The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
Hossein Hashemi - One of the best experts on this subject based on the ideXlab platform.
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electronic Laser Phase Noise reduction
Radio Frequency Integrated Circuits Symposium, 2013Co-Authors: Firooz Aflatouni, Behrooz Abiri, Angad Rekhi, Hooman Abediasl, Hossein Hashemi, Ali HajimiriAbstract:The first integrated wideband Laser Phase Noise reduction scheme is presented where the Laser Phase Noise is first detected using a photonic chip, processed using an electronic chip, and subtracted from the Laser Phase in a feed-forward manner. The proof-of-concept experiments on a commercially available 1553nm distributed feedback Laser show linewidth reduction from 6MHz to 250kHz equivalent to 14dB Phase Noise improvement. The hybrid integration of the photonic and electronic chips enables dramatic power consumption and area reduction compared to bench-top designs. This feed-forward scheme performs wideband Phase Noise reduction independent of the light source and, as such, it is compatible with several types of Lasers.
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wideband tunable Laser Phase Noise reduction using single sideband modulation in an electro optical feed forward scheme
Optics Letters, 2012Co-Authors: Firooz Aflatouni, Hossein HashemiAbstract:A wideband Laser Phase Noise reduction scheme is introduced where the optical field of a Laser is single sideband modulated with an electrical signal containing the discriminated Phase Noise of the Laser. The proof-of-concept experiments on a commercially available 1549 nm distributed feedback Laser show linewidth reduction from 7.5 MHz to 1.8 kHz without using large optical cavity resonators. This feed-forward scheme performs wideband Phase Noise cancellation independent of the light source and, as such, it is compatible with the original Laser source tunability without requiring tunable optical components. By placing the proposed Phase Noise reduction system after a commercial tunable Laser, a tunable coherent light source with kilohertz linewidth over a tuning range of 1530-1570 nm is demonstrated.
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Semiconductor Laser Phase-Noise cancellation using an electrical feed-forward scheme
Optics letters, 2009Co-Authors: M. Bagheri, Firooz Aflatouni, Alireza Imani, Ankush Goel, Hossein HashemiAbstract:We demonstrate the reduction of semiconductor Laser Phase Noise by using an electrical feed-forward scheme. We have carried out proof-of-concept experiments on a commercially available distributed-feedback Laser emitting at the 1550 nm communication band. The preliminary results show more than 20 times reduction in the Phase-Noise power spectrum. The feed-forward scheme does not have the limited bandwidth, stability, and speed issues that are common in feedback systems. Moreover, in the absence of electronic Noise, feed-forward can completely cancel the close-in Phase Noise. In this scheme, the ultimate achievable Phase Noise will be limited by the electronics Noise. Using the proposed feed-forward approach, the linewidth of semiconductor Lasers can be reduced by 3-4 orders of magnitude in a monolithic approach using today's low-Noise scaled transistors with terahertz gain-bandwidth product.
Adolfo V. T. Cartaxo - One of the best experts on this subject based on the ideXlab platform.
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ICTON - Assessment of the Combined Effect of Laser Phase Noise and Intercore Crosstalk on the Outage Probability of DD OOK Systems
2019 21st International Conference on Transparent Optical Networks (ICTON), 2019Co-Authors: Joao L. Rebola, Tiago M. F. Alves, Adolfo V. T. CartaxoAbstract:We study the influence of the combined effect of Laser Phase Noise and intercore crosstalk on the outage probability of direct-detection 10 Gbit/s on-off keying optical communication systems. We show that the Laser Phase Noise can affect significantly the outage probability, for Lasers with linewidths in the MHz range, for low and high skew-bit rate products. We also show that the Laser Phase Noise effect on the received eye-pattern is qualitatively similar to the one found for high skew-bit rate product in the absence of Laser Phase Noise.
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Intercore crosstalk in direct-detection homogeneous multicore fiber systems impaired by Laser Phase Noise
Optics Express, 2017Co-Authors: Tiago M. F. Alves, Adolfo V. T. Cartaxo, Ruben S. Luis, Benjamin J. Puttnam, Yoshinari Awaji, Naoya WadaAbstract:The impact of the Laser Phase Noise on the photodetected intercore crosstalk and performance of direct-detection orthogonal frequency division multiplexing multicore fiber systems is experimentally investigated. A new solution to overcome the performance fluctuations over time induced by the combined effect of Laser Phaser Noise and intercore crosstalk is proposed. The solution uses adaptive modulation with extended time memory to estimate the bit loading scheme of each subcarrier from the mean and maximum error vector magnitude evaluated over the last ten blocks of transmitted training symbols. During measurements of up to 90 hours, intercore crosstalk power variation induced by fast Laser Phase Noise variations exceeded 20 dB in both time and frequency, and error vector magnitude fluctuations of 4 dB were observed on a sub-second timescale. It is shown that direct-detection orthogonal frequency division multiplexing multicore fiber based systems employing a typical adaptive modulation solution, in which the bit loading scheme is evaluated from a single set of training symbols, suffer from unacceptable outage probabilities and are unable to counteract the fast power variations of intercore crosstalk and Phase Noise induced impairments. By extending the system memory used to estimate the bit loading scheme employed by the adaptive technique, an outage probability reduction by one order of magnitude is achieved. This reduction is attained by using the mean of the error vector magnitude evaluated over the last ten blocks of training symbols to estimate the bit loading scheme of subcarriers. Further reduction of the outage probability by four orders of magnitude is also demonstrated using a more conservative approach to estimate the bit loading scheme of the subcarriers. However, this conservative approach, based on the maximum error vector magnitude, may lead to additional loss of the average throughput.
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DD-OFDM multicore fiber systems impaired by intercore crosstalk and Laser Phase Noise
2017 19th International Conference on Transparent Optical Networks (ICTON), 2017Co-Authors: Adolfo V. T. Cartaxo, Tiago M. F. Alves, Ruben S. Luis, Benjamin J. Puttnam, Yoshinari Awaji, Naoya WadaAbstract:The photodetected intercore crosstalk (ICXT) of multicore fiber (MCF) based systems employing direct-detection (DD) is characterised. The impact of the Laser Phase Noise on the photodetected ICXT and on the performance of DD orthogonal frequency division multiplexing (OFDM) MCF-based systems is experimentally demonstrated.
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Virtual Carrier-Assisted Direct-Detection MB-OFDM Next-Generation Ultra-Dense Metro Networks Limited by Laser Phase Noise
Journal of Lightwave Technology, 2015Co-Authors: Tiago M. F. Alves, Adolfo V. T. CartaxoAbstract:The impact of the Phase-to-intensity conversion of the Laser Phase Noise due to the optical band selector (BS) used for band extraction on the performance of direct-detection (DD) optical multiband orthogonal frequency-division multiplexing (MB-OFDM) networks employing single-sideband (SSB) modulation is assessed. Compared to conventional double-sideband DD systems, in which the amplitude shape of the optical filter is quasi-symmetric relative to the centre of the signal spectrum, ultra-dense optical SSB-MB-OFDM networks employing virtual carrier-assisted DD are differently affected by the Phase-to-intensity conversion. This is due to the detuned BS required by these networks, which modify the converted Phase Noise (CPN) features. A reduction of the power spectral density of the CPN achieving 30 dB can occur along the frequency range in which the BS bandwidth and detuning lead to a filtering attenuation that is similar in both sides of the virtual carrier. For single band, when the ratio between the BS detuning and bandwidth increases from 0% to 28%, an error vector magnitude improvement of 7 dB due to the CPN reduction is observed. The optical signal-to-Noise ratio (OSNR) penalty due to the Laser Phase Noise in 112-Gb/s SSB-MB-OFDM networks comprising 12 OFDM bands and employing an ultra-dense band spacing of 3.125 GHz is lower than 1 dB for external cavity Lasers and is 1.6 dB for distributed feedback Lasers. These OSNR penalties are obtained for an optimized ratio between the BS detuning and bandwidth of 14%.
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Influence of Laser Phase Noise on dispersive optical fiber communication systems
IEEE Photonics Technology Letters, 1995Co-Authors: R. Ribeiro, F. Da Rocha, Adolfo V. T. CartaxoAbstract:Noise from semiconductor Lasers in dispersive optical communication systems can give rise to a BER floor. Due to frequency-to-intensity Noise conversion, the impact of Laser Phase Noise increases with the fiber length. It is shown that the maximum transmission distance for dispersion-supported transmission obtained in laboratory experiments is mainly determined by the Laser Phase Noise.
Mohammad M. Banat - One of the best experts on this subject based on the ideXlab platform.
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Exact Moments of Filtered Laser Phase Noise
Journal of Lightwave Technology, 2007Co-Authors: Mohammad M. BanatAbstract:In this paper, we derive an exact finite power series expression of the nth-order moment of a complex filtered Phase Noise random variable. This random variable is usually encountered in the error probability analysis of coherent heterodyne optical receivers. The result is then used to derive an infinite power series expression for the moment generating function of the same random variable. The two expressions represent a novel full statistical characterization of filtered Phase Noise. They also constitute an important step toward deriving optimal heterodyne receiver designs in the presence of Phase Noise. In a previous work Banat (J. Opt. Commun., vol. 5, 267-271, Dec. 2004), the author presented an approximate finite power series moment expression for filtered Laser Phase Noise. The new results will be compared to those of Banat (J. Opt. Commun., vol. 5, 267-271, Dec. 2004)
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A Novel Closed Form Moment Expression for Filtered Semiconductor Laser Phase Noise
Journal of Optical Communications, 2004Co-Authors: Mohammad M. BanatAbstract:A novel closed form expression for the moments of a filtered semiconductor Laser Phase Noise random variable is derived. These moments are essential for statistical characterization of filtered Phase Noise in heterodyne optical receivers, where some function of the Phase Noise process is usually integrated over a symbol interval. The derived expression enables the computation of a given moment from the knowledge of the product of the Laser linewidth and the symbol interval. The latter quantity will be referred to as the linewidth-duration product (LDP).
Jeremy Witzens - One of the best experts on this subject based on the ideXlab platform.
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Laser Phase Noise in Ring Resonator Assisted Direct Detection Data Transmission
IEEE Journal of Selected Topics in Quantum Electronics, 1Co-Authors: Jovana Nojic, Alireza Tabatabaei-mashayekh, Talha Rahman, Alvaro Moscoso-mártir, Florian Merget, Xu Sun, Jeremy WitzensAbstract:We introduce an analytical model describing the statistical and spectral properties of Laser Phase Noise induced intensity Noise in ring-resonator-based modulation. The model is validated with single sideband orthogonal frequency division multiplexing (SSB-OFDM) implemented with a silicon photonics resonantly-assisted Mach-Zehnder modulator (RA-MZM). Excellent agreement of experimental data with full link simulations, in which Phase Noise conversion is treated with the analytical model, confirms its validity. Moreover, we demonstrate 30 Gb/s raw data rate transmission with SSB-OFDM over 20 km of single-mode fiber with a bit error ratio below the 20% forward error correction (FEC) limit for three independently run channels of the RA-MZM, each supplied with off-the-shelf 1 MHz linewidth distributed feedback Lasers.
James Camparo - One of the best experts on this subject based on the ideXlab platform.
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Conversion of Laser Phase Noise to amplitude Noise in an optically thick vapor
Journal of the Optical Society of America B, 1998Co-Authors: James CamparoAbstract:As Laser light propagates through a resonant vapor, Laser Phase Noise (PM) is converted to Laser intensity Noise (AM) because of the sensitivity of atomic coherence to Laser Phase fluctuations. In experiments reported here it is shown that this PM-to-AM conversion process is highly efficient and can cause the relative intensity Noise of transmitted diode Laser light to be 1 to 2 orders of magnitude larger than the Laser’s intrinsic relative intensity Noise. By use of a semiclassical description of the phenomenon, including the effect of optical pumping, reasonably good agreement between theory and experiment is obtained. The PM-to-AM conversion process discussed here has important consequences for atomic clock development, in which diode-Laser optical pumping in thick alkali vapors holds the promise for orders-of-magnitude improvement in atomic clock performance.
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Quantum-mechanical interference between optical transitions and the effect of Laser Phase Noise
Physical Review A, 1997Co-Authors: James Camparo, P. LambropoulosAbstract:We consider three-photon\char21{}one-photon Phase control of resonance-enhanced photonioization with a Phase-diffusion field. As is well known, control is achieved because excitation via the fundamental field interferes with excitation via the third harmonic field, and the form of the interference (i.e., constructive or destructive) depends on the relative Phase difference between the two fields. In the problem, the stochastic nature of the field influences control because the propagation constant of a dispersive medium depends on the field's fluctuating frequency. Here, we approach the influence of Laser Phase Noise on control via (i) a physically intuitive zeroth-order approximation, (ii) first-order perturbation theory, and (iii) numerical simulation. Our results show that first-order perturbation theory is not attractive for the study of this problem, since it requires the evaluation of very high order correlation functions associated with the fundamental field"s fluctuating frequency. More importantly, however, numerical simulation demonstrates that highly efficient control can be attained even in the presence of very large linewidth fields.
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Reduction of Laser Phase-Noise to amplitude-Noise conversion in the gas-cell atomic clock
Proceedings of the 2002 IEEE International Frequency Control Symposium and PDA Exhibition (Cat. No.02CH37234), 1Co-Authors: James CamparoAbstract:In the Laser-pumped gas-cell atomic clock, the short-term stability is significantly influenced by Laser Phase-Noise (PM) to amplitude-Noise (AM) conversion. Here, we discuss the influence of pressure-broadening on the conversion process, and find that when collisional dephasing is very rapid there is a significant decrease in the efficiency of PM-to-AM conversion. Normally, since pressure-broadening increases the linewidth of an atomic transition, collisional dephasing decreases spectroscopic sensitivity. However, the present results imply that when Laser PM-to-AM conversion is dominant, pressure broadening can actually increase spectroscopic sensitivity. Thus, under conditions of significant PM-to-AM conversion, pressure-broadening should improve the performance of Laser-pumped atomic clocks.
