Physical Impairment Based Regenerator Placement and Routing in Translucent Optical Networks

Abstract

A novel constraint-based routing (CBR) algorithm taking into account the dominant linear and nonlinear fiber optical transmission impairments has been analyzed. It is shown that CBR and intelligent regenerator placement decrease the blocking probability significantly. IntroductionIn future transparent optical transmission systems automatic wavelength switching will be introduced (automatically switched optical network, ASON). The rapidly increasing traffic demands require solutions, which reduce the operational expenditure by efficient routing. In the past, opaque (employing optoelectronic conversions at each node), fully-transparent or translucent (with selective regeneration) networks have been investigated. Because of the high cost of optoelectronic conversions and limited reach in fully-transparent networks the translucent topology seems to be the most promising candidate for future wavelength agile longhaul networks.Physical degradation effects such as noise, linear impairments and nonlinear fiber effects affect the signal quality along the transmission path. Depending on the channel load and transmission distance some paths cannot be set up fully transparently because the transmission quality requirements (i.e. pre-FEC bit error ratio (BER) = 10 -9 or Q-factor = 15.56 dB) cannot be fulfilled. In the last couple of years the inclusion of physical layer effects in the network operation and routing has been a topic of intensive research (e.g., [1],[2]). In this paper we propose a combined approach of regenerator placement based on the estimated signal degradation along the links and nodes and constraint-based routing (CBR) to set up paths according to the demands. We show -for the first time to our knowledge -that the combined approach of regenerator placement and routing, both based on physical degradation effects, may significantly decrease the blocking probability in a realistic network scenario with a varying dispersion map and different span lengths. Investigated networkFor the investigations the COST266 reference network (large topology) has been chosen [3]. This network has pan-European dimensions (37 nodes and 57 links) in a mesh topology (Fig. 1, left). System simulations have shown that for very long paths in the COST266 network the nonlinear fiber effects of cross-phase modulation (XPM) and four-wave mixing (FWM) cannot be neglected when 10 Gb/s NRZ-OOK modulation is employed (Fig. 2). This is why we included the analytical models presented in [4] in our CBR approach to assess XPM and FWM. From Fig. 2 an average transparent reach of approximately 1820 km for SSMF can be observed. However, there are short paths with poor signal quality (min. 1280 km) and long paths with good quality (max. 2220 km) making an accurate assessment of the actual signal quality desirable. In the COST266 reference network only link lengths and demands have been defined. For the assessment of the signal quality, however, it is essential to know the physical parameters of the links. For this purpose a heuristic ap...

Offline Impairment-Aware RWA and Regenerator Placement in Translucent Optical Networks

“…Commonly, the regenerator placement is solved first, producing a network for which the IA-RWA problem is then addressed. This strategy has been followed in [14]- [18] for static traffic, and in [11]- [13], [19]- [21] considering dynamic traffic. Other works have been presented which focus on minimizing the number of nodes with signal regeneration capability in the network, guaranteeing a certain degree of connectivity [19], [22], [23].…”

“…To this end, they suggest a two-step algorithm which is compared to a k-coverage algorithm for mobile and ad hoc wireless networks. The authors in [19], [23] propose a regenerator placement based on the greedy algorithm from [24] to get full-connectivity and two simple RWA algorithms based on shortest path and assigning the wavelengths by first-fit. One model considers the worst-case physical transmission penalties, while the other model takes into account the current network status in order to obtain the physical impairments.…”

On the physical impairments constraint in OBS networks

“…Recent studies in OCS (e.g. [5]) show that better network performance can be achieved by treating the RP and the routing problem together in the so-called RRP problem.…”

Impairment-Aware Lightpath Routing and Regenerator Placement in Optical Transport Networks With Physical-Layer Heterogeneity

“…First, because 3R regenerator is one of the most expensive components in the optical transport networks, much effort was dedicated to efficiently choosing regeneration sites and allocating regenerators [12]- [14], [8], [7], [15]. Second, given a set of regeneration sites and regenerators, a range of lightpath routing and wavelength assignment algorithms were developed to efficiently utilize the regeneration capability, such that lightpath demands are maximally satisfied and a minimum lightpath blocking probability is achieved [12], [7], [16]- [19].…”