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An all-fiber sensor scheme for simultaneous strain and temperature measurement is presented. The sensing head is formed by serially connecting a polarization maintaining photonic-crystal-fiber-based intermodal interferometer (IMI) with a fiber Bragg grating (FBG). The IMI, exhibiting an opposite strain response as compared to that of the FBG, is highly sensitive to strain, while it is insensitive to temperature. This has potential for improving the strain and temperature measurement resolutions. A sensor resolution of [+ or -] 8.3 [micro][epsilon] in strain and [+ or -] 2[degrees]C in temperature are experimentally achieved within a strain range of 0-957.6 [micro][epsilon] and a temperature range of 24[degrees]C-64[degrees]C, respectively. OCIS codes: 060.2310, 060.2370.

Two time-division-multiplexed (TDM) sources based on fiber Bragg gratings were applied to monitor gas temperature, [H.sub.2]O mole fraction, and C[H.sub.4] mole fraction using line-of-sight absorption spectroscopy in a practical high-pressure gas turbine combustor test article. Collectively, the two sources cycle through 14 wavelengths in the 1329-1667 nm range every 33 [micro]s. Although it is based on absorption spectroscopy, this sensing technology is fundamentally different from typical diode-laser-based absorption sensors and has many advantages. Specifically, the TDM lasers allow efficient, flexible acquisition of discrete-wavelength information over a wide spectral range at very high speeds (typically 30 kHz) and thereby provide a multiplicity of precise data at high speeds. For the present gas turbine application, the TDM source wavelengths were chosen using simulated temperature-difference spectra. This approach is used to select TDM wavelengths that are near the optimum values for precise temperature and species-concentration measurements. The application of TDM lasers for other measurements in high-pressure, turbulent reacting flows and for two-dimensional tomographic reconstruction of the temperature and species-concentration fields is also forecast. OCIS codes: 300.1030, 120.1740, 120.6780.

Width-increased dual-pump enhanced coherent anti-Stokes Raman spectroscopy (WIDECARS) is a technique that is capable of simultaneously measuring temperature and species mole fractions of [N.sub.2], [O.sub.2], [H.sub.2], [C.sub.2][H.sub.4], CO, and C[O.sub.2]. WIDECARS is designed for measurements of all the major species (except water) in supersonic combustion flows fueled with hydrogen and hydrogen/ethylene mixtures. The two lowest rotational energy levels of hydrogen detectable by WIDECARS are [H.sub.2] S(3) and [H.sub.2] S(4). The detection of these lines gives the system the capability to measure temperature and species concentrations in regions of flow containing pure hydrogen fuel at room temperature. OCIS codes: 120.1740, 300.6230.

In the present work, a picosecond lidar system aiming at single-ended combustion diagnostics in full-scale combustion devices with limited optical access, such as power plants, is described. The highest overall range resolution of the system was found to be OCIS codes: 120.1740, 280.3640, 280.1910, 280.6780.

We focus on the development of a remote temperature sensing technology, i.e., an optical laser-based sensor, using thermographic phosphors for medical applications, particularly within an electromagnetically hostile magnetic resonance imaging (MRI) environment. A MRI scanner uses a strong magnetic field and radio waves to generate images of the inside of the body. The quality of the image improves with increasing magnetic resonance; however, the drawback of applying a greater magnetic strength is the inducement of heat into the body tissue. Therefore, monitoring the patient's temperature inside MRI is vital, but until now, a practical solution for temperature measurement did not exist. We show europium doped lanthanum oxysulphide ([La.sub.2][O.sub.2]S:Eu) and terbium doped lanthanum oxysulphide ([La.sub.2][O.sub.2]S:Tb) are both temperature sensitive to a low temperature range of 10-50 [degrees]C when under ultraviolet (UV) excitation. The emission spectra and decay time characteristics of these phosphors were demonstrated. The results indicate that [La.sub.2][O.sub.2]S:Eu has a quenching rate of 13.7 m[degrees][C.sup.-1] and 4 m[degrees][C.sup.-1] at 512nm and 538nm, respectively. In addition, [La.sub.2][O.sub.2]S:Tb has a lower quenching rate of 4.19m[degrees][C.sup.-1] at 548nm due to its faster decay time. OCIS codes: 120.0120, 160.5690, 280.6780, 250.5230, 170.3650, 300.2530.

Fiber-optic single-point and quasi-distributed evanescent temperature sensors recoated with a blend of poly(methyl methacrylate) and poly(vinylidene fluoride) are proposed. Solid cladding enables the construction of small-size, low-cost, relatively wide-range and fast-response temperature sensors. The diameter of the sensor does not exceed the dimensions of the original optical fiber, while the response time of the sensor is 7.4 ms. Different mass ratios of polymers in the blend enable fine tuning of the applied cladding's refractive index. This allows the construction of sensors for different temperature ranges, while the application of all-silica graded-index multimode fibers enables the construction of quasi-distributed sensor systems with considerably reduced cross talk. OCIS codes: 060.2370, 120.6780, 120.7000, 160.5470, 280.6780.

The modeled performance of an Fe Boltzmann temperature lidar system is compared with existing Na narrow-band temperature techniques. The Fe Boltzmann technique employs mesospheric Fe as a fluorescence tracer and relies on the temperature dependence of the population difference of two closely spaced Fe transitions. The relative performance of the new technique is compared with an existing Na narrowband temperature technique, and a link analysis is performed with measured data for both Na and Fe. It is shown that for currently available laser technology the two systems yield similar performance but the Fe system allows for the use of more broadband lasers.

The use of a highly elliptical core two-mode fiber for simultaneous measurement of pressure (radial pressure or hydrostatic pressure) and temperature is presented. The sources of errors are discussed. Expressions are developed to calculate the cross sensitivities. From the numerical examples, some useful conclusions are given. Key words: Optical-fiber sensors, simultaneous measurement of pressure and temperature, cross sensitivity.

The use of optical fiber in a temperature probe or sensor for optical pyrometry in the 100-1000 [degrees] C range is affected by the low thermal stability of classical fibers. We have studied the different sources of perturbations induced by exposure to high temperature. Two specific fibers especially suited for a high-temperature environment were tested and compared. Low (100 [degrees] C/min) and very fast (100 [degrees] C/s) fiber heating was performed to evaluate its influence on the guided flux and the induced error on temperature measurement. The metallic-coated fiber shows a reproducible temperature error that can be predicted. This important result permits the development of an uncooled fiber probe for temperature monitoring in high-temperature environments such as aerospace engines. Key words: Fiber-optic probe, bichromatic pyrometry, high temperature, thermal shocks, thermal emission.

Laser-induced fluorescence (LIF) observations of CH and C2 radicals in a dc-arcjet plasma are reported. A hydrogen and methane gas mixture flows through a dc-arc and expands through an orifice in the anode to form a luminous jet; diamond film grows under this jet on a water-cooled substrate. At the substrate position for best diamond growth, laser excitation spectra determine a rotational population distribution of CH(X) and C2(a), which yields Boltzmann gas temperatures of 2100 + or - 200 K. The C2 Swan-band emission from the same observation volume yields an excited C2(d) rotational and vibrational population distribution well described by a 5000 K temperature. The difference between the LIF and emission temperatures indicates that chemiluminescent reactions are the dominant excitation mechanism for the optical emission from the gas jet.

Radio-frequency (rf) beat frequencies between two longitudinal modes and two polarization modes of a birefringent dual-longitudinal-mode moire distributed-feedback fiber laser are employed to measure strain and temperature simultaneously. Operating entirely in the rf domain, this approach potentially allows one to employ low-cost and precise rf measuring techniques. A strain-temperature cross sensitivity of the strain- and the thermo-optic coefficients, which can be neglected in wavelength-based grating sensors, has been observed. The achieved sensor accuracy was [+ or -] 15 [micro][element of] and [+ or -] 0.2 [degrees] C. OCIS codes: 060.2370, 140.3490, 140.3510, 280.3420.

The strain sensitivity of the fluorescence intensity ratio temperature-sensing technique has been measured to be (2 [+ or -] 3) x [10.sup.-4]%/[micro][Epsilon] in [Yb.sup.3+]-doped fiber, implying a temperature-to-strain cross sensitivity of (2 [+ or -] 3) x [10.sup.-4] [degrees] C/[micro][Epsilon]. The near-zero strain sensitivity means that this optical-fiber sensor technique is well suited for temperature measurement in strain-affected environments. [C] 2000 Optical Society of America OCIS codes: 060.2370, 120.6780, 160.5690, 300.2530.

The Hall-effect of thermoelectric materials are measured by a computerized equipment at temperatures ranging from ambient to 1200 K. The use of a computer assures improved data resolution. The measurements are done through a prescribed order and the computer decides if all requirements are met before the process is allowed to continue. It takes only 3 1/2 days for the computerized equipment to complete the measurement while a semiautomated measurement procedure would take 11 days.