Changyun Miao

Preliminary Investigation of an SOI-based Arrayed Waveguide Grating Demodulation Integration Microsystem

An arrayed waveguide grating (AWG) demodulation integration microsystem is investigated in this study. The system consists of a C-band on-chip LED, a 2 × 2 silicon nanowire-based coupler, a fiber Bragg grating (FBG) array, a 1 × 8 AWG, and a photoelectric detector array. The coupler and AWG are made from silicon-on-insulator wafers using electron beam exposure and response-coupled plasma technology. Experimental results show that the excess loss in the MMI coupler with a footprint of 6 × 100 μm2 is 0.5423 dB. The 1 × 8 AWG with a footprint of 267 × 381 μm2 and a waveguide width of 0.4 μm exhibits a central channel loss of −3.18 dB, insertion loss non-uniformity of −1.34 dB, and crosstalk level of −23.1 dB. The entire system is preliminarily tested. Wavelength measurement precision is observed to reach 0.001 nm. The wavelength sensitivity of each FBG is between 0.04 and 0.06 nm/dB.

Refractive Index Fiber Laser Sensor by Using Tunable Filter Based on No-Core Fiber

A novel refractive index fiber laser sensor based on a fiber Bragg grating (FBG) integrated with a section of no-core fiber (NCF) is proposed and experimentally demonstrated. The oscillating wavelength of the fiber laser is only decided by the central wavelength of the FBG that is insensitive to the surrounding refractive index (SRI). However, the output power of the fiber laser varies with the SRI because the laser output is filtered by the edge of the bandpass filter (BPF) formed by the multimode interference (MMI) effect in the NCF, which is sensitive to the SRI. By measuring the variation of the output power, a cost-effective power detection RI sensor could be realized. The fiber laser sensor has a linear relationship with SRI and a sensitivity of 113.73 dB/RIU in the RI range of 1.333-1.4076.

Curvature and temperature sensor based on bulge-taper structures interferometer with embedded fiber Bragg grating

Abstract. A sensor head consisting of an all single-mode fiber (SMF) in-line Mach–Zehnder interferometer (MZI) with an embedded fiber Bragg grating (FBG) is proposed and experimentally demonstrated for simultaneous measurement of curvature and temperature. It is fabricated by cascading two bulge-taper fusion structures in a section of SMF including an FBG. The MZI is sensitive to fiber bending and ambient temperature with a sensitivity of −16.59  nm/m−1 in the range of 1.05 to 4.05  m−1 and 58  pm/°C in the range of 30°C to 100°C, respectively. However, the FBG is only sensitive to the latter with a sensitivity of 13  pm/°C. Simultaneous measurement of curvature and temperature is obtained and the cross-sensitivity issue can be solved. The experimental results show that the average relative error of the curvature is 0.38%, which is about 18 times better than that without temperature compensating. The average error of temperature is only 0.21°C.

Widely tunable ultra-narrow linewidth single-longitudinal-mode Brillouin fiber laser with low threshold

A widely tunable ultra-narrow linewidth single-longitudinal-mode Brillouin fiber laser (SLM–BFL) with low threshold is proposed and experimentally demonstrated by using a 205 m long high-nonlinear fiber (HNLF) as Brillouin gain media. The single-longitudinal-mode (SLM) operation is guaranteed by cascaded filters composed of a fiber ring Fabry–Perot filter and a self-induced narrow filter based on a 4 m unpumped erbium-doped fiber. Owing to the long ring cavity, the BFL has a low threshold of 12.8 mW and ultra-narrow linewidth of 0.29 kHz. The BFL can be tuned from 1532 to 1577 nm. The optical signal-to-noise ratio of the fiber laser is higher than 70 dB during the 45 nm tune range.

Double Brillouin frequency spaced multiwavelength Brillouin-erbium fiber laser with 50 nm tuning range

A 50 nm tuning range multiwavelength Brillouin-erbium fiber laser (MWBEFL) with double Brillouin frequency spacing is presented. Two separated gain blocks with symmetrical architecture, consisted by erbium-doped fiber amplifiers (EDFAs) and Brillouin gain media, are used to generate double Brillouin frequency spacing. The wider tuning range is realized by eliminating the self-lasing cavity modes existing in conventional MWBEFLs because of the absence of the physical mirrors at the ends of the linear cavity. The Brillouin pump (BP) is preamplified by the EDFA before entering the single-mode fiber (SMF), which leads to the reduction of threshold power and the generation enhancement of Brillouin Stokes (BS) signals. Four channels with 0.176 nm spacing are achieved at 2 mW BP power and 280 mW 980 nm pump power which can be tuned from 1525 to 1575 nm.

Maximum-Torque-Per-Ampere Control of Interior Permanent Magnet Synchronous Machine Applied for Hybrid Electric Vehicles

Permanent magnet synchronous machines are known as a good candidate for hybrid electric vehicles (HEV) due to their unique merits. According to the characteristic that d,q-axis inductances are not equal in interior permanent magnet synchronous motors (IPMSM), this paper introduces a maximum- torque-per-ampere (MTPA) control scheme, which can get a larger torque output under certain current condition. A relationship about the minimum d, q- axis currents required under certain torque output is derived by the maximum principle. In same capacity, relative to id=0 control, this method can significantly improve the low-speed torque and dynamic performance of the system. Moreover, the inductance saturation effect is considered¿C and an approximate algorithm for engineering applications is presented and applied to engineering practice. Finally, Experimental results verify the effectiveness and engineering practicability of the proposed approach.

Multipoint refractive index and temperature fiber optic sensor based on cascaded no core fiber-fiber Bragg grating structures

Abstract. A multipoint fiber optic sensor based on two cascaded multimode interferometer (MMI) and fiber Bragg grating (FBG) structures is proposed and demonstrated for simultaneous measurement of refractive index (RI) and temperature. The MMI is fabricated by splicing a section of no-core fiber (NCF) with two single-mode fibers. The suitable NCF lengths of 19.1 and 38.8 mm are selected by simulations to achieve wavelength division multiplexing. The two MMIs are sensitive to RI and temperature with the maximal RI sensitivities of 429.42228 and 399.20718  nm/RIU in the range of 1.333 to 1.419 and the temperature sensitivities of 10.05 and 10.22  pm/°C in the range of 26.4°C to 100°C, respectively. However, the FBGs are only sensitive to the latter with the sensitivities of 10.4 and 10.73  pm/°C. Therefore, dual-parameter measurement is obtained and cross-sensitivity issue can be solved. The distance between the two sensing heads is up to 12 km, which demonstrates the feasibility of long-distance measurement. During measurement, there is no mutual interference to each sensing head. The experimental results show that the average errors of RI are 7.61×10−4  RIU and 6.81×10−4  RIU and the average errors of temperature are 0.017°C and 0.012°C, respectively. This sensor exhibits the advantages of high RI sensitivity, dual-parameter and long-distance measurement, low cost, and easy and repeatable fabrication.

Differential Intensity Modulation Refractometer Based on SNS Structure Cascaded Two FBGs

A differential intensity modulation refractometer based on single-mode-no-core-single-mode (SNS) structure cascaded with two fiber Bragg gratings (FBGs) is proposed. The SNS structure acts as a band pass fiber (BPF), and the Bragg wavelengths of the two FBGs located at each edge of the BPF. Because the interference spectrum of the SNS is sensitive to refractive index (RI) but FBG is not, the reflective powers of the FBGs are modulated by the surrounding refractive index (SRI) and have contrary changing trends. The reflective intensity difference of the FBGs is used to describe the change of the SRI, which not only increases the RI sensitivity but diminishes the influence of the input light fluctuation as well. In addition, as the SNS and the FBGs have approximate temperature sensitivities, this sensor can accomplish temperature self-compensation. The experiments show that the RI sensitivity of this sensor is about –199.6 dB/RIU in the range of 1.3326–1.3702 and –355.5 dB/RIU in the range of 1.3702–1.4066, which is greater than the traditional SNS-FBG structure. However, its temperature sensitivity is only 0.0148 dB/°C. When the input light varies 7 mW, the shift of the intensity difference is only 0.28 dB, which is much smaller than the intensity shift of the single FBG.

A widely tunable double-Brillouin-frequency spaced multiwavelength fiber laser with a 110 nm tuning range

A wideband double-Brillouin-frequency spaced multiwavelength Brillouin?erbium fiber laser (MWBEFL) with 110 nm tuning range is demonstrated. The fiber laser utilizes simple compound-ring cavity structures which confine the odd-order Brillouin?Stokes (BS) signals within the right ring and couple out the initial Brillouin pump signal (BP) and even-order BS signals to generate a 0.176?nm spacing multiwavelength. A wavelength-?and bandwidth-tunable optical band-pass filter (TBF) is used to manipulate the location of self-lasing cavity and to get a wideband tuning range. All the generated output channels exhibit good stability.

Smart textile sensing system for human respiration monitoring based on fiber Bragg grating

Magnetic resonance imaging (MRI) has become an indispensable aid to diagnosis and treatment. As the doctor cannot accompany the patient, it is essential that the patient be monitored remotely to avoid the risk of respiration being impaired by anesthetic drugs or upper airway obstruction. A smart wearable textile sensing system is described in this paper. A fiber Bragg grating (FBG) with polymer encapsulation has been woven into an elastic bandage to detect the respiration motion. According to the strain principle of FBG, the breathing rate and intensity can be obtained by measuring the variety of FBG reflected wavelength. In order to eliminate the temperature cross-sensitivity, a FBG temperature sensor has also been woven into the bandage to achieve the temperature compensation computing. Based on the tunable Fabry-Perot filter wavelength demodulated theory, wavelength measuring method and data processing arithmetic have been presented, and the system with ARM microprocessor has been designed to process and display the breathing information. The experiments to the system have proved that the wavelength measuring range is about 40nm, the resolution of wavelength can arrive at 2pm, and the sampling rate is 5Hz.