Presently, fibre optics are the best medium for long haul communication links. However due to the limitation of modulation schemes available, fibre optics-based communication systems are under utilized. Amplitude-Shift Keying (ASK) is generally the modulation scheme of choice because its signals are easy to produce and detect. To better utilise this system, our project uses Binary Phase-Shift Keying (BPSK) instead of ASK.

This project concerns itself with simulating and designing a balance Phase Locked-Loop (PLL) for a coherent detection of BPSK signals. Coherent demodulation provides superior link performance in the form of lower Bit Error Rate (BER) for a received signal with a given signal to noise ratio (SNR). Generally, PLL is a feedback system combining a Voltage Control Oscillator (VCO) and a phase comparator so connected that the oscillator frequency (or phase) accurately tracks that of an applied frequency (or phase) - modulated signal. In practice, PLL is frequently used in applications such as FM detection, frequency multiplication and division, tracking as well as establishing a noise-free reference in the presence of noise. Additionally, PLL’s are also used for extraction of data clock synchronization and for data detection in high-speed fibre optic systems. By applying these techniques to fibre optic communication links, we will be able to further increase the links performance, there by decreasing the cost per user.

Dr William Shieh, David Zammit, Muhammad Lukman Al Hakim