. Moreover, an extraction of the laser linewidth using computer-aided design tools is performed.

The Allan Variance - challenges and opportunities

The Allan variance has historically been estimated using heterodyne measurement systems, which have low noise and preserve the carrier phase information needed for long-term stability. The single-sideband phase noise has traditionally been estimated using phase detectors that suppress the carrier to achieve even lower noise. The recent development of the direct-digital phase noise measurement technique makes it possible to estimate both statistics accurately and simultaneously from the same time series of the phase. Our comparison of the 3 techniques has revealed several challenges to the accurate estimation of the Allan variance including undesired aliasing, biased estimators, and spurious signal generation. Investigation of these difficulties has led to several opportunities to improve Allan variance estimation, including the ability to estimate the instrumentation noise floor during a measurement and the existence of an optimum measurement bandwidth. In the end, this has led to faster, easier, more reliable, and more accurate measurement methods.

Six-Port Interferometric Technique for Accurate $W$-Band Phase-Noise Measurements

An innovative six-port (SP) phase-noise measurement technique for millimeter-wave high-power sources is proposed in this paper. Simulation results using a 94-GHz rectangular waveguide SP circuit model validates the measurement principle for both millimeter-wave oscillators and amplifiers. Phase-noise measurement results of a 100-W extended interaction Klystron amplifier are presented and discussed. Compared to conventional methods, this new method allows accurate low-cost phase-noise measurements.

A Low Phase-Noise Voltage-Controlled SAW Oscillator With Surface Transverse Wave Resonator for SONET Application

A surface transverse wave (STW) resonator-based oscillator was developed in response to SONET OC-48 application. To meet the low jitter objective, a high-Q STW resonator was designed and fabricated in this study. The residual phase-noise measurement techniques are used to evaluate the feedback oscillator components, such as the loop amplifier, STW resonator, and electronic phase shifter, which can play important roles in determining the oscillator's output phase-noise spectrum. The oscillator's white phase-noise floor is -170dBc/Hz for carrier-offset frequency greater than 1 MHz. The oscillator's phase-noise level is -67dBc/Hz at a 100-Hz carrier offset. Both low close-in phase-noise and low white phase-noise floor makes the oscillator meet low jitter requirement. The electronic frequency tuning range exceeds plusmn200ppm. The oscillator provides 13.5 dBm of output power and consumes 65 mA from +5-V power supply

Phase-noise measurement using two inter-injection-locked microwave oscillators

Phase noise in two mutually coupled oscillators is analyzed by the describing function method, and the after-lock phase noise of the oscillators is calculated in terms of their free-running phase noise. A new phase-noise measurement technique based on inter-injection locking of two similar oscillators is proposed. Experimental results are presented, which confirm the theory. It is shown that in the case of zero phase of coupling coefficient, the system is in the optimum state where the only required parameter for the measurement is the locking bandwidth. In this optimum state, as far as the locking bandwidth is measured correctly, imperfections such as the frequency drift, parameters discrepancy, and nonlinear susceptance of the oscillators have no serious effect on the measurement accuracy. The proposed method is compared to the conventional ones.

Use of induced noise to calibrate injection-locked phase noise measurements

A new calibration approach is described for phase noise measurements of free-running voltage controlled oscillators using the injection locking technique. The injection locking technique allows the locking of free running oscillators to a reference over a wide bandwidth during a phase noise measurement. Compared to conventional phase noise measurement techniques, the injection locking technique involves a calibration procedure, which may be tedious and time consuming. The new approach may be used to perform an automated calibration procedure of the system commonly used for these measurements.

High-dynamic-range laser amplitude and phase noise measurement techniques

We describe techniques for making sensitive and high-dynamic-range measurements of laser amplitude and envelope phase noise (timing jitter) in the frequency domain at the shot-noise limit. Examples of amplitude noise measurements on continuous-wave argon-ion and diode-pumped solid-state lasers used for pumping a femtosecond Ti:sapphire laser are presented. Amplitude and phase noise measurements for the Ti:sapphire laser are also presented, showing correlation between pump laser amplitude modulation (AM) spectra and the resulting AM and phase noise. Characteristics of the measurement system components are discussed, along with examples of the impact these have on achieving reliable high-dynamic-range measurement capability.