In this paper, several photonic generating methods for optical triangular pulses were reviewed. Four frontier research methods for generating optical triangular pulses were introduced, these four methods are respectively based on the frequency-to-time conversion, using normally dispersive fiber, by single-stage dual-drive Mach-Zehnder modulator （MZM）, and using dual-parallel MZM. These four methods can be classified into two categories in terms of the optical source employed, such as mode-lock laser （MLL） and continuous-wave （CW） respectively. Compared with the methods based on MLL, those based on CW have many advantages, such as simpler structure, lower price, higher stability, more flexible and wider tunability. Besides, the method using single-stage drive MZM can generate versatile waveform optical pulses, which has better performance than the first two methods in tunable capability of both repetition rate and center wavelength. With the same driving signal applied, the optical source using the dual-parallel MZM can generate signal with higher frequency than that of using the single-stage MZM.
Optical waveguide is used to guide the transmission of light. This paper reviews multilayer optical waveguide and some devices based on it. The optical waveguide can be divided into single-layer and multilayer optical waveguides in general. Here, multilayer cylindrical waveguide and multilayer planar waveguides were mainly focused. The analyzing method and the structures of waveguides were also demonstrated in briefly. Both these multilayer optical waveguide used in different kinds of optical devices including optical modulator, laser, optical amplifier, optical switch and special fiber were further presented. At last, the principle and structure of these multilayer optical devices were compared.
Sijun WENG, Li PEI Li PEI Ruifeng ZHAO Junjie YANG Yiqun WANG
