Tunable Wavelength Conversion Based On FWM In Semiconductor Fiber Ring Laser

Tunable all-optical wavelength converters will be one of the essential devices in future intellectualized dense wavelength-division multiplexed (DWDM) all-optical networks. Tunable wavelength converter based on four-wave mixing (FWM) in semiconductor fiber ring laser (SFRL) has advantages, which are possessed by the wavelength converter based on FWM, such as strict transparency to bit the rate and modulation format of signals, phase conjunction, multiple channels simultaneous conversion ability etc. Furthermore, it possesses the virtues of saving an external pump source to simplify device and expediently being tuned. So many attentions were paid to this kind of wavelength conversion. In this dissertation, theoretical and experimental research on wavelength conversion based on FWM in SFRL is presented. The main contents are as follows: (1) Theoretical basis for wavelength conversion based on SFRL is investigated. The propagation equation for the optical field and the rate equation for the carrier density in semiconductor optical amplifier (SOA) are derived. And the nonlinearities of SOA, especially the third-order nonlinearities, are discussed. The mechanisms of wavelength converters based on across-gain modulation (XGM) in SFRL and wavelength converters based on FWM in SFRL are given. (2) Besides the simple and convenient lump model, the comprehensive broad-band dynamic model of a tunable wavelength conversion based on FWM in a SFRL is presented firstly. In the broad-band dynamic model, SOA and the amplified spontaneous emission (ASE) spectrum are divided into many subsections. Critical factors, e.g., the material gain profile, the longitudinal variation of the optical field, the carrier density, photon density, and the broad-band spontaneous noise emission, are considered in the model. Therefore, the static and dynamic characteristics of this kind of wavelength conversion can be predicted more accurately. This broad-band dynamic model is the theoretical basis of a tunable wavelength converter based on FWM in a SFRL. (3) Using the broad-band dynamic model of tunable wavelength converter based on FWM in a SFRL, the static characteristics and the dynamic characteristics are investigated by numerical simulation, such as the conversion efficiency, signal-to-background-noise ratio (SBR), the extinction ratio, and the frequency chirp of the conjugate signal. And some of contributing factors including the input signal power, injection current, coupling coefficient of the two couplers, the lasing wavelength, and the length of SOA are analyzed. Also the effects of the linewidth enhancement factor and the limiting factor on the extinction ratio and the frequency chirp of the conjugate signal are studied. (4) 20Gbit/s tunable wavelength conversion based on FWM in a SFRL is experimentally demonstrated firstly. Tunable wavelength conversion based on FWM in a SFRL is experimentally investigated at 10Gbit/s. The effects of the input signal power, injection current, the coupling coefficient of the two couplers, and the lasing wavelength on the conversion efficiency and SBR of this kind of wavelength converter, as well as the effects of the input signal power on the extinction ratio of the conjugate signal are investigated. (5) New scheme for FWM wavelength converter based on single-port-coupled SFRL is brought forward firstly. Theoretical and experimental investigations are investigated. Theoretical analysis shows that high conversion efficiency and high SBR can be achieved by using this scheme if the proper reflectivity of the rear facet of SOA is selected. (6) Improved scheme for FWM wavelength conversion based on double output wavelength SFRL with an assisted beam is put forward. Theoretical analysis shows that polarization-free, high conversion efficiency and high SBR in wide wavelength range can be achieved by using this scheme. Also the broad-band dynamic model of this kind of wavelength conversion is presented.