Performance of DQPSK, NRZ and RZ modulation formats in different optical fibres

Abstract

With the development of high-speed, long distance optical fibre communication systems, linear factors become one of the important factors limiting high-speed, long distance optical fibre transmission. This linear effect includes attenuation, polarization mode dispersion (PMD), Chromatic dispersion (CD) and optical signal to noise ratio (OSNR). In this paper, theoretical investigation has been done on the performance of Single Mode Fibres (SMFs) namely standard (SSMF), Large Area (LA), Reach (R) and Reduced Slope (RS). The performance of Return to Zero (RZ), Non Return to Zero (NRZ) and differential quadrature phase shifting keying (DQPSK) were also compared in different fibre types at bit rate of 10 Gb/s. The effect of variation in system length, dispersion and core effective area is observed in terms of bit error ratio (BER) and quality
(Q) value. The power penalty suffered by the system is evaluated at BER= 10-9 threshold for SMF operating at 1550 nm. The Q factor was used to evaluate the performance of the system at a BER= 10-9 which corresponds to a Q factor of 6. It is found that SSMF has the highest BER and lowest Q factor values. It is also found that BER and Q factor performance of the system is highly dependent on fibre length, core effective area and dispersion parameters. DQPSK has better performance than NRZ and RZ modulation formats.