High-resolution Si3N4 spectrometer: architecture & virtual channel synthesis and experimental demonstration.

Up-to-date network telemetry is the key enabler for resource optimization by capacity scaling, fault recovery, and network reconfiguration among other means. Reliable optical performance monitoring in general and, specifically, the monitoring of the spectral profile of WDM signals in fixed- and flex- grid architectures across the entire C-band, remains challenging. This article describes a two-stage spectrometer architecture amenable to integration on a single chip that can measure quantitatively the spectrum across the entire C-band with a resolution of ∼ 1.4 GHz. The first stage consists of a ring resonator with intra-ring phase shifter to provide a tuneable fine filter. The second stage makes use of an AWG subsystem and a novel processing algorithm to synthesize a tuneable coarse filter with a flat passband which isolates individual resonances of a multiplicity of ring resonances. The spectrometer is capable of scanning the entire C-band with high resolution using only one dynamic control. Due to its maturity and low loss, CMOS compatible Si3N4 is chosen for fabrication of the ring resonator and two cyclic AWGs. Complete spectrometer operation is demonstrated experimentally over a selected portion of the C-band. A novel virtual channel synthesis algorithm based on the weighted summation of the AWG output port powers relaxes the conventional AWG design requirement of a flat passband and sharp transition to stopband. The operation of the circuit is invariant to the optical path length between individual components and the algorithm corrects to some extent fabrication process variation impairments of the AWG channel spectra substantially improving robustness.

Exposure to Sedation and Analgesia Medications: Short-term Cognitive Outcomes in Pediatric Critical Care Survivors With Acquired Brain Injury.

Background/Objective: Pediatric intensive care unit (PICU) survivors risk significant cognitive morbidity, particularly those with acquired brain injury (ABI) diagnoses. Studies show sedative and analgesic medication may potentiate neurologic injury, but few studies evaluate impact on survivor outcomes. This study aimed to evaluate whether exposures to analgesic and sedative medications are associated with worse neurocognitive outcome. Methods: A retrospective cohort study was conducted of 91 patients aged 8 to 18 years, undergoing clinical neurocognitive evaluation approximately 1 to 3 months after PICU discharge. Electronic health data was queried for sedative and analgesic medication exposures, including opioids, benzodiazepines, propofol, ketamine, and dexmedetomidine. Doses were converted to class equivalents, evaluated by any exposure and cumulative dose exposure per patient weight. Cognitive outcome was derived from 8 objective cognitive assessments with an emphasis on executive function skills using Principal Components Analysis. Then, linear regression was used to control for baseline cognitive function estimates to calculate a standardized residualized neurocognitive index (rNCI) z-score. Multivariable linear regression evaluated the association between rNCI and medication exposure controlling for covariates. Significance was defined as P < .05. Results: Most (n = 80; 88%) patients received 1 or more study medications. Any exposure and higher cumulative doses of benzodiazepine and ketamine were significantly associated with worse rNCI in bivariate analyses. When controlling for Medicaid, preadmission comorbid conditions, length of stay, delirium, and receipt of other medication classes, receipt of benzodiazepine was associated with significantly worse rNCI (ß-coefficient = -0.48, 95% confidence interval = -0.88, -0.08). Conclusions: Exposure to benzodiazepines was independently associated with worse acute phase cognitive outcome using objective assessments focused on executive function skills when controlling for demographic and illness characteristics. Clinician decisions regarding medication regimens in the PICU may serve as a modifiable factor to improve outcomes. Additional inquiry into associations with long-term cognitive outcome and optimal medication regimens is needed.

Follow-up after PICU discharge for patients with acquired brain injury: the role of an abbreviated neuropsychological evaluation and a return-to-school program.

Objective: To present the results of an abbreviated testing protocol used to screen for neurocognitive and psychological sequelae of critical illness among pediatric intensive care unit (PICU) survivors with acquired brain injury in our post-discharge follow-up programs, and describe our process for facilitating this population's return to academic life. Design: Retrospective cohort study. Setting: Neurocritical care follow-up programs at two U.S. academic, tertiary medical/surgical PICUs. Patients: Children age > 4 years enrolled in the neurocritical care follow-up programs (n=289) at these institutions who underwent neurocognitive and psychological testing between 2017-2021. Interventions: None. Measurements and Main Results: One month after discharge from the hospital, nearly half of the children and/or their parents (48%) in our neurocritical care follow-up programs identified some type of emotional or behavioral concern compared to their premorbid state, and 15% reported some type of cognitive concern. On evaluation, 35% of the children were given a new neurocognitive diagnosis. Neurocognitive domains regulated by the executive functioning system were the most commonly affected, including attention (54%), memory (31%) and processing speed (27%). One-quarter of the children were given a new psychological diagnosis, most commonly post-traumatic stress disorder (PTSD) or stress-related symptoms (12%). Over 80% of patients in the programs were given new recommendations for school, for both new academic services and new classroom accommodations. Over half of children (57%) were referred for comprehensive follow-up neuropsychological evaluation. Conclusions: Abbreviated neurocognitive and psychological evaluation successfully identifies the same deficits commonly found among PICU survivors who undergo longer, more complete testing protocols. When combined with services aimed at successfully re-integrating PICU survivors back to school, this focused evaluation can provide an effective and efficient means of screening for cognitive and emotional deficits among PICU survivors, and establish a rationale for early academic support upon the child's return to school.

A Core Outcome Measurement Set for Pediatric Critical Care.

OBJECTIVES: To identify a PICU Core Outcome Measurement Set (PICU COMS), a set of measures that can be used to evaluate the PICU Core Outcome Set (PICU COS) domains in PICU patients and their families. DESIGN: A modified Delphi consensus process. SETTING: Four webinars attended by PICU physicians and nurses, pediatric surgeons, rehabilitation physicians, and scientists with expertise in PICU clinical care or research ( n = 35). Attendees were from eight countries and convened from the Pediatric Acute Lung Injury and Sepsis Investigators Pediatric Outcomes STudies after PICU Investigators and the Eunice Kennedy Shriver National Institute of Child Health and Human Development Collaborative Pediatric Critical Care Research Network PICU COS Investigators. SUBJECTS: Measures to assess outcome domains of the PICU COS are as follows: cognitive, emotional, overall (including health-related quality of life), physical, and family health. Measures evaluating social health were also considered. INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Measures were classified as general or additional based on generalizability across PICU populations, feasibility, and relevance to specific COS domains. Measures with high consensus, defined as 80% agreement for inclusion, were selected for the PICU COMS. Among 140 candidate measures, 24 were delineated as general (broadly applicable) and, of these, 10 achieved consensus for inclusion in the COMS (7 patient-oriented and 3 family-oriented). Six of the seven patient measures were applicable to the broadest range of patients, diagnoses, and developmental abilities. All were validated in pediatric populations and have normative pediatric data. Twenty additional measures focusing on specific populations or in-depth evaluation of a COS subdomain also met consensus for inclusion as COMS additional measures. CONCLUSIONS: The PICU COMS delineates measures to evaluate domains in the PICU COS and facilitates comparability across future research studies to characterize PICU survivorship and enable interventional studies to target long-term outcomes after critical illness.

Autism and attention-deficit/hyperactivity disorders and symptoms in children with neurofibromatosis type 1.

AIM: To evaluate if autism symptoms and diagnoses are more common in children with neurofibromatosis type 1 (NF1) than in typically developing children, to which levels, and to determine if co-occurring attention-deficit/hyperactivity disorder (ADHD) symptomatology accounts for this increase. METHOD: We searched hospital electronic medical records (EMR) for International Classification of Diseases, 10th Revision NF1 and co-occurring diagnoses codes. We recruited a subsample of 45 children (mean age 9y 2mo; SD 2y 7mo; range 5-12y; 22 males, 23 females) and collected parental reports of autism symptomatology, adaptive behavior, and behavioral problems that were compared to those of 360 age- and sex-matched controls from the Simons Simplex Collection (SSC) with autism spectrum disorder (ASD; SSC-ASD) or typically developing (SSC-TD). RESULTS: The EMR search identified 968 children with NF1; 8.8% had ADHD and 2.1% had ASD co-occurring diagnoses. In the subsample, the mean autism scale score for participants with NF1 was below cut-off for significant autism symptoms. Participants with NF1 had significantly more autism and behavioral symptoms than SSC-TD participants, and significantly less than SSC-ASD participants, with one exception: ADHD symptom levels were similar to those of SSC-ASD participants. In analyses that controlled for internalizing, ADHD, and communication scores, the difference in autism symptom levels between participants with NF1 and typically developing controls disappeared almost entirely. INTERPRETATION: Our results do not support an association between NF1 and autism, both at the symptom and disorder levels. WHAT THIS PAPER ADDS: Diagnoses of attention-deficit/hyperactivity disorder (ADHD) were more common in children with neurofibromatosis type 1 (NF1) than in the general child population. Diagnoses of autism spectrum disorder were no more common in children with NF1 than in the general child population. Increases in autism symptoms did not reach clinically significant thresholds. Co-occurring ADHD symptoms accounted for increased autism questionnaire scores. Adaptive behavior in participants with NF1 showed normal socialization but lower communication proficiency.

The Association Between Functional Status and Health-Related Quality of Life Following Discharge from the Pediatric Intensive Care Unit.

BACKGROUND: Despite one third of children with acquired brain injury (ABI) experiencing new functional impairments following critical care admission, there is limited research investigating the impact of new functional impairments on overall health-related quality of life (HRQOL) or among important HRQOL domains. We aimed to investigate the association between new functional impairments, measured by the Functional Status Scale (FSS), and HRQOL in pediatric patients with ABI after critical care. METHODS: We conducted a secondary analysis of a prospective observational study of 275 children aged 2 months to 18 years with ABI. The primary exposure evaluated was change in FSS from baseline at hospital discharge, categorized per prior work (no change, 1-2 point increase, and ≥ 3 point increase). The primary outcome was overall HRQOL 6 months after hospital discharge, measured by the Pediatric Quality of Life Inventory (PedsQL) total score. Secondary outcomes were PedsQL domain scores. PedsQL total and domain scores were transformed into age-standardized z scores for analyses. Multiple linear regression models evaluated the association between FSS change category and HRQOL (overall and domain z scores) when controlling for demographic and clinical characteristics and were reported as ß-coefficients with 95% confidence intervals. RESULTS: Complete data were analyzed for 195 (71%) children, including 127 with traumatic brain injury. New functional impairment was common with 32 (16%) patients experiencing FSS increases ≥ 3, 50 (26%) patients with FSS increases of 1-2 points, and 113 (58%) patients with no change from prehospital baseline. The majority of children (63%) demonstrated HRQOL ratings ≥ 1 standard deviation below healthy age-based standards (z scores ≤ - 1). Regression models demonstrated older age, female sex, presence of comorbidities, and preadmission cardiopulmonary resuscitation were all significantly associated with poorer overall HRQOL (all p < 0.05). FSS increase ≥ 3 at discharge was significantly associated with worse overall HRQOL at follow-up (ß = - 1.07; 95% confidence interval = - 1.63 to - 0.52) when controlling for the aforementioned significant factors, and significantly improved model fit (p value for change = 0.001). Similar findings in secondary analyses were found for physical domain scores, with FSS increase showing a significant association with worse physical HRQOL scores and improvements in model fit. Change in FSS was not significantly associated with other HRQOL domain scores (emotional, social, school, psychosocial). CONCLUSIONS: Many children with ABI after critical care experience new functional impairments (FSS increases) and worse HRQOL than healthy peers. FSS increase at discharge is a significant risk factor for worse HRQOL in the months after hospital discharge and improves HRQOL models beyond illness and demographic variables alone.

Sleep Measure Validation in a Pediatric Neurocritical Care Acquired Brain Injury Population.

BACKGROUND/OBJECTIVE: Lingering morbidities including physical, cognitive, emotional, and psychosocial sequelae, termed the Post-Intensive Care Syndrome, persist years after pediatric neurocritical care (PNCC) hospitalization. Sleep disturbances impact other Post-Intensive Care Syndrome domains and are under-evaluated to date due to a lack of appropriate measurement tools. The present study evaluated the validity of the Sleep Disturbance Scale for Children (SDSC) to address the growing need for assessing sleep problems after PNCC. METHODS: We conducted a prospective observational study of youth aged 3-17 years with acquired brain injury (N = 69) receiving care through longitudinal PNCC programs at two tertiary academic medical centers. Parents completed the SDSC and provided proxy reports of internalizing symptoms, health-related quality of life (HRQOL), fatigue, pain behavior, and cognitive function within 3 months of hospital discharge. Evidence for the validity of the SDSC was established by utilizing the full sample for psychosocial measure comparisons and by comparing SDSC outcomes by severity (Low Risk, Mild-Moderate Risk, and High Risk defined by reported standardized T-scores). RESULTS: Internal consistency of the SDSC was good (α = .81). Within the full sample, increased sleep disturbances on the SDSC were significantly correlated with Post-Intensive Care Syndrome measures, including worse physical (r = .65), psychological (r = .62), and cognitive (r = - .74) sequelae. Youth in the High Risk group evidenced greater dysfunction in mental acuity, pain behavior, internalizing symptoms, and social engagement. Findings revealed both statistically and clinically significant impacts of sleep disturbances as measured by the SDSC on HRQOL. CONCLUSIONS: The SDSC is a valid and reliable measure for assessing sleep disturbances in children after PNCC. Results support the use of the SDSC to measure sleep disturbances after PNCC. Targeted interventions for sleep disturbances may be key to overall patient recovery.

Symmetric signal and local oscillator polarization diverse coherent optical receiver.

An improved coherent optical receiver architecture that compensates for a random drift in the state of polarization (SOP) of both the signal and the local oscillator (LO) is presented for the first time. The proposed architecture comprises two conventional coherent optical receiver front-ends in tandem, where the SOP of the LO is first divided into its two orthogonal components and then distributed to each coherent optical receiver front-end module. Two distinct methods of polarization diversity recovery of the modulation based on the MRC technique and an eigenvalue-eigenvector decomposition of the covariance matrix have been used to effectively recover the transmitted signal. The concept is validated by numerical simulations, where a differential quadrature phase-shift keyed (DQPSK) modulated signal with a random time-varying SOP is first generated. After its mixing with a LO also possessing a random time-varying SOP, the algorithms that have been developed are provided with eight input variables to be digitally processed. The constellation diagrams corresponding to the recovered DQPSK modulation obtained using the two polarization diversity methods are presented.

Universal discrete Fourier optics RF photonic integrated circuit architecture.

This paper describes a coherent electro-optic circuit architecture that generates a frequency comb consisting of N spatially separated orders using a generalised Mach-Zenhder interferometer (MZI) with its N × 1 combiner replaced by an optical N × N Discrete Fourier Transform (DFT). Advantage may be taken of the tight optical path-length control, component and circuit symmetries and emerging trimming algorithms offered by photonic integration in any platform that offers linear electro-optic phase modulation such as LiNbO3, silicon, III-V or hybrid technology. The circuit architecture subsumes all MZI-based RF photonic circuit architectures in the prior art given an appropriate choice of output port(s) and dimension N although the principal application envisaged is phase correlated subcarrier generation for all optical orthogonal frequency division multiplexing. A transfer matrix approach is used to model the operation of the architecture. The predictions of the model are validated by simulations performed using an industry standard software tool. Implementation is found to be practical.

Cylindrical Talbot effect for ultra-compact multimode interference couplers.

Tapered multimode interference (MMI) couplers have been broadly studied for applications in integrated photonic circuits due to their footprints being smaller than conventional MMIs. The operation of an MMI is fundamentally related to the Talbot effect. In this Letter, the Talbot effect is analyzed in cylindrical coordinates, rather than conventional Cartesian coordinates. A cylindrical geometry is found to result in a significant reduction of Talbot distance and, hence, more compact MMIs. Simulation results are compared to theoretical predictions to confirm the accuracy of the method.

Photonic circuit for high order USB and LSB separation for remote heterodyning: analysis and simulation.

A novel photonic integrated circuit is proposed that, using an RF source, generates at its output ports the same magnitude but opposite sign high order single optical side bands of a suppressed optical carrier. A single stage parallel Mach-Zehnder Modulator (MZM) and a two-stage series parallel MZM architecture are described and their relative merits discussed. A transfer matrix method is used to describe the operation of the circuits. The theoretical analysis is validated by computer simulation. As an illustration of a prospective application, it is shown how the circuit may be used as a key element of an optical transmission system to transport radio signals over fibre for wireless access; generating remotely a mm-wave carrier modulated by digital IQ data. A detailed calculation of symbol error rate is presented to characterise the system performance. The circuit may be fabricated in any integration platform offering a suitable phase modulator circuit element such as LiNbO(3), Silicon, and III-V or hybrid technology.

Cascade photonic integrated circuit architecture for electro-optic in-phase quadrature/single sideband modulation or frequency conversion.

A photonic integrated circuit architecture for implementing frequency upconversion is proposed. The circuit consists of a 1×2 splitter and 2×1 combiner interconnected by two stages of differentially driven phase modulators having 2×2 multimode interference coupler between the stages. A transfer matrix approach is used to model the operation of the architecture. The predictions of the model are validated by simulations performed using an industry standard software tool. The intrinsic conversion efficiency of the proposed design is improved by 6 dB over the alternative functionally equivalent circuit based on dual parallel Mach-Zehnder modulators known in the prior art. A two-tone analysis is presented to study the linearity of the proposed circuit, and a comparison is provided over the alternative. The proposed circuit is suitable for integration in any platform that offers linear electro-optic phase modulation such as LiNbO(3), silicon, III-V, or hybrid technology.

Dual-function photonic integrated circuit for frequency octo-tupling or single-side-band modulation.

A dual-function photonic integrated circuit for microwave photonic applications is proposed. The circuit consists of four linear electro-optic phase modulators connected optically in parallel within a generalized Mach-Zehnder interferometer architecture. The photonic circuit is arranged to have two separate output ports. A first port provides frequency up-conversion of a microwave signal from the electrical to the optical domain; equivalently single-side-band modulation. A second port provides tunable millimeter wave carriers by frequency octo-tupling of an appropriate amplitude RF carrier. The circuit exploits the intrinsic relative phases between the ports of multi-mode interference couplers to provide substantially all the static optical phases needed. The operation of the proposed dual-function photonic integrated circuit is verified by computer simulations. The performance of the frequency octo-tupling and up-conversion functions is analyzed in terms of the electrical signal to harmonic distortion ratio and the optical single side band to unwanted harmonics ratio, respectively.

Theoretical analysis and modeling of a photonic integrated circuit for frequency 8-tupled and 24-tupled millimeter wave signal generation: erratum.

A novel photonic circuit design for implementing frequency 8-tupling and 24-tupling was presented [Opt. Lett.39, 6950 (2014)10.1364/OL.39.006950OPLEDP0146-9592], and although its key message remains unaltered, there were typographical errors in the equations that are corrected in this erratum.

Narrow linewidth two-electrode 1560 nm laterally coupled distributed feedback lasers with third-order surface etched gratings.

We report on the design and characterization of a re-growth free InGaAsP/InP multiple quantum well two-electrode laterally coupled distributed feedback (LC-DFB) lasers. Third-order surface etched gratings have been defined on the ridge sidewalls along the laser cavity by means of stepper lithography. The lasers oscillate in single-mode around 1560 nm with high side mode suppression ratios (>52 dB), a wavelength tuning (≥ 3nm), an output power (≥ 6 mW), and narrow linewidth (<170 kHz) under various current injection ranges at room temperature. A minimum linewidth of 94 kHz has been recorded for 1500 µm-long two-electrode LC-DFB laser while providing non-uniform current injection through the two electrodes. The effect of the width of the inter-electrode gap on these different performance measures is also studied.

Narrow linewidth 1560 nm InGaAsP split-contact corrugated ridge waveguide DFB lasers.

We demonstrate a split-contact corrugated ridge waveguide InGaAsP distributed feedback laser at 1560 nm. The laser cavity has been defined with uniform third-order gratings etched along the sidewalls of the ridge waveguide. The gratings were fabricated using a standard I-line stepper lithography technique along with an inductively coupled reactive ion-etching process. Stable single-mode operation has been achieved with side-mode suppression ratios ≥50 dB, output powers ≥7 mW, a wavelength tuning range ≥2.3 nm, and narrow linewidths (≤140 kHz) for different biasing conditions, with a minimum of 70 kHz. The effect of p-contact partition on device performance is also studied.

Theoretical analysis and modeling of a photonic integrated circuit for frequency 8-tupled and 24-tupled millimeter wave signal generation.

A photonic circuit design for implementing frequency 8-tupling and 24-tupling is proposed. The front- and back-end of the circuit comprises 4×4 MMI couplers enclosing an array of four pairs of phase modulators and 2×2 MMI couplers. The proposed design for frequency multiplication requires no optical or electrical filters, the operation is not limited to carefully adjusted modulation indexes, and the drift originated from static DC bias is mitigated by making use of the intrinsic phase relations of multi-mode interference couplers. A transfer matrix approach is used to represent the main building blocks of the design and hence to describe the operation of the frequency 8-tupling and 24-tupling. The concept is theoretically developed and demonstrated by simulations. Ideal and imperfect power imbalances in the multi-mode interference couplers, as well as ideal and imperfect phases of the electric drives to the phase modulators, are analyzed.

Simulation of optoelectronic oscillator injection locking, pulling & spiking phenomena.

Complex envelope and reduced phase simulation models describing the dynamical behaviour of an optoelectronic oscillator (OEO) under injection by an external source are described. The models build on the foundations of a previously reported delay integral/differential equation (DDE) theory of injection locking of time delay oscillators (TDO) such as the OEO. The DDE formulation is particularly amenable to high precision simulation using the Simulink™ block diagram environment. The correspondence between the blocks and the oscillator components offers intuition and considerable freedom to explore different circuit architectures and design variations with minimal coding effort. The simulations facilitate the study of the profound effect the multimode nature of a TDO has on its dynamical behavior. The reduced phase models that make use of the Leeson approximation are generally successful in reproducing the results of complex envelope models for established oscillations except for spiking phenomena for which the Leeson approximation fails. Simulation results demonstrating phenomena not captured by classical injection theory are presented, including multimode oscillation, the appearance of sidemodes in the RF and phase noise spectrum, and persistent spike trains redolent of recent experimental observations of [Formula: see text] phase pulse trains in a broadband OEO under injection.

Post-PICU sleep efficiency and quality of life in infants and toddlers with acquired brain injury.

STUDY OBJECTIVES: We aimed to investigate the use of sleep efficiency (SE) as a measure of sleep disturbance in infants and toddlers with acquired brain injury (ABI) and evaluate associations between SE and child health-related quality of life and family outcomes. METHODS: Retrospective cohort study of 101 children ages 3-36 months who survived critical care for ABI. SE was quantified from the Brief Infant Sleep Questionnaire as a ratio of nighttime sleep to total time in bed; poor SE was defined as < 80%. Outcome measures included the Pediatric Quality of Life Inventory Core Total Score (health-related quality of life) and Family Impact Module Total Score. Spearman's correlation quantified associations between SE and outcomes. Multivariable linear regression tested association between poor SE and health-related quality of life controlling for significant covariates (age, diagnosis, comorbidities, worsening Functional Status Scale). RESULTS: Following ABI, median SE was 91.7 (interquartile range = 83.3, 95.5). Nineteen (19%) children had poor SE (< 80%). SE correlated significantly with quality of life (Spearman's correlation = .307) and Family Impact Module (Spearman's correlation = .309; both P < .01). When controlling for covariates, poor SE significantly increased risk for lower health-related quality of life (ß-coefficient = -7.0; 95% confidence interval= -13.4, -0.6). CONCLUSIONS: One in five infants and young children with ABI have poor SE that is associated with poorer child and family health outcomes. Our study underscores the potential importance of sleep following ABI to optimize recovery and the need for additional investigation of SE in infants and young children. CITATION: Klapp JM, Hall TA, Riley AR, Janzen D, Williams CN. Post-PICU sleep efficiency and quality of life in infants and toddlers with acquired brain injury. J Clin Sleep Med. 2024;20(1):75-83.