Chromatic Dispersion Measurement Research Articles

Development of wavelength dispersion measurement method using Fresnel reflection of fiber under test at both end faces

The phase shift method is generally used for wavelength (chromatic) dispersion measurement of optical fibers. However, the phase shift method requires a long fiber under test (FUT) of several hundred meters or more to obtain high temporal resolution. Therefore, measuring specialty fibers with short production lengths and amplification fibers that absorb light at specific wavelengths used for fiber lasers is difficult with this method. We have developed a method to measure the beat spectrum, by incident, an incoherent tunable light source (I-TLS) composed of amplified spontaneous emission (ASE) to a FUT. The FUT constitutes a Fabry–Perot resonator using Fresnel reflections at both end faces of the fiber. Chromatic dispersion can be calculated from the wavelength dependence of the refractive indices of the FUT, enabling measurement with short fiber lengths. The standard deviation of the chromatic dispersion @1550 nm was 0.352 ps/(nm km) based on five measurements of a FUT of approximately 3 m. The error between the manufacturer's measurement of chromatic dispersion @1550 nm, and the average value measured in this study was measured at 0.56%, indicating that it can be measured with very high accuracy.

Real-time optical fibre near-infrared chromatic dispersion analyser using collocated optical fibre gratings.

We present what we believe to be a novel optical fibre device for real-time measurements of near-infrared chromatic dispersion of a liquid medium from 1100 nm to 1700 nm. This inline optical fibre chromatic dispersion analyser is based upon collocated fibre long-period gratings written adjacently in the core by femtosecond laser inscription yielding 8 attenuation bands associated with different cladding modes, yielding 8 independent measurements. This fibre device is tested on a series of chemical compounds associated with wines. The results for each compound yielded distinctive chromatic responses. A machine learning pipeline was developed that successfully clustered and classified spectral responses of the different chemicals to illustrate the distinctive responses. The limits of detection for these fibre devices ranged from 1×10-3 to 6×10-5 mol/L for the compounds associated with wines, demonstrating the potential usefulness of an optical fibre chromatic dispersion analyser is capable of monitoring in real-time effective chromatic dispersion that is not offered by any current technology.

Measurement of Chromatic Birefringence Dispersion of Phase Plates Written in Glasses by Femtosecond Pulses

Measurement of Chromatic Birefringence Dispersion of Phase Plates Written in Glasses by Femtosecond Pulses

Chromatic dispersion measurement of optical fiber using spectroscopic optical coherence tomography

Chromatic dispersion (CD) in optical fibers results in the broadening and overlapping of transmitted lights, and thus reduces the capacity of information transmission and increases the bit-error-rate of communication system. Hence it needs to be accurately measured and then compensated. There have been various methods for fiber CD measurement, but most of them are complicated to obtain wavelength components and require adjustment during measurement, and thus have the drawbacks of being time-consuming, and susceptible to system stability and environmental influences. In this work, a measurement method of fiber CD based on the principle of spectroscopic optical coherence tomography (OCT) was proposed by using a swept-source OCT system to capture interference signal, and using Wigner-Villy distribution as time-frequency analysis method to extract spectral − spatial distribution. Wavelength − OPD curve could be obtained from the distribution, where the OPD (optical path difference) is the spatial delay induced by the fiber CD, and the CD profile varying with the wavelength was finally obtained from the curve. One fiber sample was measured with 1060 and 1310 nm band systems, and another different type of fiber sample was measured with 1310 nm band system. The measured results are agreement with the claimed or theoretical results, demonstrating the feasibility of this method. It has some significant advantages and is a promising method for fiber CD measurements.

In situ measurement of chromatic dispersion in an optical hypertelescope: a laboratory demonstration.

Optical interferometry is a technique capable of achieving better spatial resolution than the world's largest monolithic telescopes at a fraction of the cost. Most interferometer architectures split the imaging bandwidth into a number of channels in order to prevent image degradation due to a large spectral bandwidth. An optical hypertelescope permits a much broader spectral bandwidth on a single channel than a conventional interferometer. However, a broader spectral bandwidth becomes more sensitive to differential chromatic dispersion, and this dispersion must be measured and corrected in order to maintain a high signal-to-noise ratio. A prototype dispersion measurement system is presented that is capable of measuring chromatic dispersion in an eight aperture hypertelescope. The optical design, calibration, data acquisition, and dispersion measurement process are described in detail. This system is capable of measuring differential dispersion to better than λ/100R M S and is scalable to a system with an order of magnitude more apertures.

Plug-and-Play Measurement of Chromatic Dispersion by Means of Two-Photon Interferometry

Plug-and-Play Measurement of Chromatic Dispersion by Means of Two-Photon Interferometry

Chromatic dispersion measurement of few-mode fiber based on low coherence off-axis digital holography

A method based on low coherence off-axis digital holography is proposed to measure the chromatic dispersion of few-mode fiber (FMF). A measurement system based on the Mach–Zehnder interferometer with a delay stage is established. The holograms, which vary with the delay stage at different wavelengths, are recorded using the system. The interference energy is extracted from the holograms to construct the time domain mode energy curve at each wavelength to obtain the delays of the fundamental mode and each higher-order mode. According to the relationship between the delay and the wavelength, the dispersion curves of the fundamental mode and each higher-order mode are calculated. The higher-order modes are selectively excited by controlling the tilt angle of the incident light to separate the higher-order modes with a close group delay in the short fiber in the time domain. The FMF is measured using this method, and the dispersion curves of the fundamental mode and each higher-order mode are obtained. The measurement results are consistent with the design parameters. This method is suitable for measuring short optical fibers and has several advantages, including high measurement resolution and simple experimental device.

Chromatic Dispersion Measurements of Single-Mode Fibers, Polarization-Maintaining Fibers, and Few-Mode Fibers Using a Frequency Domain Method

Chromatic dispersion is an important fiber attribute affecting transmission performance over optical fibers. Various chromatic dispersion measurement methods have been developed primarily for single-mode fibers. In the literature, measurement techniques were also developed to characterize few-mode fibers and multi-mode fibers. These methods are often subject to some limitations. In this paper, a simple and robust measurement method for chromatic dispersion measurement of single-mode fibers, polarization--maintaining fibers, and few-mode fibers is presented using a frequency domain instrument and a vector network analyzer. The method is applied to all three types of fibers through one measurement methodology uniformly. Using a vector network analyzer, the measurement instrument obtains the complex transfer function of fiber transmission. The inverse Fourier transform of the measured complex transfer function is used to determine the group delays for each mode of the fiber. Although the sampling is highly under-sampled for the whole fiber link, through proper treatment of the data, we can de-alias the signals and obtain accurate values of the group delays of each mode. By measuring the group delays over different wavelengths, the data can yield the chromatic dispersion of each mode over the wavelength window.

GS-FrFT Algorithmic Method for Measurement of CD in Fibre Optics

The migration of present data network to the IoT interface, witty utilization of huge liable Single Mode Fiber rather than re-installing the whole network with Dispersion Shifted Fiber for their upgrading to ultra data speed Optical Fiber System based MPLS network for countering the main impediment of Chromatic Dispersion by estimating the real foe and compensating it at the receiver end and hence results the system more efficient with the existing Fiber network. The present scanning method of Fractional Fourier Transform (FrFT) to measure the Chromatic Dispersion (CD) encounters constraints of high latency time along with worst dispersion estimation error 250 picoseconds/nanometre which can be drastically improved with Golden Scan Search (GS) FrFT based algorithm method with 5 to 6 sec latency time and estimation error improved and obtained less than 80 picoseconds/nanometre.

The measurement of chromatic dispersion of liquids based on rainbow technology with empirical mode decomposition

An acquisition system is designed to collect the rainbow signals at two different wavelengths simultaneously. The empirical mode decomposition (EMD) method was used to decompose and reconstruct the first-order rainbow signal. Airy, ripple and noise signal components were completely separated from the signal of the first-order rainbow by the EMD, and the refractive index of the droplet can be obtained by analyzing the separated airy structures. In our experiments, the rainbows from droplets of water, NaCl and C6H12O6 aqueous solutions were collected and the rainbow signals were analyzed by EMD. Based on the Cauchy dispersion model, the coefficients and the dispersion relation of water, NaCl and C6H12O6 aqueous solutions at different concentrations were obtained by measuring the refractive index at the wavelengths of 632.8 and 473 nm. We demonstrate an EMD-rainbow method to detect the chromatic dispersion of liquids.

Broadband chromatic dispersion measurements in higher-order modes selectively excited in optical fibers using a spatial light modulator.

We propose an improvement of the interferometric method used up to now to measure the chromatic dispersion in single mode optical fibers, which enables dispersion measurements in higher-order modes over a wide spectral range. To selectively excite a specific mode, a spatial light modulator was used in the reflective configuration to generate an appropriate phase distribution across an input supercontinuum beam. We demonstrate the feasibility of the proposed approach using chromatic dispersion measurements of the six lowest order spatial modes supported by an optical fiber in the spectral range from 450 to 1600 nm. Moreover, we present the results of numerical simulations that confirm sufficient selectivity of higher-order mode excitation.

Chromatic dispersion measurement in optical fibers using optoelectronic oscillations

In this paper, a novel technique is introduced that enables the measurement of chromatic dispersion (CD) in optical fibers. This technique is based on a relatively low-frequency optoelectronic oscillation (OEO) to provide a fast, precise and a relatively low-cost method for CD measurement that can be implemented easily in commercial instruments. In addition, another technique is introduced to compensate for the thermal fluctuations in fiber during measurement. The proposed setup is implemented to measure CD in normal single-mode fibers with lengths of 40 km, 10 km, and 1 km. Moreover, it is implemented to measure CD in 400 m of non-zero dispersion shifted fiber to test the system ability to resolve small chromatic delays. The proposed setup can resolve delays less than 0.1 ps/nm and measure CD with precision as low as 0.005 ps/nm·km over a wavelength range from 1500 to 1630 nm in only 20 s with 5 nm steps. The precision and the speed of measurement can be improved by increasing the wavelength steps to 10 nm.

Effective Method for Determining Chromatic Dispersion From a Spectral Interferogram

We present a novel method for determining chromatic dispersion profile from a broadband spectral interferogram obtained by using a white-light interferometry technique. The proposed method is based on direct calculations of a second derivative of the registered spectral intensity at extremal points, which in result gives a spectral phase difference derivative further used for dispersion determining. Although the method is best suited for processing interferograms with modulation around a zero level (zero-mean value interferograms) and slowly changing envelope, the conducted numerical tests show that it is highly tolerable to different types of perturbations of the input interference signal. The proposed method can be applied both to spectral interferograms with monotonically changing phase difference as well as containing stationary phase difference points. We demonstrate the effectiveness and accuracy of the proposed method in measurements of chromatic dispersion of commercially available samples like the BK7 glass plate and the Corning SMF-28 optical fiber.

Chromatic dispersion measurement based on a high-Q optoelectronic oscillator incorporating cascaded FIR and IIR filters

An approach for chromatic dispersion measurement is proposed and experimentally demonstrated based on an optoelectronic oscillator (OEO) incorporating a single bandpass microwave photonic filter (MPF), which is implemented by cascading a finite impulse response (FIR) MPF and an infinite impulse response (IIR) MPF jointly. The key concept of the proposed design is mapping the chromatic dispersion of a device under test (DUT) to the oscillating frequency of the OEO by embedding the DUT into the OEO loop. The oscillating frequency is mainly determined by the central frequency of the MPF, which depends on the length difference of the two arms of the Mach-Zehnder interferometer (MZI) and the chromatic dispersion value of the fiber cooperatively. The bandwidth of the MPF is further narrowed by an IIR filter based on a recirculating fiber loop for stabilizing OEO oscillation. The chromatic dispersion of fibers with lengths ranging from 20 km to 100 km are measured in the experiment.

Self-referenced axial chromatic dispersion measurement in multiphoton microscopy through 2-color third-harmonic generation imaging.

With tunable excitation light, multiphoton microscopy is widely used for imaging biological structures at subcellular resolution. Axial chromatic dispersion, present in virtually every transmissive optical system including the multiphoton microscope, leads to focal (and the resultant image) plane separation. Here, we experimentally demonstrate a technique to measure the axial chromatic dispersion in a multiphoton microscope, using simultaneous 2-color third-harmonic generation imaging excited by a 2-color soliton source with tunable wavelength separation. Our technique is self-referenced, eliminating potential measurement error when 1-color tunable excitation light is used which necessitates reciprocating motion of the mechanical translation stage. Using this technique, we demonstrate measured axial chromatic dispersion with 2 different objective lenses in a multiphoton microscope. Further measurement in a biological sample also indicates that this axial chromatic dispersion, in combination with 2-color imaging, may open up opportunity for simultaneous imaging of 2 different axial planes.

Measurement of chromatic dispersion of liquid in a wide spectral range based on liquid-prism surface plasmon resonance sensor

We present, in this work, a new method to measure the chromatic dispersion of liquid based on the surface plasmon resonance sensor. The liquid sample is serving as the liquid prism at the same time. Both angular and spectral interrogations are used in the experiments. The chromatic dispersions of six kinds of liquids with the wavelengths from 450nm to 1050nm are obtained, respectively. The experimental data are also compared with the data of Abbe refractometer, and they are in good agreement. The method provides a practical application for measuring the chromatic dispersion of liquid in a wide spectral range.

Chromatic dispersion measurement along both polarization directions of a birefringent hollow-core photonic crystal fiber using spectral interferometry.

Applications based on photonic crystal fibers depend strongly on their dispersion properties that might differ from the desired specifications due to deficiencies in the manufacturing process. Since dispersion characteristics might also be affected by the placement of the fiber, in this paper the effect of various placements on the chromatic dispersion properties of a commercially available HC-800-02 photonic crystal fiber was investigated between 760 and 870 nm with Fourier-transform spectral interferometry. To test the scaling of dispersion with fiber length, samples of different lengths ranging from 10 to 97 cm were used in the measurements. It was found that the dispersion properties of the orthogonal directions were different. The dispersion parameter showed small dependence on the placement and fiber length. The polarization-mode dispersion (PMD) of the fiber was measured using an indirect and a direct technique. To retrieve the PMD directly in the case of the shorter fibers where the fringes were too sparse for the Fourier method, the so-called minima-maxima method was employed. The precision was comparable with both techniques; however, the direct approach proved to be more accurate when longer samples were measured, and the indirect method seemed to be more reliable in the case of shorter fibers.

Simultaneous Measurement of Chromatic and Modal Dispersion in FMFs Using Microwave Photonic Techniques

A microwave-photonic technique for measuring dispersion characteristics of few-mode fibers is proposed and experimentally demonstrated. We extract these dispersion parameters by sweeping the frequency of microwave signals modulated on an optical carrier. For the first time, simultaneous high-precision measurement of chromatic dispersion and modal dispersion are made possible. Experimental results obtained on a two-mode group fiber match well with simulation results, as well as those obtained using time-domain methods. The proposed scheme is scalable to measuring fibers with a large number of modes.

Fully guided-wave photon pair source for quantum applications

We report a fully guided-wave source of polarisation entangled photons based on a periodically poled lithium niobate waveguide mounted in a Sagnac interferometer. We demonstrate the source’s quality by converting polarisation entanglement to postselection-free energy-time entanglement for which we obtain a near-optimal S-parameter of 2.75 ± 0.02, i.e. a violation of the Bell inequality by more than 35 standard deviations. The exclusive use of guided-wave components makes our source compact and stable which is a prerequisite for increasingly complex quantum applications. Additionally, our source offers a great versatility in terms of photon pair emission spectrum and generated quantum state, making it suitable for a broad range of quantum applications such as cryptography and metrology. In this sense, we show how to use our source for chromatic dispersion measurements in optical fibres which opens new avenues in the field of quantum metrology.

Dispersion-optimized multicladding silicon nitride waveguides for nonlinear frequency generation from ultraviolet to mid-infrared

Nonlinear frequency conversion spanning from the ultraviolet to the mid-infrared (beyond 2.4 μm) is experimentally demonstrated in multicladding silicon nitride (SiXNY) waveguides. By adjusting the waveguide cross-section the chromatic dispersion is flattened, which enhances both the efficiency and the bandwidth of the nonlinear conversion. How accurately the dispersion is tailored is assessed through chromatic dispersion measurements and an experiment/simulation comparison of the dispersive waves’ wavelength locations. Undesirable fluctuations of both the refractive index and the dimensions of the waveguide during the fabrication process result in a dispersion unpredictability of at least 20 ps/nm/km. Finally, manipulation of the effective refractive index allows for multiple third harmonic generated tones spanning from 381 to 715 nm.