Enhancing Iodine Capture of Porous Organic Cages through N-Heteroatom Engineering.

Iodine radioisotopes, produced or released during nuclear-related activities, severely affect human health and the environment. The efficient removal of radioiodine from both aqueous and vapor phases is crucial for the sustainable development of nuclear energy. In this study, we propose an "N-heteroatom engineering" strategy to design three porous organic cages with N-containing functional groups for efficient iodine capture. Among the molecular cages investigated, FT-Cage incorporating tertiary amine groups and RT-Cage with secondary amine groups show higher adsorption capacity and much faster iodine release compared to IT-Cage with imine groups. Detailed investigations demonstrate the superiority of amine groups, along with the influence of crystal structures and porosity, for iodine capture. These findings provide valuable insights for the design of porous organic cages with enhanced capabilities for capturing iodine.

Hypertension treatment in patients with sleep apnea from the European Sleep Apnea Database (ESADA) cohort - towards precision medicine.

We recruited 5,970 hypertensive patients with obstructive sleep apnea (OSA) on current antihypertensive treatment from the European Sleep Apnea Database (ESADA) cohort. The group was subdivided into those receiving monotherapy (n = 3,594) and those receiving dual combined therapy (n = 2,376). We studied how major OSA confounders like age, gender, and body mass index as well as the degree of sleep apnea modified office systolic and diastolic blood pressure. Beta-blockers alone or in combination with a diuretic were compared with other antihypertensive drug classes. Monotherapy with beta-blocker was associated with lower systolic blood pressure, particularly in non-obese middle-aged males with hypertension. Conversely, the combination of a beta-blocker and a diuretic was associated with lower systolic and diastolic blood pressure in hypertensive patients with moderate-severe OSA. Systolic blood pressure was better controlled in female patients using this combined treatment. Our cross-sectional data suggest that specific clinical characteristics and type of antihypertensive medication influence the degree of blood pressure control in hypertensive OSA patients. Controlled trials are warranted.

A Randomized Controlled Clinical Trial Exploring Safety and Tolerability of Sulthiame in Sleep Apnea.

Rationale: Current therapies for obstructive sleep apnea (OSA) are limited by insufficient efficacy, compliance, or tolerability. An effective pharmacological treatment for OSA is warranted. Carbonic anhydrase inhibition has been shown to ameliorate OSA. Objectives: To explore safety and tolerability of the carbonic anhydrase inhibitor sulthiame (STM) in OSA. Methods: A 4-week double-blind, randomized, placebo-controlled dose-guiding trial was conducted in patients with moderate and/or severe OSA not tolerating positive airway pressure treatment. Measurements and Main Results: Intermittent paresthesia was reported by 79%, 67%, and 18% of patients receiving 400 mg STM (n = 34), 200 mg STM (n = 12), and placebo (n = 22), respectively. Dyspnea was reported after 400 mg STM (18%). Six patients in the higher dose group withdrew because of adverse events. There were no serious adverse events. STM reduced the apnea-hypopnea index from 55.2 to 33.0 events/h (-41.0%) in the 400-mg group and from 61.1 to 40.6 events/h (-32.1%) after 200 mg (P < 0.001 for both). Corresponding placebo values were 53.9 and 50.9 events/h (-5.4%). The apnea-hypopnea index reduction threshold of ⩾50% was reached in 40% of patients after 400 mg, 25% after 200 mg, and 5% after placebo. Mean overnight oxygen saturation improved by 1.1% after 400 and 200 mg (P < 0.001 and P = 0.034, respectively). Patient-related outcomes were unchanged. Conclusions: STM showed a satisfactory safety profile in moderate and/or severe OSA. STM reduced OSA, on average, by more than 20 events/h, one of the strongest reductions reported in a drug trial in OSA. Larger scale clinical studies of STM in OSA are justified. Clinical trial registered with www.clinicaltrialsregister.eu (2017-004767-13).

New pharmacologic agents for obstructive sleep apnoea: what do we know and what can we expect?

PURPOSE OF REVIEW: This review provides a condensed description of pharmacological remedies explored in patients with obstructive sleep apnoea (OSA) as well as projections of what we might expect in terms of clinical performance of these drugs. RECENT FINDINGS: Conventional drug therapies explored in OSA have generally produced disappointing results and there is a shortage of pharmacological treatment alternatives in this disorder. Recent insights into pathophysiological mechanisms potentially involved in OSA suggest that the condition may be divided into distinct subgroups based on clusters or defined by means of unique functional endotypic criteria. In fact, positive outcomes in clinical trials have now resulted in several drug candidates that show a convincing reduction of sleep disordered breathing in both short and intermediate term. Such drugs may be particularly useful in certain variants of OSA but not in others. These insights have also raised the ambition to create personalized therapies in OSA. Another recent development is the insight that OSA-linked conditions such as obesity, daytime somnolence and various forms of cardiovascular/metabolic disease may provide drug-based targets. For instance, pharmacological obesity therapy may provide not only positive metabolic effects but may also be a way to eliminate the anatomic component in obese OSA patients. SUMMARY: Recent insights into the pathophysiology of OSA have opened possibilities to develop personalized therapy. Drugs addressing fundamental aspects of the sleep and breathing disorder provide a particularly promising avenue for development of novel forms of treatment in OSA.

Beyond the AHI-pulse wave analysis during sleep for recognition of cardiovascular risk in sleep apnea patients.

Recent evidence supports the use of pulse wave analysis during sleep for assessing functional aspects of the cardiovascular system. The current study compared the influence of pulse wave and sleep study-derived parameters on cardiovascular risk assessment. In a multi-centric study design, 358 sleep apnea patients (age 55 ± 13 years, 64% male, body mass index 30 ± 6 kg m-2 , apnea-hypopnea index 13 [5-26] events per hr) underwent a standard overnight sleep recording. A novel cardiac risk index was computed based on pulse wave signals derived from pulse oximetry, reflecting vascular stiffness, cardiac variability, vascular autonomic tone and nocturnal hypoxia. Cardiovascular risk was determined using the ESC/ESH cardiovascular risk matrix, and categorized to high/low added cardiovascular risk. Comparisons between cardiac risk index and sleep parameters were performed for cardiovascular risk prediction. Apnea-hypopnea index, oxygen desaturation index and cardiac risk index were associated with high cardiovascular risk after adjustment for confounders (p = .002, .001, < .001, respectively). In a nested reference model consisting of age, gender and body mass index, adding cardiac risk index but not apnea-hypopnea index or oxygen desaturation index significantly increased the area under the receiver operating characteristic curve (p = .012, .22 and .16, respectively). In a direct comparison of oxygen desaturation index and cardiac risk index, only the novel risk index had an independent effect on cardiovascular risk prediction (pCRI  < .001, pODI  = .71). These results emphasize the association between nocturnal pulse wave and overall cardiovascular risk determined by an established risk matrix. Thus, pulse wave analysis during sleep provides a powerful approach for cardiovascular risk assessment in addition to conventional sleep study parameters.

Carbonic anhydrase, obstructive sleep apnea and hypertension: Effects of intervention.

Whole blood carbonic anhydrase activity (CAa) is increased in patients with obstructive sleep apnea (OSA). Our study investigated the influence of positive airway pressure (PAP) or CA inhibitor acetazolamide (ACT) therapy on CAa, OSA and blood pressure. Thirty-three OSA patients (21 hypertensive, body mass index (BMI) 37 ± 7 kg/m2 and apnea-hypopnea index (AHI) of 47 ± 31 events/hr) were followed-up after PAP treatment (compliance, 4.7 ± 1.5 hr/day; duration, median 6 [IQR 6,6] months) (Cohort A). A second OSA Cohort (B) contained nine hypertensive patients (BMI, 29 ± 4 kg/m2 ; AHI, 39 ± 20 events/hr) with 2-week treatment of ACT, PAP or ACT + PAP in an open crossover study. CAa was assessed at baseline and at the end of each treatment period. In Cohort A, baseline CAa was higher in hypertensive, compared with normotensive, patients (1,033 ± 204 versus 861 ± 201 units, p = .028). PAP treatment reduced systolic/diastolic blood pressure but not CAa (-9 ± 11/-5 ± 7 mmHg and -20 ± 289 units, p < .001, <.001 and .70). In Cohort B, blood pressure was reduced in both ACT-treated groups (-10 ± 10/-5 ± 7 mmHg, p = .043 and .019; and -5 ± 5/-13 ± 13 mmHg, p < .001 and .009). AHI was reduced in both groups: ACT only, -17 ± 9 events/hr p = .001; and ACT + PAP, -39 ± 19 events/hr, p < .001. PAP did not change CAa (p = .98) but activity tended to decrease after ACT with or without PAP (p = .081 and .056). CAa is elevated in hypertensive OSA patients. Long-term PAP reduced blood pressure without affecting CAa. ACT reduced blood pressure and CAa. Increased CAa may constitute a physiological characteristic in OSA, contributing to comorbid hypertension.

Lrrc34 Is Highly Expressed in SSCs and Is Necessary for SSC Expansion In Vitro.

Objective To discover critical genes contributing to the stemness and maintenance of spermatogonial stem cells (SSCs) and provide new insights into the function of the leucine-rich repeat (LRR) family member Lrrc34 (leucine-rich repeat-containing 34) in SSCs from mice. Methods Bioinformatic methods, including differentially expressed gene (DEG), gene ontology (GO) enrichment and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses, were used to uncover latent pluripotency-related genes. Reverse transcription-polymerase chain reaction (RT-PCR) and immunofluorescence analyses were utilized to verify the mRNA and protein expression levels, respectively. RNA interference of Lrrc34 using siRNA was performed to detect its transient impact on SSCs. Results Eight DEGs between ID4-EGFP+ (G) and ID4-EGFP+/TSPAN8High (TH), eight DEGs between G and ID4-EGFP+/TSPAN8Low (TL) and eleven DEGs between TH and TL were discovered, and eleven protein-protein interaction (PPI) modules were found to be significant in the PPI network of DEGs. One of the DEGs, Lrrc34, was selected as a potential pluripotency-related gene due to its differential expression among ID4-EGFP+ spermatogonia subsets and its interaction with fibroblast growth factor 2 in the fifth module. Immunofluorescence experiments exhibited specific expression of Lrrc34 in a subpopulation of undifferentiated spermatogonia marked by LIN28A, and RT-PCR experiments confirmed the high expression of Lrrc34 in SSCs from P7 and adult mice. The transient knockdown of Lrrc34 in SSCs resulted in reduced colony sizes and significant changes in the transcriptome and apoptotic pathways. Conclusion Lrrc34 is highly expressed in mouse SSCs and is required for SSC proliferation in vitro through effects on transcriptome and signaling transduction pathways.

Solution-processed, top-emitting, microcavity polymer light-emitting diodes for the pure red, green, blue and near white emission.

Top-emitting microcavity polymer light-emitting diodes (TMPLEDs) are of great significance for active matrix PLED displays with high color purity. However, the complex device structures of highly efficient microcavity organic light-emitting diodes fabricated by the full vapor deposition technology are not suitable for solution-processed PLEDs. Solution-processed TMPLEDs with simple device structures are promising candidates for large-area, mass production display techniques. In this work, three strategies were used to apply microcavity into PLEDs: (1) double Ag electrodes performed as the mirrors of cavity, instead of a multi-layer Bragg reflector, which simplified the device structure and fabrication process; (2) three solution-processed functional layers were specially designed for avoiding the inter-infiltration between the different solutions and to improve the interface contacts; (3) high order microcavities were utilized according to the optical simulation results, in which thick EMLs benefited from thickness control and reproductivity. As a result, the full-color emission including pure red, green, blue was realized, and quasi-white light was also achieved from a single polymer emitting material. The achievement of color purity always requires the sacrifice of part of the current efficiency due to the spectra narrowing, while the higher current efficiency of green TMPLED (10.08 cd A-1) compared to that of non-cavity PLED (~8.60 cd A-1) cast a light on future improvements.

Insomnia and cardiorespiratory fitness in a middle-aged population: the SCAPIS pilot study.

BACKGROUND: The relationship between insomnia and cardiorespiratory fitness (CRF), a well-established risk factor for cardiovascular disease, has not been extensively studied. We aimed to assess the independent association between insomnia and CRF in a population-based cohort of subjects aged 50 to 64 years. METHODS: Subjects participating in the Swedish CArdioPulmonary bioImaging Study (SCAPIS) pilot cohort (n = 603, men 47.9%) underwent a submaximal cycle ergometer test for estimation of maximal oxygen consumption (VO2max). Data on physical activity and sedentary time were collected via waist-worn accelerometers. An insomnia severity index score ≥ 10 was used to define insomnia. RESULTS: Insomnia was identified in 31.8% of the population. The VO2max was significantly lower in insomnia subjects compared with the non-insomnia group (31.2 ± 6.3 vs. 32.4 ± 6.5 ml* kg-1 *min-1, p = 0.028). There was no difference in objectively assessed physical activity or time spent sedentary between the groups. In a multivariate generalized linear model adjusting for confounders, an independent association between insomnia status and lower VO2max was found in men, but not in women (ß = - 1.15 [95% CI - 2.23-- 0.06] and - 0.09 [- 1.09-0.92], p = 0.038 and 0.866, respectively). CONCLUSIONS: We found a modest, but significant, association between insomnia and lower CRF in middle-aged men, but not in women. Our results suggest that insomnia may link to cardiovascular disease via reduced CRF. Insomnia may require a specific focus in the context of health campaigns addressing CRF.

Run-time reconfigurable adaptive LDPC coding for optical channels.

In this paper, we proposed a class of large-girth QC-LDPC codes designed to maximize the girth property with code rates ranging from 0.5 to 0.8, which leads to well-structured parity-check matrix and generator matrix. Instead of implementing several FEC encoder and decoder engines in hardware, we design an efficient unified FPGA-based architecture enabling run-time reconfigurable capability. Apart from four principle LDPC codes being incorporated into a unified design, shortening is adopted to bridge the rate gap between principle codes. With our proposed unified LDPC engine, the signal-to-noise ratio (SNR) limits of -1 dB to 2.2 dB have been demonstrated at BER of 10-12 in additive white Gaussian noise (AWGN) channel by FPGA emulation. It is desirable for the application to both free-space optical (FSO) and fiber optics communications. Large code rate range is preferred to deal with various channel impairments. To further verify the proposed unified code engine for FSO applications, we tested the scheme through a spatial light modulator (SLM)-based FSO channel emulator. We showed that in medium atmospheric turbulence regime, a post-FEC BER below 10-8 can be achieved without any interleaver and adaptive optics.

Change in weight and central obesity by positive airway pressure treatment in obstructive sleep apnea patients: longitudinal data from the ESADA cohort.

The effect of positive airway pressure treatment on weight and markers of central obesity in patients with obstructive sleep apnea remains unclear. We studied the change in body weight and anthropometric measures following positive airway pressure treatment in a large clinical cohort. Patients with obstructive sleep apnea with positive airway pressure treatment from the European Sleep Apnea Database registry (n = 1,415, 77% male, age 54 ± 11 [mean ± SD] years, body mass index 31.7 ± 6.4 kg/m2 , apnea-hypopnea index 37 ± 24 n per hr, Epworth Sleepiness Scale 10.2 ± 5.0) were selected. Changes in body mass index and neck/waist/hip circumferences at baseline and at follow-up visit were analysed. Overall, body mass index (0.0 [95% confidence interval, -0.1 to 0.2] kg/m2 ) and neck circumference (0.0 (95% confidence interval, -0.1 to 0.1] cm) were unchanged after positive airway pressure treatment compared with baseline (follow-up duration 1.1 ± 1.0 years and compliance 5.2 ± 2.1 hr per day). However, in non-obese (body mass index <30 kg/m2 ) patients, positive airway pressure treatment was associated with an increased body mass index and waist circumference (0.4 [0.3-0.5] kg/m2 and 0.8 [0.4-1.2] cm, respectively, all p < 0.05), and weight gain was significantly associated with higher positive airway pressure compliance and longer positive airway pressure treatment duration. In the obese subgroup, body mass index was reduced after positive airway pressure treatment (-0.3 [-0.5 to -0.1] kg/m2 , p < 0.05) mainly in patients with a strong reduction in Epworth Sleepiness Scale. In conclusion, positive airway pressure therapy was not found to systematically change body mass index in the European Sleep Apnea Database cohort, but the response was heterogeneous. Our findings suggest that weight gain may be restricted to an obstructive sleep apnea phenotype without established obesity. Lifestyle intervention needs to be considered in both lean and obese patients with obstructive sleep apnea receiving positive airway pressure treatment.

Obstructive sleep apnoea independently predicts lipid levels: Data from the European Sleep Apnea Database.

BACKGROUND AND OBJECTIVE: Obstructive sleep apnoea (OSA) and dyslipidaemia are independent risk factors for cardiovascular disease. This study investigates the association between OSA and plasma lipid concentrations in patients enrolled in the European Sleep Apnea Database (ESADA) cohort. METHODS: The cross-sectional analysis included 8592 patients without physician-diagnosed hyperlipidaemia or reported intake of a lipid-lowering drug (age 50.1 ± 12.7 years, 69.1% male, BMI: 30.8 ± 6.6 kg/m2 , mean apnoea-hypopnoea index (AHI): 25.7 ± 25.9 events/h). The independent relationship between measures of OSA (AHI, oxygen desaturation index (ODI), mean and lowest oxygen saturation) and lipid profile (total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C) and fasting triglycerides (TG)) was determined by means of general linear model analysis. RESULTS: There was a dose response relationship between TC and ODI (mean ± SE (mg/dL): 180.33 ± 2.46, 184.59 ± 2.42, 185.44 ± 2.42 and 185.73 ± 2.44; P < 0.001 across ODI quartiles I-IV). TG and LDL concentrations were better predicted by AHI than by ODI. HDL-C was significantly reduced in the highest AHI quartile (mean ± SE (mg/dL): 48.8 ± 1.49 vs 46.50 ± 1.48; P = 0.002, AHI quartile I vs IV). Morbid obesity was associated with lower TC and higher HDL-C values. Lipid status was influenced by geographical location with the highest TC concentration recorded in Northern Europe. CONCLUSION: OSA severity was independently associated with cholesterol and TG concentrations.

FPGA-based LDPC-coded APSK for optical communication systems.

In this paper, with the aid of mutual information and generalized mutual information (GMI) capacity analyses, it is shown that the geometrically shaped APSK that mimics an optimal Gaussian distribution with equiprobable signaling together with the corresponding gray-mapping rules can approach the Shannon limit closer than conventional quadrature amplitude modulation (QAM) at certain range of FEC overhead for both 16-APSK and 64-APSK. The field programmable gate array (FPGA) based LDPC-coded APSK emulation is conducted on block interleaver-based and bit interleaver-based systems; the results verify a significant improvement in hardware efficient bit interleaver-based systems. In bit interleaver-based emulation, the LDPC-coded 64-APSK outperforms 64-QAM, in terms of symbol signal-to-noise ratio (SNR), by 0.1 dB, 0.2 dB, and 0.3 dB at spectral efficiencies of 4.8, 4.5, and 4.2 b/s/Hz, respectively. It is found by emulation that LDPC-coded 64-APSK for spectral efficiencies of 4.8, 4.5, and 4.2 b/s/Hz is 1.6 dB, 1.7 dB, and 2.2 dB away from the GMI capacity.

Independent associations between arterial bicarbonate, apnea severity and hypertension in obstructive sleep apnea.

BACKGROUND: Obstructive sleep apnea is characterized by intermittent hypoxia and hypercapnia. CO2 production, transport and elimination are influenced by the carbonic anhydrase enzyme. We hypothesized that elevated standard bicarbonate, a proxy for increased carbonic anhydrase activity, is associated with apnea severity and higher blood pressure in patients with obstructive sleep apnea. METHODS: A retrospective analysis of a sleep apnea cohort (n = 830) studied by ambulatory polygraphy. Office systolic/diastolic blood pressure, lung function, and arterial blood gases were assessed during daytime. RESULTS: Arterial standard bicarbonate was increased with apnea severity (mild/moderate/severe 24.1 ± 1.8, 24.4 ± 1.7 and 24.9 ± 2.9 mmol/l, respectively, Kruskal-Wallis test p < 0.001). Standard bicarbonate was independently associated with apnea hypopnea index after adjustment for sex, age, body mass index, smoking, alcohol, hypertension, pO2 and pCO2 (standard bicarbonate quartile 1 vs. quartile 4, ß = 10.6, p < 0.001). Log-transformed standard bicarbonate was associated with a diagnosis of hypertension or diastolic blood pressure but not systolic blood pressure adjusting for cofounders (p = 0.007, 0.048 and 0.45, respectively). CONCLUSIONS: There was an independent association between sleep apnea severity and arterial standard bicarbonate. The link between high standard bicarbonate and daytime hypertension suggests that carbonic anhydrase activity may constitute a novel mechanism for blood pressure regulation in sleep apnea.

FPGA-based rate-adaptive LDPC-coded modulation for the next generation of optical communication systems.

In this paper, we propose a rate-adaptive FEC scheme based on LDPC codes together with its software reconfigurable unified FPGA architecture. By FPGA emulation, we demonstrate that the proposed class of rate-adaptive LDPC codes based on shortening with an overhead from 25% to 42.9% provides a coding gain ranging from 13.08 dB to 14.28 dB at a post-FEC BER of 10-15 for BPSK transmission. In addition, the proposed rate-adaptive LDPC coding combined with higher-order modulations have been demonstrated including QPSK, 8-QAM, 16-QAM, 32-QAM, and 64-QAM, which covers a wide range of signal-to-noise ratios. Furthermore, we apply the unequal error protection by employing different LDPC codes on different bits in 16-QAM and 64-QAM, which results in additional 0.5dB gain compared to conventional LDPC coded modulation with the same code rate of corresponding LDPC code.

Capacity achieving nonbinary LDPC coded non-uniform shaping modulation for adaptive optical communications.

A mutual information inspired nonbinary coded modulation design with non-uniform shaping is proposed. Instead of traditional power of two signal constellation sizes, we design 5-QAM, 7-QAM and 9-QAM constellations, which can be used in adaptive optical networks. The non-uniform shaping and LDPC code rate are jointly considered in the design, which results in a better performance scheme for the same SNR values. The matched nonbinary (NB) LDPC code is used for this scheme, which further improves the coding gain and the overall performance. We analyze both coding performance and system SNR performance. We show that the proposed NB LDPC-coded 9-QAM has more than 2dB gain in symbol SNR compared to traditional LDPC-coded star-8-QAM. On the other hand, the proposed NB LDPC-coded 5-QAM and 7-QAM have even better performance than LDPC-coded QPSK.

Parameters of Overnight Pulse Wave under Treatment in Obstructive Sleep Apnea.

BACKGROUND: Sleep-related breathing disorders may promote cardiovascular (CV) diseases. A novel and differentiated approach to overnight photoplethysmographic pulse wave analysis, which includes risk assessment and measurement of various pulse wave characteristics, has been evaluated in obstructive sleep apnea (OSA). OBJECTIVES: The purpose of this study was to assess if and which of the differentiated pulse wave characteristics might be influenced by OSA treatment with positive airway pressure (PAP). METHODS: The study included two protocols. In the case-control study (group A), pulse wave-derived CV risk indices recorded during PAP therapy were compared with those obtained in age, body mass index, and CV risk class-matched patients with untreated OSA (n = 67/67). In the prospective PAP treatment study (group B), 17 unselected patients undergoing a full-night sleep test at baseline and after 23 ± 19 weeks of treatment were analyzed. RESULTS: In untreated OSA patients (group A), the overnight hypoxic load was increased (SpO2 index 38.7 ± 17.5 vs. 24.0 ± 11.1, p < 0.001) and the pulse wave attenuation index (PWA-I) was lower (29.4 ± 9.2 vs. 33.5 ± 11.8, p = 0.022) than in treated patients. In group B, PAP therapy reduced the hypoxic load and increased the PWA-I significantly. The composite CV risk index was slightly but not significantly reduced. CONCLUSIONS: PAP therapy modified the hypoxic load and pulse wave-derived markers. The PWA-I - associated with sympathetic vascular tone - was most prominently modified by PAP. This novel approach to markers of CV function should be further evaluated in prospective studies.

FPGA implementation of concatenated non-binary QC-LDPC codes for high-speed optical transport.

In this paper, we propose a soft-decision-based FEC scheme that is the concatenation of a non-binary LDPC code and hard-decision FEC code. The proposed NB-LDPC + RS with overhead of 27.06% provides a superior NCG of 11.9dB at a post-FEC BER of 10-15. As a result, the proposed NB-LDPC codes represent the strong FEC candidate of soft-decision FEC for beyond 100Gb/s optical transmission systems.

Achievable information rates calculation for optical OFDM few-mode fiber long-haul transmission systems.

We propose a method to estimate the lower bound of achievable information rates (AIRs) of high speed orthogonal frequency-division multiplexing (OFDM) in spatial division multiplexing (SDM) optical long-haul transmission systems. The estimation of AIR is based on the forward recursion of multidimensional super-symbol efficient sliding-window Bahl-Cocke-Jelinek-Raviv (BCJR) algorithm. We consider most of the degradations of fiber links including nonlinear effects in few-mode fiber (FMF). This method does not consider the SDM as a simple multiplexer of independent data streams, but provides a super-symbol version for AIR calculation over spatial channels. This super-symbol version of AIR calculation algorithm, in principle, can be used for arbitrary multiple-input-multiple-output (MIMO)-SDM system with channel memory consideration. We illustrate this method by performing Monte Carlo simulations in a complete FMF model. Both channel model and algorithm for calculation of the AIRs are described in details. We also compare the AIRs results for QPSK/16QAM in both single mode fiber (SMF)- and FMF-based optical OFDM transmission.