HAL (Le Centre pour la Communication Scientifique Directe), Mar 1, 2010
DBR (Distributed Bragg Reflector) semiconductor lasers that are used in DWDM (Dense Wavelength Di... more DBR (Distributed Bragg Reflector) semiconductor lasers that are used in DWDM (Dense Wavelength Division Multiplexing) fiber optic transmissions are single-frequency tunable optical sources. A particular optical frequency is dedicated for each transmission channel. Our aim is to measure the switching time between two adjacent oscillation modes of different frequencies. However, commercial optical spectrum analysers are too slow for our purpose. Therefore, we propose here an ultra fast spectral analysis method. Results obtained with a typical DBR semiconductor lasers using our method are finally presented.
ABSTRACT Isotropic broadband probes or spectrum analyzers (SAs) may be used for the measurement o... more ABSTRACT Isotropic broadband probes or spectrum analyzers (SAs) may be used for the measurement of rapidly varying electromagnetic fields generated by emerging wireless communication systems. In this paper this problematic is investigated by comparing the responses measured by two different isotropic broadband probes typically used to perform electric field (E-field) evaluations. The broadband probes are submitted to signals with variable duty cycles (DC) and crest factors (CF) either with or without Orthogonal Frequency Division Multiplexing (OFDM) modulation but with the same root-mean-square (RMS) power. The two probes do not provide accurate enough results for deterministic signals such as Worldwide Interoperability for Microwave Access (WIMAX) or Long Term Evolution (LTE) as well as for non-deterministic signals such as Wireless Fidelity (WiFi). The legacy measurement protocols should be adapted to cope for the emerging wireless communication technologies based on the OFDM modulation scheme. This is not easily achieved except when the statistics of the RF emission are well known. In this case the measurement errors are shown to be systematic and a correction factor or calibration can be applied to obtain a good approximation of the total RMS power.
ABSTRACT We present the design, realization and test of a high bit-rate optical communication sys... more ABSTRACT We present the design, realization and test of a high bit-rate optical communication system dedicated to underwater operations at the bottom of the sea transmitting data between sensor hubs and remote operated vehicles.
Conference on Lasers and Electro-Optics Europe, 1996
Semiconductor laser evolution throughout threshold is continuous in both power and linewidth show... more Semiconductor laser evolution throughout threshold is continuous in both power and linewidth showing a phase transition like behaviour. It is not correct to consider the below threshold behaviour as that of a light emitting diode and the above one as a fully coherent laser. The two regions obey to different mechanisms such as cavity filtered amplified spontaneous emission and carrier recombination below threshold and gain, photon lifetimes and linewidth enhancement above threshold. Few measurements of coherence behaviour have been made in the threshold region. We have previously developed a method using the Schawlow-Townes slopes below and above threshold in order to extract the linewidth enhancement factor α. [1]. Coherence evolution at threshold has been studied for classical detuned lasers based on analysis of the Fokker-Planck equation [2] but no useful expression adapted to semiconductor lasers has been given so far. We use here an analytical model enabling us, by fitting, to extract all major internal parameters of a semiconductor laser.
HAL (Le Centre pour la Communication Scientifique Directe), Mar 1, 2010
DBR (Distributed Bragg Reflector) semiconductor lasers that are used in DWDM (Dense Wavelength Di... more DBR (Distributed Bragg Reflector) semiconductor lasers that are used in DWDM (Dense Wavelength Division Multiplexing) fiber optic transmissions are single-frequency tunable optical sources. A particular optical frequency is dedicated for each transmission channel. Our aim is to measure the switching time between two adjacent oscillation modes of different frequencies. However, commercial optical spectrum analysers are too slow for our purpose. Therefore, we propose here an ultra fast spectral analysis method. Results obtained with a typical DBR semiconductor lasers using our method are finally presented.
ABSTRACT Isotropic broadband probes or spectrum analyzers (SAs) may be used for the measurement o... more ABSTRACT Isotropic broadband probes or spectrum analyzers (SAs) may be used for the measurement of rapidly varying electromagnetic fields generated by emerging wireless communication systems. In this paper this problematic is investigated by comparing the responses measured by two different isotropic broadband probes typically used to perform electric field (E-field) evaluations. The broadband probes are submitted to signals with variable duty cycles (DC) and crest factors (CF) either with or without Orthogonal Frequency Division Multiplexing (OFDM) modulation but with the same root-mean-square (RMS) power. The two probes do not provide accurate enough results for deterministic signals such as Worldwide Interoperability for Microwave Access (WIMAX) or Long Term Evolution (LTE) as well as for non-deterministic signals such as Wireless Fidelity (WiFi). The legacy measurement protocols should be adapted to cope for the emerging wireless communication technologies based on the OFDM modulation scheme. This is not easily achieved except when the statistics of the RF emission are well known. In this case the measurement errors are shown to be systematic and a correction factor or calibration can be applied to obtain a good approximation of the total RMS power.
ABSTRACT We present the design, realization and test of a high bit-rate optical communication sys... more ABSTRACT We present the design, realization and test of a high bit-rate optical communication system dedicated to underwater operations at the bottom of the sea transmitting data between sensor hubs and remote operated vehicles.
Conference on Lasers and Electro-Optics Europe, 1996
Semiconductor laser evolution throughout threshold is continuous in both power and linewidth show... more Semiconductor laser evolution throughout threshold is continuous in both power and linewidth showing a phase transition like behaviour. It is not correct to consider the below threshold behaviour as that of a light emitting diode and the above one as a fully coherent laser. The two regions obey to different mechanisms such as cavity filtered amplified spontaneous emission and carrier recombination below threshold and gain, photon lifetimes and linewidth enhancement above threshold. Few measurements of coherence behaviour have been made in the threshold region. We have previously developed a method using the Schawlow-Townes slopes below and above threshold in order to extract the linewidth enhancement factor α. [1]. Coherence evolution at threshold has been studied for classical detuned lasers based on analysis of the Fokker-Planck equation [2] but no useful expression adapted to semiconductor lasers has been given so far. We use here an analytical model enabling us, by fitting, to extract all major internal parameters of a semiconductor laser.
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Papers by Zeno TOFFANO