Higher-order dispersion compensation to enable a 3.6 micros wavelength-maintaining delay of a 100 Gb/s DQPSK signal.

We demonstrate a method for dispersion slope compensation of a conversion/dispersion-based optical delay to enable 100 Gb/s operation based on a spatial light modulator and fiber Bragg gratings. A continuous delay of up to 3.6 micros for 100, 80, and 20 Gb/s differential quadrature phase-shift-keyed (DQSPK) and 50, 40, and 10 Gb/s differential phase-shift-keyed (DPSK) waveforms is shown. A time-delay bit-rate product of approximately 360,000 for 100 Gb/s DQPSK with wavelength-maintaining operation is achieved.

Continuously tunable 1.16 micros optical delay of 100 Gbit/s DQPSK and 50 Gbit/s DPSK signals using wavelength conversion and chromatic dispersion.

We demonstrate a variable optical delay element that uses tunable wavelength conversion and phase conjugation in highly nonlinear fiber and uses chromatic dispersion in dispersion-compensating fiber. A continuous delay of up to 1.16mus, equaling a >110,000 time-delay bit-rate product for 100 Gbit/s non-return-to-zero differential quadrature phase-shift-keying (NRZ-DQSPK) and >55,000 for 50 Gbit/s NRZ differential phase-shift-keying (NRZ-DPSK) modulation formats, is demonstrated. Bit error rates <10(-9) are demonstrated for each waveform at various delay settings.

Fine tuning of conversion/dispersion based optical delays with a 1 pm tunable laser using cascaded acousto-optic mixing.

We demonstrate a technique for fine tuning of optical delays using cascaded acousto-optic modulators to improve the delay resolution by 5 orders of magnitude compared to a 1 pm tunable laser. A 256 ns delay with <0.5 ps resolution is shown for 40 Gbits/s return-to-zero on-off keying with no added penalty.

Optical signal-to-noise ratio monitoring of an 80 Gbits/s polarization-multiplexed return-to-zero differential phase-shift keying channel.

We propose and experimentally demonstrate an optical signal-to-noise ratio (OSNR) monitoring technique for an 80 Gbits/s polarization-multiplexed return-to-zero differential phase-shift keying channel utilizing a narrowband optical filter and a low-speed detector. A maximum power increment of 19.7 dB is measured at a radio frequency (rf) of 250 MHz for monitoring of OSNR up to 27 dB, insensitive to chromatic dispersion of 0-300 ps/nm and polarization-mode dispersion (PMD) of 0-50 ps.

Variable rate, multi-format receiver design for 10 to 40 Gb/s DPSK and OOK formats.

We demonstrate a continuously-variable bit-rate receiver from 10 to 40 Gbit/s for DPSK demodulation. Unlike previous DPSK demodulators, this receiver is also capable of passing intensity modulated waveforms without distortion. Degradations imposed by receiver imperfections are presented and compared with a traditional DPSK delay-line interferometer.

All-optic scheme for automatic polarization division demultiplexing.

We describe a cost effective scheme to automatically separate two polarization channels in a polarization division multiplexing (PDM) system, without having to modify the existing transmitter or receiver electronics or software. We experimentally validate the concept by achieving an extinction ratio of more than 28-dB between two demultiplexed channels. Finally, we successfully demonstrate the PDM scheme in a 1.12-Tb/s (14x2x40-Gb/s) system over 62-km of transmission fiber.

Continuously-tunable, bit-rate variable OTDM using broadband SBS slow-light delay line.

We conceptually compare the advantages of the proposed slow-light-based tunable OTDM to conventional fiber-based fixed OTDM multiplexer. We experimentally demonstrate continuously-controllable OTDM of two 2.5-Gb/s return-to-zero (RZ) signals using broadband SBS-based slow-light as the tunable optical delay line. We show that the time slot of one signal path can be manipulated relative to the other by as much as 75-ps. This continuous slow light tunability dramatically enhances the OTDM system performance which results in a power penalty reduction of 9-dB for the multiplexed data stream. We also demonstrate variable-bit-rate OTDM by dynamically adjusting the tunable slow-light delay according to the input bit-rates. We show efficient two-by-one optical time multiplexing of three different input data streams at 2.5-Gb/s, 2.67-Gb/s and 5-Gb/s.

A 10-Gbit/s EML link using detuned narrowband optical filtering.

In this paper, the effects of asymmetric narrowband optical filtering are investigated in a 10-Gbit/s optical communication link using integrated electro-absorption modulated lasers (EML). We investigate the effect of EML chirp on link performance as well as the optimal filter bandwidth and wavelength detuning. We show that both the phase response and the spectral narrowing of the filter will enable a longer distance transmission by interacting with the EML transient chirp and compensating for the fiber chromatic dispersion. Experimentally, an 8.75-GHz filter is shown to improve the link distance by 40 km from 65 to 105 km, when transmitting over standard single mode fiber.

Reach extension in 10-Gb/s directly modulated transmission systems using asymmetric and narrowband optical filtering.

Optical filtering has been used to extend the reach of directly modulated laser in 10Gb/s WDM systems via two separate mechanisms: narrowing the broadened spectrum, and converting frequency modulation into useful amplitude modulation. We investigate in detail, the impact of asymmetric and narrowband optical filtering at the transmitter or receiver. Experimental demonstrations for both shorter distance and long-haul like transmission using optical filtering are performed. The transmission reach is nearly doubled from <25-km to >45-km without dispersion compensation. 1400-km error-free transmission (Q > 15.6-dB) is further achieved over dispersion-managed link for a directly modulated DFB laser within an 8x10-Gb/s WDM system.

Loop-mirror filters based on saturable-gain or-absorber gratings.

We present a novel all-fiber narrow-band filter based on pump-induced saturable-gain or-absorber gratings in a loop mirror. Our design provides built-in interferometric phase alignment of the signal to the grating for optimal filtering. Notch or bandpass functionality is determined by the choice of gain or absorption and the input ports selected for the pump and signal. The loop-mirror filter has potential bandwidths from the submegahertz to beyond the gigahertz regimes, and one can tune it optically by changing the wavelength of the pump light that establishes the grating. Such filters have potential applications to wavelength-division-multiplexed optical networks and optical rf signal processing.

Modeling of riblike waveguides with isolation trenches of finite width.

A method for calculating the propagation and loss characteristics of riblike waveguiding structures having isolation trenches of finite width is presented.

Cognitive dysfunction and tardive dyskinesia.

From a prospective study of tardive dyskinesia (TD), psychiatric patients with neuroleptically-induced "persistent" TD were contrasted with controls on a neuropsychological measure of abstracting ability. A significant association is demonstrated between impaired cognitive performance and TD, even when the neuropsychological measure was obtained in advance of TD onset.

Analogy tests and psychopathology at follow-up after open heart surgery.

A study of 100 coronary bypass and cardiac valvular surgery patients investigated whether preoperative brain damage, as measured by the Conceptual Level Analogy Test (CLAT), is a major risk factor for postoperative psychiatric symptoms and mortality. Three cognitive psychological tests, including the CLAT, and psychatric interviews were given preoperatively, postoperatively, and at 18-month follow-up. Surgical outcome was specified as: Catastrophic Outcome (death or severe stroke), Psychiatric Complications, or Good Outcome (survival with no psychiatric complications). Inhospital outcome related significantly to analogy test scores, as did both surgical procedure and diagnosis of rheumatic heart disease. However, long-term outcome was unrelated to medical diagnosis and only weakly related to surgical procedure, but highly significantly related to preoperative analogy scores. The CLAT was a more consistent predictor of both short- and long-term outcome than any of the other ten variables considered (medical and surgical variables, inhospital outcome, demographic measures, other psychological tests).

Psychopathology observed on follow-up after coronary bypass surgery.

Forty-six of 51 coronary bypass patients whose inhospital postoperative adjustment was reported earlier, were studied about 18 months postoperatively. In addition, 32 of 46 cardiac valvular surgery patients were seen as a comparison group. The incidence of postoperative psychiatric symptoms observed in the hospital, eight of 51 (16 per cent), and on follow-up, seven of 46 (15 per cent), was very similar; however, the patients who had these psychiatric symptoms comprised two almost entirely different groups. There were no indications that patients who developed psychiatric symptoms in the immediate postoperative period than patients asymptomatic postoperatively. There was a significant relationship between preoperative psychiatric illness and symptoms in the follow-up period.

Analogical reasoning and postoperative outcome. Predictions for patients scheduled for open heart surgery.

We investigated whether postoperative outcome of open heart surgery is related to preoperative cognitive dysfunction. Patients ill enough to require open heart surgery frequently have gravely compromised circulation and, hence, possible brain damage. The Conceptual Level Analogy Test (CLAT), a new, rigorously constructed analogy test, was used to measure cognitive dysfunction. The results indicated that the CLAT, aministered preoperatively to open heart surgery patients, differentiated between patients having different types of postoperative outcome. A significant relationship between type of surgical procedure and poor postoperative outcome was also found; cardiac valvular surgery patients had significantly worse outcome than coronary bypass surgery patients. The incidence of good outcome (survival with no psychiatric complications) was 28% for cardiac valvular surgery patients with extremely poor preoperative CLAT scores, but 74% for valvular surgery patients with higher preoperative CLAT scores.

Psychiatric complications following coronary bypass surgery.

Previous studies of psychiatric complications following open heart surgery have included few if any patients who had coronary bypass surgery. This experiment reports the relative incidence of psychiatric complications in a sample of 97 open heart surgery patients of whom 51 patients (53 per cent) had coronary bypass surgery. The results suggest that the incidence of psychiatric symptoms following coronary bypass surgery is significantly lower (16 per cent) than that following cardiac valvular surgery (41 per cent). Several possible reasons for this large discrepancy in incidence of psychiatric complications are considered.