Semiconductor Optical Amplifiers (SOAs) are vital elements in future optical networks whether as amplifying elements to boost the optical signal. In addition to be used as amplifiers, SOAs can also be used as switching elements operating either as ON-OFF switches or as wavelength converters for wavelength routing switching. Additionally, their performance is compatible with nowadays and future transmission rates of 10, 40 and 80Gb/s and beyond. Hence, the impact they will have in all future optical networks is paramount and it is unimaginable that there will be any future optical network without them. With this knowledge a look into future optical networks reviles that the modulation format will be influenced by this development due to the physical impacts of the SOAs on the signal transmission. Hence the modulation format needs to be investigated. Here we pursue the investigation of different optical formats by means of optical simulation and do a comparison of the modulation formats with respect to the performance selected for this paper.
By eliminating optical synchronizers in optical IP routers, more complex scheduling algorithms are needed to schedule asynchronous packets. This will result in voids at the switch output thus reducing switch throughput. A novel scheduling algorithm had previously been proposed to reduce these excess losses by filling voids caused by asynchronous and variable length operation. Non-degenerate (i.e. non-uniform) buffer depth has previously been shown to improve the packet loss performance especially under bursty traffic. We investigated the performance of the void filling algorithm by combining non-degenerate and degenerate (uniform) fiber delay lines. Performance is studied for different threshold levels, i.e. the number of uniform delay lines in the feedback delay line before introducing the non-degenerate delay lines. The packet loss performance for combined non-degenerate and degenerate delay lines with void filling algorithm is presented for an optical router with a feedback delay lines buffer under self similar traffic. The recirculating delay lines buffer emulates a two-stage buffer where first stage buffers smaller packets whilst the second stage stores larger packets. This buffering mechanism is similar to SLOB (i.e. Switch With Large Optical Buffer).
A novel buffering mechanism for IP packets over WDM links is proposed by exploiting the packet nature. ACK packets which do not carry any payload can be singled out to be processed and stored purely in the electronic control plane without getting through the optical path which consists of the switching matrix and optical delay line buffers. An optical path is then reserved at the output for these ACK packets by extending the optical delay lines to be integral of ACK packets. Simulation results have shown an improvement both in the packet loss probability and the mean delay for using this scheme.
The increasing volume of Internet packet traffic in the telecommunications network has instigated a revolution in traffic modelling techniques, where self-similar instead of Markovian traffic models are now used to produce a realistic representation of data traffic. This paper presents a brief introduction to self-similar traffic and its impact on the performance of an optical node, in terms of packet loss probability and delay. It is demonstrated from simulation results that by employing multiple wavelength channels within the switch and incorporating void-filling, a packet loss probability of 10-6 can be attained. The generated traffic was subject to statistical tests, and its Hurst parameter was determined using parameter estimation to verify the theoretical assumptions inherent in using infinite variance ON/OFF sources to capture self-similarity.