Search results for "switching."
showing 10 items of 276 documents
Determination of third-order nonlinear optical properties of ABI derivatives
2019
This material is based upon work supported by the ERDF 1.1.1.1 activity project Nr. 1.1.1.1/16/A/046 “Application assessment of novel organic materials by prototyping of photonic devices”.
Transform-limited pulses generated by an actively Q-switched distributed fiber laser.
2008
A single-mode, transform-limited, actively Q-switched distributed-feedback fiber laser is presented, based on a new in-line acoustic pulse generator. Our technique permits a continuous adjustment of the repetition rate that modulates the Q factor of the cavity. Optical pulses of 800 mW peak power, 32 ns temporal width, and up to 20 kHz repetition rates were obtained. The measured linewidth demonstrates that these pulses are transform limited: 6 MHz for a train of pulses of 10 kHz repetition rate, 80 ns temporal width, and 60 mW peak power. Efficient excitation of spontaneous Brillouin scattering is demonstrated.
Design and implementation of a portable fNIRS embedded system
2015
We report on the design, development and operation of a portable, low cost, battery-operated, multi-channel, functional Near Infrared Spectroscopy embedded system, hosting up to 64 optical sources and 128 Silicon PhotoMultiplier optical detectors. The system is realized as a scalable architecture, whose elementary leaf consists of a probe board provided with 16 SiPMs, 4 couples of bi-color LED, and a temperature sensor, built on a flexible stand. The hardware structure is very versatile because it is possible to handle both the switching time of the LED and the acquisition of the photodetectors, via an ARM based microcontroller.
Q switching and mode locking pulse generation from an all-fiber ring laser by intermodal acousto-optic bandpass modulation
2018
Q-switched and mode-locked (QML) pulse generation from an all-fiber ring laser based on intermodal acousto-optic bandpass modulation is reported. The modulator relies on full-acousto-optic mode re-coupling cycle induced by a standing flexural acoustic wave, with a transmission response that is controlled by amplitude modulation of the acoustic wave signal. The Q factor of the cavity is controlled by a rectangular pulse wave with variable frequency and duty cycle, whereas mode locking is achieved by amplitude modulation derived from a standing flexural acoustic wave. The best QML pulses were obtained at 0.5 kHz repetition rate, with a pump power of 549.2 mW, at the optical wavelength of 1568…
Enhanced supercontinuum generation in the nanosecond pump regime using specialty microstructured fibers
2009
Several alternatives have been investigated to achieve enhanced supercontinuum generation in the nanosecond pump regime using specialty silica-based microstructured optical fibers (MOFs). Among these alternatives we can point out the use of (a) MOF tapers, (b) highly Ge-doped core Y-shaped MOF and (c) Er-doped MOF. These specialty MOFs provide either an increased material nonlinear response or a rather small effective area, at the same time that the dispersion characteristics are adjusted to work at different excitation conditions. In our experiments, we have been using either a Q-switched Nd:YAG laser (10 Hz repetition rate) or an Yb-doped fiber laser (2 kHz repetition rate), both emitting…
Supercontinuum Q-switched Yb fiber laser using an intracavity microstructured fiber
2009
We report on an intracavity configuration for supercontinuum generation in a Q-switched Yb fiber laser. The supercontinuum laser includes a section of microstructured fiber within the Q-switched laser cavity. With 380 mW of pump power, the supercontinuum laser can emit broadband pulses of 6 microJ energy and 10 ns temporal width, at repetition rates from few hertz up to 2 kHz. The supercontinuum spectrum spans over a wavelength range in excess of 1.4 microm.
User bandwidth usage-driven HNN neuron excitation method for maximum resource utilization within packet-switched communication networks
2006
Mobile and wireless systems beyond 3G are being designed under the user-centric paradigm. Dynamic resource allocation (DRA) is a topic on intensive research to address efficiently such paradigm. Hopfield neural networks (HNN) have proved useful in the past to solve this kind of complex optimization problems. Recently, various approaches have been proposed to realize HNN-based user-centric DRA. However, the initial algorithms suffer from severe instability problems impacting the overall performance. This letter analyses the source of the existing limitations and proposes an enhanced formulation, ensuring maximum resource utilization while optimizing the convergence of the neural network. The…
Switching from Transdermal Drugs: An Observational "N of 1" Study of Fentanyl and Buprenorphine
2007
The aim of this study was to confirm that the concomitant presence of transdermal fentanyl (TTS FE) and buprenorphine (TTS BU) may be feasible without important consequences, using doses presumed to be equianalgesic. A prospective "N of 1" study was carried out in a sample of volunteers with cancer pain receiving stable doses of TTS FE or TTS BU, with adequate pain and symptom control. In the study design, each patient provided data before and after a switch from one opioid to the other and then back to the previous one. Sixteen patients receiving daily stable doses of 0.6 or 1.2 mg of TTS FE were switched to TTS BU using an FE-BU ratio of 0.6-0.8. After three days, the TTS BU patch was rem…
H<inf>&#x221E;</inf> synchronization of Markovian jump master-slave systems with delay
2012
The problem of synchronization is investigated for a class of master-slave systems with time-varying delays and Markovian switching parameters. Using an appropriate Lyapunov-Krasovskii functional, a synchronization law which includes the master-slave parameters is established for designing a mode-dependent output feedback control law in terms of LMIs. A numerical example is given to show the effectiveness of the method.
Letter Throughput and Delay Analysis of the Ideal Window
1999
We consider the problem of random access communications over a time slotted channel with feedback of infinitely multiplicity at the beginning of each collision resolution interval (CRI), i.e., users know via instantaneous feedback the number of users involved in that collision. Once this is known, the resolution algorithm (CRA) operates with binary (successful / non successful, s/ns) feedback. The analysis of this simple full feedback sensing window random access algorithm, named ideal window stabilized ALOHA, (IWSA), algorithm, provides a throughput of 0.5052 packets/slot, Its delay is also analyzed and compared with similar algorithms.