Dispersive Optical Fiber Research Articles

Dispersion and light loss reduction in photonic crystal fibers using nanoparticles optimization

The dispersion of optical fiber can damage optical information, thus limiting data transfer speed and transmission distances. In this paper, a new structure is presented by applying metal nanoparticles for photonic crystal fibers (PCF) so that minimizes dispersion and optical loss. The proposed PCF uses circular and elliptical shape nanoparticles, then their number and location is optimized by PSO algorithm. Applying metal nanoparticles in PCF substrate causes increases the conductivity and increases light excitation, which increases light absorption and decreasing dispersion. By changing the shape, location, and type of nanoparticles, a structure with minimal dispersion and light loss is provided. In this paper, we applied three elliptical and three circular nanoparticles using the PSO results. The hexagonal PCF is designed with air grids and radius of 5.8 µm, and then circular and elliptical gold particles are used instead of air holes. Simulation results show that the loss is 7e−4 dB/cm at wavelengths between 1.3 and 1.65 µm and the dispersion is obtained less than 0.3 ps/nm/km. The light loss and dispersion are reduced compared to other related studies.

Impact of Wind Gust on High-Speed Characteristics of Polarization Mode Dispersion in Optical Power Ground Wire Cables.

Polarization mode dispersion is recognized as a key factor limiting optical transmission systems, particularly those fiber links that run at bit rates beyond 10 Gbps. In-line test and characterization of polarization mode dispersion are thus of critical importance to evaluate the quality of installed optical fibers that are in use for high-speed signal traffics. However, polarization-based effects in optical fibers are stochastic and quite sensitive to a range of environmental changes, including optical cable movements. This, in turn, gives rise to undesired variations in light polarization that adversely impair the quality of the signal transmission in the link. In this work, we elaborate on experimental testing and theoretical analysis to asses changes of polarization mode dispersion in optical fibers that are caused by environmental variations, here wind gusts in particular. The study was performed on commercially harnessed optical fibers installed within optical power ground wire cables, taking into account different weather conditions. More specifically, we showed that changes caused by wind gusts significantly influence the differential group delay and the principal state of polarization in those optical fibers. For this, we experimentally measured a number of parameters to characterize light polarization properties. Measurements were carried out on C-band operated fiber-optic link formed by 111-km-long power ground wire cables and 88 spectral channels, with a test time step of 1 min during 12 consecutive days. Variations in differential group delay allowed for sensitive testing of environmental changes with measured maxims up to 10 ps under the worst wind conditions. Moreover, measured parameters were used in a numerical model to assess the quality of transmitted high-bit-rate optical signals as a function of wind conditions. The analysis revealed a negligible impact of wind on a 10 Gbps transmission, while substantial influence was noticed for higher bit rates up to 100 Gbps. These results show promises for efficient sensing of environmental changes and subsequent monitoring of the quality of recently used fiber-optic link infrastructures.

Vectorial dispersive shock waves on an incoherent landscape

We study numerically and experimentally the impact of temporal randomness on the formation of analog optical blast waves in nonlinear fiber optics. The principle of operation is based on a two-components nonlinear interaction occurring between a partially coherent probe wave co-propagating in a normally dispersive optical fiber together with an orthogonally polarized intense short pulse. The cross-polarized interaction induces a dual phase singularity in the probe profile which leads to the formation of two sharp fronts of opposite velocities. An optical blast wave is then generated and leads to an expanding rarefaction area surrounded by two dispersive shock waves which regularize the shock onto the probe landscape. Here, we focus our study on the impact of randomness in the shock formation. In particular, we show that the lack of coherence in the probe wave acts as a strong diffusive term, which is able to hamper or inhibit the shock formation. Our experimental observations are confirmed by numerical predictions based on a system of two incoherently coupled nonlinear Schrödinger Manakov equations.

Investigation of dispersion and nonlinear characteristics of liquid core optical fiber filled with olive oil

This paper introduces a prospective material for photonic laser applications. Different high purity samples of olive oil were subjected to a spectrophotometer to determine the absorption spectra. The transmission behavior of olive oil is about (44.28) % at a wavelength of 532 nm, while it is (62.94) % at 1064 nm. Then, the nonlinear optical properties represented by the nonlinear refractive index and nonlinear absorption coefficient are determined using a highly sensitive method known as the Z-scan technique. Z-Scan experiment was performed using 1064 nm CW Nd:YAG and 532 nm SHG Nd:YVO4 lasers. n2 = 3.99×10-6W/cm2 and beta = -0.0017 m/W for 1064nm wavelength and n2 = 2.45×10-7W/cm2 and beta =-7.26×10-4 m/W for 532nm wavelength. This paper gives simulation results for a liquid-core optical fiber (LCOF) filled with olive oil. The nonlinear propagation constant and group velocity dispersion (GVD) properties are estimated. The simulation of the generation of LCOF is also obtained. The calculations show that LOCF can provide huge nonlinear parameters and a large span of slow varying GVD characteristics in the visible and infrared region, which have potential applications in optical communications and nonlinear optics. The material is olive oil which is classified as an organic compound, having good nonlinear optical properties making it a potential candidate to be for photonic applications.

Effect of Fractional Profile-index on Nonlinearity and Dispersion in Single-Mode Optical Fibers

Effect of Fractional Profile-index on Nonlinearity and Dispersion in Single-Mode Optical Fibers

Compensation of Chromatic Dispersion and Nonlinear Phase Noise Using Iterative Soft Decision Feedback Equalizer for Coherent Optical FBMC/OQAM Systems

In this article, we propose an iterative soft decision feedback (ISDF) equalizer to compensate for the chromatic dispersion and nonlinear phase noise effects in 30-Gbaud coherent optical filter bank multicarrier with off-set quadrature amplitude modulation (FBMC/OQAM) system. Conventional optical FBMC/OQAM system usually uses a 1-tap zero-forcing equalizer per subcarrier to combat the inter-symbol interference (ISI) caused by the chromatic dispersion (CD) in optical fiber. However, residual ISI and inter-carrier interference (ICI) still remain in the system and have significant impact on the system performance. To overcome this problem, a new ISDF N-tap frequency sampling (FS) equalizer is proposed to jointly mitigate the residual ISI and ICI which permits a better trade-off between performance and complexity. Simulation results show that, the proposed technique is capable of suppressing the interference more effectively than using only 1-tap equalizer. The feedback branch of the proposed ISDF equalizer can be exploited further to compensate for the nonlinear effect of the optical fiber. With compensation of linear and nonlinear impairments the proposed technique acts as a backpropagation method for optical FBMC/OQAM system.

Linear and Nonlinear Fiber Propagation of Partially Coherent Fields Exhibiting Temporal Correlations

AbstractUsing an ultrafast photonic first‐order differentiator applied on a partially coherent field, the generation of two correlated temporal waveforms is reported and their correlation properties upon linear and nonlinear propagation along the two orthogonal polarization axes of a dispersive optical fiber are studied. Temporal correlations are maintained in linear propagation whereas Kerr nonlinearity generates anticorrelated temporal intensity patterns for both partially and uncorrelated fields. Experiments are in close agreement with the theoretical analysis.

ZnS Nanospheres for Optical Modulator in an Erbium‐Doped Fiber Laser

AbstractZinc sulfide (ZnS), which belongs to transition metal monochalcogenides, is a semiconductor material with wide direct band gap. It can potentially show some special applications (such as luminescence, phosphor, sensors, infrared window materials, photocatalysis) by changing the morphology, size, and crystal structure of semiconductor materials. However, ZnS nanospheres have not been studied as optical modulators until now. Herein, ZnS nanospheres are synthesized by the hydrothermal method and are used to realize optical modulators in an Er‐doped fiber laser. The evanescent field effect is utilized to incorporate the ZnS nanospheres on a tapered fiber. Furthermore, with the increase in pump power, the modulation interval gradually decreases to a minimum of 34.36 ns corresponding to the modulation frequency of 29.1 MHz, which is the highest modulation frequency to our knowledge in a ring cavity all‐fiber laser. These results demonstrate ZnS nanospheres together with the interaction of dispersion and nonlinearity in optical fibers can modulate the proposed lasers. This not only provides a new method for controlling the power and frequency of all optical modulators, but also marks an important step for ZnS materials in optics research and device applications.

Tuning of group delay with stimulated Raman scattering-induced dispersion in gas-filled optical fiber

We report the first demonstration of group delay tuning with stimulated Raman scattering-induced dispersion in a hydrogen-filled hollow-core optical fiber. A pump laser induces a sharp refractive index change near the S0(0) Raman transition of hydrogen molecules, enabling the control of the group velocity of signal pulses around the Stokes wavelength. Experiments with an 80-m-long hollow-core fiber filled with 2.5 bar hydrogen achieved continuous tuning of the pulse delay up to 1.42 ns by varying the Raman amplification from 0 to 10 dB. The tunable pulse delay is realized by changing the pump power as well as the hydrogen pressure. This work provides a new technique for controlling the pulse propagation in optical fibers with high flexibility.

Solitary Waves and Property Management of Nonlinear Dispersive and Flattened Optical Fiber

In this work, we establish the Conditions that must satisfy the characteristic coefficients of the nonlinear and flattened dispersive optical fiber so that certain classes of solitary waves propagate there with fewer fluctuations. Once the conditions are established, we determine the exact solutions as well as the corresponding nonlinear partial differential equations that govern the propagation dynamics in this transmission medium. The propagation of the solutions obtained is also tested. The method used to obtain the analytical solutions is based on the control of the properties of the Bogning implicit functions whereas the numerical simulations are made through the split-step method which is very adapted to simulate the propagation of the signals.

Vectorial dispersive shock waves on an incoherent landscape

We study the impact of temporal randomness on the formation of vectorial dispersive shock-waves that emerge due to the interaction of a partially coherent probe wave co-propagating together with an orthogonally polarized intense short pulse. Experiments carried out in a normally dispersive optical fiber demonstrate that the lack of coherence of the probe landscape acts as a strong diffusive term, which is able to hamper or inhibit the vectorial shock formation.

Optical fiber-based dispersion for spectral discrimination in fluorescence lifetime imaging systems.

.The excited state lifetime of a fluorophore together with its fluorescence emission spectrum provide information that can yield valuable insights into the nature of a fluorophore and its microenvironment. However, it is difficult to obtain both channels of information in a conventional scheme as detectors are typically configured either for spectral or lifetime detection. We present a fiber-based method to obtain spectral information from a multiphoton fluorescence lifetime imaging (FLIM) system. This is made possible using the time delay introduced in the fluorescence emission path by a dispersive optical fiber coupled to a detector operating in time-correlated single-photon counting mode. This add-on spectral implementation requires only a few simple modifications to any existing FLIM system and is considerably more cost-efficient compared to currently available spectral detectors.

Impact of fifth order dispersion on soliton solution for higher order NLS equation with variable coefficients

In this paper, the variable coefficient nonlinear Schrödinger equation with fifth order dispersion in the inhomogeneous optical fiber is investigated to study the impact of fifth order dispersion on attosecond soliton propagation. Based on the Darboux transformation method, soliton solution is constructed with modulated coefficients though Lax pair. We show that the coefficients of GVD and fifth order term are the main keys to control the amplitude, width and phase shift in the model. With the suitable choices of coefficients for the obtained soliton solution, some new types of soliton management through fifth order are presented for the first time. Especially, the influence of fifth order dispersion of the higher order NLS equations with and without modulated coefficients is discussed in detail. We will also highlight the impact of the studies on application in ocean engineering. Obtained results may be potentially useful in the soliton shaping and management in inhomogeneous fibers.

Optical coherence tomography using physical domain data compression to achieve MHz A-scan rates.

The three-dimensional volumetric imaging capability of optical coherence tomography (OCT) leads to the generation of large amounts of data, which necessitates high speed acquisition followed by high dimensional image processing and visualization. This signal acquisition and processing pipeline demands high A-scan rates on the front end, which has driven researchers to push A-scan acquisition rates into the MHz regime. To this end, the optical time-stretch approach uses a mode locked laser (MLL) source, dispersion in optical fiber, and a single analog-to-digital converter (ADC) to achieve multi-MHz A-scan rates. While enabling impressive performance this Nyquist sampling approach is ultimately constrained by the sampling rate and bandwidth of the ADC. Additionally such an approach generates massive amounts of data. Here we present a compressed sensing (CS) OCT system that uses a MLL, electro-optic modulation, and optical dispersion to implement data compression in the physical domain and rapidly acquire real-time compressed measurements of the OCT signals. Compression in the analog domain prior to digitization allows for the use of lower bandwidth ADCs, which reduces cost and decreases the required data capacity of the sampling interface. By leveraging a compressive A-scan optical sampling approach and the joint sparsity of C-scan data we demonstrate 14.4-MHz to 144-MHz A-scan acquisition speeds using a sub-Nyquist 1.44 Gsample/sec ADC sampling rate. Furthermore we evaluate the impact of data compression and resulting imaging speed on image quality.

Frequency domain signal and noise analysis of optoelectronic oscillators under the effects of modulator frequency chirping and fiber dispersion

The effects of the Mach–Zehnder modulator-induced frequency chirping and optical fiber dispersion on the signal transmission in a microwave photonic link (MWPL) have already been investigated. Here, a more general signal/noise transmission model for MWPLs is introduced. Then a new frequency domain approach utilizing the mentioned model is proposed for analyzing the combined effects of fiber delay line dispersion and modulator frequency chirping on the signal and noise performance of a single-loop optoelectronic oscillator (OEO). It is shown that the dispersion of the fiber delay line and the modulator chirp can largely affect the open-loop gain of the OEO. Consequently they affect the oscillation amplitude such that neglecting them may result in inappropriate adjustment of the small signal gain. Although dispersion of the fiber delay line is the main mechanism through which the laser frequency noise (LFN) contributes to the output phase noise, it is shown that dispersion can reduce the output phase noise due to the noise of the RF amplifier (RFA) up to about 30 dB. In addition, it is shown that a negative chirp results in about 0.5 dB extra reduction of the contribution of the RFA noise in the output phase noise, but for positive chirp values it results in about 15 dB deterioration of noise compared to the dispersion-only case. The chirp effect is negligible for the LFN-induced phase noise. The validity of the new approach is verified by comparing its results with those from other simulation approaches in the literature.

Centralized Fiber-Distributed Data Communication and Sensing Convergence System Based on Microwave Photonics

A unified data communication and radar sensing system towards millimeter-wave (mm-wave) applications with extended coverage is proposed and experimentally demonstrated. In the unified system, the transmission and reception of mm-wave signals are implemented by microwave photonics technologies, and the orthogonal frequency division multiplexing (OFDM) signal is employed for communications and radar sensing simultaneously. The superheterodyne optical carrier suppression (HeteroOCS) is used to up-convert the intermediate frequency (IF) OFDM signal to the mm-wave band in the central office (CO). The optical mm-wave signal is transmitted to the remote antenna units (RAUs) via optical fibers. The echo signal is received by the RAU which is remotely connected to the CO by an analog photonic link based on a polarization modulator (PolM). In the transmitter and receiver links, the chromatic dispersion of optical fibers is overcome by the HeteroOCS and the PolM, respectively. The baseband units (BBU) centralized in the CO is used to process the radar sensing signal. A pre-delayed trigger signal is proposed to overcome the fiber length limitation. A proof-of-concept experiment is performed. Two targets with distances of 1.64 m and 3.40 m are successfully detected separately. The communication function of the system is also verified. 1 m wireless transmission of 1.56 Gb/s data rate is achieved below the forward error correction limit.

Binary Darboux transformation and vector-soliton-pair interactions with the negatively coherent coupling in a weakly birefringent fiber

Soliton-based data transmission provides the hope of surmounting the limitations caused by the dispersion of optical fibers. In this letter, we investigate the coherently coupled nonlinear Schrödinger system with the negatively coherent coupling in a weakly birefringent fiber. With respect to the two interacting modes in the fiber, we construct a binary Darboux transformation with the zero seed solutions, which is different from the existing one, and analytically and graphically study the vector bright solitons and their interactions. Besides the vector degenerate and nondegenerate solitons, the vector soliton pairs are derived with the associated parameter conditions. Two interaction mechanisms between the two degenerate solitons, with the phase shifts or not, are used to explain the elastic and inelastic interactions between the soliton pairs and degenerate solitons. From the elastic interactions between the nondegenerate solitons and soliton pairs, we find that the amplitudes of the formers are changed and converted back to the initial shapes in two components. Elastic interactions between the two soliton pairs are exhibited as well.

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.

Transmission Performance Comparison of 16*100 Gbps Dense Wavelength Division Multiplexed Long Haul Optical Networks at Different Advance Modulation Formats under the Influence of Nonlinear Impairments

Abstract Higher spectral efficiency and data rate per channel are the most cost-effective approaches to meet the exponential demand of data traffic in optical fiber network communication system. In this paper, diverse modulation formats are analyzed for Dense Wavelength Division Multiplexed system at 100 Gbps * 16=1600 Gbps data rates. The performance analysis of proffered system for Non-Return to Zero, Return to Zero, Carrier- Suppressed Return to Zero and Duo binary RZ with duty cycle 0.5 to 0.7 ranges like modulation formats are considered to find optimum modulation format for a 100 Gbps bit rate per channel optical fiber transmission network system. The simulations are analyzed for different values of input power, length of fiber, nonlinear refractive index, nonlinear dispersion and nonlinear effective area for all above mentioned modulation formats with spacing 100 to 250 GHz. to evaluate the effect of modulation format Fiber Bragg Gratting, optical fiber amplifier and Dispersion Compensation Fiber dispersion compensation techniques are enacted on this proposed optical network system.

Simulation Study of Waveguide and Chromatic Dispersion of a Single Mode Step Index Optical Fiber

Simulation Study of Waveguide and Chromatic Dispersion of a Single Mode Step Index Optical Fiber