Tunable Fabry-Perot Filter Research Articles

Investigation of smart multifunctional optical sensor platform and its application in optical sensor networks

In this article, a smart multifunctional optical system-on-a-chip (SOC) sensor platform is presented and its application for fiber Bragg grating (FBG) sensor interrogation in optical sensor networks is investigated. The smart SOC sensor platform consists of a superluminescent diode as a broadband source, a tunable microelectromechanical system (MEMS) based Fabry-Perot filter, photodetectors, and an integrated microcontroller for data acquisition, processing, and communication. Integrated with a wireless sensor network (WSN) module in a compact package, a smart optical sensor node is developed. The smart multifunctional sensor platform has the capability of interrogating different types of optical fiber sensors, including Fabry-Perot sensors and Bragg grating sensors. As a case study, the smart optical sensor platform is demonstrated to interrogate multiplexed FBG strain sensors. A time domain signal processing method is used to obtain the Bragg wavelength shift of two FBG strain sensors through sweeping the MEMS tunable Fabry-Perot filter. A tuning range of 46 nm and a tuning speed of 10 Hz are achieved. The smart optical sensor platform will open doors to many applications that require high performance optical WSNs.

Continuous-Wave Sub-THz Photonic Generation With Ultra-Narrow Linewidth, Ultra-High Resolution, Full Frequency Range Coverage and High Long-Term Frequency Stability

We report on a photonic system for generation of high quality continuous-wave (CW) sub-THz signals. The system consists on a gain-switching-based optical frequency comb generator (GS-OFCG), a two-optical-modes selection mechanism and a n-i-pn-i-p superlattice photomixer. As mode selection mechanism, both selective tunable optical filtering using Fabry-Perot tunable filters (FPTFs) and Optical Injection Locking (OIL) are evaluated. The performance of the reported system surpasses in orders of magnitude the performance of any commercially available optical mm-wave and sub-THz generation system in a great number of parameters. It matches and even overcomes those of the best commercially available electronic THz generation systems. The performance parameters featured by our system are: linewidth <;10 Hz at 120 GHz, complete frequency range coverage (60-140 GHz) with a resolution in the order of 0.1 Hz at 120 GHz (10-12 of generated frequency), high long term frequency stability (5 Hz deviation over one hour). Most of these values are limited by the measurement instrumentation accuracy and resolution, thus the actual values of the system could be better than the reported ones. The frequency can be extended straightforwardly up to 1 THz extending the OFCG frequency span. This system is compact, robust, reliable, offers a very high performance, especially suited for sub-THz photonic local oscillators and high resolution spectroscopy.

Wavelength-Division Multiplexing Fiber Bragg Grating Vibration Sensing Demodulation System

A fiber Bragg grating (FBG) sensing network for vibration measurement is proposed and demonstrated in this paper. The light source of the described sensing technique is an erbium-doped fiber laser applying a 980-nm laser diode and a fiber Fabry-Perot tunable filter. The fiber laser has a 40nm tuning range, allowing many vibration sensors to be multiplexed on the same fiber. Reflected light wavelength shift of the FBG sensor caused by strain variation is converted to intensity deviation, which avoids a complex demodulation process. This sensing scheme can effectively increase the demodulation speed of sensing system up to 20 KHz. At least 20 FBGs can be multiplexed alone a fiber.

가변 페브리-페로 필터와 FBG를 이용한 광세기 기반 자기기준 광섬유 센서

본 논문에서는 자기기준 특성을 가지는 광세기 기반 광섬유 센서 구조를 제안하고 실험적으로 구현하여 성능을 제시한다. 제안하는 광섬유 센서는 광대역 광원(BLS), fiber Bragg grating (FBG), 가변 페브리-페로(Fabry-Perot) 필터, LabVIEW 프로그램으로 구성된다. 제안한 자기기준 광섬유 센서의 이론적인 해석을 통하여 측정 변수(Χ)와 보정 변수(β)를 정의하고, 이를 바탕으로 전달함수(Η)를 구한다. 또한 실험을 통하여 이론적인 해석의 타당성을 제시한다. 제안한 광섬유 센서 구조는 광대역 광원의 출력 광세기가 0 dB, 3 dB, 6 dB 감소해도 측정결과에 영향을 미치지 않는 자기기준 특성을 가진다. 또한 다른 특성의 FBG를 사용하여도 측정 가능하므로, 제안한 광섬유 센서 구조는 임의의 규격을 가진 FBG를 사용할 수 있다. 광원의 광세기가 감소하였을 때와 세 가지 다른 특성의 FBG 쌍을 이용하여 측정한 결과 이론적인 값과 잘 일치함을 보였다. 따라서 제안한 광섬유 센서는 자기기준 특성과 구성하는 FBG의 규격이 비교적 엄격하지 않아도 되는 장점을 가진다.

High resolution and wide scale fiber Bragg grating sensor interrogation system

This paper demonstrates a high resolution and wide scale fiber Bragg grating sensor interrogation system based on fiber Fabry–Perot tunable filter (FFP-TF) and Fabry–Perot ITU filter (FPIF). By automatic control of the driving voltage of the FFP-TF, the wavelength of the laser can be tracked to the −3dB reflectivity spectrum of the FBG. Using FPIF as the reference channel, the measurement resolution of the system is improved by wiping out the nonlinearity of the FFP-TF. A high resolution of better than 2pm within wide strain measurement range was verified by experiments.

Design and experimental research of a high-precision wavelength controller for tunable fiber Fabry-Perot filters

A high-precision wavelength controller is presented in this paper. It is necessary to find out the difference between the central wavelength of a tunable fiber Fabry-Perot (FFP) filter and that of the input laser, while the wavelength controller operates at the states of wavelength-scanning and wavelength-locking modes. Firstly, a dynamic simulation model of tunable FFP filter is established, and the dynamic characteristic of tunable FFP filter modulated by an alternating current (AC) signal is simulated. Then the measuring time at wavelength-scanning mode compared with the theory time is discussed, and this time difference shows the difference between the central wavelength of a tunable FFP filter and that of the input laser. At last, the effects on wavelength-locking precision of time delays, including the time delay of opened-loop circuit, the time constant of the closed-loop circuit and the intrinsic hysteresis of piezoelectric (PZT) element, are analyzed. A wavelength controller of tunable FFP filter is designed and prepared. The experimental results at wavelength-locking mode show that a high locking precision is obtained.

Algorithm for Excitation Optimization of Fabry–Pérot Filters Used in Swept Sources

We investigate the improvement in the nonlinearity of a conventional wavelength swept laser source on the basis of a fiber Fabry-Perot tunable filter using a well-established optimization method, simulated annealing (SA). The signal driving the filter is constructed from many short ramps of different slopes that are interconnected. The values of the slopes are optimized through the SA algorithm to achieve maximum amplitude for the Fourier transformed peaks of the photodetected interferometric signal.

Recognition of Bragg Wavelength Disturbed by Time Delay of Fiber Length in Prepositive Tunable Filter

The wavelength shift in fiber Bragg grating does not depend directly on the total light levels, losses in the connecting fibers and couplers, or source power. However, if the tunable Fabry-Perot filter is place on the end of incident fiber, the detected time delay of modulation light is occurred due to the unmatch between the scanning time and light transmission time in the transmission fiber. Consequently, the detected peak wavelength shifts with the length of transmission fiber. Thus, the peak wavelength shift effect of Bragg reflective light transmitted in fiber with different fiber length can be obvious in the demodulator with a prepositive tunable Fabry-Perot filter. The experiment indicates the shift rates of 0.109 - 0.126 nm/km increase approximately linearly with the original peak wavelength of 1532.917 - 1560.300 nm at the fiber length of 0 - 6 km. To certify the consistency of measurement data, the criterion correction is introduced. By using the differential method of two fiber Bragg gratings with an optical path, the differential worth is compensated from the disturbance modulated by the time delay of fiber length.

Fiber Fabry-Perot tunable filter based Fourier domain mode locking swept laser source

An all-fiber Fourier domain mode locking (FDML) swept laser source at 1300 nm for swept source optical coherence tomography is reported. The swept laser source is realized with power amplification and laser resonator which includes gain medium, tunable filter and dispersion managed delay line. FDML swept laser can realize high-speed tuning, and phase is stable since its highly stable mode locking operation. The turning range of fiber Fabry-Perot tunable filter (FFP-TF) based FDML swept laser is 130 nm, and the 3 dB bandwidth is 70 nm with an average output power of 11 mW. The tunable speed of FDML laser is 48.12 kHz compared with 8 kHz of short-cavity FFP-TF based swept laser. The axial resolution in OCT imaging of FDML swept laser is 7.8 μm (in tissue), which is improved by 1.9 μm compared with that of short-cavity swept laser.

167 赤外分光ハイパースペクトルイメージングのための圧電駆動可変ファブリペローフィルタ(マイクロ・ナノ工学II/エンジンシステム,一般講演)

167 赤外分光ハイパースペクトルイメージングのための圧電駆動可変ファブリペローフィルタ(マイクロ・ナノ工学II/エンジンシステム,一般講演)

6PM2-A-4 圧電駆動可変ファブリペローフィルタ統合型ハイパースペクトルイメージャー(6PM2-A マイクロナノプロセス技術III(センサシンポジウムとの合同セッション))

An infrared hyper-spectral imager based on a piezoelectrically driven tunable Fabry-Perot filter and a two dimensional scanning detector for spectrum analysis has been developed. The Fabry-Perot filter consisting of two parallel ZnSe mirrors and a miniaturized movable stage actuated by a stacked piezoelectric actuator was fabricated. The measured transmittance of Fabry-Perot filter using a laser with wavelength of 1550 nm showed a good agreement with the theoretical value. In addition, interferogram of broadband source (hot water in quartz beaker) through Fabry-Perot filter was also obtained, which meets with the theoretical waveform. Furthermore, according to the comparison of conditions with or without a polyethylene film placed in the optical path, we find an absorption point whose corresponding gap distance is times to the half of released absorption band of polyethylene.

분광 영역 모드록킹 레이저를 이용한 공진형 광섬유 격자 센서

We report a resonance fiber Bragg sensor interrogation based on a Fourier domain mode-locking (FDML) laser. The FDML laser is constructed based on a conventional ring laser cavity configuration with fiber Fabry-Perot tunable filter (FFP-TF). There are two sensor parts which are composed with two FBGs inside the laser cavity. Each sensor part provides a separate laser cavity for the FDML laser. The resonance frequencies of the laser cavities are 46.687 kHz and 44.340 kHz, respectively. We applied a static and a dynamic strain on the FBG sensor system. The slope coefficients of the measured relative wavelength shift and relative time interval from the static strain are found to be and , respectively.

A piezoelectric active mirror suspension system embedded into low-temperature cofired ceramic

Low-temperature cofired ceramic (LTCC) has proven to be a cost-effective, flexible technology for producing complicated structures such as sensors, actuators, and microsystems. This paper presents a piezoelectric active mirror suspension system embedded into LTCC. In the structure, the LTCC was used as a package, for the passive layers of piezoelectric monomorphs, as support for the mirrors, and as a substrate for the conductors. The active mirror structure, 17 mm in diameter, was made by compiling 20 LTCC layers using common LTCC processing techniques. Each sample contained a laser-micromachined bulk lead zirconate titanate (PZT) structure which formed a monomorph with the LTCC during the firing process. A mirror substrate (diameter 4 mm) was mounted in the middle of the monomorph arms for evaluation of the positioning performance, where each of the three arms had independent signal electrodes and a common ground electrode. Electrical and electromechanical properties were investigated with an LCR meter, network analyzer, and laser vibrometer for the different arms and the mirror. The active mirror structure exhibited more than 1 μm dc displacement for mirror leveling and also allowed small changes in mirror angle up to 0.06°. The first bending resonance frequency of the structure with the mirror was detected at 11.31 kHz with 4.0 μm displacement; 13.02 kHz and 2.7 μm were obtained without the mirror. The structure exhibited characteristics feasible for further utilization in tunable Fabry-Perot filter applications, allowing the mounting of active mirrors on both sides with distance and angle control.

Microelectromechanical systems–based visible-near infrared Fabry-Perot tunable filters using quartz substrate

There is a need to develop miniature optical tunable filters for small hyperspectral imagers. We plan to develop a number of miniature Fabry-Perot tunable filters (FPTFs) using microelectromechanical systems (MEMS) technology, each operating over a different wavelength region, to cover spectral regions from the visible to the longwave infrared (IR). Use of a MEMS-based FPTF as a dispersive element will reduce the size, weight, and power requirements of hyperspectral imagers and make them less expensive. A key requirement for such a filter is a large optical aperture. Recently, we succeeded in fabricating FPTFs with a 6 mm optical aperture operating in the visible to near IR spectral region (400 to 800 nm) using commercially available thin quartz wafers as the substrate. The FPTF design contains one fixed silver (Ag) mirror and one electrostatically movable Ag mirror, each grown on a quartz substrate with a low total thickness variation. Gold (Au) bumps are used to control the initial air gap distance between the two mirrors, and Au-Au bonding is used to bond the device. We describe material selection, device design, modeling, fabrication, interferometric, and spectral characterizations.

Spectral imaging characterization of quartz MOEM tunable Fabry-Perot filter

Recently, prototype MOEM tunable Fabry-Perot filters operating from 400 to 800 nm were fabricated under a program to design miniature hyperspectral imagers operating from the visible to the longwave infrared. The filter design uses two semitransparent 30 nm thick silver-film mirrors, one fixed and the other moving, on a low-cost thin commercial quartz substrate. The moving mirror is supported by three leaf spring arms, which are fabricated by wet etching of the quartz substrate. The tuning of the transmitted wavelength of light from the filter is achieved by electrostatically actuating the moving mirror to vary the distance between the two mirrors. The size of the device is 18×24 mm2. The fixed part has a 6 mm diameter mirror and three electrodes to apply voltages, and the moving mirror is used as a ground electrode. Au bumps deposited on both parts control the initial air gap distance, and an Au-Au bonding is used to bond the two parts together. The spectral imaging performance of the MOEM filter is characterized using a spectrally tunable source and a CCD camera with suitable optics. The authors present a brief description of the filter, its characteristics, spectral imaging characterization experiment and results.

All-fiber widely wavelength-tunable thulium-doped fiber ring laser incorporating a Fabry-Perot filter

We demonstrate 1940 to 2010 nm continuous CW wavelength-tuning in a thulium-doped fiber laser (TDFL), using only fiber-format components. A fiber Fabry-Perot (FP) tunable filter is employed to achieve the wavelength tunability of 70 nm. By imposing a 200 Hz triangle wave signal on the filter, rapid wavelength-sweeping is demonstrated from 1952 to 1992 nm every 5 ms, corresponding to 8 nm/ms. This all-fiber wavelength-tunable and swept laser may find applications such as gas monitoring in the wavelength region of 2 μm.

Fiber-optic tunable filter with a concave mirror

In order to implement a fiber-optic Fabry-Perot tunable filter with a simple configuration, a concave mirror is made at the end of the optical fiber. The concave mirror is fabricated by attaching a thin polycarbonate (PC) film on the fiber end, pressing the PC film with a fiber ball to form a dimple, and then depositing a multilayer dielectric mirror. The concave mirror aligned to the fiber core makes the cavity alignment easy with a simple alignment configuration. Because of the self-alignment function of this cavity, a small, reliable, and fast filter could be fabricated.

Wideband Visible Wavelength Range MEMS Fabry-Perot Tunable Filter with Ag Alloy Mirror

In this paper, we report the structure and the fabrication process of the new Micro-Electro-Mechanical Systems (MEMS) Fabry-Perot Tunable Filter (FPTF) device with Ag alloy mirror which is tunable in the wide wavelength range of visible light. The device has very simple structure, which consists of two substrates that are bonded by using novel bonding technology, polymer films, and inert gas plasma treatments. We confirmed that the wavelength of the 1st order transmission peak of fabricated device can be adjusted to a 400-700nm range by applying the different DC voltage. Our MEMS FPTF device successfully operates in the wide wavelength range of visible light, shows good agreement with simulation result.

基于波长扫描的差分吸收光纤煤矿瓦斯传感系统设计

Utilizing a super-luminescent diode(SLD) in 1 330 nm band and a fiber Fabry-Perot tunable filter(FFP-TF),an optical fiber methane sensing system is experimentally demonstrated.The differential absorption technique and a reference method are employed: a reference channel is introduced to eliminate the fluctuation of light source spectrum,and the two wavelengths are acquired by tuning the FFP-TF.The influence of the light source,loss of leading fiber,and the filters′ variations are all avoided.A minimum detectable methane concentration of 0.15% achieved.

Wavelength-tunable and pulse-width variable Fourier domain mode-locking lasers

In this study, wavelength-tunable and pulse-width variable Fourier domain mode-locking lasers were developed with a repetition rate of 60.9 kHz. A spectral laser tuning range of over 100 nm was achieved by tuning the offset voltage to a fiber Fabry-Perot tunable filter (FFP-TF). The pulse width variation was achieved with amplitude modulation of the driving voltage to the FFP-TF. The pulse width ranged from 6.2 μs to 55 ns. The linewidth of the laser changed, from 0.109 to 0.083 nm, according to the pulse width variation.