This PDF file contains the front matter associated with SPIE Proceedings Volume 11569, including the Title Page, Copyright information and Table of Contents

In this paper, we introduce an optimal bias voltage searching strategy and maintaining method in BOTDA system based on dual sideband modulation. The system utilizes both up shifted and down shifted continuous wave light to generate Brillouin scattering light, while using the amplified pulsed light to boost the signal by stimulated Brillouin scatting effect. In order to obtain a clean Brillouin shifted curve along the fiber under test, the probe light must be in good signal to noise ratio. In addition, the intensity of shifted light should be stable as well. Therefore, we propose a novel control method of frequency shift in sideband modulation of a BOTDA system, which keeps the first order frequency-shifted light at its maximum signal to noise ratio and minimum light intensity fluctuation. We also implement static experiments to verify our proposed scheme. Strain/temperature tests were taken out to evaluate the performance of the BOTDA. Results showed that the resolution of BOTDA system could reach 13με/0.65°C at 50 km fiber cable with spatial resolution of 0.5m.

Magnetic field sensors have important application values in the fields of geophysical surveying and navigation, military equipment applications, biomedical sensing, and aerospace field. This paper proposes a magnetic field sensor based on side-polished fiber and microsphere. The sensor uses optical fiber microspheres as the light sensing platform and magnetic fluid as the magnetic field response and sensitizing material. The magnetic field sensor is made of a multi-mode side-polished optical fiber and SiO₂ microspheres, which are put into a capillary package, and Fe₃O₄ magnetic fluid is injected into the capillary.We used COMSOL Multiphysics 5.4 based on finite element analysis to simulate the proposed sensor structure. Simulation results show that the magnetic field sensor has a maximum intensity sensitivity of 0.75dB / Oe, a refractive index sensitivity of 125nm / RIU, a Q-factor of 2.5x10⁴, and the FOM of 2.5x10³. Compared with the traditional magnetic fluid magnetic field sensor, the proposed sensor has a simple structure, low production cost, high Q-factor and high FOM. It has potential application prospects in developing magnetic field sensors compatible with high-sensitivity sensing and high-precision detection.

The performance of a decode-and-forward (DF) serial relay OFDM free-space optical (FSO) communication system with exponentiated Weibull (EW) distribution is investigated in this paper. Considering that the optical signal propagation in free space is affected by a variety of destructive effects such as atmospheric turbulence, fog, path loss and pointing error, the closed expression of system outage probability and symbol error rate is derived using the Meijer G function respectively. The effects of key factors such as the number of different relay nodes, weather conditions, link length between relays, and number of subcarriers on the outage and symbol error rate performance of the serial relay OFDM FSO system are analyzed by simulation. The results show that the system's performance decreases with the increase of the distance between relays, and the communication will be interrupted in foggy days.

In the optical transport network, the high-dimension equiprobable constellation is used to increase the information transmission rate and the forward error correction code is used to improve the system performance. However, adopting the equiprobable constellation will lead to some information loss according to the Shannon theory and the performance of the FEC code needs to be strengthened. Based on this, unequiprobable constellation is designed to reduce the information loss by optimizing the probability of the first bit taking the value zero or one. In order to further improve the system performance, polar code, an advanced channel code with good performance and low decoding computation complexity, is combined with the probabilistic shaping to realize the unequiprobable constellation in this paper. The simulation results show that the unequiprobable constellation can provide nearly 1dB gain compared to the equiprobable constellation.

Twist direction and degree of interference fringes collected in double-slit interference experiment can be used to determine the topological properties of vortex beams, and the modulation depth of interference fringes indicates the spatial coherence of vortex beams. The effects of distance between double slits and the initial coherence length of the beam on the visibility and the twist degree of interference fringes in the partially coherent vortex beam topological charge interference measurement are analysed by adjusting the double-slit distance and the coherence length of the partially coherent vortex beam under near-field conditions. The study found that the interference fringes are distorted with the increase of the double slit distance, but the interference fringes and their distortion are not obvious when the initial coherence length of the partially coherent vortex beam is shorter than the beam width. Visible interference fringes will appear when the initial coherence length is longer than the beam width and the twist degree of interference fringes also increase. The coherence length has little effect on the visibility and distortion of the interference fringes when the initial coherence is greater than the size of the light spot on cross-section where the double slits are located, but the distance between the double slits still affects the observation to the visibility of interference fringes and distortion phenomenon. The research results may be useful for the measurement of orbital angular momentum of partially coherent vortex beams.

An optical length measuring method exploiting microwave interrogated cascaded fiber Mach-Zehnder interferometer (MZI) is proposed. The frequency response of the filter with respect to the fiber length change of MZI is studied and an length measuring sensitivity of 2.580 GHz/mm is obtained. The proposed sensing configuration is with high sensitivity, easy to implement and shows the capability for other parameters measurement such as temperature, strain, and vibration.

The fiber optic current sensor (FOCS) is susceptible to external temperature in actual operation, which will lead to its accuracy deviation, even malfunction. In order to improve the temperature stability of FOCS’s ratio error, a temperature compensation method based on RBF neural network is established by taking the temperature as input and the ratio error as output to the network. Compared with BP neural network, the simulation results show that the temperature compensation model based on RBF neural network has better accuracy whose prediction error is less than 3%. At the same time, the experimental results show that the drift deviation of ratio error can remain as low as ±0.1% in the range of -40 °C to 70°C, and the 0.2S-level accuracy of GBT20840.8 standard can be achieved.

The engineering application number of fiber optic current sensor (FOCS) is decreasing year by year since 2012 in China due to its reliability problems. However, the researchers and related enterprises have also made some constructive attempts on the study of fault diagnosis of FOCS. In this paper, the application status and the common fault modes of FOCS are analyzed. Three ways to diagnosing the soft and hard fault of FOCS are reviewed, including based on analytical model, on signal processing and on knowledge. Finally, the research direction of FOCS fault diagnosing is prospected. It is concluded that the diversified and intelligent fault diagnosis method based on knowledge has more advantages compared with the other two methods. In addition, the development of FOCS for integrated optical path is of great help in improving its reliability and will be a research hotspot in the future.

This paper reports a wavelength selective switch (WSS) employing a thermally expanded core (TEC) fiber array (FA) as the input/outputs, which enables a compact WSS with convenience for alignment and assembly. Simulation of the WSS module based on ZEMAX shows that conical diffraction of the grating results in horizontal offset of the output beam spots. An excess insertion loss will be caused due to the offset if a linearly aligned FA is employed as the input/outputs. This paper designs a parabolically aligned TEC FA that the fibers in the array can be positioned by V-grooves with different depth. With the parabolically aligned TEC FA as the input/outputs, the WSS module is expected to be compact with low loss.

We propose a tilted fiber grating (TFG) sensor for ammonium ion detection in aqueous solution. The sensor is made by coating a nano-film of polyvinylidene-fluoride-bromothymol-blue (PVDF-BTB) over the TFG surface. As the ammonium ion can react with the bromothymol blue, the smoothness of the PVDF-BTB film will be destroyed, leading to the transmission spectrum changing correspondingly. The reaction strength between the ammonium ion and the bromothymol blue is proportional to the concentration of ammonium ion. Therefore, through monitoring the change of a selected cladding mode in the transmission spectrum with time, we can measure the concentration of ammonium ion. Experimental results show that our sensor can detect ammonium ion in concentration as low as 1 mg/L within 140 seconds, and after that the intensity variation of the monitored mode almost keeps stable, which agrees with the theoretical analysis. Furthermore, through monitoring the core mode during the experiment, we can eliminate the temperature-induced cross-sensitivity, thus improving the measured accuracy of the sensor. Our proposed TFG sensor for ammonium ion detection has advantages of simple structure, easy fabrication and comparable performances.

As a new generation of optical gyroscope, fiber optic gyroscope has the characteristics of high precision, zero start, all solid state, high theoretical reliability, and has been widely used in many fields, such as sea, land, air and so on. In the assembly process of FOG, the fiber fusion technology is one of the key technologies of FOG. Its process method and parameters have a decisive influence on the performance and reliability of FOG. In this paper, the flow chart based on FOG fusion technology is established firstly, and the influence mechanism of FOG fusion technology on its performance and reliability is analyzed. Then, the relevant tests are designed and verified. Finally, the performance and reliability of FOG are improved by optimizing the technological parameters of fiber fusion and carrying out strict technological management system.

We analyze theoretically and verify experimentally a low-cost and effective scheme to realize detection of Bragg wavelength shift with high resolution based on an Erbium-doped fiber Bragg grating. The phase-shifted fiber Bragg grating is used in our experiments in order to achieve tunable single sideband modulation. Through the combination of the microwave domain and the optical domain, the Bragg wavelength shift of the grating induced by the 980-nm pump laser is translated to the amplitude variation of the beat signal generated in the photodetector. The experimental results indicate that 0.008 nm-wavelength shift is detected, which breaks out the resolution of commercial optical spectrum analyzer. Moreover, this resolution can be further improved by employing more accurate temperature and environment controlling systems. Compared with traditional optical domain detecting methods, the proposed approach shows obvious advantages in high resolution and convenient operation.

A sapphire-derived fiber (SDF)-air based composite Fabry–Perot interferometer (FPI) for simultaneous measurement of strain and temperature has been proposed and demonstrated. The FPI was fabricated by cascading a lead-in single mode fiber and a short section of SDF with a small air cavity left in between. The structure was inserted into capillaries and fixed by an arc fusion. The air cavity was used for strain sensing. Its strain sensitivity was improved by increasing the ratio of capillary based active length to air based interference cavity length, while its temperature sensitivity was compensated by the SDF with a well-designed length and alumina content. The SDF cavity served as a thermometer. The reflection spectrum was demodulated by tracing the wavelength shifts of the low- and high-frequency fringes, which were caused by the air-cavity and the combination of the air and SDF based cavities, respectively. A dual-parameter sensitivity matrix was introduced to realize the simultaneous measurement of strain and temperature. In the experiments, an enhanced strain sensitivity of 55.52 pm/με in the range of 0-500με and a reduced temperature sensitivity of 0.05pm/°C in the range of (20-600)°C were obtained from the lowfrequency fringe, while a strain sensitivity of 5.38 pm/με and a temperature sensitivity of 10.81 pm/°C were obtained from the high-frequency fringe.

Fiber-optic hydrophone is a new type of sensor which can detect acoustic signal in harsh seawater environment. For some application, the fiber-optic hydrophones should be serving for years or even decades, due to the high cost of placement. Because of multiple fiber-optic hydrophones are made into a hydrophone array by multiplexing generally, thus realize signal detection as a whole. To ensure the detection effect, sufficient number of elements in the array must be working order, otherwise the array may lose efficacy. Slow degradation of fiber-optic hydrophone is inevitable as time goes on. So, it is particularly important to control early failures. In this paper, a research on early failure mechanism of fiber-optic hydrophone has been present. In details, the actual service environment of fiber-optic hydrophone is analyzed firstly, and the weak links of fiber-optic hydrophone which may degrade rapidly are discussed and the early failure mechanisms are also analyzed. Further, the verification test was designed for the possible failure mechanism, and the failure analysis of the samples was carried out by using the advanced failure analysis instrument such as the scanning electron microscope (SEM) and the Fourier transform infrared spectrometry (FTIR). Results show that the bonding process defects is one of main reason for early failure of the fiber-optic hydrophone and the strength of package may degrade rapidly in seawater environment until the early failure occurs. This research will help to improve the process reliability of fiber-optic hydrophones and control the occurrence of early.

The edge demodulation structure consisting of a micro-ring resonator and an asymmetric M-Z interferometer is proposed and investigated for applications in sensing system. According to the linear conversion between wavelength and intensity in the demodulation principle, the parameters affecting the linear region of spectral response are analyzed theoretically. Numerical analysis shows that the ratio of δ to ΔΦ is 0.5 is the best premise to realize wavelength demodulation. The accuracy decreases with the increase of coupling coefficient K, but the demodulation range is improved. The change of coupling angle k₁ and k₂ makes the waveform shrink according to a certain rule, thus changing the detection sensitivity. Meanwhile, the demodulation performance improves as the transmission factor α increases.

In this paper, a novel Double-Deviations mathematical model and Uniform Design Method for flattop all-fiber MZI interleaver is proposed. It provides an innovative, versatile and practical solution for the design of cascaded MZI filters. Obtain the parameters of the all-fiber comb filters by constructing the uniform design table, then the scheme is numerically simulated and verified in three different structures. When evaluating the performance of flattop all-fiber interleave , a new goodness-of-fit criterion named "double difference function of the optical comb transform output spectrum and the target square wave" was established. It can adequately consider the information provided by evaluation index of the output waveform. The geometrical significance of Double-Deviations and the convergence proof of function sequence based on it is described and analyzed. The preliminary numerical simulation results show that the flattop all-fiber MZI filters designed under Uniform Design Method have optimum performance. When compared with the output waveform obtained by the traditional algorithm, the scheme proposed has less calculation time, high approximation accuracy, flatter pass-band and stop-band of the filter, whose advantage is highlighted obviously for solving high dimension parameter optimization problem in the optical fiber field.

As a kind of all solid-state FOG, high-precision FOG(HPFOG) has the characteristics of anti-shock and anti-vibration. However, when it suffers strong shock, the gyro structure and fiber loop will produce high-frequency resonance components. The projection of the resonance component in the sensitive axis of the gyro is equivalent to the input of high frequency angular vibration of the gyro, and when the frequency approaches or exceeds the working frequency of the gyro, the gyro feedback loop will generate positive feedback. Due to the low frequency of the feedback loop of HPFOG, the above-mentioned positive feedback results that the output of the cross-stripe, which makes the gyro output the wrong angular rate information. In this paper, the closed-loop feedback loop model and the structural mode of FOG are modeled and analyzed, and the mechanism of cross-stripe is discussed in detail. Then, three methods of restraining cross-stripe are given by combining the closed-loop algorithm, and the advantages and disadvantages of the method are analyzed. Finally, the test results show that the three methods can effectively suppress the HPFOG cross-stripe, and improve the HPFOG's ability to resist strong impact.

As the key factor that affects the performance of the spindle bearing, the thermal induced preload determines the running status of the bearing directly. Hence, the temperature rises of the spindle unit components, especially the spindle bearing rings, cause thermal deformation of the spindle bearing and the bearing housing, resulting in thermal induced preload. The real-time monitoring of the spindle bearing preload is the crucial step for obtaining the optimum bearing preload, which can improve the service performance of the spindle unit and the machine tool. However, at the present stage, the monitoring methods are mostly completed by the electric sensors in the experimental state, and the real-time preload cannot be achieved under the spindle working process. This article breaks through the limitations of the existing methods, taking advantages of fiber gratings sensors “one line multi-point, passive multi-field”, small size and corrosion resistance, et al. Based on the fiber Bragg grating (FBG) sensors embedded in the spindle, the online force test system realizes the measurement of the bearing preload in real-time.The relationship between spindle speed and thermal induced preload is analyzed. The results of two kinds of sensors were compared and the consistency was verified the accuracy of the test results of the FBG sensor and the feasibility of real-time measurement of the thermal induced preload of the spindle bearing.

In this paper, an unsupervised clustering algorithm based on the Gaussian Mixture Model (UCGMM algorithm) for the coherent optical OFDM communication system is proposed to determine the constellation diagram. The purpose of nonlinear equalization of communication systems is achieved. In a back to back transmission system, compared to the Kmeans algorithm and the without any clustering algorithm, the UCGMM algorithm can obtain gains of approximately 0.6dB and 2dB respectively. For the cases of simulation in optical fiber transmission, the transmission distance of UCGMM algorithm is extended by 45km relative to the K-means algorithm, and 75km relative to without any clustering algorithm. In both cases, the effectiveness of the proposed UCGMM algorithm in nonlinear equilibrium is proved.

Campus security is a very important part of smart campus. How to conduct comprehensive, real-time, efficient and accurate campus security monitoring is a key issue among them. At present, the monitoring method commonly used in colleges is video surveillance, which has the disadvantages of blind spots, easy to be blocked, easy to be affected by factors such as weather and visibility, and not easy to realize automation and intelligence. This paper proposes for the first time the use of microseismic signals for campus security monitoring in the smart campus, using distributed fiber optic acoustic sensing technology (DAS) as the monitoring method, and proposed corresponding detection algorithms. Distributed fiber optic acoustic sensing technology uses optical fibers as sensors to detect changes in microseismic signals, thereby detecting the surrounding environment. Compared with traditional methods, DAS has the advantages of high sensitivity, strong real-time performance, anti-interference, no obstruction, easy deployment, and low cost. This paper also carried out on-site detection experiments of campus security, focusing on several directions such as emergency detection, vehicle location, over speed warning and congestion warning, and obtained experimental results. According to the experimental results, the detection accuracy of campus security incidents is relatively high, so this method has strong practical significance.

With the continuous progress of science and technology and the rapid development of the Internet, higher requirements have been put forward for network performance. EONs (Elastic Optical Networks) is proposed as an optical network with high reliability, high efficiency and high survivability. Although there have been many researches on EONs and various performance indexes, it is still a problem how to evaluate the comprehensive ability of optical networks comprehensively. This paper designs a network design scheme evaluation model based on AHP (Analytic Hierarchy Process) and business priority. According to the evaluation results, different protection schemes are adjusted, which provides valuable reference for the construction of network planning scheme. The basic performance index is obtained according to the scheme and network planning algorithm, and the survival performance index is obtained according to the protection algorithm. AHP was used to establish the hierarchical structure model for these two categories, paired comparison matrix was constructed through the comparison of two performance indicators, consistency test was conducted, and the final weight was calculated. Finally, according to the weight of the total order of the weighted hierarchical weighted calculation, the final decision basis. Multiply the weight of the decision by 100 to get a percentage score. Based on the score, it can determine whether the solution is suitable, and then adjust the business priority and network design solution, as well as provide effective reference for network planning.

Compared with laser gyro, the scale factor performance of high-precision FOG(HPFOG) restricts its application to high-precision and strategic applications. According to the characteristics of HPFOG with well temperature sensitivity and poor nonlinearity, In this paper, the temperature error model of fiber optic loop and the scale factor error output curve of gyro at different angular rates of each temperature point are analyzed. An optical fiber temperature sensor embedded in the optical fiber loop is proposed to accurately measure the temperature of the optical fiber loop. Compared with the existing single point or multi-point external temperature model, the model can accurately measure the internal temperature field of the optical fiber loop, and establish a reliable Shupe error model of the optical fiber loop temperature. A hybrid model is established by introducing the input angular rate information of gyroscope into the model, and the multi coefficient scale error is compensated according to the model. The experimental results show that the scale factor of HPFOG is greatly improved after compensation based on the accurate error model, and the performance index of the scale factor of HPFOG is effectively improved.

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.

The characteristic absorption lines of carbon monoxide gas cross with that of other gases in near-infrared and midinfrared bands, the detection results are easily disturbed. Especially in some environments such as coal mines and petrochemicals, it is more important to avoid cross interference, in order to achieve accurate measurement of carbon monoxide. In this paper, a DFB laser beam at 2330nm was selected and scanned for absorption line of carbon monoxide. Although interference of other gas components was avoided, the overlap of carbon monoxide and methane spectra still existed. Firstly, the absorption lines of methane and carbon monoxide were studied. According to the theory of molecular spectroscopy, the FWHM of methane and carbon monoxide absorption lines are different. Once, there is methane gas in the background, the harmonic signals will be different due to different line shape. The second harmonic signals with different modulation coefficients are simulated. So the troughs width is selected as the evaluation function of the harmonic signal characteristics for component judgement. Secondly, after component determination, when mixed gas is present, adjacent methane absorption peaks are also scanned for deduction. The influence of temperature is also calculated and the evaluation function is modified again. Finally, the free calibration measurement of carbon monoxide concentration in the mixture is realized. In summary, for the working conditions of complex background gas such as coal mine and petrochemical. This paper presents a calibration-free method for reliable carbon monoxide concentration detection based on a TDLAS technique.

In this paper, a scheme for on-line monitoring of multi-component decomposition based on TDLAS is presented, which is mainly composed of hydrogen sulfide, carbon monoxide and hydrogen fluoride. Considering that the most important problem of multi-component gas detection is the crossover of components, the characteristic spectra were first analyzed. The characteristic absorption peaks of hydrogen fluoride are very strong, which makes it easy to detect hydrogen fluoride with high sensitivity. However, the absorption peak of hydrogen fluoride covers hydrogen sulfide and carbon monoxide, making it difficult to detect. The interference problem is analyzed and the solution is given. In addition, multi-parameter transmitter in power industry is used to provide data for on-line calibration. The concentration of sulfur hexafluoride is retrieved from SF6 density information provided by multi-parameter transmitter. According to the temperature information, decomposition gas concentration value is calibrated. In this paper, an on-line monitoring device for SF6 decomposition mixture gas based on laser absorption spectroscopy is developed. The results of temperature cycle test show that the influence of environmental parameter changes on the concentration results can be reduced after on-line calibration.

An approach for photonic generation dual-chirp microwave waveform (DCMW) with frequency and bandwidth multiplication without filtering is proposed and demonstrated. A continuous-wave (CW) optical signal is sent to a polarization division multiplexing modulator. In the modulator, one part of the CW optical signal is modulated by the radio-frequency (RF) driving signals to generate ±2 nd-order single-frequency sidebands, while another one is modulated by the baseband chirped signals to generate ±2 nd-order chirped sidebands. After that, a frequency-doubled and bandwidth-quadrupled DCMW can be generated by photoelectric balanced detection. In the simulation experiments, by using a RF driving signal at 5GHz and a baseband single-chirp signal with bandwidth of 0.5GHz as the input electrical signals, a DCMW with central frequency of 10GHz and bandwidth of 2GHz is generated.

Based on the Sagnac effect, the small changes in thermally induced stresses and microcosmic size of optical fiber coil can cause the drift of the Shupe error and scale factor of fiber optic gyroscope (FOG). As polymer functional resin represents a high proportion in optical fiber coil, its physical and chemical properties determine largely the thermally induced stresses and dimensional stability of the coil, thus influencing the performance of FOG. Given the demands for the long-term stability and temperature characteristics of FOG, this paper studies the influence of molecular chain structure and thermal conductivity of polymer functional resin for optical fiber sensing on FOG. The experimental results suggest: high thermal conductivity can reduce the thermal induced stresses of polymer functional resin of reticular molecular structure, greatly improving the zero bias stability of FOG at all temperature; hyperbranched molecular structure reports outstanding creep-resistant characteristics thanks to the significantly reduced internal free volume of optical fiber coil after encapsulation and insignificant dimensional changes at all temperatures, thus ensuring long-term stability of the scale factor of FOG.

The random walk coefficient (RWC) is the index of white noise of FOG, which determines the minimum detection sensitivity of FOG. The white noise of FOG mainly focuses on optical or photoelectric detection, which can be divided into three categories: detector thermal noise, shot noise and relative intensity noise (RIN). In practice, the RWC of FOG is determined by the signal-to-noise ratio (SNR) in the phase detection process rather than the white noise. When the photocurrent is small, the SNR of FOG is determined by the shot noise. When the photocurrent is large, the signal-tonoise ratio of FOG is determined by the RIN. Therefore, the suppression of RIN is the key to improve the precision of FOG. Through the analysis of the macro input and output characteristics of semiconductor optical amplifier (SOA) and the noise spectrum analysis of saturated SOA, it is demonstrated that the gain saturation effect of SOA can effectively suppress the RIN of wide spectrum light source. Through calculation, the theoretical noise rejection ratio is more than 20dB. Therefore, an erbium-doped fiber source with low RIN is designed. The verification is carried out at the light source level and gyro level respectively. In the light source level verification, the RIN suppression effect of 10dB is achieved. In the gyro level verification, the noise suppression effect under different modulation depth is analyzed, and the random walk reduction of gyro achieves 30% - 60%.

Recently, new types of nanostructured surface plasmon resonance sensors (SPR) are developing rapidly, and have a wide application prospect. However, most sensors face the disadvantages of low sensitivity or complex structure, which raise the problems that are not able to detect precisely or cost high price to produce. In this work, we proposed a new type of gold-silicon (Au-Si) nanograting structured SPR sensor, which takes the advantages of characteristics of transmission spectrum easier to detect and mass production. The most importantly, it has relatively high sensitivity compared to the commercial sensors. The structure is also incorporated a microfluidic channel as a slot cavity with Silicon dioxide (SiO₂) cap. In the case of vertical incidence of light, the analyte in the Microfluid cavity will has a high transmission peak in the near infrared band (near the wavelength of 1500nm actually), which will significantly move when the reflective index(RI) of the analyte changes. The electromagnetic fields of the structure is greatly concentrated in the area of the cavity, which contributes to the high sensitivity up to 1063nm/RIU, which refers to the ratio of the change of the movement of the transmission peak to the change of the RI of the analyte. This structure was simple enough to produce on a large scale easily with low price, and easy to detect due to the concentration on the transmission peak, which make it to be a new type of surface plasmon sensor.