Fiber Michelson Interferometer Research Articles

Single-Mode Fiber Refractive Index Sensor Based on Core-Offset Attenuators

Mach-Zehnder and Michelson interferometers using core-offset attenuators were demonstrated. As the relative offset direction of the two attenuators in the Mach-Zehnder interferometer can significantly affect the extinction ratio of the interference pattern, single core-offset attenuator-based sensors appear more robust and repeatable. A novel fiber Michelson interferometer refractive index (RI) sensor was subsequently realized by a single core-offset attenuator and a layer of ~ 500-nm gold coating. The device had a minimum insertion loss of 0.01 dB and maximum extinction ratio over 9 dB. The sensitivity (0.333 nm) of the new sensor to its surrounding RI change (0.01) was found to be comparable to that (0.252 nm) of an identical long period gratings pair Mach-Zehnder interferometric sensor, and its ease of fabrication makes it a low-cost alternative to existing sensing applications.

A Compact Fiber-Optic Flow Velocity Sensor Based on a Twin-Core Fiber Michelson Interferometer

A novel fiber-optic flow velocity sensor based on a twin-core fiber Michelson interferometer has been proposed and demonstrated. The sensor only is a segment of twin-core fiber acting as cylinder cantilever beam. The force exerted on the cylinder by the slow flow speeds of order mm/s of the fluid with unknown velocity bends the fiber, which corresponds to the shift of the phase of the twin-core in-fiber integrated Michelson interferometer.

A performance study of a nonlinear all Fibre Michelson interferometer, add-drop multiplexer, based in Fibre Bragg grating mirrors

In this paper we report a numerical investigation of an all-fibre narrowband transmission filter in the arrangement of two identical photo-imprinted Bragg gratings symmetrically located in each arm of a Michelson Interferometer, simulating, thus, an add-drop filter. The transmission characteristics and in addition the crosstalk level and extinction ratio, were studied. The coupled mode theory and the fourth-order Runge-Kutta method were applied, respectively, to solve the coupled differential equations. This is the first study, as far as we now, of the performance of this device considering the nonlinearity of the fibre coupler and linearity of the fibre Bragg gratings. The device is presenting a highly nonlinear behavior dependence in dephasing and pump power.

基于3×3耦合器的迈克耳孙干涉仪相位特性分析

基于3×3耦合器的迈克耳孙干涉仪相位特性分析

Optical fiber multiplexing interferometer system with a single laser diode and its application to online displacement measurement

A multiplexed optical fiber Michelson interferometer system that is self-referenced with a stabilizing feedback loop is presented. This system employs fiber Bragg gratings and wavelength division multiplexing technique to combine two optical fiber interferometers that share the same optical path in the main part of the optical system. When one Michelson interferometer, which uses the fiber Bragg gratings as reflective mirrors and is used as reference interferometer, is stabilized by an electric feedback loop, the other interferometer, which is used for the measurement, is also stabilized. This system is therefore suitable for online precision measurement. An active phase-tracking technique is applied for signal processing to achieve high resolution.

Non-contact and non-destructive testing of silicon V-grooves: A non-medical application of optical coherence tomography (OCT)

The paper reports a non-medical optical coherence tomography (OCT) application namely, the use of OCT to test a micro-electro-mechanical systems (MEMS) technology device. The OCT system used in this initial study combined a fibre Michelson interferometer and a 10 mW 1300 nm super luminescent diode (SLD). The system supported a measured depth resolution of 21 μm as well as a transverse resolution of around 3 μm. As a first demonstration, the depth and width of a MEMS V-shaped groove in silicon were measured to within 7% (6%) and 12% (14%) of the values determined by stylus contacting (standard microscopy) method, respectively. The OCT technique combines advantages of non-contact, non-invasive and non-destructive operation making it suitable for on-line precision measurement of V-shaped grooves in silicon.

Experimental research on all polarization maintaining fibre magnetostrictive sensor

The structure and experimental results of an all polarization maintaining optical fibre magnetostrictive sensor are reported in this paper. The sensing head, an all polarization maintaining optical fibre Michelson interferometer with the sensing arm jacketed with 2 µm thick and 5 cm long TbDyFe film, is packaged in a polyurethane tube 15 mm in diameter and 60 mm in length. When the sensor is used to measure magnetic field up to 17 mT at the frequency of 1 kHz with 60 mT dc biasing magnetic field, the linearity of the response is better than 1% and the noise-equivalent magnetic field reaches 2 × 10−8 T Hz−1/2.

Hybrid optical spectral bistability in fiber Michelson interferometer by use of a tunable fiber laser

We report the observation of hybrid optical spectral bistability in an unbalanced fiber Michelson interferometer by use of an electrooptically tuned continuous-wave fiber laser in which a fiber Bragg grating is employed to constitute a tunable resonant cavity. The potential applications of such a device as a wavelength shift monitor or a fiber-optic sensor working in digital type are also discussed.

Rapid and scalable scans at 21 m/s in optical low-coherence reflectometry

An optical low-coherence reflectometer is presented that uses a fiber Michelson interferometer with a rotating cube to generate rapid depth scans at a high repetition rate. A folded optical path geometry allows the reference arm to scale up the scan range, scan speed, and scan repetitiveness. Thickness measurements with a repetitiveness of 384 Hz and a longitudinal scanning speed of 21 m/s in air over a range of ~3 mm are demonstrated.

Optical fiber vibration sensor using (Pancharatnam) phase step interferometry

A fiber-optic vibration sensor based on polarization and phase-step interferometry is reported. Left- and right-circularly polarized light coming back from the reference and signal arms of a modified Michelson fiber interferometer is processed with an array of five linear analyzers separated angular steps of /spl pi//4 (rad) from each other. Thus, five interference patterns are acquired simultaneously and the dynamical phase retrieval problem is reduced to five-step interferometry in the time-domain. A vibration sensor as described above was built by the authors and its performance was investigated.

Broadband Lamb wave measurements in aluminium and carbon/glass fibre reinforced composite materials using non-contacting laser generation and detection

Abstract Broadband measurements of Lamb wave dispersion characteristics have been performed in aluminium, carbon and carbon/glass fibre hybrid composite materials using a non-contacting optical technique. A high powered Q-switched Nd:YAG laser was used to initiate the Lamb wave spectrum in the materials, and an optical fibre Michelson interferometer was used to monitor the outof-plane displacements associated with the propagating modes. Comparison of experimental results with theoretical modelling in both the aluminium and composite samples indicated good agreement for the excited modes. The application of this technique to the non-destructive testing and elastic property measurement of composite materials is discussed.

Synchronized triggering for ultrasonic transient detection using optical fibre interferometers and application to the measurement of broadband Lamb wave dispersion characteristics

A method of synchronous acoustic source triggering is described for the detection of ultrasound using an optical fibre interferometer. The comparative noise immunity was higher than that for a comparable homodyne detection technique. The system was used in conjunction with an optical fibre Michelson interferometer to record spark-gap-source-generated ultrasonic Lamb waves propagating in aluminium and carbon fibre composite plates. A two-dimensional fast Fourier transform approach enabled the broadband Lamb wave dispersion characteristics of aluminium to be measured.

Interferometric measurement of KrF-laser-induced refractive index changes in germanosilicate fibers

Photosensitivity in germanosilicate optical fibers is studied with a fiber Michelson interferometer. Saturation characteristics for multiple KrF-laser exposure are measured, and the origin of the index change is discussed. The total index change of a high-Ge (35 mol%) fiber is 6 times that of a low-Ge (3 mol%) fiber. In both fibers, the fast and the slow saturation components are found. An analysis using the Frantz-Nodvik equation shows that they are attributed to GeSi and Ge 2+ defects, resectively. The saturated index changes in highly reflective fiber gratings are due to Ge 2+ defects.

Application of a fiber Fourier transform spectrometer to the detection of wavelength-encoded signals from Bragg grating sensors

We describe an all-fiber Fourier transform spectrometer for decoding the wavelength shifts from a series of Bragg grating sensors. The system described uses an optical fiber Michelson interferometer with one arm wrapped on a piezoelectric driven stretcher capable of inducing a /spl sim/10 cm fiber length change. Passive polarization compensation is utilized which eliminates the possibility of random polarization fading in the interferometer causing apodization of the interferogram. This permits an all-fiber design without the need for speciality optical fiber or external polarization adjustments. A reference Nd:YAG laser is used to stabilize the interferometric scan in a phase-locked loop configuration by way of slow and fast feedback correction elements. A spectral resolution of <0.07 cm/sup -1/ was obtained, which corresponds to a Bragg wavelength shift of /spl sim/0.015 nm in the 1.55 /spl mu/m region. The simultaneous wavelength determination capacity of the device also permits it to be used in a variety of other applications for analysis of optical spectra.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

White-light scanning fiber Michelson interferometer for absolute position–distance measurement

A white-light fiber interferometer working in the spatial domain, using two fiber ends in a hollow tube as the sensing head and an electric magnetic actuator-mirror reflector as the path-compensation-measurement element, is presented. Analysis and preliminary experiments have demonstrated a repeatability of 0.5 microm (2sigma) for position-distance measurement, and the measurement uncertainty was estimated to be 1.5 microm (2sigma) over a distance range of 150 microm. Suggestions for further improving the measurement accuracy and response speed are also given.

Force microscopy with actively stabilized differential fiber detection mechanism

We present the design and theory of operation of a new fiber-optic detection mechanism for force microscopy. The technique comprises a differential fiber Michelson interferometer, in which most spurious signals due to environmental variations are automatically rejected. Any residual fluctuations are canceled by the action of a feedback mechanism, which also ensures operation at maximum sensitivity. This detection technique is capable of high sensitivity response to both high and low frequency tip variations, and can thus be used in the attractive and repulsive modes. A number of results are presented on the applications of a force microscope utilizing this detection mechanism. Both ac and dc modes of operation are demonstrated.

Fiber Michelson interferometer with loss compensation

A fiber amplifier containing a waveguide activated with Er3+ ions was used for the first time to reduce the losses and thus improve the resolving power of a fiber Michelson interferometer. An interferometer with a path difference between the arms amounting to 5 km was constructed and the losses in this interferometer were fully compensated by the use of such an amplifier.

Precise length measurements in multimode optical fibers

Selective optical excitation permits both the group index and the group delay of on-axis modes of multimode fibers to be determined with high precision. The group index of several types of fiber was measured at 1310 nm in a fiber Michelson interferometer, and the values were tabulated. Group delays were obtained from the transit time of short-duration optical pulses. From these data the length of reference fibers approximately 2 km long was calculated. Length-measurement accuracy was limited by group-index uncertainties to approximately 0.04%. Also, a technique that uses these reference fibers to minimize uncertainties in distance measurements made with multimode optical-time-domain reflectometers is described.

Absolute optical ranging using low coherence interferometry

We describe a method for measuring submicrometer distances with an asymmetric fiber Michelson interferometer having an LED as a source of radiation. By measuring the phase slope of the Fourier components in the frequency domain, it is possible to locate the position of reflections with nanometer precision even in the presence of sample dispersion. The method is compatible with time domain sampling at the Nyquist rate which assures efficiency in data acquisition and processing.

Fiber Michelson interferometer with a 50-km difference between its arms

Single-mode fiber waveguides were used in constructing a Michelson interferometer with a 50-km difference between its arm lengths. An analysis was made of its resolving power as a function of the parameters of the optical part and of the characteristics of the electronic apparatus used in the system. The width of a spectral emission line of a semiconductor laser with a distributed Rayleigh fiber resonator was determined.