Performance evaluation of direct-detection OFDM optical receivers with RF down-conversion

A new method based on the moment generating function is proposed to assess the performance of a direct-detection OFDM optical communication system with radio-frequency I/Q demodulation and its accuracy is validated by Monte Carlo simulation.info:eu-repo/semantics/acceptedVersio

Accuracy of Gaussian approach for the performance evaluation of direct-detection receiver with partially polarized noise

We investigate the accuracy of a Gaussian approach (GA) developed to estimate the performance of a direct-detection optical receiver with arbitrary optical and electrical filtering and in the presence of partially polarized noise due to polarization-dependent loss (PDL). The accuracy is assessed by comparison of the performance estimates obtained from the GA with the estimates obtained from a rigorous method (RM) based on the calculation of the moment-generating function of the current at the optical receiver output. We show that the GA has a good accuracy when considering the variation of the optical filter bandwidth, extinction ratio, degree of polarization of the noise (DOP), and angle between signal and noise polarizations. However, it fails to predict the receiver sensitivity within 2 dB of the RM when DOP is greater than 0.7 and signal and noise polarizations are orthogonal in the Jones space. Nevertheless, it is shown that the GA provides receiver sensitivity estimates with good accuracy in most cases of long-haul optical communication systems influenced by PDL, where the typical average DOP is below 0.15. Due to its simplicity, shorter computation time, and good accuracy, the GA is a good tool to assess the performance of such optical systems.info:eu-repo/semantics/acceptedVersio

On the use of the Gaussian approach for the performance evaluation of direct-detection OFDM receivers impaired by in-band crosstalk

The Gaussian approach (GA) is used to assess the impact of in-band crosstalk on the performance of direct-detection orthogonal frequency division multiplexing (OFDM) optical communication systems. The GA accuracy is compared with estimates of the bit error probability (BEP) and crosstalk penalty obtained using Monte Carlo (MC) simulation. The GA revealed a reduced accuracy when estimating the BEP. However, when estimating the 1 dB crosstalk penalty, the GA exhibited a good accuracy (less than 0.5 dB in comparison with the crosstalk level estimated using MC simulation), for 16-quadrature amplitude modulation (QAM) and 64-QAM mappings in the OFDM subcarriers. The GA leads to very discrepant estimates of the crosstalk penalty for high crosstalk levels.info:eu-repo/semantics/acceptedVersio

Moment Generating Function for the Rigorous Performance Assessment of Direct-Detection Baseband OFDM Communication Systems

WOS:000312036100008 (Nº de Acesso Web of Science)“Prémio Científico ISCTE-IUL 2013”A new moment generating function (MGF) is proposed to assess rigorously the performance of optically preamplified receivers with direct-detection employing baseband orthogonal frequency division multiplexing (OFDM). By comparison with Monte Carlo simulation, the proposed MGF-based method shows very good accuracy when predicting the bit error probability for arbitrary optical and electrical filters, different numbers of OFDM subcarriers, and double sideband and single sideband optical OFDM signals. Its good accuracy when estimating the bit error probability in each individual subcarrier is also demonstrated. The new MGF-based method exhibits a significant improvement of accuracy when compared to the MGF-based method previously reported in the literature, especially for filter bandwidths not exceeding the OFDM signal bandwidth, which is the range corresponding to the optimum filter bandwidth

Characterization of the stochastic time evolution of short-term average intercore crosstalk in multicore fibers with multiple interfering cores

A theoretical model for the stochastic time evolution of the intercore crosstalk (ICXT) in homogeneous weakly-coupled multicore fibers (MCF) with multiple interfering cores is proposed and validated experimentally. The model relies on the introduction of non-stationary time varying random phase shifts at every center point between the phase matching points of the MCF where the di erence of the e ective refractive indexes of the core of the originating signal and the core su ering from ICXT is zero. Closed form-expressions for the autocovariance of the short-term average ICXT (STAXT) with stationary and non-stationary phase shift models in MCFs with multiple excited cores are derived and validated by comparison with experimental results. These expressions enable estimating the decorrelation time of the STAXT generated by multiple interfering cores from the decorrelation times of the STAXT generated by each pair of cores. The proposed model and the ICXT measurements taken continuously over more than 150 hours show that the decorrelation time of the STAXT generated by multiple interfering cores exceeds the one obtained for the pair of cores with shorter decorrelation time. The proposed model is increasingly important to simulate and design MCF-based systems where the ICXT dynamics must be properly accounted for to develop e cient ICXT-tolerant techniques.info:eu-repo/semantics/publishedVersio

Transmission of CPRI signals along weakly-coupled multicore fibers for support of 5G networks

The impact of intercore crosstalk (ICXT) of weakly-coupled multicore fibers on the transmission performance of a Common Public Radio Interface (CPRI) signal in 5G networks is studied by numerical simulation. The results show that forward error correction-supported CPRI signals (accepting higher bit error rates) have more tolerance to ICXT, which increases with the skew between cores. Improvement of the tolerance of CPRI signals to the ICXT, due to the increase of the skew, by 1.7 dB is shown.info:eu-repo/semantics/publishedVersio

Assessment of the combined effect of laser phase noise and intercore crosstalk on the outage probability of DD OOK Systems

We study the influence of the combined effect of laser phase noise and intercore crosstalk on the outage probability of direct-detection 10 Gbit/s on-off keying optical communication systems. We show that the laser phase noise can affect significantly the outage probability, for lasers with linewidths in the MHz range, for low and high skew-bit rate products. We also show that the laser phase noise effect on the received eye-pattern is qualitatively similar to the one found for high skew-bit rate product in the absence of laser phase noise.info:eu-repo/semantics/acceptedVersio

Characterization of crosstalk-impaired OOK signals in WC-MCF systems with high and low skew×bit rate

The received amplitudes of crosstalk-impaired on-off keying signals in weakly-coupled multicore fibre (WC-MCF) systems are experimentally assessed for high and low skew×bit-rate. Gaussian-distributed crosstalk-induced amplitudes are shown for high skew×bit-rate. The mean of these amplitudes can also be modelled by Gaussian distributions.info:eu-repo/semantics/acceptedVersio

Influence of the SSBI mitigation on the in-band crosstalk tolerance of virtual carrier-assisted DD multi-band OFDM metro networks

In this work, the tolerance to in-band crosstalk of virtual carrier (VC)-assisted direct detection (DD) multi-band orthogonal frequency division multiplexing (MB-OFDM) metro networks, with and without signal-to-signal beat interference (SSBI) mitigation, is compared numerically for 4-ary, 16-ary and 64-ary quadrature amplitude modulation (QAM) formats in the OFDM subcarriers. Our results show that the tolerance to in-band crosstalk is improved for lower modulation format orders. The tolerance to in-band crosstalk of DD OFDM receivers considering 4-QAM modulation format at the DD OFDM subcarriers is above 14 dB higher than the one obtained for the 64-QAM modulation format, regardless the receiver configuration. We have also shown that, the tolerance to in-band crosstalk for a given modulation format order depends on the difference between the virtual carrier-to-band power ratio (VBPR) of the selected and interfering signals, as interferers with same VBPR as the selected signal leads to equal tolerance to in-band crosstalk, independently from the DD OFDM receiver configuration and the subcarrier modulation format order considered.info:eu-repo/semantics/acceptedVersio

Weakly-coupled MCF direct-detection OOK systems impaired by laser phase noise

On-off-keying multicore fiber systems employing different lasers are experimentally investigated. Laser phase noise increases the instantaneous fluctuations of the crosstalk. DFB-based systems may require an additional crosstalk margin of 4 dB relative to ECL-based systems.info:eu-repo/semantics/acceptedVersio