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Intensity-modulated direct-detection (IM/DD) optical systems are most widely employed in short-reach optical interconnects due to their simple structure and cost-effectiveness. However, IM/DD systems face mixed linear and nonlinear channel impairments, mainly induced by the combination of square-law detection and chromatic dispersion, as well as the utilization of low-cost non-ideal transceivers. To solve this issue, recent years have witnessed a growing trend of introducing machine learning technologies such as neural networks (NNs) into IM/DD systems for channel equalization. NNs usually present better system performance than traditional approaches, and various types of NNs have been investigated. Despite the excellent system performance, the associated high computational complexity is a major drawback that hinders the practical application of NN-based equalizers. This paper focuses on the performance and complexity trade-off of NNs employed in IM/DD systems, presenting a systematic review of the current status of NN-based equalizers as well as a number of effective complexity reduction approaches. The future trends of leveraging advanced NN in IM/DD links are also discussed. [ABSTRACT FROM AUTHOR]

Background: The effectiveness and safety of pituitrin injection coupled with hysteroscopy and suction curettage as treatment for type I cesarean scar pregnancy (CSP) have not been studied enough in the literature, by comparing it to uterine artery embolization (UAE) followed by suction curettage we aim to determine its efficacy. Materials and Methods: Data of 53 patients (the PIT group) with type I CSP treated with pituitrin injection combined with hysteroscopic suction curettage and 137 patients (the UAE group) with type I CSP treated with UAE followed by suction curettage were collected in retrospect. The clinical data were analyzed statistically to compare the efficacy and safety between the two groups. Results: The PIT group had a shorter duration of postoperative vaginal bleeding, postoperative hospitalization, and overall hospitalization length (P < 0.05). The PIT group had lower overall hospitalization costs and a lower rate of adverse events than the UAE group (P < 0.05). There was no significant difference between the two groups in terms of treatment success rate, the average length of operation, blood loss during the procedure, time when serum β-hCG returned to normal range, and menstrual recovery time after hospital release (P > 0.05). Conclusion: UAE and pituitrin injection followed by hysteroscopic suction curettage are good choices for type I CSP treatment. However, pituitrin injection with hysteroscopic suction curettage outperforms UAE followed by suction curettage. Thus, pituitrin injection may be an option of high priority for type I CSP. [ABSTRACT FROM AUTHOR]

Neural network (NN)-based nonlinear equalizers have been shown effective for various types of short-reach direct detection systems. However, they work best for a certain channel condition and need to be trained again when the channel environment is changed, which hinders the efficient deployment of future optical switched data center networks. In this article, we propose transfer learning (TL)-aided feedforward neural networks (FNN) and recurrent neural networks (RNN) for nonlinear equalization in short-reach direct detection optical links, which enables a fast transition to new equalizers when the channel condition is changed. A 50-Gb/s 20-km pulse amplitude modulation (PAM)-4 optical link is experimentally demonstrated as the target system, and links of varying bit-rates and fiber lengths are selected as the source system. Experimental results show that TL could help reduce the number of epochs and training symbols of FNNs/RNNs required for nonlinear equalization in the target system, taking advantage of FNNs/RNNs trained for source systems. A reduction of 90%/87.5% in epochs and 62.5%/53.8% in training symbols is achieved with FNNs/RNNs transferred from the most similar source system. We also find that FNNs can be transferred to their corresponding RNNs for equalization in the target system, while TL from RNNs to FNNs cannot work properly. TL enables a fast transition between different NN-based equalizers, which is critical for future optical switched data center networks, where the optical links need to be dynamically reconfigured. [ABSTRACT FROM AUTHOR]

The recent decade has witnessed the evolution and enormous demand of the high-capacity data center interconnect (DCI), in such application scenarios spectral efficiency, optical field recovery and cost-effectiveness are highly desirable. Compared to coherent detection, direct detection does not require local oscillators, resulting in a simpler transceiver structure and thus a lower-cost solution for DCIs. To overcome chromatic dispersion induced power fading, field recovery enabled by direct detection has drawn extensive research interests. To date, various proposed direct detection schemes concentrate mainly on single sideband (SSB) modulation. Compared to double sideband (DSB) modulation, however, one sideband of SSB is unfilled and hence SSB poses higher requirement on the receiver bandwidth. Besides, the complexity and cost of implementing precisely aligned optical filtering poses burden for adopting SSB. Accordingly, we recently proposed a novel direct detection scheme called carrier assisted differential detection (CADD), which can realize the field recovery of complex-valued DSB signals with the aid of an optical carrier. In this letter, we carry out the first-time experimental demonstration of the CADD receiver. 54-Gb/s OFDM signals are transmitted over 160-km standard single-mode fiber with digital chromatic dispersion compensation at the receiver, indicating the ability to reconstruct optical field of DSB signals. For signal-signal beat interference (SSBI) which extensively exists in direct detection, experimental results show that merely two iterations of cancellation are sufficient to mitigate SSBI. More importantly, compared to various SSB based receiver schemes, the requirement of receiver bandwidth for DSB based CADD scheme is relaxed by 41%. [ABSTRACT FROM AUTHOR]

We proposed a new method to monitor the optical signal-to-noise rate (OSNR) for 112-Gb/s non-return-to-zero polarization-division-multiplexed quadrature phase-shift keying systems, using support vector regression trained with Stokes parameters. The numerical simulations show that OSNR levels between 11 and 35 dB can be estimated within ±1 dB with the interference of chromatic dispersion, polarization mode dispersion, and polarization-dependent loss. [ABSTRACT FROM AUTHOR]

Intrauterine adhesion (IUA) is a disease characterized by endometrial fibrosis caused by injury to the endometrium. In the present study, decellularized and lyophilized human amniotic membrane (DL-AM) material was transplanted in a rat model to explore the preventive effect against IUA. A total of 24 Sprague Dawley rats were randomly divided into an IUA (n=12) group and an IUA + DL-AM (n=12) group. To establish the model, the endometrium of the left uterus was scraped, while that of the right uterus was used as a control. In the IUA group, scraped uteri were sutured without any other treatment, whereas DL-AM was transplanted onto the scraped uteri in the IUA + DL-AM group. Uteri were resected for histological and immunohistochemical evaluation at 3, 7, 14 and 28 days after surgery. The results confirmed the development of IUA, which was accompanied by an increase in the rate of fibrotic area. Integral optical density (IOD) values of connective tissue growth factor (CTGF) were elevated in the IUA group, while matrix metalloproteinase-2 (MMP-2) decreased relative to the control group (P<0.05). After DL-AM transplantation, the IOD value of CTGF dropped, while MMP-2 increased compared with the IUA group (P<0.05). However, compared with that in the control group, the IOD value of CTGF was still higher, whereas MMP-2 was still lower in the IUA + DL-AM group (P<0.05). Furthermore, no evidence of endometrial regeneration was detected in both the IUA and IUA + DL-AM groups. Overall, these results indicated that in the rat model of IUA, transplantation of DL-AM had the potential to prevent the formation of fibrosis to a certain extent and may thus be an alternative strategy for managing the condition. [ABSTRACT FROM AUTHOR]