Ralph Urbansky

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Considering the growing demand for high-rate data services, the capacity of optical fibers has to be exploited close to its theoretical limit. In addition to techniques mitigating dispersions, coherent detection and polarization multiplexing (PolMUX) as well as forward error correction (FEC) using high-rate block codes are already applied. However, to(More)
Thsday, M arch 27 Fig. 2 shows calculated sensitivity using Q factor estimation [1]. Indicated with lines are theoretically analyzed sensitivities as a function of bit rate without an SOA, with an SOA, and with an SOA and an optical band-pass filter, respectively. Our experimental result with SOA demonstrated later, a previous work with SOA [2], and the(More)
Forward error correction (FEC) coding, modulation formats like differential phase shift keying (DPSK) and adaptive electronic equalization to mitigate, e.g. polarization mode dispersion (PMD) are some of the methods applied in current direct-detection optical communication systems, which are limited to a spectral efficiency of 1 bit/s/Hz. Coherent(More)
In case of unknown carrier phase and/or imperfect channel estimation in communication systems using QPSK it is well known that phase and channel uncertainty can be resolved by differential modulation at the expense of doubling the bit error ratio. Such a differentially modulated QPSK approach has to be applied in wavelength division multiplexing (WDM) fiber(More)
Applying LDPC codes to turbo equalization of PMD channels requires them to be adopted to the equalizer. A design using fitted EXIT functions offers improved OSNR tolerance of ca. 5dB compared to MLSE equalization. 2007 Optical Society of America OCIS codes: (060.4510) Optical communications; (060.2360) Fiber optics links and subsystems; (999.9999)(More)
Iterative “turbo” decoding of parallel or serial concatenated convolutional codes (CC) allows for a performance close to Shannon's channel capacity limit. Whereas “turbo” equalization (TE) for intersymbol interference (ISI) channels corresponds to serial concatenation, we show that the turbo decoding principle for parallel(More)
It is widely known that turbo equalization with low-rate forward error correcting (FEC) codes significantly reduces the bit error ratio (BER) in low signal to noise ratio (SNR) channels, and recently in this workshop it was reported that also for non-linear channels and high-rate codes remarkable turbo decoding gains can be achieved [1]. However, for a(More)