As the development of the technology, fiber-to-the-home (FTTH) becomes a feasible solution to meet the increasing demand on bandwidth. Due to the massive number of end users, cheap and reliable components become the bottleneck to deploy the new technology. Triplexer is one of the key components in the FTTH and is used by every end user. Currently, the available triplexers are either based on bulk optics or fiber optics with large size and high price due to manual labor involved. Planar lightwave circuit (PLC) is a possible technology for massive production and cost reduction. However, it is very challenging to design such bi-directional triplexer on PLC. The first challenge is that three channels, at λ=1310nm, 1490nm, and 1555nm, are separated unevenly over a very large wavelength range; Secondly, the bandwidths of the three channels, Δλ=100nm, 20nm, and 10nm, are very different. In the paper, we proposed a novel design by combining both coarse WDM and dense WDM. In the design, a multi-mode interference (MMI) device is used for coarse WDM to separate the 1310nm from the other two channels. The dense WDM for the remaining two channels is performed by an array waveguide gratings (AWG). The MMI and AWG are built on the same wafer with monolithic integration. Initial simulation results show it is a very promising device.
Modal characteristics of the one-dimensional (1D) photonic crystal waveguides (PCWs) are investigated thoroughly. By employing the transfer matrix method, we can put the design parameters related to the general multiplayer structure into a compact analytical expression, which serves as the basis for analysis of the band-gap structure of the general 1D photonic crystals (PCs) and the modal characteristics of the general 1D PCWs. The band structure of 1D PCs and modal properties of 1D PCWs, such as the effective index, the modal field profile, the dispersion, the confinement loss, and the confinement factor, are all calculated and simulated. With the help of the band-gap map of the 1D PCs, four guiding regimes for the 1D PCWs are recognized, in accordance with the index of the guiding core. It is shown that the modal characteristics for each regime behave differently from the point of view of guiding mechanism. Furthermore, some related issues such as PCFs are discussed.
A kind of optical fiber sensor mainly used for the terminal winding vibration monitoring in electric generator is discussed. Within this sensor, the light from a LED passes through an optical fiber; the fiber end is mounted on a reflecting cantilever beam, which is sensitive to the vibration of the detected object; the reflected light coupled back through the same fiber is modulated by the vibration and detected by a photodetector. With signal processing, the vibration acceleration, velocity and displacement can be obtained. The cantilever beam, which is the key component of the sensor, is a micromechanical silicon structure. The bandwidth of the sensor is 10 - 1000 Hz, resolution 0.1 m/s<SUP>2</SUP>, dynamic range 0 - 10 multiplied by 9.8 m/s<SUP>2</SUP>, weight 15 grams, fiber length 1000 m. The result of the experiment in a real electric generator is proposed.