Optical CPFSK Research Articles

Baysian Channel Equalizers for Optical CPFSK Receivers with Gaussian Frequency Pulse Shape

Article Baysian Channel Equalizers for Optical CPFSK Receivers with Gaussian Frequency Pulse Shape was published on August 1, 2004 in the journal Journal of Optical Communications (volume 25, issue 4).

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.

System Performance of Optical Heterodyne CPFSK Receivers with AFCs

We analyze the system performance of optical heterodyne CPFSK receivers with AFC loops. The effects of closed loop gain and postdetection filters are taken into account. The GQR (Gaussian quadrature rule) method is used to deal with the laser phase noise characteristics in computing the bit-error rates. The impact of closed loop gain on the system performance is investigated. The optimum design of postdetection filters is outlined in showing the improvement of system performance compared with the system without AFC.

Sensitivity Penalty for Direct Detection CPFSK Receiver due to Laser Phase Noise and Chromatic Dispersion

The sensitivity penalty of a direct detection 10 Gbit/s optical CPFSK receiver due to laser phase noise, interferometric intensity noise and chromatic dispersion is determined analytically at a BER of 10 -9 . The analysis is based on linear approximation of the output phase of a linearly filtered CPFSK signal. The significant contributory role of the laser phase noise with increasing value of chromatic dispersion index is highlighted. The theoretical results have been found to be in excellent agreement with the simulation results.

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.

Frequency Spectra in an Optical CPFSK Heterodyne Delay Demodulating Receiver using Manchester Coding

Article Frequency Spectra in an Optical CPFSK Heterodyne Delay Demodulating Receiver using Manchester Coding was published on June 1, 1996 in the journal Journal of Optical Communications (volume 17, issue 3).

Sensitivity penalty for AMI-coded CPFSK in heterodyne delay demodulation receiver

Bit-error rate performance and sensitivity penalty for 2.5 Gb/s AMI-coded optical CPFSK in a delay demodulation receiver are obtained. It has been found that an optimum modulation index of 0.9 yields a theoretical system penalty of 2 dB at a bit-error rate of 10/sup -9/ using a DFB laser with nonflat FM response and normalized laser linewidth /spl Delta//spl nu/T=4/spl times/10/sup -4/. >

Performance analysis of a direct detection receiver for AMI-coded CPFSK signals

A theoretical analysis of a direct detection receiver for AMI encoded optical CPFSK signals is presented. The results of the analysis show that AMI-CPFSK with nonuniform laser FM response approaches NRZ-CPFSK with flat FM response to within 0.25 dB at a bit-error rate of 10/sup -9/ with modulation index h=0.8 and normalized line width /spl Delta//spl nu/T=5/spl middot/10/sup -3/. The theoretical results are confirmed by simulation. >

GaAs MMIC demodulator using a distributed mixingprinciple for high-sensitivity 5 Gbit/s CPFSK receiver

A distributed GaAs MMIC mixer is designed to be employed in an integrated demodulator for a coherent optical CPFSK receiver with an IF bandwidth of 7-14 GHz and a baseband bandwidth of 4 GHz. At 5 Gbit/s a receiver sensitivity of -39.0 dBm is obtained using the demodulator.

Probability of Error for a Coherent Optical Heterodyne CPFSK Receiver Employing Limiter-Discriminator Demodulation

Article Probability of Error for a Coherent Optical Heterodyne CPFSK Receiver Employing Limiter-Discriminator Demodulation was published on October 1, 1995 in the journal Journal of Optical Communications (volume 16, issue 5).

Performance evaluation of FSK and CPFSK optical communication systems: a stable and accurate method

The modified moments method for evaluating the performance of coherent optical FSK and CPFSK systems is presented. Since the classical procedure becomes ill-conditioned as the order of the moments increases, we consider the construction of Gaussian quadrature rules (GQR) from the modified moments. The analysis accounts for the influences of IF bandwidth, transmitter and local oscillator laser phase noise, postdetection filters, and additive Gaussian noise. It is found that the proposed approach is a highly reliable and efficient method for calculating the error probability. A comparison with results obtained from the Gaussian quadrature rule, Gaussian approximation method, and analytical approximation formulas shows that this technique is very accurate. Analytical expressions are derived for FSK and CPFSK receivers which include polarization and phase diversity techniques. The use of numerical programming to avoid many unnecessary computations is discussed. This evaluation method can be used to account for the effects of crosstalk in multichannel systems and the influence of error-control codes.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

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.

Performance Analysis of Optical CPFSK Receivers with Gaussian Frequency Pulse Shape

The performance of an optical CPFSK receiver can be improved by choosing adequate shape of Gaussian frequency pulse and the delay time of the delay- and-multiply frequency discriminator. Exact mean and variance of the output statistic are derived. The results of Gaussian approximation are applied to finding the system bit error rate floors and the optimum delay times. For various Gaussian frequency pulse shapes, the delay times should be set accordingly. The effects of laser linewidth and shot noise are taken into account

Monolithic demodulator for high sensitivity 2.5Gbit/s CPFSK receiver

A completely monolithic quadrature demodulator for an optical heterodyne CPFSK receiver is reported for the first time. The demodulator is realised as a GaAs MMIC and operates up to 2.5 Gbit/s at an intermediate frequency of 9.8 GHz, yielding a receiver sensitivity of -42.5 dBm. >

Spectral Density Function of Optical CPFSK Signals in the Presence of Laser Phase Noise

Spectral Density Function of Optical CPFSK Signals in the Presence of Laser Phase Noise

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.

Optical CPFSK receiver with BER &lt; 10 −9 : Monte Carlo simulation and experiment

Simulation results for an optical heterodyne CPFSK receiver are presented and compared with measurements on a well defined experimental system. 3.4 × 1010 bit were simulated during the run at the lowest BER.

Influence of if narrow‐band filtering on bit error rates in coherent optical heterodyne CPFSK receiver using variable delay demodulation

AbstractIn this article we discuss a coherent optical heterodyne CPFSK receiver using optimum variable delay demodulation considering the effect of narrow‐band IF filtering or intersymbol interference (ISI) caused by it. First we investigate the error probability at the normalized bandwidth of IF filter BT = 1 for a Gaussian IF filter. Numerical results show that the impact of narrow‐band IF filtering increases with an increase in normalized IF spectral linewidth ΔvT and a decrease in modulation index h. Second, in order to decrease the impact of ISI, the optimum BT values are determined, which can minimize the error probability for given SNR. If a Gaussian IF filter is used, the optimal BT values are 1.3 for ΔvT = 0.25%, 1.4 for ΔvT = 0.5% at h = 0.5, 1.2 for ΔvT = 0.25%, 1.4 for ΔvT = 0.5% at h = 0.7, and 1.2 for all ΔvT ≤ 0.5% at h = 1. Finally, the performance of an optimal receiver employing optimum Gaussian IF filter is studied. We know that h = 1 is optimum and ΔvT ≤ 0.5% is necessary for 1‐dB EB/N0 penalty per bit at BER of 10−9. © 1992 John Wiley &amp; Sons, Inc.