14,513 research outputs found
High-efficiency crystalline silicon technology development
The rationale for pursuing high efficiency crystalline silicon technology research is discussed. Photovoltaic energy systems are reviewed as to their cost effectiveness and their competitiveness with other energy systems. The parameters of energy system life are listed and briefly reviewed
Effect of side-mode suppression ratio on the performance of self-seeded gain-switched optical pulses in lightwave communications systems
The side-mode suppression ratio (SMSR) of self-seeded gain-switched optical pulses is shown to be an extremely important factor for the use of these pulses in optical communications systems. Experiments carried out involving pulse propagation through dispersion-shifted fiber and a bandpass optical filter demonstrate that, for SMSR values of less than 25 dB, the buildup of noise due to the mode partition effect may render these pulses unsuitable for use in optical communications system
Generation of widely tunable picosecond pulses with large SMSR by externally injecting a gain-switched dual laser source
The authors demonstrate a procedure of generating picosecond optical pulses that are tunable over a wide wavelength range (65 nm) and have very high spectral purity side-mode suppression ratio [(SMSR)>60 dB]. The large tuning range is obtained by employing external injection into a gain-switched source containing two Fabry-Pe/spl acute/rot lasers. The use of a widely tunable Bragg grating at the output improves the SMSR such that it exceeds 60 dB over the entire tuning range
Effects of weak input side mode suppression ratio and output filtration on the intensity noise of a self-seeded gain switched optical pulses at 2.5 GHz
Mode partition noise is shown to be a cause for concern in terms of the intensity noise induced on a self-seeded gain-switched pulse when filtering is used to increase the side mode suppression ratio (SMSR) of the output signal to >30 dB. The inherent SMSR of a self-seeded gain switched pulse is revealed to be a vital parameter especially when output filtration is used. Our results portray the fact that such a procedure would lead to an introduction of noise on the SSGS pulses if the inherent SMSR is weak, and may ultimately determine whether or not a source is suitable for use in WDM or OTDM optical communication networks
Effects of intermodulation distortion on the performance of a hybrid radio/fiber system employing a self-pulsating laser diode transmitter
A self-pulsating laser is used to generate a multicarrier (five radio frequency (RF) channels) microwave optical signal for use in a hybrid radio/fiber system. The self-pulsation is achieved by external light injection into the laser diode. By varying the RF channel spacing, we have been able to estimate the degradation in system performance due to intermodulation distortion (caused by the nonlinear dynamic response of the laser). The power penalty on the central RF channel is found to be 3.2 dB for operation at the RF band around the laser self-pulsation frequency of 18.5 GHz. We have also characterized the performance of the multicarrier hybrid radio/fiber system in the frequency band corresponding to the inherent relaxation frequency of the laser
Multifunctional operation of a fiber Bragg grating in a WDM/SCM radio over fiber distribution system
A radio over fiber distribution system incorporating both sub-carrier multiplexing (SCM) and wavelength division multiplexing (WDM) technologies is presented. The SCM signal contains five 155-Mbit/s data channels, centered around 18.5 GHz with 450 MHz spacing. This signal is directly modulated onto three high-speed lasers with emission frequencies spaced by 50 GHz. Bragg filters are employed at the receiver base-station in order to both demultiplex the required optical channel and ensure that the detected signal is single sideband (in order to overcome dispersion limitations on the link). Our results show negligible degradation in system performance for the demultiplexing of the WDM signal compared with the back-to-back performance curves
Optical pulse generation at frequencies up to 20 GHz using external-injection seeding of a gain-switched commercial Fabry-Pérot laser
We demonstrate that by using strong external-injection seeding of gain-switched Fabry-Perot (FP) lasers, it is possible to generate optical pulses at repetition rates far in excess of the laser bandwidth. Experimental results illustrate the generation of optical pulses at frequencies up to 20 GHz from a FP laser with a 3-dB bandwidth of only 8 GHz. The optical pulses generated have a duration around 12 ps, and a spectral width of 40 GHz
Multiple RF carrier distribution in a hybrid radio/fiber system employing a self-pulsating laser diode transmitter
A self-pulsating laser diode is used to generate a multicarrier microwave optical signal for use in a hybrid radio/fiber system. The self-pulsation frequency of the laser is controlled by external light injection, and can be varied between 14-24 GHz. The hybrid radio/fiber system, employing the self-pulsation laser, is used to distribute two 155-Mb/s data signals on two radio frequency (RF) carriers (at 18.5 and 18.9 GHz). Experimental results show the overall system performance for both RF channels, and demonstrate that the performance is improved by around 17 dB compared with the case when the laser is used without external injection, and thus, does not self-pulsat
Continuous repetition rate tuning with timing window independent self-seeding of a gain-switched Fabry-PÉrot Laser
In this work, we propose a novel self-seeding technique that yields timing window independent operation allowing continuous repetition rate tuning of the self-seeded gain-switched (SSGS) laser. This is achieved by employing a highly linearly chirped fiber Bragg grating (LC FBG) as a wavelength selective element. The reflected gain-switched pulses are dispersed to such an extent, that temporal overlap occurs between them. This overlap creates a pseudo continues wave like signal that is re-injected into the gain-switched laser
Improved performance of a hybrid radio/fiber system using a directly modulated laser transmitter with external injection
A directly modulated laser diode with external light injection is used to generate microwave optical signals for a hybrid radio/fiber system. The external light injection greatly enhances the frequency response of the laser, and thus, significantly improves the overall performance of the hybrid system. Experimental results show a 14-dB improvement in system performance for the externally injected laser in a hybrid radio/fiber communication link used for distributing 155-Mb/s data signal
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