Reach improvement of mode division multiplexed systems using fiber splices

This letter proposes the introduction of discrete modal crosstalk (XT) through fiber splices for the improvement of the distance reach (DR) of mode division multiplexed (MDM) transmission systems over few mode fibers (FMFs). The proposed method increases the DR, reducing the time spread of the FMFs' impulse response. The effectiveness of this method is assessed through simulation considering 3 × 136-Gbit/s MDM-coherently-detected polarization-multiplexed quadrature-phase-shift-keying ultralong haul transmission systems employing inherently low differential mode delay (DMD) FMFs or DMD compensated FMFs. A maximum DR increase factor of 1.9 is obtained for the optimum number of splices per span and optimum splice XT level

Stabilization of self-coherent OFDM with injection locked laser

With the rebirth of coherent detection, various algorithms have come forth to alleviate phase noise, one of the main impairments for coherent receivers. These algorithms provide stable compensation, however they limit the DSP. With this key issue in mind, Fabry Perot filter based self coherent optical OFDM was analyzed which does not require phase noise compensation reducing the complexity in DSP at low OSNR. However, the performance of such a receiver is limited due to ASE noise at the carrier wavelength, especially since an optical amplifier is typically employed with the filter to ensure sufficient carrier power. Subsequently, the use of an injection-locked laser (ILL) to retrieve the frequency and phase information from the extracted carrier without the use of an amplifier was recently proposed. In ILL based system, an optical carrier is sent along with the OFDM signal in the transmitter. At the receiver, the carrier is extracted from the OFDM signal using a Fabry-Perot tunable filter and an ILL is used to significantly amplify the carrier and reduce intensity and phase noise. In contrast to CO-OFDM, such a system supports low-cost broad linewidth lasers and benefits with lower complexity in the DSP as no carrier frequency estimation and correction along with phase noise compensation is required

Mode-division-multiplexed 3x112-Gb/s DP-QPSK transmission over 80 km few-mode fiber with inline MM-EDFA and blind DSP

We show transmission of a 3x112-Gb/s DP-QPSK mode-division-multiplexed signal up to 80km, with and without multi-mode EDFA, using blind 6x6 MIMO digital signal processing. We show that the OSNR-penalty induced by mode-mixing in the multi-mode EDFA is negligible

İkinci Dünya Savaşı’nın en başarılı casusu : İlyas Bazna

Ankara : İhsan Doğramacı Bilkent Üniversitesi İktisadi, İdari ve Sosyal Bilimler Fakültesi, Tarih Bölümü, 2014.This work is a student project of the The Department of History, Faculty of Economics, Administrative and Social Sciences, İhsan Doğramacı Bilkent University.by Öztürk, İbrahim Mert

Impact of LED nonlinearity on discrete multitone modulation

In the context of communications based on light-emitting diodes (LEDs), spectrally efficient modulation has been considered for overcoming their limited bandwidth, and one scheme under investigation is quadrature-amplitude modulation on discrete multitones. The dependence of the output optical power on the driving current of practical LEDs is nonlinear, which distorts the transmitted signal. We investigate the impact of the nonlinear LED transfer function, i.e., the dependence of the emitted optical power on the driving current, on discrete multitone modulation. The effect incurred by this distortion was analyzed by using detailed numerical simulations addressing the impact of clipping, individual subcarriers, signal-to-noise ratio, and bit-error ratio. The approach was generalized to describe the impact of the nonlinearity of arbitrary LEDs and laser diodes, resulting in a powerful tool for assessing the impact of the nonlinearity on the link performance. This approach was applied to three types of LED, showing anything from a minuscule effect to the case in which error-free data transmission is made impossible by the transfer-function nonlinearity

The impact of LED transfer function nonlinearity on high-speed optical wireless communications based on discrete-multitone modulation

\u3cp\u3eThe nonlinear dependence of the optical power from white LEDs on the applied driving current and its impact on discrete-multitone modulation was investigated by use of numerical simulations for the case of optical wireless communications.\u3c/p\u3

Impact of LED nonlinearity on discrete multitone modulation

\u3cp\u3eIn the context of communications based on light-emitting diodes (LEDs), spectrally efficient modulation has been considered for overcoming their limited bandwidth, and one scheme under investigation is quadrature-amplitude modulation on discrete multitones. The dependence of the output optical power on the driving current of practical LEDs is nonlinear, which distorts the transmitted signal. We investigate the impact of the nonlinear LED transfer function, i.e., the dependence of the emitted optical power on the driving current, on discrete multitone modulation. The effect incurred by this distortion was analyzed by using detailed numerical simulations addressing the impact of clipping, individual subcarriers, signal-to-noise ratio, and bit-error ratio. The approach was generalized to describe the impact of the nonlinearity of arbitrary LEDs and laser diodes, resulting in a powerful tool for assessing the impact of the nonlinearity on the link performance. This approach was applied to three types of LED, showing anything from a minuscule effect to the case in which error-free data transmission is made impossible by the transfer-function nonlinearity.\u3c/p\u3

Excess mortality in istanbul during extreme heat waves between 2013 and 2017

Heat waves are one of the most common direct impacts of anthropogenic climate change and excess mortality their most apparent impact. While Turkey has experienced an increase in heat wave episodes between 1971 and 2016, no epidemiological studies have examined their potential impacts on public health so far. In this study excess mortality in Istanbul attributable to extreme heat wave episodes between 2013 and 2017 is presented. Total excess deaths were calculated using mortality rates across different categories, including age, sex, and cause of death. The analysis shows that three extreme heat waves in the summer months of 2015, 2016, and 2017, which covered 14 days in total, significantly increased the mortality rate and caused 419 excess deaths in 23 days of exposure. As climate simulations show that Turkey is one of the most vulnerable countries in the Europe region to the increased intensity of heat waves until the end of the 21st century, further studies about increased mortality and morbidity risks due to heat waves in Istanbul and other cities, as well as intervention studies, are necessary.Scientific Research Projects Coordination Unit of Istanbul University-Cerrahpas

12-mode OFDM transmission using reduced-complexity maximum likelihood detection

We report the transmission of 163-Gb/s MDM-QPSK-OFDM and 245-Gb/s MDM-8QAM-OFDM transmission over 74 km of few-mode fiber supporting 12 spatial and polarization modes. A low-complexity maximum likelihood detector is employed to enhance the performance of a system impaired by mode-dependent loss