Distributed Optoelectronic Signal System

Results from the development of a special design of the sensing surface of a distributed fiber-optic measuring network that constitutes the basis of an optoelectronic signal system are presented. Using the system, it is possible to determine the coordinates of external solitary deformation actions on a distributed fiber-optic measuring network and to track the movements of these actions on a control surface. __________ Translated from Izmeritel'naya Tekhnika, No. 7, pp. 28–32, July, 2005.     

A piezoelectric sensor for pressure measurements behind a shock front

The construction and measuring circuit of a pressure pickup designed for measurements in ionized gases behind a shock front are described. Calibration results are given, along with oscillograms of the pressure up to the arrival of the rarefaction wave.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 21, No. 1, pp. 168–171, July, 1971.     

Standard apparatus for measuring polarization mode dispersion in fiber-optic data transmission systems

Methods and instruments for ensuring the uniformity of polarization mode dispersion measurements in fiber-optic data transmission systems are described. The results of the development of a standard measuring instrument and working standards of the unit of dispersion are presented. The results of metrological investigations of a standard measuring instrument are also given.     

Proposal and testing for a fiber-optic-based measurement of flow vorticity

A fiber-optic arrangement is devised to measure the velocity difference, deltav(l), down to small separation l. With two sets of optical fibers and couplers the new technique becomes capable of measuring one component of the time- and space-resolved vorticity vector omega(r, t). The technique is tested in a steady laminar flow, in which the velocity gradient (or flow vorticity) is known. The experiment verifies the working principle of the technique and demonstrates its applications. It is found that the new technique measures the velocity difference (and hence the velocity gradient when l is known) with the same high accuracy and high sampling rate as laser Doppler velocimetry does for the local velocity measurement. It is nonintrusive and capable of measuring the velocity gradient with a spatial resolution as low as ~50 mum. The successful test of the fiber-optic technique in the laminar flow with one optical channel is an important first step for the development of a two-channel fiber-optic vorticity probe, which has wide use in the general area of fluid dynamics, especially in the study of turbulent flows.     

Unification of measurements of the average power of optical radiation in fiber-optic transmission systems

The current status of measurement uniformity, the design and characteristics of new standard calorimeters and high-precision apparatus, and a hierarchical testing sequence are discussed in application to instruments for measuring the average power of optical radiation in fiber-optic transmission systems. Translated from Izmeritel'naya Tekhnika, No. 8, pp. 31–37, August, 2000.     

Differential low-coherence interferometry for <Emphasis Type="Italic">in situ</Emphasis> diagnostics of transparent structures

We describe and demonstrate a new differential method capable of measuring the profiles of transparent structures. Based on fiber-optic low-coherence interferometry and possessing a high noise immunity, the proposed technique can be used for the noncontact in situ diagnostics of microstructures under extremal conditions.     

Measurement of the Levels of Multicomponent Media by a High-Frequency Method

A high-frequency method of measuring the levels of multicomponent media is described which enables up to five interfaces to be measured simultaneously. A mathematical model of the propagation of the signal in the pickup and ways of simplifying it for use in engineering problems is proposed. An example of a practical form of the method for measuring the position of the boundaries in a three-component system is given.     

Low-coherence fiber-optic sensor with a large numerical aperture for topographic measurements

We describe a compact fiber-optic setup for three-dimensional topometry. The measuring principle is based on low-coherence interferometry in combination with a confocal microscope. Integrating an optical arrangement based on compact disk optics together with fiber optics into one sensor yields a compact unit. The sensor has a numerical aperture of 0.45 and is suitable for measuring large surface slopes with high spatial resolution. Further, a depth measuring range of more than 1 mm can be achieved. The capabilities of our setup for three-dimensional measurements are demonstrated.     

Fiber-optic thermometry and its application

The design of a distributed fiber-optic sensor of radiation heat flow (RHF) is presented. A measuring technique has been developed and results of measuring the “effective” transmission coefficient of an uncladded fiber under its lateral illumination have been obtained. An algorithm for measuring the RHF supplied in the process of testing specimens of materials on the radiant heating facility is proposed. Testing experiments have been performed and a good correlation between the readings of the distributed RHF sensor and the temperature in the specimens of materials measured by thermocouples has been observed. __________ Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 80, No. 2, pp. 180–185, March–April, 2007.     

马赫-曾德尔光纤干涉仪的研制及应用

介绍了作者在测量单纵模激光器线宽参数的过程中,研制的马赫-曾德尔光纤干涉仪,并给出了实验结果.     

Fiber-optic interferometric refractometer for deep-water studies of sea water

A fiber-optic interferometric refractometer is proposed for precise monitoring of the refractive index of sea water at depths of 30–100 m by means of a measuring probe controlled automatically from onboard by underwater equipment. __________ Translated from Izmeritel’naya Tekhnika, No. 12, pp. 26–32, December, 2006.     

Use of microprocessors in devices utilizing fiber-optic sensors

An examination is made of the basic types of measuring and monitoring instruments utilizing externally modulated fiber-optic sensors with built-in microprocessors, making it possible to achieve a considerable improvement in their metrological characteristics and also to lower the apparatus costs and reduce the overall dimensions and power consumption. The basic algorithms for the functioning of these instruments are presented and the circuitry required for implementing them is considered. Translated from Izmeritel'naya Tekhnika, No. 12, pp. 21–24, December, 1996.     

Fiber-optic interferometric refractometer for deep-water monitoring

A method is proposed for organizing deep-water refractometric studies and fiber-optic interference systems for precise monitoring of the absolute refractive index of sea water at depths up to 1000 m with measuring probes submerged independently or together with underwater equipment. __________ Translated from Metrologiya, No. 4, pp. 23–38, June, 2007.     

Development of a Fiber-Optic Probe Hydrophone for a Cryogenic Liquid

We report the progress of developing a fiber-optic probe hydrophone (FOPH) system applicable to the measurement of local density/pressure fluctuations in a cryogenic liquid. The measurement principle is based on a law of classical optics known as “Fresnel’s reflection loss.” We use this principle at the end-face of a single-mode optical fiber that is immersed in liquid helium. Since the refraction index of liquid ⁴He is a function of density, and the refraction index of the core of the optical fiber is constant, the pressure can be obtained by measuring the reflectivity. We have succeeded in measuring the temperature dependence of the static density, and we go on to discuss the possibility of application to acoustic pressure measurements.     

New technique for measuring low fiber-optic attenuation usingdouble square-law detection

A new technique for precision measurement of low fiber-optic attenuation has been developed using double square-law characteristics in a subcarrier lightwave detection system. It magnifies the effect of a small attenuation four times and a 0.01 dB change in optical attenuation produces a 0.04 dB change in electrical attenuation. The present system is capable of measuring attenuation changes less than 0.01 dB with system resolution 0.001 dB     

Combined time and wavelength multiplexing technique of optical fiber grating sensor arrays using commercial OTDR equipment

The use of a commercial optical time domain reflectometry device for simultaneous wavelength and time domain multiplexing of fiber-optic Bragg grating sensors is proposed and demonstrated. The realization of such systems provides an inexpensive way of interrogating several hundreds of sensors in a single fiber. Strain resolution of 30 /spl mu/m/m over a strain measuring range of 0.5% was obtained.     

Design, Fabrication, and Multiplexing of Magnetic Calorimeter X-ray Detectors with High-Efficiency SQUID Readout

Metallic magnetic calorimeters, where deposited energy is detected by measuring a temperature-dependent magnetization with a low-noise SQUID, remain a promising potential route to X-ray spectrometers with energy resolution approaching 1 eV. In this paper we describe our recent work toward array-compatible, high-resolution MMCs fabricated entirely using thin-film techniques. We describe a meander-style pickup loop designed for good coupling to high-efficiency, low noise SQUIDs, as well as considering various routes to a thin-film paramagnetic sensor. We also briefly overview the most promising technology for multiplexing arrays of non-dissipative metallic magnetic calorimeters.      

Monitoring and methods of early diagnostics of damage to optical fibers

Problems related to monitoring of branched fiber-optic networks and the technical implementation of an optical fibers testing system are analyzed. Methods of early diagnostics of damage to optical fibers based on the use of the effects of Brillouin scattering and the principles of the technical implementation of a strain measuring instrument are considered.     

Optoelectronic neural system for processing the output data from a fiber-optic measuring network

The results of an investigation of an optoelectronic neural system for processing the output data from a distributed fiber-optic tomographic-type measuring network are reported. The processing system is based on the operation principle of an optical perceptron in which the interneuron coupling matrix is implemented using a collection of amplitude holograms recorded on a disk-shaped holographic carrier. It is shown experimentally that this system makes it possible to reconstruct to within 20% the spatial distribution functions of the physical quantity under investigation. Pis’ma Zh. Tekh. Fiz. 25, 65–70 (March 26, 1999)     

Theoretical and experimental considerations for a single-mode fiber-optic bend-type sensor

A novel single-mode bend fiber-optic sensing principle is presented. The design makes use of the translucent protective sheath that encases a typical fiber as a means of locating the position of a small bend present on an otherwise straight fiber. We can simultaneously determine bend magnitude by measuring the reduction in the fiber's core light. The theoretical model presented and the experimental results obtained are in excellent agreement, suggesting that a single-point sensor system is feasible with the proposed technique.