A Robust Threshold for Iterative Channel Estimation in OFDM Systems

A novel threshold computation method for pilot symbol assisted iterative channel estimation in OFDM systems is considered. As the bits are transmitted in packets, the proposed technique is based on calculating a particular threshold for each data packet in order to select the reliable decoder output symbols to improve the channel estimation performance. Iteratively, additional pilot symbols are established according to the threshold and the channel is re-estimated with the new pilots inserted to the known channel estimation pilot set. The proposed threshold calculation method for selecting additional pilots performs better than non-iterative channel estimation, no threshold and fixed threshold techniques in poor HF channel simulations

Money Earning Activities and Empowerment Experiences of Rural Migrant Women in the City: The Case of Turkey

Cataloged from PDF version of article.This article investigates empowerment in relation to money-earning activities in the context of rural-to-urban migrant women in poor families in Turkey. Acknowledging the exploitative character of employment accessible to migrant women, it asks whether working migrant women gain something in their families in return for their economic contributions. The article points to the traditional role of men as the heads of the family and family honor (namus) as the cultural basis which acts against the empowerment of migrant women in Turkish society. It attempts to understand empowerment as articulated by the women themselves based upon their lived experiences. While doing so, it examines women’s positions in the family with regard to their role in the intra-family decision making, their degree of control over their earned money, and male violence in the family. It further discusses whether or not the experiences of migrant women can be considered as empowerment, and in this way it aims to contribute to the theoretical development of the concept ‘‘empowerment.’

Fiber amplification of pulse bursts up to 20 mu J pulse energy at 1 kHz repetition rate

Cataloged from PDF version of article.We demonstrate burst-mode operation of a polarization-maintaining Yb-doped fiber amplifier. Groups of pulses with a temporal spacing of 10 ns and 1 kHz overall repetition rate are amplified to an average pulse energy of similar to 20 mu J and total burst energy of 0.25 mJ. The pulses are externally compressed to similar to 400 fs. The amplifier is synchronously pulsed-pumped to minimize amplified spontaneous emission between the bursts. We characterize the influence of pump pulse duration, pump-to-signal delay, and signal burst length. (C) 2011 Optical Society of Americ

Fiber amplification of pulse bursts up to 20 μj pulse energy at 1 kHz repetition rate

We demonstrate burst-mode operation of a polarization-maintaining Yb-doped fiber amplifier. Groups of pulses with a temporal spacing of 10 ns and 1 kHz overall repetition rate are amplified to an average pulse energy of ∼20 μJ and total burst energy of 0:25 mJ. The pulses are externally compressed to ∼400 fs. The amplifier is synchronously pulsed-pumped to minimize amplified spontaneous emission between the bursts. We characterize the influence of pump pulse duration, pump-to-signal delay, and signal burst length. © 2011 Optical Society of America

Femtosecond laser-induced TiO2 nano structures on titanium

We report formation of polarization-dependent nanostructures (nanolines, nanocircles) by high repetition-rate femtosecond laser pulses on titanium surface through a novel mechanism, converting Ti to TiO2. Arbitrarily large-area patterns are created by self-stitching of these patterns. © 2010 Optical Society of America

1 mJ pulse bursts from a Yb-doped fiber amplifier

Cataloged from PDF version of article.We demonstrate burst-mode operation of a polarization-maintaining Yb-doped fiber amplifier capable of generating 60 mu J pulses within bursts of 11 pulses with extremely uniform energy distribution facilitated by a novel feedback mechanism shaping the seed of the burst-mode amplifier. The burst energy can be scaled up to 1 mJ, comprising 25 pulses with 40 mu J average individual energy. The amplifier is synchronously pulse pumped to minimize amplified spontaneous emission between the bursts. Pulse propagation is entirely in fiber and fiber-integrated components until the grating compressor, which allows for highly robust operation. The burst repetition rate is set to 1 kHz and spacing between individual pulses is 10 ns. The 40 mu J pulses are externally compressible to a full width at half-maximum of 600 fs. However, due to the substantial pedestal of the compressed pulses, the effective pulse duration is longer, estimated to be 1.2 ps. (C) 2012 Optical Society of Americ

All-fiber burst mode laser system integrated with OCT for cataract surgery

We demonstrate a burst-mode Yb all-fiber femtosecond laser system integrated with OCT for cataract surgery and aim to enhance further the procedure with lower collateral tissue damage, cleaner, efficient cuts with compact and robust structure. © 2015 IEEE

All-fiber laser systems that can operate in burst mode

Fiber lasers which operate in burst-mode where densely spaced pulses occur inside bursts repeated at much lower repetition rates can be valuable tool for sensing and imaging. We introduce such lasers and propose possible applications. © OSA 2016

Doping management for high-power fiber lasers: 100 W, few-picosecond pulse generation from an all-fiber-integrated amplifier

Cataloged from PDF version of article.Thermal effects, which limit the average power, can be minimized by using low-doped, longer gain fibers, whereas the presence of nonlinear effects requires use of high-doped, shorter fibers to maximize the peak power. We propose the use of varying doping levels along the gain fiber to circumvent these opposing requirements. By analogy to dispersion management and nonlinearity management, we refer to this scheme as doping management. As a practical first implementation, we report on the development of a fiber laser-amplifier system, the last stage of which has a hybrid gain fiber composed of high-doped and low-doped Yb fibers. The amplifier generates 100 W at 100 MHz with pulse energy of 1 mu J. The seed source is a passively mode-locked fiber oscillator operating in the all-normal-dispersion regime. The amplifier comprises three stages, which are all-fiber-integrated, delivering 13 ps pulses at full power. By optionally placing a grating compressor after the first stage amplifier, chirp of the seed pulses can be controlled, which allows an extra degree of freedom in the interplay between dispersion and self-phase modulation. This way, the laser delivers 4.5 ps pulses with similar to 200 kW peak power directly from fiber, without using external pulse compression. (C) 2012 Optical Society of Americ

Compact 1.5-GHz intra-burst repetition rate Yb-doped all-pm-fiber laser system for ablation-cooled material removal

[No abstract available