ALL OPTICAL WAVELENGTH REGENERATION BY SOA’s IN A MACH ZEHNDER CONFIGURATION

Abstract

ABSTRACT In this project, All-optical Wavelength regeneration using SOA in machzehnder configuration is investigated. These processes may find a variety of applications in future high-capacity fiber-optic transmission systems including low-noise amplification. With the outcome of the EDFA and dispersion compensation techniques, transmission of optical signals over hundreds or thousands of kilometers became possible without intermediate OEO regenerators. The increasing demand for optical bandwidth has lead to the development of WDM systems and to the increase of the per channel bit rate. In parallel to the explosion of per channel bit rates and transmission distances, optical systems are also evolving from simple transmission systems to a higher level of complexity, where switching and signal processing is supported by the optical layer. By eliminating the electronic bottleneck, all-optical signal transmission and processing are expected to enable the next generation of optical networks, by dramatically reducing costs, energy consumption, and increasing the network throughput. The increase of the per-channel bit rate usually leads to a reduction of the signal tolerance to optical impairments. Such optical impairments are mostly originated from propagation and from signal processing. Propagation degrades the optical signal due to various distortion sources; such as: uncompensated chromatic dispersion, polarization mode dispersion, non-linear effects, or noise accumulation. Optical signal processing degrades the signals by tight optical filtering; crosstalk in photonic-cross connects; polarization dependent losses (PDL) of components; and by imperfect optical functionalities, like wavelength or format conversion. Signal degradation in optical systems is typically overcome by adding regeneration stages at periodic transmission distance intervals. The most common type of regeneration consists in detecting the optical signal, recovering it in the electrical domain and retransmitting it. However, this technique suffers from the general disadvantages of OEO signal processing. On the other hand, all-optical regenerators are expected to overcome the drawbacks of OEO converters and are considered essential elements for fully-functional optical networks; however, all-optical regeneration at high bit rates is still a research topic. Regeneration can be divided in the three main functionalities: re-amplification, re-shaping, and re-timing. The simplest functionality is re-amplification (or 1R), which consists in xi simple optical amplification. A device which also provides reshaping in addition to reamplification is known as 2R. Re-shaping consists in increasing the contrast between the two logical levels; which improves the required optical signal to noise ratio (OSNR) for a specific bit error rate (BER) level. Finally, 2R is combined with re-timing, to create a full 3R. Re-timing refers to the reduction of the signal jitter.