Study On Key Technologies In Optical Label Switching Network

Optical label switching (OLS) network inherits the soul of packet switching. The routing and switching information is embedded in the low speed label signal and it keeps the high speed all optical switching capacity, which is a promising solution for the future optical packet switching networks. Optical label processing methods and novel modulation formats are the key technologies in OLS network, which have attracted much attention.A novel Lyot-Sagnac polarization maintenance fiber loop filter is developed for erasing optical label in 10Gb/s subcarrier modulation (SCM) label format. This optical label eraser has the characters of double output ports, flatten transmission band, high extinction ratio and multi-channel operation. In this dissertation, the principle of the Lyot-Sagnac filter is analyzed theoretically and demonstrated experimentally.Two kinds of new modulation formats used in beyond 40Gb/s optical networks are proposed. One format combines the vestigial sideband payload and wavelength label. The feasibility and crosstalk between the payload and label are theoretically analyzed. Not only optical label adding and erasing methods of two wavelength labeling schemes are tested, but also 160km long distance transmission experiment is carried out. The results show that this format has the frequency efficiency up to 0.8bit/s/Hz. In this dissertation, the analytical results for vestigial filtering signals in conjunction with various modulation formats, e.g. NRZ, RZ, CSRZ, MDRZ, are derived, which also considering different pseudo-random bit sequences length. The performance of vestigial sideband CSRZ format employing two kinds of filters is experimentally demonstrated with meaningful results.The other high spectral efficiency modulation format is the orthogonal labeling scheme based on polarization modulation. This scheme utilizes the polarization states changes of payload to carry the label signal which avoidsthe extinction ratio limitation in the traditional orthogonal modulation. The polarization modulation is realized by only one LiNbO3 crystal phase modulator. The birefringence in the crystal causes imperfection polarization modulation with the input 40Gb/s pulses which can be eliminated by optical filtering method in this paper. Good performance is achieved through theoretical analysis as well as experiment verification. The novel orthogonal modulation format is analyzed and experimentally demonstrated by adding and erasing labels. At the same time, the polarization mode dispersion (PMD) and long distance transmission test are carried out. The results show that this format can be used in high speed optical label switching networks. A novel optical label re-writing scheme for this orthogonal format is given out. This scheme can omit the optical label erasing operation, simplify label processing and network node structure simultaneity.