Dispersion Compensation Methods Research Articles

Energy-efficient dispersion compensation for digital micromirror device

Due to the wave nature of light, the diffraction pattern generated by an optical device is sensitive to the shift of wavelength. This fact significantly compromises the digital micromirror device (DMD) in applications, such as full-color holographic display and multi-color fluorescence microscopy. The existing dispersion compensation techniques for DMD involve adding diffractive elements, which causes a large amount of waste of optical energy. Here, we propose an energy-efficient dispersion compensation method, based on a dispersive prism, for DMD. This method simulates the diffraction pattern of the optical fields reflected from the DMD with an angular spectrum model. According to the simulation, a prism and a set of optical components are introduced to compensate for the angular dispersion of DMD-modulated optical fields. In the experiment, our method reduced the angular dispersion, between the 532 nm and 660 nm light beams, by a factor of ∼8.5.

Optimizing High Data Rate Up to 2.5 Tbps Transmission using 64-Channel DWDM System with DCF and NRZ Modulation

Objectives: This study aims to enhance and optimize a modern communication system for high data rate transmission using Dense Wavelength Division Multiplexing (DWDM). The objectives include employing a 64-channel DWDM system, implementing different data speeds, and utilizing a dispersion compensation method. Methods: To achieve the objectives, we simulate and analyze the effects of Dispersion Compensation Fiber (DCF) in a DWDM system with 64 channels. The system employs Non-Return-to-Zero (NRZ) modulation format at varied bit rates and multiple energy levels. We propose a method for achieving data rates of 10 to 40 Gbps using NRZ modulation and Erbium-Doped Fiber Amplifier (EDFA) over a single-mode fiber transmission distance of 40 to 160 km, along with a dispersion compensation fiber of 8 to 32 km (DCF). The performance of the developed model is evaluated based on Quality Factor, Bit Error Rate (BER), Eye Height, and Threshold. These metrics are measured at two input energy levels from an optical power source, covering a communication capacity ranging from 0.625 Tbps to 2.5 Tbps. Findings: Through the simulations and analyses, we uncover the impact of dispersion and demonstrate the effectiveness of the proposed method in compensating for dispersion effects. Performance analysis of two different input transmitter power levels, -10 dBm is more efficient compared to 0 dBm input transmitter power in terms of bit error rate and quality factor. Novelty: This study presents a novel approach to improving modern communication systems by utilizing DWDM with a dispersion compensation method. The use of a 64-channel DWDM system, combined with the proposed NRZ modulation technique and dispersion compensation fiber, provides an efficient solution for achieving high data rates over long transmission distances while minimizing the effects of dispersion. The findings contribute to the advancement of communication systems for high data rate transmission. Keywords Dispersion effect, Bit Error Rate, Q-factor, Optisystem software, Erbium doped fiber amplifier

Ultra-broadband magneto-optical isolators and circulators on a silicon nitride photonics platform

Broadband optical isolators and circulators are highly desirable for wavelength-division multiplexing, light detection, and ranging systems. However, the silicon-integrated optical isolators and circulators reported so far have a limited isolation bandwidth of only several nanometers, due to waveguide and material dispersion. In this paper, we report the development of broadband magneto-optical isolators on silicon nitride waveguides. We proposed a general method of dispersion compensation to achieve a constant phase difference between reciprocal and nonreciprocal phase shifts in a Mach–Zehnder interferometer over a wide frequency range. This method enabled a theoretical 30 dB isolation/circulation bandwidth of more than 240 nm, which covers the S, C, L, and U bands. The fabricated devices showed a maximum isolation ratio of 28 dB, crosstalk of −28dB, high 20-dB isolation bandwidth of 29 nm (3.48 THz), and a relatively low loss of 2.7 dB in the wavelength range of 1520–1610 nm. By further heating the reciprocal phase shifter based on the thermo-optic effect, the experimental 20 dB isolation bandwidth of the device increased to 90 nm (11.03 THz). This method has also been applied to the design of broadband, low-loss isolators, and O/C dual-band isolators/circulators. Our work experimentally demonstrated broadband-integrated optical isolators and circulators on silicon, paving the way for their use in optical communication, data communication, and LiDAR applications.

Dual-Parameter Correction Method for Dispersion Compensation in Polarized Low-Coherence Interferometry with High Accuracy

Dual-Parameter Correction Method for Dispersion Compensation in Polarized Low-Coherence Interferometry with High Accuracy

Dispersion Compensation Method for Accuracy Improvement of Optical Frequency Domain Polarimetry

Dispersion Compensation Method for Accuracy Improvement of Optical Frequency Domain Polarimetry

Distributed Chromatic Dispersion Compensation Method Based on Mismatch Factor for High Resolution OFDR

Distributed Chromatic Dispersion Compensation Method Based on Mismatch Factor for High Resolution OFDR

Evaluation of impairment mitigations for optical fiber communications using dispersion compensation techniques

This study discusses dispersion as a key issue influencing the performance of optical fiber communication technology. Poor bit rate, pulse broadening, and transmission distance restrictions are the outcomes. The dispersion correction method frequently employs fiber with dispersion compensation (DCF) and fiber Bragg grating (FBG). A model transmission system has been analyzed in light of numerous parameters using the Opti System 20.0 simulator. The DCF and FBG dispersion compensation methods are two that have been proposed. The Q-factor, BER, and eye height measured at the receiver end will be utilized as three metrics to describe the results of the two dispersion-correcting strategies. Additionally, the system's transmission performance will vary as a result of varied compensatory approaches. The DCF approach does not significantly increase system performance compared to the compensation technique. In addition, the properties of the optical fiber used for transmission in the system affect the characteristics of the FBG and the fiber used for the compensating process. It has been demonstrated that post-compensation, followed by symmetrical compensation, produces the best result. In addition, the transmission performance of the system with different compensation methods will be different, and the compensation technique will improve the system performance much better than the DCF technique. Moreover, the characteristics of the FBG and the fiber that is used for the compensation process depend on the characteristics of the optical fiber that is used for the transmission in system. It is shown that the symmetrical compensation performance is the best. Due to the nonlinear nature of propagation, system performance depends on power levels, followed by post-compensation.

A Generic and Effective System Dispersion Compensation Method: Development and Validation in Visible-Light OCT

Compared with optical coherence tomography (OCT) in the near-infrared domain, the visible-light OCT (vis-OCT) system affords a higher axial resolution for discerning subtle pathological changes associated with early diseases. However, the significant material dispersion at the visible-light range leads to a severe problem for dispersion management in vis-OCT systems, which results in a compromised axial resolution. While dispersion compensators (such as prism pairs) are commonly used, a digital method is still highly desirable and has been widely used to compensate for the residual dispersion imbalance between the reference and sample arms in an OCT system. In this paper, we develop a generic approach to effectively compensate for the system dispersion, especially the higher-order dispersion in the vis-OCT system, by using a single arbitrary measurement of the mirror-reflection (SAMMR) method and its resulting phase information. Compared with the previous methods, including the method based on the Taylor series iterative fitting and differential method, the proposed method does not need to extract the dispersion coefficients or use the metric functions and affords a better performance for axial resolution and the signal-to-noise ratio in vis-OCT systems. Its effectiveness is further validated in an OCT system operating in the near-infrared domain.

Physical compensation method for dispersion of multiple materials in swept source optical coherence tomography.

An ophthalmic swept source-optical coherence tomography (SS-OCT) system based on a high-speed scanning laser at 1060 nm with a scanning rate of 100 KHz is constructed. Since the sample arm of the interferometer is comprised of multiple glass materials, the ensuing dispersion severely degrades imaging quality. In this article, second-order dispersion simulation analysis for various materials was performed first, and dispersion equilibrium was implemented utilizing physical compensation methods. After dispersion compensation, an imaging depth in air of 4.013 mm was achieved in model eye experiments, and signal-to-noise ratio was enhanced by 11.6%, with a value of 53.8 dB. In vivo imaging of the human retina was performed to demonstrate structurally distinguishable retinal images, characterized by an axial resolution improvement of 19.8%, with a value of 7.7 μm close to the theoretical value of 7.5 μm. The proposed physical dispersion compensation method enhances imaging performance in SS-OCT systems, enabling visualization of several low scattering mediums.

Accurate Thickness Measurement Based on Dispersion Compensation via Terahertz Time-Domain Spectroscopy

Terahertz time-domain spectroscopy (THz-TDS) has shown significant potential in thickness detection. The time-of-flight (TOF) method is most widely used for judgment. However, the method only refers to peak information, and waveform information, such as deformation, is simply ignored. Consequently, errors are introduced when testing samples with high dispersion and large absorptive properties. As a result, the signals are broadened, and the peaks become smooth or even disappear, which makes the TOF method fail. In this article, we propose a dispersion compensation (DC) algorithm to solve the above problems. Thickness can be accurately determined by nondispersive signals in the spatial domain. Amplitude compensation is used for materials with large absorption. The DC algorithm’s error is less than 1% of the TOF algorithm’s error in simulations. While measuring LiNbO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{3}$</tex-math> </inline-formula> and water film, errors are, respectively, reduced by 96.24% and 50% compared with using the TOF method, and corresponding deviations are 0.2% and 1.6% compared with the reference thickness. Moreover, the DC algorithm is noniterative, stable, and requires much less calculations than the fitting method. The DC method drastically improves the accuracy by overcoming inherent drawbacks of the TOF method. It can be applied in fields such as nondestructive testing and in-line quality control because of noncontact and real-time advantages.

Dispersion compensation of Lamb waves based on a convolutional auto-encoder

Lamb wave-based detection has become a promising technique for structural health monitoring in plate-like structures. However, the dispersion effect of Lamb waves makes the wave packets elongated, which degrades the resolution for damage identification. Hence, it is necessary to develop effective methods for the dispersion removal of Lamb waves. Recently, deep learning has drawn much attention for Lamb wave detection due to its powerful feature extraction capability. Most current deep learning models are developed directly for damage classification or location estimation tasks on the Lamb wave signals, rather than signal processing for further manipulation. Therefore, in this paper, a novel approach based on a convolutional auto-encoder is proposed for the dispersion compensation of Lamb waves. The convolutional auto-encoder model is utilized to construct the mapping relationship between the dispersive signal and the time of flight of the wave packet. The dispersion compensated signal is reconstructed by combining the estimated time of flight from the network with the waveform of the excitation signal. Numerical and experimental validations on aluminum and composite plates are implemented to verify the effectiveness of the proposed method. Compared with conventional methods for dispersion compensation, the results demonstrate that our proposed method not only separates the overlapped wave packets but also enables dispersion compensation of multimodal and multi-packet Lamb wave signals. In addition, this method is still applicable in the case of inaccurate dispersion data due to the generalizability of the data-driven model.

COMPARING DISPERSION COMPENSATION METHODS FOR 120 GB/S OPTICAL TRANSMISSION: PRE, POST, AND SYMMETRICAL SCHEMES

One of the major factors that limit the performance of an optical fiber communication system isdispersion. In order to get a high transmission range with high data rates, techniques must be in place to compensate for the dispersion caused by fiber nonlinearity. Dispersion Compensating Fiber (DCF) and Fiber Bragg Grating (FBG) are the trending dispersion compensation techniques in optical fiber communication. The use of DCF and FBG as a method of dispersion compensation can notably enhance the overall performance of the system. Broadening is a function of distance as well as the Dispersion parameter (D). The dispersion parameter is given in ps/nm/km and changes from fiber to fiber and also is a function of wavelength. In this paper, we investigate pre-, post-, and symmetrical compensating schemes in three different compensating models: DCF, FBG, and DCF cascaded to FBG. The system performance was evaluated in terms of Q-factor and Bit Error Rate (BER) for one optical channel communication system at 120 Gbps Return to Zero (RZ) signal launched over Single-Mode Fiber (SMF) of 100 km by using OptiSystem 7.0 software.

57-fs, Er-doped all-fiber all-polarization-maintaining amplifier based on a hybrid DCF/FBG scheme for dispersion compensation

In this paper we experimentally demonstrate a femtosecond all-polarization- maintaining laser amplifier in an all-fiber scheme, which consists of a mode-locked oscillator and a two-stage amplifier. A hybrid method of dispersion compensation is proposed based on a dispersion compensation fiber and two fiber Bragg gratings with different group velocity dispersion. The output pulse from the amplifier is 57 fs with average power of 150 mW and repetition rate of 60 MHz, corresponding to peak power of 38.6 kW. By evaluation of pulse shaping, one third of group velocity dispersion in the amplifier was compensated by the pair of gratings, and the remained amount compensated by the dispersion compensation fiber.

Comparison of pre and post-dispersion compensation schemes with RZ, NRZ and Gaussian modulations for 10 GBPS and 40 GBPS transmission rates / Comparação de esquemas de compensação pré e pós-dispersão com modulações RZ, NRZ e Gaussina para as taxas de transmissão de 10 GBPS e 40 GBPS

In this paper, we investigate two dispersion compensation methods: post-compensation, and pre-compensation for transmission rates from 10Gbps to 40Gbps with return to zero (RZ), non-return to zero (NRZ) and Guassian modulations using single fiber mode-fiber (SMF) and dispersion compensating fiber (DCF). The influence of the DCF compensator dispersion with different transmission rates was studied in order to evaluate the performance of the proposed systems. The simulation results were validated through the analysis of the quality factor (Q-factor) and the bit error rate (BER), where it was verified that the post-compensation system with Gaussian modulation offered better performance results in function of the transmission rate variation.

Depth-resolved dispersion compensation method for optical coherence tomography imaging based on rectangular window function optimization

In the optical coherence tomography system, the mismatch in dispersion between the two interference arms will reduce the axial resolution of the system. Therefore, dispersion compensation is required. However, the current depth-resolved dispersion compensation method uses a fixed window function to extract signals at different depths, which has phase calculation error and reduces the accuracy of dispersion compensation. In this paper, we optimized the rectangular window function for the signal interception. According to the functional relationship between the phase and the wave number in the presence of dispersion, the second-order fit to the obtained phase is performed and the standard error of the fit result is used as the criterion. The optimized rectangular window is used to intercept the signal and perform FFT, thereby effectively reducing the phase error caused by the window function. And we accurately extracted the dispersion coefficients of samples to improve the accuracy of dispersion compensation.

Dispersion compensation for spectral domain optical coherence tomography by time-frequency analysis and iterative optimization

We report a new numeric dispersion compensation method for the device’s dispersion mismatch in a spectral-domain optical coherence tomography (SD-OCT) for imaging the iridocorneal angle of human cadaver eyes. The dispersion compensation term is calculated by an automated iterative process that minimizes the wavenumber-dependent variance of the ridge extracted from the spatial-spectral distribution of a mirror’s spectral interferogram using short-time Fourier transform (STFT). Our method can extract different amounts of dispersion robustly, and the algorithm can work in a wide range of combinations of window sizes and overlaps when using an STFT. Comparable point spread functions (PSFs) are shown to a traditional polynomial fitting method. Lastly, we verified that our imaging system is able to visualize the iridocorneal angle details, such as trabecular meshwork (TM), Schlemm’s canal (SC), and collector channels (CCs), which are important ocular outflow structures associated with glaucoma management.

Broadband angular dispersion compensation for digital micromirror devices.

In this Letter, we present a compact broadband angular dispersion compensation method for digital micromirror devices (DMDs) and ultrashort pulse lasers, which effectively extends the conventional single-wavelength compensation design to a wide wavelength range of 300 nm. First, a parametric model was developed for the dispersion compensation unit, consisting of a transmission grating and a 4f telescope sub-unit, to guide the selection of components and parameter optimization for broadband applications. In the experiments, we designed a single slit-based metrology system to measure and quantify the compensated angular dispersion of a Ti:sapphire femtosecond laser with a pulse width of 75 fs. The results indicate that our method can reduce the angular dispersion to 0.04°, i.e., pulse widening less than 20 fs, over a wavelength range of 750-1050 nm. To demonstrate this, the DMD system was used as a multi-wavelength beam shaper to reconstruct a wavefront that contains the "CUHK" pattern and the results confirmed its ability to provide effective broadband angular dispersion compensation. This means the DMD can be used in different applications that employ a broadband light source, e.g., wavelength tunable femtosecond laser, attosecond laser, supercontinuum laser, and multi-color LED.

Use of double-grating Offner stretcher for dispersion control in petawatt level optical parametric chirped pulse amplification systems

The aberration-free characteristic endows the double-grating Offner stretcher with the advantages of good beam quality and perfect-dispersion-match with conjugated Treacy compressor, and therefore makes it an ideal pulse stretcher for optical parametric chirped pulse amplification (OPCPA) systems featuring with low material dispersion. We numerically and experimentally demonstrate the feasibility of dispersion control in OPCPA systems by the use of double-grating Offner stretcher. The numerical results indicate that near Fourier-transform-limited (FTL) pulses can be realized in the double-grating Offner stretcher based petawatt (PW) level broadband OPCPA systems. Moreover, in a proof-of-principle experiment, amplified pulses with ∼210 nm spectral bandwidth and ∼3 ns chirped pulse duration are also compressed to near FTL pulse duration of 15.4 fs just by cooperating a double-grating Offner stretcher with a Treacy compressor. To our knowledge, it is the first time to realize near FTL compression of laser pulses with such a broadband spectrum and such a large chirped pulse duration simultaneously, while without using any extra dispersion compensation methods.

Single A-Line Method for Fast Sample-Structure-Nondependent Dispersion Compensation of FD-OCT

Here we proposed a single A-line sample-structure-nondependent (SSNd) dispersion detection and compensation method for Fourier-domain optical coherence tomography (FD-OCT), without need for acquiring and processing B-scan data. A new FD-OCT dispersion mismatch index, based on the line slope of the bright line in the A-line spectrogram, has been presented in the proposed method. With the new dispersion mismatch index, the proposed single A-line method can fast and visually detect the dispersion mismatch states of FD-OCT setup and perform the SSNd dispersion compensation, just using a single A-line. Experimental results of multiple samples demonstrated the advantages and convenience of the proposed method, and also proved that the proposed method can be used to analyze the relation of OCT imaging and optical path difference between the sample and reference arms.

Efficient method for the compensation of dispersion mismatch in the frequency-scanning interferometry

Absolute distance measurements could be achieved by the technique of frequency scanning interferometry (FSI), which could provide a micron-level accuracy over several tens of meters. However, as the scanning range and distance increasing, the measurement accuracy and resolution would be seriously influenced by the dispersion mismatch effect, which is mainly caused by the dispersion difference between optical fiber and air. A dispersion compensation method was proposed in this paper, and the mismatch effect would be suppressed effectively without complicated calculations for each single measurement. The chirp in resampling clock would be corrected with a pre-calibration procedure, and the compensation factor is demonstrated for different distances. A calibration method of dispersion compensation factor is also proposed, and the linear regression residual is employed as the criterion. Then, the compensation method is evaluated by experiments with different spatial distances and scanning ranges. Finally, a 60-m experiment is carried out for accuracy comparison, and the measurement accuracy is better than 15 µm by comparing with commercial interferometers.