Ralph Urbansky

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In modern lightwave systems error correction has become a common feature to improve noise immunity. Electronic equalization increases tolerance against chromatic dispersion and polarization mode dispersion. Combination of both methods promises further impovement. Introduction Electronic equalization and forward error correction (FEC) are well known(More)
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 state-of-the-art with(More)
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)
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)
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)
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. 1. Introduction Recent simulation results for turbo equalization (TE) of polarization mode dispersion (PMD) channels [1] have shown a gain up to(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)
With Today's demands in quality assurance, a thorough inspection of products becomes mandatory for a lot of industrial branches. For example, X-ray scanners replace more and more the simple metal detectors used in food industry. For such scanning applications continuous processing is desirable, because it fits most production processes without the need for(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)