The fiber Bragg grating has been widely used in sensors. We have studied the spectral properties of uniform Bragg gratings in photonic crystal fibers under transverse pressure. By the finite element method, the relation between the birefringence and the pressure was simulated in bare photonic crystal fibers. The results show that the birefringence is changed even under weak pressure. A new method based on polarization-dependent loss is presented for measuring pressure. The maximal amplitude of the polarization-dependent loss varies linearly in the pressure range of 0 to 4 MPa with a slope of 0.75 MPa−1.
A New magnetic field measurement based on polarization effect of fiber grating was analyzed in theory and
experiment. The simulations show the linear relationship between the peak value of PDL and magnetic field in
certain range. Moreover, this method is temperature insensitive. The precision of this method is 2Gs using the
optical vector analyzer in experiment and agree well with the theory.
Fiber grating is sensitive to the stress, temperature and other entironmental factors. It has caused much attention and has
been used widely. In this paper a new magnetic field measurement using different group delay (DGD) of fiber grating is
proposed. When the magnetic field applied the refractive index difference of the two circularly polarized light in fiber
grating will be changed because of the faraday effect. So the DGD of fiber grating is changed. Through the formula
derivation in certain condition, the linear relationship between the peak value of DGD and magnetic field in
measurement range is found. Through the simulations the effect of applied magnetic field, fiber length and index
modulation coefficient on the peak value of DGD is shown. On the other hand, the linearity will tend to saturation when
magnetic field exceed the measurement range. So we can determine the mesurement range given design parameters. In
the experiments the DGD of FBG without and with magnetic field are performed. The peak value of DGD increases with
the applied magnetic field linearly. The fit curve of experimental and simulated results is parallel approximately and the
gap is because of the intrinsic DGD of fiber grating. Using the optical vector analyzer with precision of 10<sup>-5</sup>ps we get the
sensitivity of 0.001Gs in experiment. The simulations and experiments validate this method.
Next-generation wavelength routing optical networks requiring optical cross connects (OXC) in the network have the ability to direct optical signals from any input interface to suitable output interfaces by configuring their internal embedded optical switch matrices. Optical switches based on MEMS technology have the fundamental advantage of being able to exploit the benefits of free-space interconnection (including low loss and crosstalk, and low polarization- and wavelength-dependence), together with the advantages of integrated optics (including compactness, optical
pre-alignment, and low cost ). Therefore, it offers the possibility of achieving high port-count in a small, low-cost system
with excellent optical quality. In this paper, at first the basic concepts of the two kinds of optical MEMS switches--2-D and 3-D switches are reviewed and the principle of the MEMS switches is introduced. The key parameter in the assembly/packaging of optical components is the insertion losses due to misalignment between the optical components. The misalignment losses are calculated as the coupling coefficient between two Gaussian beams having certain lateral and longitudinal separations and a tilt angle. It's concluded that optical design of a free-space MEMS component is a compromise between lateral misalignment and angular misalignment from the simulations. At last the application of optical MEMS switches in the optical cross-connects is discussed including the configurable WADM
(wavelength-add-drop multiplexer) which can be achieved using 2-D MEMS crossbar matrix switches and the three-dimensional (3-D) microoptical switching system (3D-MOSS).