In this paper, our present work, which aimed at investigating a novel optical fiber biochemical sensor based on long
period grating (LPG), is introduced. Biochemical sensor is one of the most attractive fields of sensor research, especially
with the development and occurrence of all kinds of novel theory and technology such as LPG. When there is a
refraction index periodic perturbation, the guiding mode and cladding mode in LPG couple with each other. This make
the LPG is sensitive to the ambient refractive index. This means it can be a novel bio-chemical sensor when it is applied
in the fields of biochemistry. After investigating the principle of coupling in LPG, where the formulas of resonance wave
length and band width are induced by 3-layer step index model, we developed an optical fiber biochemical sensor. The
structure of its probe is designed by coating some function films whose thickness is between several tens and several
hundreds nanometers on the cladding of optical fiber. Experiments of monitoring the saline separateness process of
Bovine Serum Albumin (BSA) and Mice-Immunoglobulin G (M-IgG) by using the developed LPG sensor have been
done. The monitoring indicated that for the BSA, the saline separateness occurs when the saturation is between 50% and
60%, for the M-IgG, the percentage is between 30%-40%. Besides the monitoring, the experiments could also analyze
the effects of protein type (different molecule structure), protein consistency and saline saturation to saline separateness.
The experimental results show that the optical fiber biochemical sensor based on LPG has many advantages such as
simple structure, high sensitivity and miniature. It has a promising future in many research fields and application fields.
The development of the optic interferometric sensors is partly restricted with the demodulation technique. The Phase
Generated Carrier (PGC) modulation scheme is a useful demodulation method for interferometric sensors, for it is simple
and accurate. At first, the PGC scheme is demodulated by analog demodulation techniques. Its capability is limited by
the electronic devices, and not fit to the large-scale sensors application. In the past few years, a number of digital
demodulation processing approaches have been investigated. Another arctangent approach based on digital demodulator
exhibits more advantages than the traditional Differentiate and Cross Multiply (DCM) approach, which has a small
measurement range and rather complex circuit. In this paper, the arctangent approach on the PGC configuration used in
the array of optical fiber interferometer are discussed and emulated. The measurement range, operation complexity,
quality of operation, noise performance, and applicability are compared among the variant arctangent approaches and the
DCM approach. The variant arctangent approaches and the DCM approach will be influenced by differently factors, such
as, the intensity of the light source, the shift of visibility of the interference fringes due to the change of the state of
polarization in fiber, the phase delay. The dependence on these influences of these approaches is analyzed in detail. Their
effects and removal methods are validated through emulation.
Re-entrant fiber optic gyro (Re-FOG), using a shorter Sagnac sensitive ring (SSR), makes parts of the two counter-propagandizing lights re-enter the ring before they interference with each other when they reach the photo-detector. Multiple-integrated-optic-chip (MIOC) is one of the most important components of a Re-FOG. In this paper, the principle of the Re-FOG is first reviewed. A method of measuring the half-wave voltage is presented. The thermal induced change of half-wave voltage was tested.
Re-entrant fiber optic gyroscope (Re-FOG), using a shorter Sangnac sensitive ring (SSR), makes the two counter-propagandizing lights re-enter the ring before they interference with each other when they reach the photo-detector. By this means, the Re-FOG gets the same detecting accuracy as the conventional interferometric fiber optic gyroscope (IFOG) that has several times length of the sensitive ring. In this paper, the principle of the Re-FOG is first reviewed. Then the output signal is analyzed. Finally a method of signal detection is presented.
This paper reports an experimental research on the stability of bidirectional outputs and multi-longitudinal mode interference of laser diode end-pumped Nd:YVO4 solid-state ring laser (DPSSL). The bidirectional, multi-longitudinal and TEM00 mode continuous wave outputs are obtained and the output powers are measured and their stabilities are analyzed respectively. The spectral characteristic of the outputs is measured. The interfering pattern of the bidirectional longitudinal mode outputs is obtained and analyzed in the condition of the ring cavity with rotation velocity. The movement of the interfering fringe of the multi-longitudinal modes is very sensitive to the deformation of the setup base and the fluctuation of the intracavity air, but is stationary or
randomly dithers when the stage is rotating.
The experimental research on diode-pumped solid-state ring laser (DPSSL) is reported in this paper. The research target is to develop a new style optical gyroscope. The ring cavity is a plane, 8-shape 4-mirror laser resonator. Nd:YVO4 crystal is exploited as a laser media which is longitudinally pumped by a 2w laser diode. An optical delay path attached to the cavity is composed of a beam splitter and a prism. The bidirectional traveling waves partly output from one of the flat mirror and one directional beam interferes with the other on a photo detector with optical delay. The resonator design is discussed; the pump power threshold is about 600mW. We obtain the bidirectional continuous TEM00 mode outputs and their interfering pattern. In the experiment, Sagnac effect is watched, which indicates that the DPSSRL can be used as optical gyroscope.