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We studied a miniature optical fiber sensor based on in-line Fabry-Perot interferometer for strain measurement. The sensor was fabricated by splicing a section of hollow core tube (HCT) between two single mode fibers. The reflective spectrum of the interferometer exhibits a number of resonance wavelength dips owing to destructive interference of two reflective lights. The experiment results demonstrate that, as the strain increased, the resonance wavelength exhibits a redshift behavior. The maximal strain sensitivity obtained by linear fitting is 4.55pm/μe. The device proposed has high potential in construction engineering, industry production, and high speed rail due to its merits of electromagnetic immunity, miniature structure and ease of fabrication.

We provide a novel arithmetic for the calculation of the transmission equation in a structure based on the add-drop resonator. Moreover this method can be applied on all the structures containing add-drop resonators or analogous configurations to simplify the calculation and the light path analysis. The characteristics of the transmission spectra in add-drop interferometer with two different kinds of curves are analyzed. We find out the reason for the different transmission spectra and draw an analogy with the under coupling, over coupling, and critical coupling. These results will provide some useful information and a new track to analyze the structures in this field.

We theoretically demonstrate the transmittion spectra and dispersion characteristics based on the electromagnetically induced transparency like effect in the nested fiber double-ring resonator with the transfer matrix theory; the system which are connected by three directional couplers consists of two inner rings, one outer ring and one straight waveguide. The simulation results show that the tunable group delay can be realized by changing the coupling coefficients. In the NDRR coupled Mach-Zehnder interferometer system, we obtained fast light and slow light simultaneously. By adjusting appropriate parameters, we can archive flat band group delay curve that has a profound application in optical interferometer, optical buffer, optical filter, optical modulator, dynamic or static optical sensing field.

We investigate the phase and group delay in eye-like ring resonator with the effect of different coupling coefficients and attenuation factors. The eye-like structure is composed of two bus waveguides coupling with the outer ring and the two rings coupling together which have the same perimeters. The eye-like ring resonator has two outputs which have different transmission characteristics. In this paper, we measure the group delay of the two outputs through changing the coupling coefficients and the attenuation factors of the inner and the outer ring. The result shows that the two outputs have reverse group delay (superluminal and slow light) which will have potential use in slow light fiber, optical buffers and optical switches.

We theoretically investigate an all-fiber interleaver consisting of a two-stage cascaded Mach-Zehnder interferometer (MZI). The simulation results of the all-fiber interleaver presented symmetrical and asymmetrical output spectra and a uniform flat-top spectral response by changing the coupling coefficient of the couplers. In addition, the interleaver proposed can realize arbitrary passband width ratio between the two output ports by adjusting the coupling coefficient of the couplers involved. A near box-shaped spectral response can be generated through setting suitable parameters, at the same time, the passband and stopband of optical interleaver are improved significantly. This interleaver proposed should be useful to realize the deployment of flat-top all-fiber asymmetric interleaver in dense wavelength division multiplexing (DWDM) networks of high spectral efficiency.