Experimental Study of DQPSK in WDM Communication System

• Main Authors: Yu-jen Chuang, 莊育仁
• Other Authors: Hidenori Taga
• Format: Others
• Language: en_US
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/43864126799551373777

碩士 === 國立中山大學 === 光電工程學系研究所 === 98 === 　　The ever-increasing requirement for more bandwidth to the office, home, and mobile devices is driving the deployment of high-speed optical communication systems. Differential quadrature phase-shift keying (DQPSK) is one of the most attractive and advanced modulation format in recent years, and this format increases the capacity and efficiency in optical fiber communication systems. 　　DQPSK is able to transmit two bits per symbol. That is to say that DQPSK has twice spectral efficiency compared to DPSK. In addition, DQPSK has excellent tolerance against chromatic dispersion (CD), polarization-mode dispersion (PMD), optical add-drop multiplexing (OADM) filtering, and optical noise. It makes DQPSK play an important role for next-generation optical transmission systems. 　　The wavelength-division multiplexing system (WDM) multiplexes multiple optical carriers in the single optical fiber by using the different wavelengths of laser to carry the signal. This master thesis focuses on the study of DQPSK performance in the long-haul transmission with the WDM system. 　　In the process of experiment, a special technique for DQPSK to be set up is required. When a delay demodulator is applied for the DQPSK signal, decoding is required to make the received serial data become the same as the transmitted serial sequence. As the electronic encoder or decoder is hard to realize, a program is prepared for the experiment to calculate the pre-decoded pattern sequence. Then, calculated patterns are imported to the error detector (ED) to measure the bit error rate (BER). Finally, different channels (wavelengths) of WDM transmission were observed.