Chromatic Dispersion Measurement Research Articles

Fiber chromatic dispersion measurement by using a novel RF spectrum phase detection method based on DSP

In this paper, a novel chromatic dispersion (CD) measuring method based on a novel RF spectrum phase detection technique is proposed, this is performed using in-band tone monitoring RF, electrically down-converted to direct current (DC) or a low intermediate-frequency (IF) of less than 1MHz through electronic mixing with local oscillator (LO). We theoretically and experimentally demonstrated the CD measurement for CD components (etc. fiber). The method can support any CD range measuring with good accuracy through adjusting RF frequency.

Novel method for fiber chromatic dispersion measurement based on microwave photonic technique

In this letter, we propose and demonstrate a simple and novel method for fiber chromatic dispersion (CD) measurement based on microwave photonic technique. The radio frequency (RF) signal is modulated simultaneously on two light-waves with different wavelengths, and the light-wave carrying RF signals transmit through the dispersive medium under test. CD can be obtained by monitoring the power changing of the interference RF signals after photo detector. The CD values of the single-mode and dispersion compensation fibers are both measured within the wavelength range from 1 525 to 1 605 nm, which verifies the feasibility of this method.

Spectral interferometry-based chromatic dispersion measurement of fibre including the zero-dispersion wavelength

We report on a simple spectral interferometric technique for chromatic dispersion measurement of a short length optical fibre including the zero-dispersion wavelength. The method utilizes a supercontinuum source, a dispersion balanced Mach-Zehnder interferometer and a fibre under test of known length inserted in one of the interferometer arms and the other arm with adjustable path length. The method is based on resolving one spectral interferogram (spectral fringes) by a low-resolution NIR spectrometer. The fringe order versus the precise wavelength position of the interference extreme in the recorded spectral signal is fitted to the approximate function from which the chromatic dispersion is obtained. We verify the applicability of the method by measuring the chromatic dispersion of two polarization modes in a birefringent holey fibre. The measurement results are compared with those obtained by a broad spectral range (500–1600 nm) measurement method, and good agreement is confirmed.

Chromatic dispersion measurement using single sideband spectrum phase difference detection for OOK signal link

In this paper, we theoretically and experimentally demonstrated the residual chromatic dispersion (CD) measuring of 10Gbit/s NRZ and 40Gbit/s NRZ/RZ links by using a novel single sideband (SSB) spectrum phase difference detection technology. This method can differentiate positive and negative residual CD of the fiber link, the measuring range is dependent on frequency difference (FD) of two local oscillator (LO) and the FD can be adjusted up to CD range. This method is independent on data rate for intensity modulation direct detection (IM/DD) links. In condition of FD of 4 GHz, the measuring range was around ± 1000 ps/nm and resolution was better than 5 ps/nm for 10G NRZ link.

PMD-Insensitive CD Monitoring Based on RF Clock Power Ratio Measurement With Optical Notch Filter

We propose and experimentally demonstrate a chromatic-dispersion (CD) monitoring method based on radio-frequency (RF) clock power ratio measurement in 38-Gb/s nonreturn-to-zero differential quadrature phase-shift keying (NRZ-DQPSK) and 57-Gb/s NRZ differential 8-level phase-shift keying (D8PSK) systems. A narrowband fiber Bragg grating (FBG) notch filter is centered at the optical carrier wavelength, such that the RF clock power decreases with CD. On the other hand, RF clock power increases with CD in the absence of the notch filter. By using the RF power ratio of the filtered and nonfiltered signals, polarization-mode-dispersion (PMD) effects on RF power ratio can be eliminated and CD measurement sensitivity can be increased. The CD monitoring range is 0 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$\sim$</tex></formula> 250 ps/nm in the systems with a symbol rate of 19-Gsym/s. Moreover, the proposed CD-monitoring method is not affected by received optical power.

Precise evaluation of polarization mode dispersion by separation of even- and odd-order effects in quantum interferometry

The use of quantum correlations between photons to separate measure even- and odd-order components of polarization mode dispersion (PMD) and chromatic dispersion in discrete optical elements is investigated. Two types of apparatus are discussed which use coincidence counting of entangled photon pairs to allow sub-femtosecond resolution for measurement of both PMD and chromatic dispersion. Group delays can be measured with a resolution of order 0.1 fs, whereas attosecond resolution can be achieved for phase delays.

Measurement of Residual Chromatic Dispersion or OSNR via Nonlinear Spectral Evolution

In this work, we report a new fiber architecture providing high accuracy measurements of both residual chromatic dispersion and optical signal-to-noise ratio. Taking advantage of the nonlinear spectral evolution of pulses propagating in a Kerr medium, we have numerically and experimentally validated the use an anomalous dispersive fiber combined with a central spectral filtering.

Rapid and accurate chromatic dispersion measurement of fiber using asymmetric Sagnac interferometer

We propose and experimentally demonstrate an advanced method for chromatic dispersion measurement of fiber. This technique is based on spectral interferometry by using an asymmetric Sagnac loop and broadband optical source. The chromatic dispersion can be directly obtained from the spectral interferogram seen from an optical spectral analyzer. This method is rapid (<1 s), accurate, simple, low cost, and can provide a large dispersion measurement range.

Dispersion Estimation via Vestigial Sideband Filtering Using an Optical Delay Line Filter

Vestigial sideband filtering can be used for chromatic dispersion measurements. An optical delay line filter providing upper sideband (USB), lower sideband (LSB), and passband was designed for that application. The straightforward utilization is to measure the time delay between the USB and the LSB. A more practical approach is to estimate the chromatic dispersion (CD) by multiplying the USB and LSB signals in an electronic mixer and filtering out the DC component of the resulting signal. Due to the correlation between the USB and the LSB this signal is a measure for the delay between the sidebands induced by the CD. This approach was successfully demonstrated by experiments at a data rate of 10 Gbit/s. Furthermore, the properties of the optical filter influence (e.g., filter extinction) were assessed by numerical simulations.

Standard equipment for instruments for the measurement of chromatic dispersion in fiber-optic information transmission systems

A technique and procedure for the development of standard equipment for instruments used in the measurement of chromatic dispersion in fiber-optic information transmission systems are described. An analysis of the errors of the standard equipment is presented. Results of studies of the standard equipment and working standard of chromatic dispersion are also presented.

Low-Coherence Interferometry for Measurement of Properties of Optical Components

We present a modification of the interferometric method for the measurement of refractive index or thickness of optical devices using an easily aligned, almost all-fiber Michelson interferometer. Applicability of the method is demonstrated by the chromatic dispersion measurement of photonic crystal fiber sample. The birefringence of the optical device based on LiNbO3 obtained from the measurement of refractive indices is demonstrated and its value is determined for two different crystal samples. It is also shown that when the thickness of, for example, photopolymer material is known the refractive index of the device can be determined. The described method can be a practical tool for laboratories with the need of inexpensive and easily built setup for measurement of refractive index or thickness of optical devices even in a broad spectral range.

Measurement of fiber chromatic dispersion using spectral interferometry with modulation of dispersed laser pulses

We propose and experimentally demonstrate a method for fiber dispersion measurement based on the modulation of laser pulses stretched by the fiber under test. The measured spectrum of the modulated pulses is the result of the interference between the stretched pulse spectra shifted by the modulation harmonics. The interference pattern is processed as in Fourier transform spectral interferometry. Unlike to conventional spectral interferometry, environmental conditions do not affect the interferogram due to the lack of any interferometer; additionally, large dispersions can be characterized by the method proposed. Its high accuracy is demonstrated in experimental comparison with the widely used phase shift technique.

Measurement of chromatic dispersion of polarization modes in optical fibres using white-light spectral interferometry

We report on a white-light interferometric technique for a broad spectral range measurement (e.g. 500–1600 nm) of chromatic dispersion of polarization modes in short-length optical fibres. The technique utilizes an unbalanced Mach–Zehnder interferometer with a fibre under test of known length inserted in one of the interferometer arms and the other arm with adjustable path length. We record a series of spectral interferograms by VIS–NIR and NIR fibre-optic spectrometers to measure the equalization wavelength as a function of the path length difference, or equivalently the differential group index dispersion of one polarization mode. The differential group dispersion of the other polarization mode is obtained from measurement of the group modal birefringence dispersion. We verify the applicability of the method by measuring the chromatic dispersion of polarization modes in a birefringent holey fibre. We apply a five-term power series fit to the measured data and confirm by its differentiation that the chromatic dispersion agrees well with that specified by the manufacturer. We also measure by this technique the chromatic dispersion of polarization modes in an elliptical-core fibre.

Shape selection of wavelets for accurate chromatic dispersion measurement of white-light spectral interferograms

The group delay of chirped mirrors can be directly read from the ridge of wavelet-transform of white-light spectral interferograms. In this paper, we investigate the influence of Gabor wavelet shaping factor on the precision of the group-delay dispersion extraction. The rule of selection of shaping factor is given for accurate chromatic dispersion measurement of chirped mirrors.

Local and Spectral Characterization of Optical Fibers and Fiber Bragg Gratings with Low Coherence Interferometry

In this article, we describe local and spectral characterization of fibers and integrated optical components using low coherence interferometry. Chromatic dispersion and group birefringence measurements of erbium-doped fibers or photonic crystal fibers are presented, as well as local characterization of fiber Bragg gratings which allows the determination of strain and profile temperature gradient inside a material.

An Electronic Domain Chromatic Dispersion Monitoring Scheme Insensitive to OSNR Using Kurtosis

In this paper we present an electronic domain solution for chromatic dispersion (CD) monitoring algorithm based on the estimated time domain channel in electronic domain using channel estimation methods. The proposed scheme utilizes kurtosis as a CD measurement, directly computed from the estimated inter-symbol-interference (ISI) channel due to the CD distortion. Hence, the proposed scheme exhibits robust performance under OSNR variation, in contrast to the existing electronic domain approach based on minimum mean squared error (MMSE) fractionally-spaced equalizer taps [1]. The simulation results verify the CD monitoring ability of the proposed scheme.

White-Light Interferometer Based on a High-Precision Chromatic Dispersion Measurement Method

White-Light Interferometer Based on a High-Precision Chromatic Dispersion Measurement Method

A comprehensive study of the chromatic dispersion measurement of the multi-channel fiber Bragg grating based on an asymmetrical Sagnac loop interferometer

A novel all-fiber asymmetrical Sagnac loop interferometer (ASLI) is proposed to measure the chromatic dispersion of a multi-channel fiber Bragg grating (FBG). Theoretical analyses to this proposed approach are presented in details. With this method, the chromatic dispersion and dispersion slope of a 51-channel FBG are simultaneously measured. The experimental results agree well with the ones obtained by using the general phase-shift method (PSM). This method has the advantages of simple configuration, low-cost, and high tolerance for the characteristics of FBG.

Chromatic dispersion measurement using optical beating null frequency

A new technique for measuring the accumulated chromatic dispersion in single-mode fibers is presented. The proposed simple and tunable technique uses the null frequency of the optical beating signal between pump, probe, and four-wave-mixing conjugated signals as the pump and probe frequency separation is changed. The null frequency of the optical beating signals varies with the accumulated chromatic dispersion in the single mode fiber. A full mathematical model of the measurement technique is developed and is supported by experimental results. The technique is successfully demonstrated experimentally using a semiconductor optical amplifier as a phase conjugator to achieve a null frequency variation of 1.2 GHz for a difference of 960-ps/nm accumulated chromatic dispersion.

Correction to “Chromatic Dispersion Measurement for Multichannel FBG Based on a Novel Asymmetrical Sagnac Loop Interferometer” [Oct 07 1601-1603

In the above titled paper (ibid., vol 19, no. 20, pp. 1601-1603, Oct. 07), equation (3) contained a typographical error. The correct equation is presented here.