A single mode fiber-tapered multi-core fiber-single mode fiber (SMFTMCF-SMF) structure for the temperature measurement with fiber ring cavity laser at 2 μm band is proposed and demonstrated. The sensor consists of a tapered MCF spliced between two single-mode fibers. By tapering the MCF, the modal fields of the different multi-cores run out and then couple with each other. Experimental results show that the proposed laser works stably at the resonant wavelength of 1979.2 nm at ambient temperature. A sensitivity of -4 pm/°C was obtained with the temperature changing from 70°C to 35°C.
A non-invasive vital signs monitoring system based on fiber-optic interferometers using single mode fiber (SMF) is presented in this paper. The fiber-optic interferometers was formed by a dual biconical structure without splicing point.The experimental setup was designed to collect the vital signs data of user on bed for processing. With optimized algorithm, human being’s heart beat and respiration signals can be monitored in an contactless and non-invasive way. The experimental results on the measurements of breathing rate and heart rate agree well with the results obtained from medical equipment.
This paper studies a humidity dual biconical fiber sensor coated with agarose gel. The sensor was fabricated by the taper drawing technique of using a LZM-100 fusion splicer from single mode fiber, forming a Mach-Zehnder interferometer. Humidity modifies the refractive index of the coating layer, which in turn alters the high order modes along the dual biconical fiber segment and causes a detectable shift to the interference pattern. Due to the strong light absorption of agarose at 2 μm, the sensitivity of sensor was greatly enhanced. It has been found that the sensor’s sensitivity operated at 2 μm is tens of times higher than that at 1.55 μm region.
In this paper, the Olympic rings pattern is generated by using freeform lens array and illumination light source array. Based on nonimaging optics, the freeform lens array is designed for point light source, which can generate the focused pattern of annular light spot. In order to obtain the Olympic logo pattern of five rings, the array with five freeform lenses is used. By adjusting the emission angle of each light source, the annular spot is obtained at different positions of the target plane and the Olympic rings logo is formed. We used the shading plate on the surface of the freeform lens to reduce the local light intensity so that the light spot overall irradiance distribution is more uniform. We designed a freeform lens with aperture of 26.2mm, focal length of 2000mm and the diameter of a single annual spot is 400mm. We modeled freeform lens and simulated by optical software TracePro. The ray tracing results show that the Olympic rings with uniform illumination can be obtained on the target plane with the optical efficiency up to 85.7%. At the same time, this paper also studies the effects of the target plane defocusing on the spot pattern. Simulations show that when the distance of the receiving surface to the focal plane varies within 300mm, a reasonable uniform and small distorted light spot pattern can be obtained. Compared with the traditional projection method, our method of design has the advantages of high optical efficiency, low cost and the pattern is clear and uniform.
We propose a novel 1×5 optical splitter (OS) for TE modes based on self-collimation effect in an air-hole silicon photonic crystal. The OS consists of two cascaded resonators which is formed with eight beam splitters. The theoretical transmission spectra of the OS is derived with multiple-beam interference theory. From our analysis of transmission spectra, it is found that the transmission spectra at five drop ports will reach the maximum values while the transmission spectra at two through ports reach zero for resonant frequencies. By scanning the radius of a beam splitter, the relationship between the radius and the reflectivity is obtained. Therefore, by changing the radii of the air-hole in eight beam splitters, we can manipulate the output light-intensity ratio at five drop ports to meet requirement. Theoretically, when reflectivity of beam splitters R1=2/11, R2=8/11, R3=5/8, R4=2/5, R5=7/12, R6 =6/7, R7=1/2, R8 =2/3, the light intensity ratio at five drop ports is 1:1:1:1:1. When R1=2/7, R2=6/7, R3=1/2, R4=2/3, R5=1/7, R6=6/7, R7=2/3, R8 =1/4, the light intensity ratio at five drop ports is 2:2:1:2:3. By means of finite-difference time-domain (FDTD) simulations, the numerical transmission spectra of OS can be figured out. The simulation results are consistent with the theoretical results. Considering micro processing technology of silicon materials is already available, this OS can be used in the photonic integrated circuits because of its small size, whole-silicon material and low insertion loss.