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We have investigated optical frequency-shift sensitivity of the transmittance channeled spectrum of cascaded-chirped long period fiber gratings (C-CLPGs) to an applied strain from the viewpoint of the sensor use. In the experiment, eight different kinds of C-CLPGs have been fabricated by changing the cascaded distance for two types of CLPGs and the strain-induced spectral shifts are measured by use of a cross-correlation technique which provides highly precise determination of the spectral shift. As a result, it is confirmed that the higher frequency-shift sensitivities of the C-CLPGs to the strain obtain with the higher order of cladding mode.

A novel tunable and switchable Erbium-doped fiber ring laser (EDFRL) is constructed from the viewpoint of sensor applications. The laser consists of a cascaded-chirped long period fiber grating (C-CLPG) and a variable optical attenuator (VOA). The oscillation wavelength is used for sensing a measurand. As a result, wavelength range selecting over about 1557.57 ~ 1570.68 nm with the tuning range within ~5.6 nm is demonstrated, and the sensitivity of ~ −0.22 nm/°C is recorded.

Wavelength scanning digital holography using laser diode current modulation is presented. A series of holograms are recorded while the phase of hologram is swept through wavelength scanning. The object wave component is extracted from recorded holograms by applying temporal frequency analysis to each pixel of the holograms. The proposed technique allows us to record a large object as digital hologram using simple and cost effective optical setup.

Cascaded long period fiber gratings are fabricated and investigated for use in intensity-based fiber optic mechanical vibration sensors. The cascaded LPGs are inscribed in photosensitive fiber by means of point-by-point technique with UV KrF excimer laser and examined in terms of axial strain sensitivity. In the experiment, much higher strain-sensitivity than that of single LPG is obtained and mechanical vibration sensing is successfully demonstrated.

A second-order multi-bit switched-capacitor complex bandpass DeltaSigmaAD modulator has been designed and fabricated for application to low-IF receivers in wireless communication systems such as Bluetooth and WLAN. We propose a new structure of a complex bandpass filter in forward path with I, Q dynamic matching which is equivalent to the conventional one but it can be divided into two separate parts. As a result, the DeltaSigma modulator which constituted with our proposed complex filter can be completely divided into two separate parts too, and there are not any signal line crossing between the upper and lower paths by a complex filter and feedback from DACs. Therefore, the layout design of the modulator can be greatly simplified. Nine-level two quantizers and four DACs are used in the modulator for lower power implementation and higher SNDR, but the nonlinearities of DACs are not noise-shaped and the SNDR of the DeltaSigma ADC degrades. We have employed a new complex bandpass data-weighted averaging (DWA) algorithm to suppress nonlinearity effects of multibit DACs in complex form to achieve high accuracy; it can be realized just by adding simple digital circuitry. Implemented in a 0.18-mum CMOS process and at 2.8 V supply, the modulator achieves a measured peak signal-to-noise-and-distortion (SNDR) of 64.5 dB at 20 MS/s with a signal bandwidth of 78 kHz while dissipating 28.4 mW and occupying a chip area of 1.82 mm2.

The Laguerre Gaussian(LG) beam is an optical beam that has doughnut-shaped intensity distribution and phase singularity. A phase singularity is a structure such that integration of the phase gradient along a closed path around the axis yields 2m/spl pi/. The integer m is called the charge of the phase singularity. Reliable generation of LG beams has been realized through computer holograms. For applications such as optical trapping and rotational manipulation, the profile of beam generated by hologram is often more important than its diffraction efficiency. Low diffraction efficiency can be compensated by high power light source, while a high power distorted beam may cause serious problems.

Summary form only. A phase singularity is a structure such that integration of the phase gradient along a closed path around the axis yields 2m/spl pi/, where m is the charge of the singularity. Laser beams with such structures have attracted much interest in recent years. We have previously reported the fabrication of blazed transmission phase holograms to generate beams with phase singularities having charges up to 10. The hologram structure was fabricated on a thin polymer layer on a glass substrate using an electron-beam lithography technique.