Analog CMOS Circuit Design and Characterization for Optical Coherence Tomography Signal Processing

This study aimed to evaluate a novel real-time rotational optical coherence tomography (OCT) imaging system (OCTIS) with a fiber-optic probe to look at endometrium and to correlate the OCTIS images with standard histology. OCT could obtain real-time images resembling histological examination. With recent development of customized probes, it allows OCT to be used in the field of gynecology.This is a pilot, prospective, ex-vivo and observational study. Women underwent hysterectomy for various gynecological conditions were recruited and OCTIS images were obtained from endometrium of 15 fresh uterus specimens immediately after hysterectomy. The excised uterus was cut open and OCTIS imaging was obtained. The scanned region of endometrium was excised for histological examination and OCTIS images were precisely compared to corresponding histological images and ultrasound images. Blinded qualitative analysis on OCTIS images was performed by 2 assessors to determine inter-rating reliability on the histopathological diagnosis.Epithelium, glands, cysts, and stroma of endometrium were clearly seen by the OCTIS. Different phases of menstrual cycle of normal endometrium could be differentiated and pathological condition such as hyperplastic and dysplasic endometrium, which corresponded well with histological findings, could be identified. The inter-rater reliability between assessors on overall OCTIS endometrium and neoplastic OCTIS endometrium was moderate (Kendall τb of 0.58) and substantial (Kendall τb of 0.76), respectively.OCTIS can provide real-time, high-resolution and rotational imaging modality to view endometrial structure with high consistency with histological examination and satisfactory agreement between observers. It has a great potential to be developed in the clinical use of endometrial assessment for gynecological applications.

To construct swept source optical coherence tomography (SS-OCT) imaging system for root canal endoscopy, and to evaluate the accuracy of diagnosing artificial root fractures. An ultra-high-speed (40 kHz) swept laser source was developed based on the piezoelectric tuning filter and the Fourier domain mode locking (FDML) swept laser technology (patent number: 200620135940.2). Ultra-miniature gradient index lens technology (patent number: 201320241218.7) was used to create a thin endoscopic probe with a diameter of 0.86 mm for real-time image transmission. The SS-OCT light source had a wavelength of 1 310 nm and a bandwidth of 100 nm. The axial and transverse image resolutions were 15 μm and 25 μm, respectively. Artificial fractures were created on human mandibular premolars with single root and the premolar roots were prepared to 41 horizontal sections (1 mm thick). 27 root sections with fractures (width: 52-284 μm) and 14 the sections without fractures were observed under an optical stereomicroscope with a cold light source as the gold standard. The horizontal root sections were scanned by self-developed SS-OCT imaging system for root canal endoscopy with a central wavelength of 1 310 nm and bandwidth of 100 nm. The data were reconstructed with 30 μm thick slices at an interval of 30 μm. Two observers, a radiologist and an endodontist, were trained and independently evaluated all the reconstructed images blindly. The diagnostic performance of SS-OCT imaging system was calculated, and statistical analysis was performed. SS-OCT root canal endoscopic imaging system composed of high-speed swept laser source, fiber coupler, endoscopic probe, reference arm and differential detector. Root sections could be scanned by SS-OCT and imaged in realtime at a depth of 1 to 2 mm. The kappa value for interobserver agreement was 0.792, and the intraobserver agreement was 1.000 and 0.709 for two observers respectively. All of 27 fractured root sections and 12 of 14 root sections without fractures were accurately diagnosed while 2 unfractured root sections were misdiagnosed. The sensitivity was 1.000 and the specificity was 0.857 for diagnosis of artificial root fractures by SS-OCT. The positive predictive value (PPV), negative predictive value (NPV) and the overall accuracy rate were 0.931, 1.000 and 0.951 respectively. The swept source optical coherence tomography imaging system for root canal endoscopy is a promising imaging method for observing root fractures．.

Optical coherence tomography (OCT) imaging systems can now produce MB=s to GB=s data streams. We present a complete solution for signal acquisition up to 4 GS/s and on-board field programmable gate array (FPGA) OCT processing matching the high acquisition speed. On-board OCT signal processing virtually eliminates the downstream signal processing and data throughput bottleneck. Complex filtering allows for windowing and dispersion compensation. Data is zero-padded when the number of samples is not a power of 2. The Fast Fourier Transform (FFT) engine can match the maximum acquisition speed when performing 4096-point FFTs. Output data can be linear amplitude or logarithmic and represented on several floating-point or integer precisions. This hardware solution comes with dedicated software and software development kit.

Summary form only given. The author discusses developments in optical signal processing and highlights the many ways in which the technology of optical and electronic signal processing is converging.

This work presents an integrated framework combining optical signal processing and VLSI system design for the performance evaluation and optimization of 5G waveform candidates under different modulation schemes. The analysis focuses on four major waveforms – OFDM, FBMC, NOMA, and OTFS – and examines their performance based on bit error rate (BER), peak-to-average power ratio (PAPR), and power spectral density (PSD) metrics. Simulation results demonstrate that OTFS outperforms the other waveforms, achieving a BER of 10 −3 at an SNR range of 7–10 dB, corresponding to an SNR gain of up to 8 dB over OFDM. Furthermore, OTFS exhibits a PAPR reduction of approximately 3.5 dB and the lowest out-of-band emissions with a PSD of around −310 dBW/MHz, indicating superior spectral efficiency and reduced interference. These characteristics make OTFS a promising waveform for high-mobility, high-capacity 5G and future 6G communication environments. The integration of optical signal processing techniques enhances system bandwidth and energy efficiency, while VLSI-based architectures support low-latency, high-throughput implementation. Future advancements will explore optical-VLSI codesign and machine learning–assisted frameworks for real-time adaptive processing, improving scalability, power optimization, and intelligent signal handling in next-generation wireless and optical communication systems.

Modeling and design of CMOS analog circuits through hierarchical abstraction

A frequency swept source optical coherence tomography (OCT) imaging system is proposed. The frequency swept source used in the system is a Fourier-domain mode-locked (FDML) laser which has a narrow instantaneous linewidth due to the nonlinear spectrum narrowing effect generated by the nonlinear semiconductor optical amplifier (SOA) used in the FDML laser ring cavity. Therefore, the OCT imaging system has the ability to achieve a large imaging depth. The concept is verified in the experiment, which demonstrates a clear two-dimensional target image and a large imaging depth up to 14 mm.

In this paper, we consider a class of N-th order lattice filter with gains as an extension to the traditional lattice filter structures and develop analysis and synthesis of such filters. In the analysis-synthesis parts, we present recursive methods to derive the input-output transfer function of the filter in terms of parameters of the lattice structure such as the time delay, gains, transmission and reflection coefficients and vice versa. Stability of the filter is analyzed and an algorithm to test the stability is proposed. This class of MIMO lattice filters with adjustable gains models integrated photonic devices under development in our labs for optical communication and high speed signal processing applications. Our signal processing approach to characterizing this type of lattice structures can also be used in filter realization by VLSI, FPGA, or programmable processors for acoustic or speech applications

Besides optical fibers are excellent communication media, they are attractive for real time, high speed signal processing on the ground of that they possess very nice merits such as low-loss, large bandwidth-delay product, light weight, and immunity to electromagnetical interferences. A typical optical fiber signal processing device is composed of light sources, delay lines, attenuators, directional couplers, and photodetectors. Many various functions such as frequency filtering, convolution, pulse compression, high speed pulse generation, encoding, and decoding for the incoherent optical fiber signal processing devices are reported in the literature. Recently the lattice optical fiber structures are investigated intensively due to convenience for mathematical formulation and implementation. Although the optical fiber signal processing devices have many attractive features, they have inherent constraints owing to positive system properties, i.e. nonnegative quantities of signals(optical intensities), attenuations, and coupling coefficients. The constraints of the finite impulse response (FIR) optical fiber filters were presented. In this paper, we establish the constraints of the infinite impulse response (IIR) optical fiber filters by means of investigating the possibility of designing the filters with the desirable properties such as maximally flat or equiripple responses. In addition, the characteristics and design principles of the optical fiber filters can be clearly understood from the processes. The mathematical derivation makes use of the state-variable analysis technique to approach this problem. This technology is suitable to describe for both cases: FIR and IIR. Hence the confirmed constraints can be directly applied to the FIR case.

A non-contact, dual-modal imaging apparatus is introduced which will be used to obtain the Metabolic Rate of Oxygen (mRO2) in the live murine eye, based on the blood flow rate and blood Oxygen Saturation (sO2) measurements. The apparatus is comprised of both Photoacoustic Remote Sensing (PARS) and Swept-Source Optical Coherence Tomography (SS-OCT) systems, operating synchronously. A phantom model will be imaged using the proposed system to validate the accuracy of the blood flow and sO2 measurements. To the best of our knowledge, this work would report for the first time, non-contact, in-vivo measurement of the mRO2 in the ophthalmic tissues.

To describe a new method to treat severe anterior capsule contraction using a femtosecond laser anterior capsulotomy. Case report. A 48-year-old woman with a history of myotonic dystrophy experienced a severe contraction of the anterior capsule following an uneventful phacoemulsification cataract surgery with a hydrophilic acrylic intraocular lens implanted in the capsular bag. A femtosecond laser anterior capsulotomy was performed using a non-applanating fluid-filled interface. The spectral-domain optical coherence tomography imaging system associated with the laser enabled precise centration and location of the capsulotomy with a posterior cut located between the anterior surface of the intraocular lens and the anterior capsule inner surface. The free-floating capsulotomy was easily removed after the laser procedure, and 8 days postoperatively visual acuity recovered and myopic shift regressed with an intraocular lens centered in the capsular bag. Femtosecond laser assisted by a high-resolution imaging system appears to be a safe and efficient treatment for severe anterior capsule contraction.

偏振敏感光学相干层析成像系统中样品光偏振对样品双折射相位延迟测量的影响

In this paper, an automated feature selection (FS) method is presented to optimize machine learning (ML) models' performances, enhancing early keratoconus screening. A total of 448 parameters were analyzed from a dataset comprising 3162 observations sourced from the swept source optical coherence tomography imaging system developed by the Chinese Academy of Sciences Institute of Automation (SS-1000 CASIA OCT) and electronic health records (EHR). To identify the most relevant features, the analysis of variance (ANOVA) method was used in this study. The performance of three classifiers namely K-Nearest Neighbors (KNN), Support Vector Machine (SVM), and Artificial Neural Networks (ANN) was evaluated, yielding classification accuracies of 96.79% and 96.68% for KNN, 98.95% and 97.08% for SVM, and 95.64% and 95.62% for ANN when distinguishing between 2 and 4 keratoconus classes, respectively. The results show that selecting 50 features can significantly improve the performance of the model while reducing the computation time. The automated feature selection method can also assist ophthalmologists in better understanding the links between various ocular characteristics and keratoconus, potentially leading to advances in early diagnosis, risk prediction, and clinical management of this condition.

The SRY-related HMG-box 5 (SOX5) gene encodes a member of the SOX family of transcription factors. Recently, genome-wide association studies have implicated SOX5 as a candidate gene for susceptibility to four cardiac-related endophenotypes: higher resting heart rate (HR), the electrocardiographic PR interval, atrial fibrillation and left ventricular mass. We have determined that human SOX5 has a highly conserved Drosophila ortholog, Sox102F, and have employed transgenic Drosophila models to quantitatively measure cardiac function in adult flies. For this purpose, we have developed a high-speed and ultrahigh-resolution optical coherence tomography imaging system, which enables rapid cross-sectional imaging of the heart tube over various cardiac cycles for the measurement of cardiac structural and dynamical parameters such as HR, dimensions and areas of heart chambers, cardiac wall thickness and wall velocities. We have found that the silencing of Sox102F resulted in a significant decrease in HR, heart chamber size and cardiac wall velocities, and a significant increase in cardiac wall thickness that was accompanied by disrupted myofibril structure in adult flies. In addition, the silencing of Sox102F in the wing led to increased L2, L3 and wing marginal veins and increased and disorganized expression of wingless, the central component of the Wnt signaling pathway. Collectively, the silencing of Sox102F resulted in severe cardiac dysfunction and structural defects with disrupted Wnt signaling transduction in flies. This implicates an important functional role for SOX5 in heart and suggests that the alterations in SOX5 levels may contribute to the pathogenesis of multiple cardiac diseases or traits.

Optical interferometry provides high-precision displacement and angle measurement solutions for a wide range of cutting-edge industrial applications. One of the key factors to achieve such precision lies in highly accurate optical encoder signal processing, as well as the calibration and compensation techniques customized for specific measurement principles. Optical interferometric techniques, including laser interferometry and grating interferometry, are usually classified into homodyne and heterodyne systems according to their working principles. In homodyne interferometry, the displacement is determined by analyzing the phase variation of amplitude-modulated signals, and common demodulation methods include error calibration methods and ellipse parameter estimation methods. Heterodyne interferometry obtains displacement information through the phase variation of beat-frequency signals generated by the interference of two light beams with shifted frequencies, and its demodulation techniques include pulse-counting methods, quadrature phase-locked methods, and Kalman filtering. This paper comprehensively reviews the widely used signal processing techniques in optical interferometric measurements over the past two decades and conducts a comparative analysis based on the characteristics of different methods to highlight their respective advantages and limitations. Finally, the hardware platforms commonly used for optical interference signal processing are introduced.