Experimental Comparison of Different Pulse Shaping Techniques for Advanced Modulation Formats using a Recirculation Loop in Fiber Optic Communications

Abstract: Internet traffic is growing exponentially. This can be attributed to the high bandwidth services that are now available. Video streaming, video on demand, on-line gaming, on-line banking, social networking and cloud computing have contributed tremendously to the increase in data traffic. Consequently, there needs to be a matched increase in the transmission data rates.

There are several ways in which this could be accomplished. One way would be to use advanced modulation formats. The major advantage of this technique is that more data can be transmitted using the same bandwidth when compared to traditional modulation formats such as on-off keying. Another way of increasing capacity would be to use different pulse shaping techniques with advanced modulation formats for efficient use of the available bandwidth.

The main purpose of this thesis is to primarily compare the performance of different pulse shaping techniques when applied to a QPSK signal. Non-Return to Zero (NRZ), Nyquist, Raised Cosine and Root Raised Cosine are the pulse shapes that are to be investigated. Furthermore, the performance of QAM signals is also to be briefly investigated. For these investigations a recirculating loop was established in-order to transmit the different signals over varying transmission distances. EVM, SNR and BER are some of the measurement metrics that were used for performance evaluation.