An Adaptive Reliable Multipath Centralized RWA Algorithm for All-Optical WDM Networks

 The abstract of this paper is :

Balancing the load among multiple paths leads to the degradation in the all-optical WDM network. It is always desirable to deliver the entire load on a single optimal path depending upon the current network-wide load status. For this case, multiple light paths need to be maintained to provide the choice of selecting the best light path, based on the changing traffic load conditions, This paper presents the design and analysis of an adaptive reliable multipath centralized routing algorithm (ARMCR) with two central management systems (CMS-1 and CMS-2) which considers load heuristic for selecting the optimal and backup paths. Initially in this algorithm when a request comes to a source it sends the information to CMS-1 for allocating the optimal primary and backup paths for the received request, depending on the number of available free wavelengths. With the assigned primary path, source starts clearing the request meanwhile CMS-2 keeps track of the changes in the available free wavelengths and failure of all the paths. In the assigned primary path if the available free wavelength number comes below the threshold number ‗N‘ and at the same time if any other path is available with more number of free wavelengths, then CMS-2 assigns this path as primary path and very next more number available free wavelengths path is assigned as backup path. The advantage of this algorithm is that it reduces the set up time by using two CMS which share the work and also if one fails the other will take over the entire process. As opposed to the reactive protocols, our proposed protocol is proactive in the sense that it avoids the chances of blocking. Furthermore, the approach is self-regulating, it automatically adapts to the traffic load variation across the network. By simulation results, we showed that our proposed protocol has low set up time and blocking.

Full paper you can read and download from the following link, 

http://www.ciitresearch.org/dl/index.php/nce/article/view/NCE042011008

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Why WDM is required in Optical Networks?

What is Optical Networking?

Optical networking is a means of communication that uses signals encoded onto light to transmit information among various nodes of a telecommunications network. They operate from the limited range of a local-area network (LAN) or over a wide-area network (WAN).

What is WDM ??

WDM means Wavelength Division Multiplexing, this technology is widely used in optical fiber communication. By using WDM technology we can multiplex many optical carrier signals on to single optical fiber cable. This is bi-directional link.

How multiple optical carrier signals can be transmitted over a single fiber?

In Optical communication, it uses optical fiber cable as medium to communicate between two nodes. The data transmission between them is in the form of light, this light is generated by a particular type of lasers which are capable to transmit a light signal for long distance. This laser generates signal with particular wavelength, physically different wavelengths will be having different colors. In WDM each request will be transmitted with different wavelength because of this multiple requests can be transmitted over a single optical fiber. Two different wavelength signal never get mixed if they have proper band gap.

Why we have to use WDM ?

In optical networks, the medium optical fiber has bandwidth in terms of Tera Bytes, with this bandwidth we no need to go for WDM or multiplexing all the data can be transmitted over a single carrier along with this loss, distortion and cost can be reduced. But practically we can not use this, even though optical fiber has capability to transmit the data in terms of Tera Bytes per second but none of the existing electronics devices can accept this data rate, data will be lost if you transmit higher rate than it support, existing devices support in terms of Mbps. This limitation is called as "Electronic Bottle Neck", because of this reason we can not transmit all data over single carrier. If we transmit each data over separate link then cost for communication will be huge, in order to reduce the cost, to utilize the bandwidth of fiber properly Wavelength Division Multiplexing is used.

Maximum how many signals can be transmitted over a single fiber using WDM?

That completely depends on the band what user selected to transmit. Every band has limited number of channels, here channels means the number of wavelengths can be transmitted without interference. Each band is divided in to channels with a proper band gap between them.  

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