Optical Modulation And Signal Detection For Advanced Optical Communication Systems

In the past several decades, optical communication has brought unprecedented communication technology to our everyday lives. With the development of Internet business, future optical networks will require better performance and higher capacity, especially in the fields of high speed backbone networks and broadband access networks. As one of the key technologies for future optical communication systems, novel modulation schemes have been attracting attention. Formats with higher spectral efficiency, better tolerance against nonlinearity and simple structure are targeted as promising solutions to meet the various requirements. By combining optical formats and other techniques in optical communications, novel communications systems and networks will enter a new development stage. In this dissertation, we focus on novel optical modulation schemes and their application in optical systems and networks, with a view to enhance system performance and make the systems cost-effective. The major research achievements are summarized as follow:A Hybrid Wavelength-polarization Labeling Scheme in Optical Packet Switching: An optical labeling scheme using hybrid multiwavelength-polarization (λP) label and amplitude shift keying (ASK) payload is introduced. This scheme exploits wavelengths with two different states of polarization (SOP), circular polarization state and linear polarization state, as label. Compared with multiwavelength labeling, it remarkably enlarges the header information and reduces the requirement of wavelength accuracy. An experiment system for generating and detecting theλP label, which is based on the difference of polarization extinction ratio (PER), is demonstrated. Theoretical analysis of signal and system performance is also discussed in detail.All-optical Inverse-RZ to NRZ Format Conversion: 10-Gbit/s all-optical format conversion from inverse-returnto-zero (inverse-RZ) to non-return-to-zero (NRZ) is realized by using a half-bit-delay Mach-Zehnder delay interferometer. A duty cycle of 50% for the inverse-RZ signal is needed to realize optimal format conversion. The input inverse-RZ signal is converted into a standard NRZ signal at the constructive port. At the destructive port, the modified NRZ signal with a phase jump in the middle of each 1 bit is obtained. Experimental results demonstrate that the converted NRZ signal has better receiver sensitivityWDM-PON Multicast Scheme by superimposing Inverser-RZ signal on NRZ signal: We propose and experimentally demonstrate a WDM-PON architechture with multicast overlay. By superimposing inverse-RZ multicast signal onto NRZ point-to-point signal, simultaneous transmission is realized for both services. Multicast control is realized by controlling the Extinction Ratio (ER) of the NRZ signal at the optical line terminal (OLT). We successfully demonstrate the proposed WDM-PON with 2.5-Gb/s downstream point-to-point signal and 2.5-Gb/s downstream multicast signal.Multi-format receiver for non-return-to-zero binary-phase-shift-keyed and non-return-to-zero amplitude-shift-keyed signal: A Multi-format receiver for both NRZ-BPSK and NRZ-ASK is demonstrated. Multi-format signal detection is based on incoherent BPSK demodulation and ASK-BPSK format conversion. Incoherent BPSK demodulation is realized by a mach-zehnder delay interferometer (MZDI) and a feedback decoder. Transmission experiments are carried out for validation. This receiver may serve as a useful terminal block for all-optical WDM networks.