José F. Rocha

Statistical Analysis and Modeling of Shortest Path Lengths in Optical Transport Networks

We analyze the shortest path lengths between node pairs of real optical transport networks. From the analysis, we find that Johnson SB distribution is suitable for the shortest path length modeling. The validity of the distributions is evaluated in terms of the Kolmogorov-Smirnov (KS) statistic. Johnson SB distribution provides an average KS statistic of 0.0423, which indicates its good accuracy. We also show that the key parameters of the shortest path lengths, such as the mean, the median, and the standard deviation, can be estimated from the convex area of the network. We develop the proposed Johnson SB distribution model for the shortest path lengths using the basic information of the networks. The developed model is able to estimate path-length dependent system parameters, such as the appropriate modulation formats in transparent optical networks with an average error of only 6.4%. It is noteworthy that these estimations can be made without full knowledge of the network. Only the node locations are required.

Estimation of link-dependent parameters in optical transport networks from statistical models

Estimation of link-dependent parameters of optical transport networks is quite complex without the availability of complete network information. However, at the network planning stage these estimations are to be done with incomplete information, and need to be accurate. In this paper, we provide effective methods to estimate link-dependent parameters of optical transport networks when only partial information about the network is available. We use the link length statistical distribution model for these estimations. This approach is applied to 40 real transport networks and shown to be more accurate than the previously proposed methods. The improved accuracy of the proposed methods is achieved without extra network details: only the network node locations and the total number of links are needed.

Estimating the parameters of optical transport networks from their circumferential ellipses

Coverage area of optical transport networks (OTNs) are used in several estimations such as the average link length. However, estimating the coverage area may become complex in some cases without appropriate computing tools. In this work, we present the geometrical properties of the OTNs such as the convex area and establish their correlation with the circumferential ellipse (CE) of the networks. We provide the estimation and application of the CEs for the OTNs by evaluating the parameters of 40 real OTNs. We show that the average link length of the OTN can be estimated from the CE and thus several other link-related parameters as well. We estimated their eccentricities, and finally present their correlations with the OTN parameters. By comparing the results obtained from the estimations using CEs with the previous outcomes using the convex areas, we show that the methods based on the CEs are as effective as the methods based on the convex areas.

Asynchronous sequential symbol synchronizers based on pulse comparison by positive transitions at half bit rate

This work studies the asynchronous sequential symbol synchronizers based on pulse comparison by both transitions at rate (atx). Their performance will be compared with the reference synchronous synchronizers based on pulse comparison by both transitions at rate (stx). For the reference and proposed variants, we consider two versions which are the manual (m) and the automatic (a). The objective is to study the four synchronizers and evaluate their output jitter UIRMS (Unit Interval Root Mean Square) versus input SNR (Signal Noise Ratio).

Carrier Wave Phase Synchronizers

This work study four carrier wave phase synchronizers (CWPS) or carrier wave Phase Lock Loop (CWPLL).The VCO (Voltage Controlled Oscillator) output of the phase synchronizer synchronizes directly with the input carrier wave.We consider four carrier synchronizers namely the analog, hybrid, combinational and sequential. The difference between them is in the phase detector.The objective is to study the synchronizers and evaluate their output jitter UIRMS (Unit Interval Root Mean Square) as function of the input SNR (Signal to Noise Ratio).

OCDMA headers properties impact on an alloptical packet router module

In this paper we assess experimentally the performance dependence of a Cross Gain Modulation all- optical router architecture module on power of Optical Code Division Multiple Access headers. The technique allows transparency of high data rate packets based on Cross Gain Modulation process, which is normally quite limited in terms of rate performance. I. INTRODUCTION Current telecommunications network traffic demands are evolving quite rapidly with the increasing number of services. This traffic growth, up to now, has been kept up with the widespread use of WDM (wavelength division multiplexing) transmission technology. However, the adoption of the latter technology has also meant that electronic packet routers will have to terminate a large number of WDM ports each carrying high data rate traffic. There is much evidence to suggest that the processing capabilities of electronic routers will not cope with the rate of traffic growth in the near future. This fact motivates the search of alternatives to route the traffic in the optical layer, which has significant speed performance advantages. There have been numerous efforts in the area of all- optical packet switching, where some of the functions of electronic routers are now performed directly in the optical layer. Most of these efforts come under the banner of GMPLS and aim to switch packets based on the contents of an optical label. One of the functions that any router, electrical or optical, has to perform, is to decode the contents of a packet header/label and look it up in a table, called LIB (label information base), to decide the appropriate destination port to forward the packet to, and replace the label with a new one. In most packet switching concepts and demonstrators presented so far, the header or lookup is most often implemented with electronics. However, some approaches are already doing it entirely on the optical domain

High data rate synchronizers operating at low speed

This paper presents a new technique which allows high baud rate with low operation speed of the synchronizer. This technique is based on parallel processing. What is done by only one clock operating at the baud rate can be done by two clocks operating only at half rate. By generalizing we propose versions of clock recovery circuits operating at the ratio 1/2/sup n/ of the data rate. Thus we obtain circuits transmitting at very high data rate but operating at very low frequency. The proposed circuits which are transition sensitive (digital) are compared with the traditional level sensitive (analog).

Groups of synchronizers for communications by fiber optic

This work studies a digital transmission system by fiber optic. We give special relevance to the synchronism block. The fiber is a transmission medium with large bandwidth and low attenuation. These characteristics allow high speed and long distances. The transmission, instead asynchronous, it is synchronous what provides a big efficiency of 100%. However, the synchronous transmission needs a synchronizer. The objective is to study the synchronizers and their performance of output jitter Unit Interval Root Mean Square (UIRMS) versus input Signal Noise Ratio (SNR).

Prefilter bandwidth effects in asynchronous sequential symbol synchronizers based on pulse comparison operating by positive transitions at half bit rate

This work investigates the prefilter bandwidth effects in four asynchronous sequential bit synchronizers. The prefilter bandwidth is changed between three discrete values, namely B1=∞, B2=2.tx and B3=1.tx, where tx is the bit rate. The synchronizers distinguish 2 variants, one asynchronous by both transitions at rate and other asynchronous by positive transitions at half rate. Each variant has two versions which are the manual and the automatic. The objective is to study the three prefilter bandwidths with the four synchronizers and to evaluate their output jitter UIRMS (Unit Interval Root Mean Square) as function of the input SNR (Signal Noise Ratio).

EXTENDED RESEARCH ON PREFILTER BANDWIDTH EFFECTS IN ASYNCHRONOUS SEQUENTIAL SYMBOL SYNCHRONIZERS BASED ON PULSE COMPARISON BY BOTH TRANSITIONS AT HALF BIT RATE

I. INTRODUCTION This work studies the asynchronous sequential symbol synchronizer based on pulse comparison operating by both transitions at half bit rate (ab/2). Their jitter is compared with the reference asynchronous synchronizers operating by both transitions at bit rate (ab) [1, 2]. For both, reference and proposal variant, we consider the versions manual (m) and automatic (a) [3, 4, 5, 6, 7]. The difference between the reference and proposal synchronizer is in the symbol phase comparator since the others blocks are similar. The phase comparator compares the input variable pulse duration Pv with the intern reference fixed pulse duration Pf and the error pulse Pe synchronizes the VCO (Voltage Controlled Oscillator) [8, 9]. The synchronizer regenerates the data, recovering a clock (VCO) that samples and retimes the data [10, 11, 12, 13]. Fig.1 shows the blocks of the general symbol synchronizer.