Generation of 83 fs mid-IR pulses with 22 W average power using an Er:ZBLAN fiber mode-locked oscillator and a nonlinear amplifier

A femtosecond laser machine consisting of femtosecond fiber laser, trepanning head, linear motor stages system and Siemens 840D system has been integrated for industry application. The femtosecond laser source is all fiber system which contains a fiber mode-lock laser at 1053 nm with a repetition rate of 3.9 MHz, a double-cladding gain fiber amplifiers and a PCF amplifier. An acoustical modulator has employed to tune repetition rate from 3.9 MHz to 100 KHz. An in-line fiber chirped grating is used to stretch the pulse duration to 700 ps. After the PCF amplifier pulse is compressed to sub-ps with 50% efficiency based two grating compressor. The system outputs an average power of 15 W at 100 KHz and 800 fs. Using four wedges trepanning head, cylinder hole is drilled in 1mm thickness SiC ceramics in 30 s.

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A New-Trend Model-Based to Solve the Peak Power Problems in OFDM Systems

Modelling and Simulation in Engineering ◽

10.1155/2008/345478 ◽

2008 ◽

Vol 2008 ◽

pp. 1-9 ◽

Cited By ~ 1

Author(s):

Ashraf A. Eltholth ◽

Adel R. Mekhail ◽

A. Elshirbini ◽

M. I. Dessouki ◽

A. I. Abdelfattah

Keyword(s):

Orthogonal Frequency Division Multiplexing ◽

Peak Power ◽

Dynamic Range ◽

Average Power ◽

Problem Definition ◽

Ofdm Systems ◽

Ofdm System ◽

Ofdm Signal ◽

Nonlinear Amplifier ◽

Power Problem

The high peak to average power ration (PAR) levels of orthogonal frequency division multiplexing (OFDM) signals attract the attention of many researchers during the past decade. Existing approaches that attack this PAR issue are abundant, but no systematic framework or comparison between them exists to date. They sometimes even differ in the problem definition itself and consequently in the basic approach to follow. In this paper, we propose a new trend in mitigating the peak power problem in OFDM system based on modeling the effects of clipping and amplifier nonlinearities in an OFDM system. We showed that the distortion due to these effects is highly related to the dynamic range itself rather than the clipping level or the saturation level of the nonlinear amplifier, and thus we propose two criteria to reduce the dynamic range of the OFDM, namely, the use of MSK modulation and the use of Hadamard transform. Computer simulations of the OFDM system using Matlab are completely matched with the deduced model in terms of OFDM signal quality metrics such as BER, ACPR, and EVM. Also simulation results show that even the reduction of PAR using the two proposed criteria is not significat, and the reduction in the amount of distortion due to HPA is truley delightful.

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The Statistical Correlation between Distortion and Adding Signal for PAPR Reduction in OFDM based Communication Systems

10.5121/csit.2020.101807 ◽

2020 ◽

Author(s):

Désiré Guel ◽

Boureima Zerbo ◽

Jacques Palicot ◽

Oumarou Sié

Keyword(s):

Communication Systems ◽

Average Power ◽

Statistical Correlation ◽

Papr Reduction ◽

Signal Power ◽

Work Related ◽

Reduction Techniques ◽

Nonlinear Amplifier ◽

First Time ◽

Good Agreement

In recent past years, PAPR (Peak-to-Average Power Ratio) of OFDM (Orthogonal FrequencyDivision Multiplexing) system has been intensively investigated. Published works mainly focus on how to reduce PAPR. Since high PAPR will lead to clipping of the signal when passed through a nonlinear amplifier. This paper proposes to extend the work related to "Gaussian Tone Reservation Clipping and Filtering for PAPR Mitigation" which has been previously published. So, in this paper, we deeply investigate the statistical correlation between PAPR reduction, and the distortion generated by three (3) adding signal techniques for PAPR reduction. Thereby, we first propose a generic function for PAPR reduction. Then, we analyse the PAPR reduction capabilities of each PAPR reduction technique versus the distortion generated. The signal-to-noise-and-distortion ratio (SNDR) metric is used to evaluate the distortion generated within each technique by assuming that OFDM baseband signals are modelled by complex Gaussian processes with Rayleigh envelope distribution for a large number of subcarriers. The results related to one of the techniques is proposed in the first time in this paper, unlike those related to the other two PAPR reduction techniques where the studies were already published. Comparisons of the proposed approximations of SNDR with those obtained by computer simulations show good agreement. An interesting result highlighted in this paper is the strong correlation existing between PAPR reduction performance and distortion signal power. Indeed, the results show that PAPR reduction gain increases as the distortion signal power increases. Through these 3 examples of PAPR reduction techniques; we could derive the following conclusion: in an adding signal context, the adding signal for PAPR reduction is closely linked to the distortion generated, and a trade-off between PAPR-reduction and distortion must be definitely found.

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