Pulse position modulation (PPM) presents several advantages in free-space optical systems, unrepeatered fiber transmission, and passive optical networks. In this paper, we study the error performance in direct-detection optically preamplified M-ary PPM optical communication systems. We consider the impact of the amplifier spontaneous emission noise, as well of the finite extinction ratio of the transmitter, on the probability of bit error at the receiver. We derive expressions for the probability of bit error under both assumptions of noise polarization, namely, single- and dual-polarized amplifier noise, and compute it numerically for different symbol sizes M and extinction ratios. In addition, we present the power penalty due to the transmitter finite extinction ratio for systems with and without forward error correction. Our findings show that, in the cases of practically achievable finite extinction ratios, systems with smaller M may perform equally well when compared to those using higher values of M. We also show that there is little benefit, if any, associated with using a polarization filter in the receiver since the additional size, weight, and power consumption requirements outweigh the error performance improvement.

This paper presents a telephony solution for local multipoint distribution service (LMDS) using technology for personal communications services (PCS). An actual system based on digital enhanced cordless telecommunications (DECT) has been implemented. The system architecture of the DECT-based LMDS telephony system is discussed. Performance measurement results show that a DECT-based system does not have stringent frequency stability requirement and therefore can allow low-cost implementation.

Summary form only given. SONET technology has made high speed self-healing ring architectures practical and economical for interoffice network applications. Self-healing ring networks using electronic add-drop multiplexers (SONET ADMs) are limited in capacity to about 10 Gb/s by the electronics. Elrefaie (1993) proposed a multiwavelength interoffice ring architecture for high capacity transport applications. Two types of multiwavelength ring have been proposed: one uses two fibers and the automatic protection switching capability of standard uni-directional SONET ADMs; the other uses four fibers together with a new capability for automatic protection using optical switching and uni-directional SONET ADMs. Both can be designed to be consistent with present SONET standards, allowing graceful upgrades from electronic SONET rings to multiwavelength SONET rings. In multiwavelength interoffice ring networks, WDM signals traverse a cascade of erbium-doped fiber amplifiers (EDFAs), each followed by optical drop-and-insert multiplexers. The amplifiers' non-flat gain spectra impose size and capacity limits that depend on the network types and the specific drop-and-insert arrangements of the network. Also, WDM signals pass through a number of concatenated optical filters which leads to network performance degradations due to laser and filter passband misalignments arising from device imperfections and temperature variations. The paper evaluates the accumulation of performance degradations in multiwavelength interoffice ring networks. The author also suggests several techniques to overcome performance degradations of multiwavelength networks.

A hybrid approach is presented for evaluating the performance of single-mode digital lightwave communication links efficiently. The hybrid approach combines simulation with analysis to provide greater accuracy and flexibility than that available with analytical calculations alone. Because simulation is used, models can be made as detailed as necessary and computed waveforms can be compared directly to measured waveforms. Measured data can be used to characterize functional components, such as sources, fibers, and detectors, accurately. Simulation models and techniques for evaluating system degradations caused by the optical-source waveforms, fiber attenuation and dispersion, and receiver noise are provided. The end-to-end performance of typical digital lightwave links with broad- and narrow-spectrum sources (light-emitting diodes and laser), using both p-i-n and avalanche photodiode detectors, is evaluated and compared to experimental results.>

The problem of designing and evaluating the performance of a minimum mean-square error equalizer (MMSEE) for binary PSK transmission over band-limited nonlinear satellite channels is considered in this correspondence. The effect of intersymbol interference followed by AM/AM and AM/PM conversions are taken into account while optimizing the performance in the presence of the downlink white Gaussian noise. In analyzing the problem, the decision is made on a typical signal in a received sequence taking into account past and future interfering signals, i.e., ISI. As an illustrative example of the receiver, a typical channel model is considered in details. Based on the analysis, an alternative receiver structure which is more suitable for implementation is introduced. The taps gain coefficients for minimum mean-square error, between the received sample and the actual transmitted bit, are obtained using numerical methods. The performance of the equalizer is evaluated using computer simulation techniques and it is shown that significant performance improvement over the single-sample sign detector can be obtained.