Optical CPFSK System Research Articles

Performance Evaluation of Optical CPFSK Systems Influenced by Phase Noise

In this paper, we address the performance evaluation of optical CPFSK systems in the presence of significant phase noise. The focus is on the envelope characterization of filtered signal. We use simple, yet very accurate expressions to describe the envelope of filtered signal influenced by phase noise. To check the accuracy of the approximation, we compare the results with those obtained from existing methods.

Performance limitations of an optical heterodyne CPFSK transmission system due to self-phase modulation

A detailed theoretical analysis is presented to evaluate the combined influence of self-phase modulation (SPM) and group velocity dispersion (GVD) of optical fiber on the bit error rate (BER) performance of a heterodyne optical CPFSK system. The power penalty suffered by the system due to the combined influence of GVD and SPM is evaluated from the BER performance results. It is found that the penalty due to SPM at a BER of 10 −9 is significant when the input power exceeds 7 dBm . Further, the CPFSK system with modulation index of 0.5 is less sensitive to the effects of GVD and SPM compared to the system with a modulation index of 1. The theoretical results are in conformity with the experimental results reported earlier.

Impact of Self-phase Modulation on Optical Direct Detection CPFSK Transmission System

A detailed theoretical analysis is presented to evaluate the combined influence of self-phase modulation (SPM) and group velocity dispersion (GVD) of optical fiber on the bit error rate (BER) performance of a direct detection optical CPFSK system. Performance results are evaluated at a bit rate of 10 Gbit/s taking into considerations the random phase fluctuations at the receiver output due to GVD and SPM. The power penalty suffered by the system due to combined influence of GVD and SPM is then determined at a BER of 10 -9 , The results show that the performance of optical direct detection CPFSK is highly degraded due to SPM at input power of more than 5 dBm and the penalty is minimum at a modulation index of 0.5.

An Accurate Analysis of Optical CPFSK Systems with Tight Pre-detection Filtering

An analysis for optical CPFSK systems with tight pre-detection filtering is presented. The intersymbol interference and the correlation between the direct and the delayed signal are considered. The receiver model is simplified so that no approximation is needed in the analysis. It is confirmed that even with tight pre-detection filtering the receiver still needs more than 40 photons per bit to obtain a bit error rate of 10 -9 . The obtained results show a clear view of how the system performance will change with the modulation index and the ratio of the pre-detection bandwidth to date rate.

Recursive simulation models of the semiconductor laser modulation characteristics for accurate performance evaluation of coherent optical CPFSK systems

Modeling of the semiconductor laser nonuniform FM response and residual IM modulation is essential for the computer-aided design of coherent optical communication systems. This paper presents an accurate simulation model, in which the FM and IM responses are represented by recursive digital filters derived directly from measurements. A comparison with previous models of the bibliography reveals the advantages of the current approach. The proposed modeling procedure is applied in the case of a single-electrode DFB laser. This DFB model, in combination with a semi-analytical technique for the evaluation of the error probability, is used to study the influence of the modulation characteristics on the performance of a coherent heterodyne CPFSK system with differential receiver operating at 1 Gb/s. Theoretical and experimental results are in excellent agreement.

Experimental reduction of phase‐noise influence for an optical CPFSK system with I.F. filtering

AbstractTheoretical modeling and experimental analysis of the influence of i.f. filtering on performance of optical heterodyne CPFSK systems with differential detection in the presence of phase noise are compared. It is shown that for a bit rate of 1 Gbits/s with a modulation index of 1, i.f. filtering reduces phase noise influence, leading to a significant reduction of the bit‐error‐rate floor.

Requirements for LD FM characteristics in an optical CPFSK system

A procedure for evaluating the influence of a nonideal FM response on the bit error rate characteristics is proposed which explains experimental results fairly well. Criteria for the laser diode (LD) FM response are obtained in order to realize low-penalty operation with a long bit pattern. The position and the shape of the dip (typical for a conventional LD FM response), especially the slope of the higher frequency part of the dip, are the dominant factors which determine the nonideal FM response influence of transmitter devices. The criteria obtained give guidelines for the LD FM response equalization, as well as the device selection. For devices to be applied in practical systems with an FM equalizer, a dip frequency sufficiently below 4*10/sup -4/ of the bit rate should be selected in order to realize less than 0.5-dB sensitivity penalty operation, since the passive electrical equalization is only effective for the frequency region higher than the dip frequency.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>