Cavity enhanced stimulated Brillouin scattering in an optical chip for multiorder Stokes generation.

We report the first demonstration of on-chip cascaded stimulated Brillouin scattering (SBS). Cascaded SBS is characterized in a 4 cm long chalcogenide (As2S3) rib waveguide where the end facet reflections provide a monolithic Fabry-Perot (FP) resonator. The presence of the FP cavity reduces the Brillouin gain threshold, which enables observation of cascaded SBS at reduced pump powers. We observe up to three orders of Stokes waves in the backscattered signal at a coupled peak power of 1.34 W. Anti-Stokes waves due to four-wave mixing between the pump and the Stokes wave were observed in the forward spectrum.

Optical phase conjugation by an As(2)S(3) glass planar waveguide for dispersion-free transmission of WDM-DPSK signals over fiber.

We report the first demonstration of optical phase conjugation (OPC) transmission of phase encoded and wavelength-division multiplexed (WDM) signals by the Kerr effect in a planar structured waveguide. The phase conjugated electric field of the signal is produced by four wave mixing pumped by a CW laser during co-propagating with the signal in a highly nonlinear waveguide fabricated in As(2)S(3) glass. Experiments demonstrate the capability of the device to perform dispersion-free transmission through up to 225 km of standard single mode fiber for a 3 × 40 Gb/s WDM signal, with its channels encoded as return-to-zero differential phase shift keying and spaced either 100 or 200 GHz apart. This work represents an important milestone towards demonstrating advanced signal processing of high-speed and broadband optical signals in compact planar waveguides, with the potential for monolithic optical integration.

Simultaneous multi-impairment monitoring of 640 Gb/s signals using photonic chip based RF spectrum analyzer.

We report the first demonstration of simultaneous multi-impairment monitoring at ultrahigh bitrates using a THz bandwidth photonic-chip-based radio-frequency (RF) spectrum analyzer. Our approach employs a 7 cm long, highly nonlinear (gamma approximately 9900 /W/km), dispersion engineered chalcogenide planar waveguide to capture the RF spectrum of an ultrafast 640 Gb/s signal, based on cross-phase modulation, from which we numerically retrieve the autocorrelation waveform. The relationship between the retrieved autocorrelation trace and signal impairments is exploited to simultaneously monitor dispersion, in-band optical signal to noise ratio (OSNR) and timing jitter from a single measurement. This novel approach also offers very high OSNR measurement dynamic range (> 30 dB) and is scalable to terabit data rates.

Photonic chip based transmitter optimization and receiver demultiplexing of a 1.28 Tbit/s OTDM signal.

We demonstrate chip-based Tbaud optical signal processing for all-optical performance monitoring, switching and demultiplexing based on the instantaneous Kerr nonlinearity in a dispersion-engineered As(2)S(3) planar waveguide. At the Tbaud transmitter, we use a THz bandwidth radio-frequency spectrum analyzer to perform all-optical performance monitoring and to optimize the optical time division multiplexing stages as well as mitigate impairments, for example, dispersion. At the Tbaud receiver, we demonstrate error-free demultiplexing of a 1.28 Tbit/s single wavelength, return-to-zero signal to 10 Gbit/s via four-wave mixing with negligible system penalty (< 0.5 dB). Excellent performance, including high four-wave mixing conversion efficiency and no indication of an error-floor, was achieved. Our results establish the feasibility of Tbaud signal processing using compact nonlinear planar waveguides for Tbit/s Ethernet applications.

Very low loss reactively ion etched Tellurium Dioxide planar rib waveguides for linear and non-linear optics.

We report on the fabrication and optical properties of the first very low loss nonlinear Tellurite planar rib waveguides ever demonstrated. A new reactive ion etch process based on Hydrogen as the active species was developed to accomplish the low propagation losses. Optical losses below approximately 0.05 dB/cm in most of the NIR spectrum and approximately 0.10 dB/cm at 1550 nm have been achieved - the lowest ever reported by more than an order of magnitude and clearly suitable for planar integrated devices. We demonstrate strong spectral broadening of 0.6 ps pulses in waveguides fabricated from pure TeO(2), in good agreement with simulations.

Terahertz bandwidth RF spectrum analysis of femtosecond pulses using a chalcogenide chip.

We report the first demonstration of the use of an RF spectrum analyser with multi-terahertz bandwidth to measure the properties of femtosecond optical pulses. A low distortion and broad measurement bandwidth of 2.78 THz (nearly two orders of magnitude greater than conventional opto-electronic analyzers) was achieved by using a 6 cm long As(2)S(3) chalcogenide waveguide designed for high Kerr nonlinearity and near zero dispersion. Measurements of pulses as short as 260 fs produced from a soliton-effect compressor reveal features not evident from the pulse's optical spectrum. We also applied an inverse Fourier transform numerically to the captured data to re-construct a time-domain waveform that resembled pulse measurement obtained from intensity autocorrelation.

Long, low loss etched As(2)S(3) chalcogenide waveguides for all-optical signal regeneration.

We report on the fabrication and optical properties of etched highly nonlinear As(2)S(3) chalcogenide planar rib waveguides with lengths up to 22.5 cm and optical losses as low as 0.05 dB/cm at 1550 nm - the lowest ever reported. We demonstrate strong spectral broadening of 1.2 ps pulses, in good agreement with simulations, and find that the ratio of nonlinearity and dispersion linearizes the pulse chirp, reducing the spectral oscillations caused by self-phase modulation alone. When combined with a spectrally offset band-pass filter, this gives rise to a nonlinear transfer function suitable for all-optical regeneration of high data rate signals.

Properties of nonblocking single-substrate optical space switching networks constructed from directional couplers.

Some of the properties of single-substrate nonblocking optical space switching networks that are constructed from directional couplers, waveguide bends, and waveguide crossovers are considered. Expressions are given for the ratio of network output signal to cross talk, insertion loss, and total switch count for ten different structures. Based on these expressions, estimates of the maximum switch sizes attainable are made. Consideration is also given to the factors that govern the practical implementation of such structures, and this shows that rearrangeably nonblocking single-substrate switches of up to 128 × 128 should be possible if technologies other than Ti:LiNbO(3) are used.

Low loss nematic liquid crystal cored fiber waveguides.

Nematic LC material in the aligned state scatters light strongly, but in low loss LC cored fiber waveguides it scatters less and has enhanced recovery time.

Psychological adjustment in children with end stage renal disease: the impact of maternal stress and coping.

OBJECTIVE: To explore maternal and child perspectives on children's adjustment in the context of paediatric renal disease, and maternal psychological variables that may account for variance in child and maternal ratings. METHODS: Forty-three children with end stage renal disease and their maternal caregivers completed the Strengths and Difficulties Questionnaire (SDQ). Mothers also reported on their own mental health, and the strategies they used to cope with their child's illness. The severity of the child's condition was rated independently by a renal clinician. RESULTS: Compared with normative data for the SDQ mothers reported their children to be at increased risk of psychological problems. However, the children themselves reported no more problems than a normative sample. Mothers' coping and mental health explained some of the variance in their ratings of the child's adjustment but were not predictive of the children's self-ratings. CONCLUSIONS: The results suggest that maternal factors may not explain the variability in children's adjustment to chronic illness, perhaps especially within the age range studied here. Practical implications of the data are also discussed. In particular, a systemic approach to paediatric liaison by psychologists is emphasized.

Cognitive and psychosocial outcome of infants dialysed in infancy.

OBJECTIVE: To contribute further to the understanding of cognitive and psychosocial outcome of children with end-stage renal disease undergoing long-term peritoneal dialysis. METHODS: In total, 16 surviving infants at a single centre beginning peritoneal dialysis in the first year of life were studied. The age range of the children at assessment was 1.6-12.1 years. Children were assessed using the Griffiths Mental Development Scales, the Wechsler Intelligence Scale for Children-Third Edition UK, and the Strengths and Difficulties Questionnaire. Information regarding the child's hospital stay and family background was also collated. A Pearson's Product Moment correlation was used to analyse the results. RESULTS: Although 67% of the children's scores fell within the average range, 87% were within at least two SDs of the norms (mean IQ = 86.6). Psychosocial adjustment measures revealed that 50% of scores fell within the borderline to abnormal category, suggesting that the frequency of psychological difficulties was above that of the normal population. CONCLUSIONS: These findings lend support to recent studies indicating that, developmentally, children undergoing long-term peritoneal dialysis are faring better than in the past. This may indeed be a reflection of improvements in renal treatment and diet. The behavioural results suggest the need to monitor psychological adjustment in this group of children.

Long-term outcome of peritoneal dialysis in infants.

Debate continues concerning the treatment of infants with end-stage renal disease. We evaluated progress and outcome of 20 infants with a mean age of 0.34 year (range, 0.02-1 year) in a long-term peritoneal dialysis program at a single center. Mean weight at the start of dialysis was 4.8 kg (range, 1.7-11.4 kg), and the duration of dialysis was 17.3 months (range, 1-59 months). Eleven infants received renal transplants, 4 were switched to hemodialysis and then received transplants, 4 died, and 1 continues to receive peritoneal dialysis. There was significant co-morbidity in 6 infants who died or required hemodialysis. Catheter interventions were frequent, with 12 infants requiring at least one replacement. There were 1.1 episodes of peritonitis per patient-year; 70% of infants had 0 to 1 episode. Mean weight standard deviation score (SDS) was -1.6 at the start, -0.3 at 1 year (P =.0008), and 0.3 at 2 years (P =.0008). Height SDSs were -1.8 at the start, -1.1 at 1 year (P =.046), and -0. 8 at 2 years (P =.06). Head circumference SDSs were -1.9 at the start, -1.3 at 6 months (P =.003), and -0.9 at 1 year (P =.015). Fourteen of 16 survivors are achieving normal developmental milestones or attend mainstream school. Peritoneal dialysis in infancy is a demanding treatment, but outcome for growth, development, and transplantation justifies this intensive approach. When parents are counseled, the importance of non-renal co-morbidity must be emphasized.