The demand for higher speed at a lesser transmission cost per bit resulted in growth of optical networks with improved spectral efficiency even at narrower channel spacing. Incorporation of multilevel modulation formats in DWDM system led to the exploration of the 25 GHz channel grid, popularly known as Ultra Dense Wavelength Division Multiplexed (UDWDM) systems, opening new research frontiers. At such channel spacing's, non-linear optical effects impose severe system impairments and hence robust modulation schemes are currently being investigated. This paper presents a simulative model to implement and analyze alternative polarized DQPSK modulated UDWDM system to evaluate its resilience to XPM and fiber nonlinearity. An UDWDM system supporting 32 channels, each operating at 40 Gbps and spaced at 25 GHz is studied numerically for long-haul optical communication system using OptiSystem simulator to estimate OSNR penalties to mitigate XPM effects. The major detrimental factors encountered in link design have been estimated to evaluate the system performance in terms of Q value for different number of channels and with varied input power. The analysis reports acceptable performance for DQPSK format up to a link distance of 1500 Km and also claims a better tolerance to dispersion and nonlinearities at higher input power levels.

/pdf/link-optimization-and-performance-analysis-of-a-40-gbps-br154ndxtc.pdf

Link Optimization and Performance Analysis of a 40 Gbps DQPSK Modulated Ultra DWDM System with 32 Orthogonally Polarized channels

The rolling bearing is an important part of rotary machineries and the health state monitoring is currently a hot research topic. There are four typical failure modes of a rolling bearing: the inner race failure, the outer race failure, the rolling element failure and the support frame failure. Based on the principle of the coherent demodulation, a new method for rolling bearing fault diagnosis is proposed in this work. This method establishes a coherent demodulator simulation model which is usually adopted in the field of radio communications. The proposed method first demodulates the vibration signal with coherent demodulation principle. Then, the characteristic frequencies related the different failures modes are extracted to obtain the fault characteristic amplitudes, to diagnose the ongoing failure mode. The bearing fault data from the Case Western Reserve University Bearing Test Center is taken as an example to verify and analyze the effectiveness of the proposed method. The results show that this method can accurately diagnose the corresponding failure mode with different locations and sizes.

/pdf/rolling-bearing-fault-diagnosis-based-on-the-coherent-3rmlhqac2x.pdf

Rolling Bearing Fault Diagnosis Based on the Coherent Demodulation Model

Dense Wavelength Division multiplexing (DWDM) is a promising technology that has ability to provide potentially unlimited transmission capacity to meet the growing demand of bandwidth in optical fiber communication systems. In this paper, we have proposed a dual polarized 128-QAM DWDM communication system consisting of 8 channels. The data rate of each channel is set to 90 Gbits/sec and simulations are carried out by using single mode fiber (SMF) of 80 km. Dispersion compensation fiber (DCF) of appropriate length is used for dispersion compensation. Linear impairments are controlled by using appropriate optical amplifier in addition to the DCF. The model is tested by varying the data rates, length of SMF and filter gain. Lumped and distributed configurations of amplifiers are used to find the optimal results. Comparison of Gaussian and Bessel optical filters is also made in the proposed system. The results are presented by using constellation diagrams, EVM and BER plots in licensed version of Optisystem v.14.

128-QAM x 8 Channels DWDM Communication for Optical Fiber Networks

In massive multiple-input multiple-output (MIMO) systems, the large number of high-resolution analog-to-digital converters (ADCs) lead to high hardware cost and power consumption. In this work, the uplink achievable rates of massive MIMO systems with low-resolution ADCs are studied with consideration of both “Uniform-ADC” that uses ADCs with the same number of quantization bits and “Mixed-ADC” that allows the use of ADCs with different resolutions. By leveraging an additive quantization noise model (AQNM), the asymptotic achievable rates are obtained for maximum ratio combining (MRC), zero-forcing (ZF), and linear minimum mean squared error (LMMSE) receivers in very simple forms. Taking advantages of the theoretical results, we propose two criteria for allocation of quantization bits. It is found that the optimal quantization bits allocation for LMMSE is Mixed-ADCs with number of quantization bits that are polarized, while Uniform-ADC is optimal for MRC and ZF. When there is a constraint on the total ADC power consumption, the proposed quantization-bit allocation scheme for LMMSE becomes Uniform-ADC when the transmit signal-to-noise ratio (SNR) is below a threshold, which is related to the system scale and the ADC power consumption. The theoretical results are verified by Monte-Carlo simulations.

/pdf/massive-mimo-systems-with-low-resolution-adcs-achievable-icdqngm5.pdf

Massive MIMO Systems with Low-Resolution ADCs: Achievable Rates and Allocation of Quantization Bits

ABSTRACT In the field of medical image analysis, object detection plays a crucial role by providing interpretable diagnostic information to healthcare professionals. Although current object detection models have achieved remarkable success in conventional images, their performance in detecting abnormalities in medical images has not been as satisfactory. This is primarily due to the complexity of anatomical structures in medical images, and the fact that some lesions may have subtle features, particularly in the case of early‐stage, small‐scale abnormalities. To address this challenge, we introduce SOCR‐YOLO, a novel lesion detection model with online convolutional reparameterization based on channel shuffling. First, it employs the SOCR (Shuffled Channel with Online Convolutional Re‐parameterization) module to establish a connection between feature concatenation and computational efficiency, aiming to extract more comprehensive information while reducing time consumption. Second, it incorporates the Bi‐FPN structure to achieve multiscale feature fusion. Lastly, the loss function has been optimized to improve the model training process. We evaluated two datasets, chest x‐ray (Vindr‐CXR) and brain tumor (Br35H), provided by the Kaggle competition. Experimental results show that the proposed method has outperformed several state‐of‐the‐art models, including YOLOv8, YOLO‐NAS, and RT‐DETR, in both speed and accuracy. Notably, in the context of chest x‐ray anomaly detection, SOCR‐YOLO exhibits a 1.8% enhancement in accuracy over YOLOv8 while simultaneously reducing floating‐point operations by 26.3%. Additionally, a similar 1.8% improvement in accuracy is observed in the detection of brain tumors. The results indicate the superior ability of our model to detect multiscale variations and small lesions. 

<scp>SOCR‐YOLO</scp>: Small Objects Detection Algorithm in Medical Images

A dual-polarization coherent heterodyne optical communication system using a simplified and low-cost demodulation scheme, for high-capacity UDWDM-PON access networks, is proposed and demonstrated. In this scheme, the signal light and reference light occupying each of the polarization modes are emitted simultaneously from the transmitter. The random phase fluctuations between the signal light and reference light are obviated completely by means of the application of the phase-correlated orthogonal lights. When the signal light in the each polarization mode is modulated with M-amplitude-shift keying (M-ASK) or M2-quadrature amplitude modulation (M2-QAM), the phase-stable intermediate frequency (IF) signal with M-ASK or M2-QAM modulation in the corresponding polarization mode is available for conversion in the electrical domain by beating the modulated signal light with the un-modulated reference light. A new IF signal with M2 or M4-QAM can be synthesized by the IF signals in both modes as long as the power ratio and time delay between the two-modes optical signals are set at the proper values. This is achieved without using polarization demultiplexing and complicated algorithms and the synthesized IF signal can be received and demodulated directly. A proof-of-concept transmission link with dual-polarization 2-ASK is demonstrated. The experimental results are consistent with theoretical predictions.

A dual-polarization coherent communication system with simplified optical receiver for UDWDM-PON architecture.

Performance analysis of massive MIMO systems with low-resolution ADCs and IQI

A Hybrid Application-Aware VHO Scheme for Coexisting VLC and WLAN Indoor Networks

This paper investigates fairness-based transmission design in Intelligent Reflecting Surface (IRS) assisted downlink transmission scheme for multi-user MISO system. IRS is dedicatedly deployed for assisting the wireless transmission and suppressing the interference among users. The minimum weighted signal-to-interference-plus-noise ratio (SINR) of users is maximized by jointly optimizing the precoding matrix and the phase shift matrix of IRS in order to improve fairness among users. We proposed Successive Convex Approximation-Alternating Optimization (SCA-AO) method to solve the non-convex problem, and analyze the effect of weighted factors on performance. Verified by simulation results the approach of SCA-AO performance is better then method of Exact-Alternating-Optimization (EAO). 

Fairness-based transmission design in intelligent reflecting surface aided multi-user MISO systems

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