We have proposed and fabricated an arrayed-waveguide grating (AWG) with an integrated lens system that is designed to obtain a flat output wavefront. A spatial filter or spatial light modulator could be integrated easily at the output facet of the waveguide. A patterned mirror was attached to the AWG, and doubling of the pulse repetition rate was successfully demonstrated.
A technique for the self-alignment of components is applied to the assembly of a passive micro-valve which is to be used for safety purposes in a miniature fuel cell. The technique uses the capillary forces originating in the interactions of HMDS (Hexadimethyldisilazane) and the faces of the components to achieve their passive alignment. HMDS is chosen because it is a volatile, low surface tension and inert liquid. The originality of this method is that the liquid area is defined by the edges of the components. Compared to a traditional pick-and-place technique, it leads to a leakage rate more than five times smaller.
We have a demonstrated self-starting mode-locked Yb-doped fiber (YDF) laser that generates femtosecond pulse trains. The system gave the pulse energy of 4.4nJ and pulse duration of 44fs with the repetition rate of 32MHz of which peak power was 100kW. The oscillation wavelength of mode-locked laser was tuned widely from 1025 to 1065nm by inserting a slit at dispersive optics stage in the cavity. The femtosecond pulse is stretched to 1.4ns in two chirped fiber Bragg grating (FBG) and then amplified by two YDF pre-amplifiers for the fiber chirped pulse amplification (CPA) laser system.
A nested Mach-Zehnder (MZ) modulator, which consists of two sub MZ interferometers embedded in a main MZ interferometer, is a multifunctional modulator. It can work as an optical single side-band (SSB) modulator, a differential quadrature phase shift keying (DQPSK) modulator and so on. Despite difficulties due to their complex structure, in order to avoid the operation instability of such modulators the bias condition of each MZ interferometer must be controlled automatically according to the modulation formats. In this paper, we proposed a specific bias condition monitor technique to the nested modulator.
Optical Burst Switching (OBS) is designed to efficiently exploit the enormous bandwidth offered by the optical fiber. Contention is one of the major problems in the deployment of OBS networks. In this paper, a new contention resolution method is introduced. This method is based on the burst segmentation scheme and the use of Nonlinear Optical Loop Mirrors (NOLMs). The NOLMs are incorporated with SOA to provide optical buffering and ultra-fast optical switching services to the segmented bursts. Furthermore, the introduced method is evaluated in term of the packet loss rate versus various traffic loads with Pareto distributed and negative-Exponentially distributed burst length.
An efficient method on selecting threshold values according to minimax test for packet detection in burst-mode OFDM systems is proposed. Packet detection decides whether a packet is coming or not by comparing a threshold value in the wireless receiver. Related with sliding window size and SNR, the threshold value affects receiving performance including probabilities of false alarm and miss. The minimax test for detection based on empirical CDF and survival functions is proposed. Also the performances of two general used detection methods are surveyed and compared.