Bit error rate computations for optical communication systems incorporating equalizers and under both noise and intersymbol interference (ISI) are discussed. An accurate method based on saddle point approximation is used. Previous work using saddle point approximation considered only basic integration-and-dump detection. The use of equalizers other than integration-and-dump complicates the computation because of the complexity of the moment generating function involved. When ISI is strong, use of an equalizer such as raised-cosine filtering is important for ISI reduction. To help optical receiver design, this paper explains the use of saddle point approximation when an equalizer is used. In addition to integration-and-dump, cosine and raised-cosine equalizers are considered for ISI reduction. To study the interdependence between the received waveform and equalizer used, two different input pulses are also considered. To verify the computation accuracy, exact contour integration based on the numerical quadrature method is performed. Results show that saddle point approximation can provide a fast and accurate computation. From the bit error rate (BER) performance computed, it is found that the traditional use of matched filtering has a poor performance when either ISI is strong or the APD gain is large, and the use of a proper equalizer can significantly improve the performance. In other words, the best choice of an equalizer design depends on the input waveform, amount of ISI, and the APD gain.>

Base stations in personal communications serve as the interface between portable terminals and their central offices. For many reasons, such as cost-effectiveness, higher reliability, simpler handover, and simple clock distribution, it is desirable to use a network instead of point-to-point links to connect base stations to their central offices. The author considers a base station network that has a regular rectangular mesh topology and an access protocol that is based on the slotted ring. The mesh topology provides clock distribution which can synchronize the timing for time-division multiple access (TDMA) or frequency-division multiaccess (FDMA) radio access when the network is physically regular. The slotted-ring protocol provides simple medium access, simple interface with TDMA or FDMA radio channels and simpler handover processing. The author also discusses how base station networks in different central office zones can be interconnected to form a metropolitan area network for both voice and data traffic.>

The author discusses a jitter model and signal processing techniques for data recovery in pulse width modulation (PWM) optical recording. A high-speed counter clock is used to convert time marks to amplitude marks, and signal processing techniques are used to minimize jitter according to the jitter model. The jitter model considered takes into account jitter from both the write and read processes, and the signal processing techniques include: velocity and intersymbol interference equalization; differential interleaving detection (DID); additive interleaving detection (AID); differential interleaving modulation (DIM); and additive interleaving modulation (AIM). These techniques are found to be effective in reducing the mark error rate (MER). Various modulation codes can be used in addition to the signal processing techniques to achieve better modulation efficiency.>

A circuit emulation scheme based on negative stuffing retiming that can effectively remove large bursty delay between packets is described. The approach can be applied to various applications such as T-carrier emulation and packet voice and video communication. The key element of the proposed negative stuffing scheme is the stuffing control or when to add negative stuffing. Two stuffing control algorithms are discussed. The first one is very simple and can provide a smooth output without the need of knowing or estimating the transmitter clock. This algorithm transforms large and fast packet arrival jitter into small and slowly varying frequency wander. The second algorithm tries to estimate the transmitter clock to further reduce the wander. Both algorithms will in principle eliminate the large packet arrival jitter completely, and they also ensure no buffer overflow and underflow. To evaluate buffer delay, jitter, and wander of the recovered clock, time domain simulation has been done for DS1 and DS3 signals over a SONET STS-3c-based switching network.>

A medium-access protocol called time-slot switching (TSS) is proposed for use in optical-fiber local area networks. This protocol incorporates features of time division, space division, and time compression for users to share a common medium. Very-large-integration (VLSI) CMOS electric crosspoints are used to switch traffic within individual time slots. With these features, data, voice, and video services can all be combined in a single network. In addition, the speed of the electronics can be maximized to match the available optical bandwidth. Operational principles of the TSS protocol are explained. A performance analysis is presented to show the tradeoffs among traffic capacity, frame guard time, blocking probability, and the results show that TSS is more attractive than broadcast protocols for voice traffic or constant-rate data traffic. An approach to integrating voice, data, and video traffic within TSS is also described.>

Time slot switching (TSS) has been proposed to switch voice, data, and video in a local area network using fiber optics and high-speed CMOS crosspoint switches. For larger networks such as metropolitan area networks (MANs), significant propagation delays necessitate some modifications to the original technique. The authors propose two medium access protocols for MANs; one is called skew time slot switching (STSS), primarily for real-time service such as voice or video, and the other slotted-ring, primarily for data packets. To provide combined voice, video, and data motivates an integration of STSS and slotted-ring. The advantages and performance of these protocols are discussed.>