J.R.F. da Rocha

Performance evaluation of EDFA preamplified receivers taking into account intersymbol interference

Exact mathematical derivation of the moment generating function for an optically preamplified receiver output current is carried out. Amplified spontaneous emission noise as well as Poisson shot-noise and thermal noise originated at the receiver front-end are considered. Optical bandpass filter is also taken into account. This new global description of the stochastic processes involved in optical signal detection enables analytical assessment of the overall receiver performance without restrictions on the optical input pulse and the electronic filter response. Various bit error rate evaluation methods such as Chernoff bound, modified Chernoff bound, Gaussian approximation and saddlepoint approximation are developed based on the moment generating function and their precision compared. >

Generating Realistic Optical Transport Network Topologies

We address the problem of generating physical realistic optical transport network topologies. This type of network has characteristics that differ from scale-free networks, such as the Internet. Based on the analysis of a set of real transport topologies, we identify and assess relevant characteristics. A method to generate realistic topologies is proposed. The proposed method is validated by comparing the characteristics of computer-generated and real-world optical transport networks.

Optical Fiber Direct Detection Receivers Optimally Tolerant to Jitter

A technique for optimizing the performance of directdetection optical communication receivers for binary signaling in the presence of signal dependent noise, additive noise, and intersymbol interference by minimizing a Chernoff bound on the average error probability is extended to accommodate timing jitter. Receivers are identified which provide significantly improved performance compared to conventional designs, and the performance of a jitter-optimized receiver is shown to be relatively insensitive to variations in the jitter level.

Statistical model for link lengths in optical transport networks

From the analysis of statistical properties of real networks, it is found that general extreme value (GEV) distribution provides an accurate model for link length statistics of optical transport networks (OTNs). The parameters of GEV distribution can be estimated from the average link length of the OTNs. Expressions for average link lengths, based only on the knowledge of network coverage area and number of nodes, are improved for better accuracy. It is shown that the optimized GEV distribution estimates the link statistics of OTNs with good accuracy (Kolmogorov-Smirnov statistic less than 0.18).

All-optical routing based on OCDMA headers

In this paper we describe a technique which associates the already matured code generation and detection technique of optical code division multiple access (OCDMA) with the all-optical routing needs and discuss its advantages and drawbacks.

Optimization of apodized fiber grating filters for WDM systems

The reflection characteristics of apodized fiber gratings are compared and optimized for WDM system applications. We show the potential of these devices as optical filters for dense WDM systems.

Uniform Polarization Scattering With Fiber-Coil-Based Polarization Controllers

A detailed study of fiber-coil-based polarization controllers (PCs) is performed. First, a method to deterministically calculate the PC configuration in order to transform between any two states of polarization is presented. In a second stage, the case in which the configuration angles are randomly changed is studied. The cases of a single PC and of the system obtained with the concatenation of several PCs are analyzed. For both cases, a general expression for the variance of the Stokes parameters is obtained. Using this expression, it is demonstrated that it is possible to achieve uniform polarization scattering using a concatenation of fiber-coil-based PCs. Finally, it is shown that fiber-coil-based PCs can be used to emulate both first- and second-order polarization-mode dispersions

New technique for implementing multiwavelength orthogonal codes for OCDMA using fiber Bragg gratings written in high birefringence fibers

In the recent past, we have seen evolution of many new classes of multiwavelength optical orthogonal codes (MWOOCs) for optical code division multiple access (OCDMA). One important characteristic of these codes is that each set follows a cyclic (modulo-m) generation scheme. In this article, a new concept of polarization-accompanied MWOOCs, based on this scheme, and its implementation is proposed. The method is based on HiBi FBG in opposition to the normal FBG in the traditional implementation.

Linear Direct-Detection Fiber-Optic Receiver Optimization in the Presence of Intersymbol Interference

A technique is developed for optimizing communication receivers by minimizing a Chernoff bound (CB) on the Bayes cost function. Being couched in terms of moment generating functions, the procedure is well suited to optical systems. Optimal CB receivers are derived and shown to coincide exactly with known minimum cost Bayes receivers for certain special cases of both electrical and optical communications for which closed form analytic solutions are possible. This provides endorsement for the method, which is then applied to more complex practical cases of linear optical fiber receivers in which both colored Gaussian noise and intersymbol interference play a part. The CB receivers are shown to offer some improvement compared with a zero forcing raised cosine equalizing receiver such as is commonly adopted, and all the evidence suggests that CB receivers achieve performance very close to the best possible with a linear receiver.

Optical versus electrical dispersion compensation: role of timing jitter

This paper calculates timing jitter in intensity-modulated/direct detection lightwave systems in which chromatic dispersion is compensated in the optical domain and in systems where the effects of chromatic dispersion are mitigated by means of electrical equalization at the receiver. The authors focus on a linear communication channel and derive a new expression for the timing jitter after the photodetector using frequency-domain analysis. It shows that timing jitter depends cubically on link length when dispersion is compensated in the electrical domain. In contrast, when dispersion is fully compensated optically, timing jitter depends only linearly on the link length. A new expression for the optimum timing jitter in the presence of residual dispersion is also presented.