In this paper, we present the experimental results of a research investigation for a hollow waveguide based fiber optic sensing device for simultaneous multiple gas detection. Gas molecules that exhibit characteristic vibrational absorption lines in the near-IR region that correspond to the transmission window for silica optical fiber have been detected by this device. An experimental setup was constructed, a fiber optic sensing device was designed and demonstrated which can monitor multiple gases simultaneously. The experimental results clearly demonstrate the characteristic absorptions in the optical spectra corresponding to the narrow molecular absorption lines of the gases tested that included acetylene and carbon monoxide.

Ethanol and methanol form the essential components in the hydrocarbon-based fuels, serving as transportation fuels also; and will likely play an increasingly important role in the future as crucial fuel components. The motivation of the present work is to differentiate such hydrocarbons from their mixture sample on the basis of their spectrum analysis for various ratios of their composition. A fiber optic Spontaneous Raman sensor is developed as a probe indicator for component detection of such hydrocarbon mixtures. The sensor employs a frequency doubled 532 nm continuous ND:YAG laser and a specially designed fiber optic Raman probe. Raman signal was collected by six optical fibers; filtered, and then fed to the spectrometer through another optical fiber bundle. Attractiveness of our scheme lies in the online determination of sample constituents without employing specially designed IR fiber with much-complicated and expensive IR spectroscopy and, with no alteration in sample physico-chemical structure. Spectral analysis techniques based on spectral shape band intensities and areas and some multi-component analysis are being tested to find the most effective tool for measuring ethanol and methanol from the mixture. The analysis results from these tests will be presented in the paper.

The feasibility of Fourier transform near infrared (FT-NIR) spectroscopic technology for rapid quantifying pear internal quality in different growing stage was investigated. A total of 248 pear samples collected at different harvest time (pre-harvest, mid-harvest and late harvest time) were used to develop the calibration models. The quality indices included soluble solids content (SSC) and titratable acidity (TA). Partial least squares (PLS) regression and principle component regression (PCR) regression were carried out describing relationships between the data sets of laboratory data and the FT-NIR spectra. Besides cross and test set validation, the established models were subjected to a further evaluation step by means of additional pear samples with unknown internal quality. Models based on the different spectral ranges and with several data pre-processing techniques (smoothing, multiplicative signal correction, standard normal variate, etc), were also compared in this research. Performance of different models was assessed in terms of root mean square errors of prediction (RMSEP) and correlation coefficients (r) of validation set of samples. The best predictive models had a RMSEP of 0.320, 0.019 and correlation coefficient (r) equal to 0.93, 0.89 for SSC and TA, respectively. Results indicated that FT- NIR spectroscopy could be an easy to facilitate, reliable, accurate and fast method for non-destructive evaluation of pears maturity.

No Abstract Available.

Owners must manage and ensure the safety of their civil structures even as use of many structures extends well beyond their design lifetime. Traditionally, most structures rely on strict maintenance procedures, visual inspections, and very few sensors. But maintenance is very expensive, visual inspections can miss critical problems, and conventional sensors can fail in harsh environments. Can fiber-optic sensing (FOS) address these issues? This is not a new question, but there are some new answers. This paper highlights several structures where FOS is used, and describes the associated successes and challenges for each application. Many successes are coupled to improved FOS tools: better sensor packages, simpler and less expensive instrumentation, improved installation techniques, and more efficient data analysis tools. Examples of each are provided. Particular attention is given to the economics of instrumenting civil structures - when and how it pays. Conclusions include recommendations for future developments that will further accelerate FOS acceptance and use.

We present recent progress on the commercial development of optical fiber strain gages for both static and dynamic applications up to 1650°C. The low mass and all dielectric nature of optical fiber sensors resists debonding in high vibration environments and completely eliminates noise induced by electromagnetic fields. In addition, the fiber sensor design ensures that it is shielded from surface shear strains that typically lead to debonding and fracture of wire filament gages exposed to long-term cyclical loading.

The objective of the work presented was to develop a suite of sensors for use in high-temperature aerospace environments, including turbine engine monitoring, hypersonic vehicle skin friction measurements, and support ground and flight test operations. A fiber optic sensor platform was used to construct the sensor suite. Successful laboratory demonstrations include calibration of pressure sensors to 500psi at a gas temperature of 800°C. Additionally, pressure sensors were demonstrated at 800°C in combination with a high-speed (1.0MHz) fiber optic readout system enabling previously unobtainable dynamic measurements at high-temperatures. Temperature sensors have been field tested up to 1400°C and as low as -195°C. The key advancement that enabled the operation of these novel harsh environment sensors was a fiber optic packaging methodology that allowed the coupling of alumina and sapphire transducer components, optical fiber, and high-temperature alloy housing materials. The basic operation of the sensors and early experimental results are presented. Each of the sensors described here represent a quantifiable advancement in the state of the art in high-temperature physical sensors and will have a significant impact on the aerospace propulsion instrumentation industry.

Evanescent field sensors provide unique analytical features. For fiber-optic fluorescence sensors the sensing zone geometry plays an important role in coupling excitation energy to the evanescent field and reciprocally collecting the fluorescence signal. In the past a tapered geometry was introduced to overcome V-number mismatch by mode conversion in the taper zone. It was later developed into a combination-taper profile to improve signal reproducibility. The spectroscopic throughput of fiber-optic evanescent-field sensors, however, is limited by the intrinsically small penetration depth and the small fiber format. In this study it was improved by dimension scale-up and cladding elimination using tapered waveguides fabricated from 6-mm quartz rods. Optimization of their profile was aided by fluorescence imaging, a technique that visually revealed the locations and intensity of the light coupled to evanescent field, as well as the light leaking to the bulk of the solution due to violation of conditions for total internal reflection. Based on this technique, a taper-cylinder profile was selected that provided the best performance among tested geometries in time-resolved luminescence. A 0.64 ppb limit of detection and a 0-500 ppb linear dynamic range (r² = 0.9996) were achieved using tetracycline as a model analyte.

Auto fluorescence of tissue depends not only on the concentration of fluoro-phores present in tissues but also on the configuration of optical fiber sensor. In this paper, feasibility of using laser induced fluorescence spectroscopy as a diagnostic tool for distinguishing malignant animal tissue from its normal counterpart under various design configurations is explored. Three different design configurations are tested for the performance optimization. The optimized Y-shaped optical reflection fiber probe gives the best laser induced fluorescence signal comparing to other probes. This instrument incorporated a continuous wave (CW) Nd:YAG laser operating at 532 nm.

Laser-induced fluorescence (LIF) is an accurate, sensitive and rapid method for the diagnosis of a normal and malignant tissue. In this paper, an optical fiber sensor was developed to enhance spectral difference between the normal and malignant tissue with sensor optimization to improve the accuracy of cancer diagnosis. This instrument incorporated a pulsed laser operating at 355 nm (frequency triple Nd:YAG and Q-switched Nd:YAG pump dye laser) with bifurcated optical fiber to allow illumination of tissue and collection of fluorescence with a single fiber. Using the laser excitation, the detection of the fluorescence signal from the tissue was performed almost instantaneously. A sufficient fluorescence contrast (of the order of more than 22.22 times) for malignant versus normal tissue was obtained. The results of our approach were compared with histopathology results and indicated excellent agreement in the classification of normal and malignant tissue.

We report a novel imaging procedure and a system implementing it, capable of acquiring two quasi-simultaneous en-face images from a multi-layer target using a single mode fiber optic interferometer. Two optical sources are employed, which are toggled on and off simultaneously with the ramp signal applied to the scanner whose movement determines the line in the raster image. In this way, half of the line in the final frame is generated by a particular source only. Imaging with two different depth resolutions or with two different wavelengths is made possible in this way. Because the switching is much faster than the observer eye can follow, the two images can be interpreted and compared simultaneously. The paper discusses the different functionality of the system depending whether the OCT image is made out of A or T-scans.

Commercial applications for fiber sensing and low-coherence interferometry are rapidly growing in medical, industrial and aerospace markets. These new instruments must be smaller, more robust and less expensive. An all-fiber optical delay line or “fiber stretcher”, using piezoelectric (PZT) actuation, offers a simple solid-state solution that eliminates free space optics. The challenges for PZT fiber stretchers include: reducing non-linearity and hysteresis, achieving sufficient scan range with minimum fiber length, maximizing scan frequency and reducing losses in the drive electronics. PZT actuators are essentially large ceramic capacitors that must be rapidly charged and discharged to achieve fast scanning. The mechanical response of the PZT ceramic is greater than 10 kHz which makes it practical to scan at four kilohertz. A thin-walled piezoelectric disk or cylinder achieves 4.5 millimeters of fiber stretch using 20 meters of coiled fiber. Digitally controlled series resonant electronics produce a 1200 volt sinusoidal drive signal at a fixed frequency of four kilohertz while dissipating only 16 Watts. An all-fiber optical delay line module, using piezoelectric actuators and a series resonant drive, is a miniature, robust and efficient alternative to free-space optics with dithering mirrors or spinning polygons.

Current inspection and QA technology is dominated in the packaging industry by on-line beta gauges, capacitance testing and infrared technology as well as off-line microscopy and basis weight processes. The optics industry uses standard interferometers, gauge block comparators and other contact technology. Current Dual light source interferometer technology, employed by Lumetrics, allows rapid off-line and on-line non-contact inspection of multi-layer plastics and coating applications, as well as optics and optical assemblies. Practical applications in numerous industries will be discussed. Results of online testing of a multi-layer label stock will also be presented.

The structure and performance of an all polarization maintaining optical fibre hydrophone element is described and a sensitivity of -158±1.5dB is achieved. A 32-element, spatially multiplexed system is constructed with a noise-equivalent sound pressure of ~3.58x10^-4 Pa per square root Hz at 1kHz and the major results of sea trials indicate that the system is useful for research and industrial applications.

In the theoretical performance evaluation of fiber Fabry-Perot interferometric sensors, sensitivity, fringe contrast and dynamic range are the three most important parameters. This paper theoretically models the effect of the cavity length, the F-P finesse, the source bandwidth, the mirror misalignments and symmetry on the sensitivity, fringe contrast and dynamic range of a white-light fiber Fabry-Perot interferometer. The developed systematic analysis approach and the numerical analysis results on both guided and unguided fiber Fabry-Perot interferometric sensors may provide useful guidance for sensor design optimization.

A low-cost design approach for Time Division Multiplexed (TDM) fiber-optic interferometric interrogation of multi-channel sensor arrays is presented. This paper describes the evolutionary design process of the subject design. First, the requisite elements of interferometric interrogation are defined for a single channel sensor. The concept is then extended to multi-channel sensor interrogation implementing a TDM multiplex scheme where “traditional” design elements are utilized. The cost of the traditional TDM interrogator is investigated and concluded to be too high for entry into many markets. A new design approach is presented which significantly reduces the cost for TDM interrogation. This new approach, in accordance with the cost objectives, shows promise to bring this technology to within the threshold of commercial acceptance for a wide range of distributed fiber sensing applications.

We have proposed and constructed a system to multiplex fiber Bragg grating (FBG) strain sensors with same reflection wavelength, adopting the synthesis of optical coherence function technique (SOCF), which has realized dynamic strain measurement. The ability to control the coherence peak position of SOCF allows random access in the spatial domain. In this paper, the function of random access strain measurement has been realized by switching the coherence peak position at every FBG, synchronizing with FBG spectrum measurement, to use the sampling rate to the full. In addition, we have proposed and confirmed the novel method for improving FBG interval by simply modulating the LD intensity.

A novel scheme of distributed fiber-optic strain sensor by localizing a dynamic grating in polarization maintaining erbium-doped fiber is proposed. The dynamic grating, which is introduced by launching two counter-propagating coherent light-beams into pumped erbium-doped fiber per the phenomenon of gain saturation, is examined. Theoretical modeling of the dynamic grating is given and used to make simulations on the reflectivity of the dynamic grating localized by synthesizing the optical coherence function. Theoretical analysis and numerical simulation on the novel sensor scheme show that the Bragg frequency of the dynamic grating will shift according to strain by 0.426MHz/με for typical polarization maintaining erbium-doped fiber.

We describe the mechanism of distribution measurement of fiber Brillouin spectrum by Brillouin Optical Correlation Domain Analysis (BOCDA), and numerically simulate the distribution of the Brillouin gain spectrum, which is expected to be measured in experiments. The simulation results agree well with the experimental results. We show the verification of the theoretical formulation of spatial resolution, by using the numerical simulations.

It is ever more important for Oil and Gas Companies to be able to efficiently and optimally manage the harvest of their production assets. Even minor differences in the ability to harvest production assets offer the potential for achieving significant competitive advantages. This presentation will provide an awareness of the various sensing system options and the role fiber optic sensors can play in obtaining the data needed for the optimal harvest of production assets. The increasing competitive pressure on companies requires them to run the enterprise in real time including management of the reservoir assets. This requires accurate and reliable data regarding well and reservoir performance on a continuous basis. In the paper I will highlight how different options for sensors and installation methods can impact data reliability and availability. Installation techniques that offer the greatest value will be discussed and to complete the picture, status highlights of several current fiber optic sensor developments will be provided. In an effort to knit the sensing and deployment technologies together into a value chain for real-time asset management some of our field test case histories will also be discussed.

With the ever increasing demand for oil coupled with the current high price per barrel, it has become imperative for oil and gas operators to cost effectively produce their oil and maximize their margins. Fiber optic sensor systems have been in the oilfield for a number of years now, however, they have had many shortcomings, including high price points, which have prevented widespread adoption. A new line of next generation fiber optic sensing systems has been developed to succeed where first generation systems have failed. These systems are diverse enough to fit into a wide range of applications, reliable enough to survive in the harshest of environments, and inexpensive enough for oil companies to integrate into their well completions, without greatly affecting their margins.

Over the last several years, fiber optic sensor technology has matured to the point that it is now ready for use in industrial applications. Fiber optic sensors have the potential for significant cost savings to the customer, primarily because installation is straightforward and maintenance is minimal. Substantial improvements in the performance of process control systems are a major benefit that has now been demonstrated and is now understood by many in the energy and petrochemical industries. This paper describes the basic principles and components that make up an industrial fiber optic sensing system, the results of an extensive characterization program performed on Fabry-Perot sensors configured to measure various parameters, the multiplexing approach for a multi-sensor system, data communications options, and potential applications of the technology within the industry. The results of a beta test program performed on a thirty-two channel temperature measurement system are reported also. The test program was conducted in an operating catalyst tube reactor to measure changes in the reactor temperature profile versus time.

There is increasing interest in the petroleum industry in the application of fiber-optic sensing techniques. In this paper, we review which sensing technologies are being adopted downhole and the drivers for this deployment. We describe the performance expectations (accuracy, resolution, stability and operational lifetime) that the oil companies and the oil service companies have for fiber-optic sensing systems. We also describe the environmental conditions (high hydrostatic pressures, high temperatures, shock, vibration, crush, and chemical attack) that these systems must tolerate in order to provide reliable and economically attractive reservoir-performance monitoring solutions.

A new class of Bragg grating components based on large diameter cylindrical waveguides has been commercially released. Unique properties of the waveguide including grating fabrication, low loss splicing to optical fibers, and specialized machining for optimization in sensor applications are reported. The waveguide structure enables packaging of Bragg gratings that overcomes attachment, mechanical creep, and hermeticity problems commonly associated with fiber Bragg gratings. This enables exceptionally robust Bragg grating sensor transducers well suited for the high temperature, corrosive downhole environment of oil and gas. Sensor transducers have been demonstrated showing no measurable drift or error after over 4-year aging tests at 150°C. More than 50 pressure/temperature installations have been successfully completed and are operational, delivering real-time data cumulatively over 500,000 operation hours. These systems integrate a range of support components specific to in-well oil and gas applications, such as downhole cables, interconnects, and platform instruments. This optical sensing platform, coupled with other optical techniques, has been extended beyond optical pressure/temperature measurements to distributed temperature measurements, multiphase flow, and in-well seismic sensing. These systems have been successfully deployed in multi-zonal, multi-parameter system architectures. This sensing technology is integrated with in-well controls, data acquisition and interpretation, and reservoir modeling. This systems approach is required to close the value loop of intelligent completions in oil and gas production.

Offshore Oil and Gas R&D has been committed to improved reservoir performance through production monitoring. Technology improvements in these areas offer the greatest potential returns through increased knowledge of the reservoir, and the improvements in real-time production control that the technology and knowledge base can provide. One area of technology that supports this development is the growing application of fiber optic sensors for reservoir and production monitoring. These sensors cannot function in isolation, and need support in the form of fiber optic connection systems for x-tree penetrations. ODI have been developing products for fiber optic tree penetrations and down-hole wet connections for the last 4 years, working with Intelligent Wells Group at BP America Production Company in Houston. This paper discusses the application and reliability of fiber optic connectors, and reviews the development of the ODI I-CONN connection system and its application for vertical and horizontal x-trees, work-over systems and running tools, and down-hole systems.

In this paper, a unique all-fiber tunable filter based on the combination of single resonant band long period grating (LPG) and harsh environment electro-optic polymer second cladding layer is presented. The single resonant band LPG is used to select the resonant wavelength and the tuning of resonant wavelength is realized by changing the refractive index of electro-optic polymer cladding layer via external electric field. Although the basic operational principle and implementation of this unique tunable filter have been previously reported by authors, this paper is focused on athermal operation design and synthesis of harsh environment electro-optic polymer, which enhances the practicability of proposed tunable filter.

A new type of optical fiber waveguide utilizing random holes in the cladding region has recently been fabricated. These random hole optical fibers (RHOFs) rely on holes that are random in both size and spatial location to confine light to the central core region. In this paper, a new technique to fabricate the holes in the cladding region will be presented. The holes are formed in-situ during the fiber drawing process. The new technique reported in this paper utilizes a material, which oxidizes to form a very large amount of “bubbles” at the temperature of the fiber draw. During the fiber drawing process, these bubbles are then drawn out into small diameter tubes within the fiber. By controlling the fabrication conditions, the amount, size, and spatial location of the porosity within the fiber can be controlled. The technique of fabrication and optical as well as SEM micrographs of the resulting structures will be discussed.

Long period gratings (LPGs) were written into a D-shaped optical fibre, which has an elliptical core with a W-shaped refractive index profile. The LPG's attenuation bands were found to be sensitive to the polarisation of the interrogating light with a spectral separation of about 15nm between the two orthogonal polarisation states. In addition, two spectrally overlapping attenuation bands corresponding to orthogonal polarisation states were observed; modelling successfully reproduced this spectral feature. The spectral sensitivity of both orthogonal states was experimentally measured with respect to temperature, surrounding refractive index, and directional bending. These LPG devices produced blue and red wavelength shifts of the stop-bands due to bending in different directions. The measured spectral sensitivities to curvatures, dλ/dR, ranged from -3.56nm m to +6.51nm m. The results obtained with these LPGs suggest that this type of fibre may be useful as a shape/bend sensor. It was also demonstrated that the neighbouring bands could be used to discriminate between temperature and bending and that overlapping orthogonal polarisation attenuation bands can be used to minimise error associated with polarisation.

This paper describes a diaphragm-based external Fabry-Perot interferometric (EFPI) fiber acoustic sensor with pressure-isolation structure. The structure minimizes the crosstalk generated by environmental pressure while enables considerable amount of acoustic signal power being delivered to the sensor, which allows the sensor to work in high-pressure environment. The detailed analysis on sensor design, pressure isolation and sensor fabrication as well as sensor performance are presented.

We demonstrated that a high-sensitivity fiber sensor based on a superstructure fiber grating (SFG) can simultaneously measure the pressure and temperature by encapsulating the grating in a polymer-half-filled metal cylinder, in which there are two openings on opposite sides of the wall filled with the polymer to sense the pressure. The mechanism of sensing pressure is to transfer the pressure into the axial extended-strain. According to the optical characteristics of an SFG composed of a fiber Bragg grating (FBG) and long period grating (LPG), the various pressure and temperature will cause the variation of the center-wavelength and reflection simultaneously. Thus, the sensor can be used for the measurement both of the pressure and temperature. The pressure sensitivity of 2.28×10^-2MPa^-1 and the temperature sensitivity both of 0.015nm/°C and -0.143dB/°C are obtained.

The feasibility of an optical fiber corrosion sensor(OFCS) is studied in the present paper. A multi-mode fiber is metallised by physical vacuum deposition(PVD) and electroplating a Fe-C alloy film on an uncladded part with 1-2cm length. Comparatively, similar methods used to form metallic film on planar quartz crystal. Electrochemical measurements including continuously inspection of electrochemical parameters show different characters between cylindrical and planar wave guide. The shift of light power transmitted through the fiber is registered with corrosion. Microanalysis is carried out to show the metallised film’s forming. Electrochemical process of the corrosion on the fiber is researched by continuously monitoring open potential Ecorr and linear polarized resistance Rp.

This work evaluates the feasibility of Fourier transform near infrared (FT-NIR) spectrometry for rapid determining the total soluble solids content and acidity of apple fruit. Intact apple fruit were measured by reflectance FT-NIR in 800-2500 nm range. FT-NIR models were developed based on partial least square (PLS) regression and principal component regress (PCR) with respect to the reflectance and its first derivative, the logarithms of the reflectance reciprocal and its second derivative. The above regression models, related the FT-NIR spectra to soluble solids content (SSC), titratable acidity (TA) and available acidity (pH). The best combination, based on the prediction results, was PLS models with respect to the logarithms of the reflectance reciprocal. Predictions with PLS models resulted standard errors of prediction (SEP) of 0.455, 0.044 and 0.068, and correlation coefficients of 0.968, 0.728 and 0.831 for SSC, TA and pH, respectively. It was concluded that by using the FT-NIR spectrometry measurement system, in the appropriate spectral range, it is possible to nondestructively assess the maturity factors of apple fruit.

In the near-infrared (NIR) region, every component is corresponding to specific absorption spectra characteristics. So NIR spectroscopy has gained wide acceptance in many research and application fields by virtue of its advantages over other analytical techniques. This study was about nondestructive sugar content detection of “Fuji” apples by means of NIR diffuse reflectance technique using optical fiber. Variance analysis of average absorbency and root mean square (RMS) noise of NIR spectra indicated that different testing positions had little influence on spectra acquisition while different testing distances had an opposite outcome. The relationship between sugar content and NIR spectra of apples was analyzed via multi linear regression (MLR) method using software SAS. Optimal single-wavelength (1453 nm), double-wavelength (1732 nm and 1790 nm), triple-wavelength (1453 nm, 1732 nm and 1790 nm) and quaternion-wavelength (1453 nm, 1732 nm, 1790 nm and 1931 nm) calibration equations were established. Correlation coefficients (R) of the calibration set were 0.754, 0.864, 0.907 and 0.921, respectively, standard error of calibration (SEC) were 1.439ºBrix, 1.103ºBrix, 0.922ºBrix and 0.851ºBrix, respectively. Of the prediction set, correlation coefficients (R) were 0.438, 0.687, 0.746 and 0.868, respectively, standard error of prediction (SEP) were 2.342ºBrix, 1.835ºBrix, 1.171ºBrix and 0.918ºBrix, respectively. The results show that NIR diffuse reflectance technique is a feasible method for nondestructive detection of apple fruit sugar content. Furthermore, this study lays a solid foundation for setting up the sugar content forecasting model of apples.

We report on the use of a cost-effective erbium-doped based optical preamplifier in a single-ended distributed fiber-optic sensor to improve receiver sensitivity and hence measurement range. The improved accuracy of spontaneous Brillouin measurements was demonstrated in a 23km sensor and was limited by amplified spontaneous emission from the preamplifier, which was verified theoretically. Reduction of amplified spontaneous emission was achieved with a 0.37nm in-fiber Bragg grating. A signal-to-noise improvement of 17dB was achieved and supported by theory, which translates to approximately 40km range improvement for a single-mode sensing fiber having losses of 0.2dB/km at 1550nm.

Extrinsic Fabry-Perot Interferometer, EFPI, is a versatile device for many fiber optic sensing applications including one in harsh environments such as oil and gas wells. Due to its unique structure, the EFPI could be designed to have an extremely small temperature cross-sensitivity (TCS), by matching the coefficients of thermal expansion (CTE's) of the outer gage capillary tube and the inner fibers. Even though it is relatively easy to get a matching condition at the atmospheric pressure, it is not a good design because the CTE of the capillary tubing is expected to change under high pressure conditions. In this paper, the method and the experimental results for the study to minimize the temperature cross-sensitivity (TCS) of the EFPI pressure sensor are presented. Test results have confirmed that the CTE of the capillary tube slightly increases under high pressure, changing the original TCS at the atmospheric pressure. By manipulating the design of the sensor to have a higher negative slope of TCS for the air-gap (dG/dT) at the atmospheric pressure, the zero TCS point can be deliberately shifted to any point of interest within the pressure range.

A fiber optic chlorine sensor having its entire length as the sensing element is reported here. The fiber consists of a silica core and a chlorine-sensitive cladding. Upon exposure to chlorine, the cladding very rapidly changes color resulting in attenuation of the light throughput of the fiber. A two-meter portion of sensor fiber responds to 10-ppm chlorine in milliseconds and to 1 ppm in several seconds. Furthermore, response to 100 ppb chlorine is realized in minutes. The high sensitivity suggests that the propagating modes of the light interact strongly with the cladding, and that these interactions are massively increased (Beers Law) due to the extended sensor length. The sensitivity to 1 ppm chlorine gas as a function of the length of fiber exposed between 0.3-30 meters is presented. The sensitivity to concentrations of chlorine from 0.1ppm-10ppm has been determined for a fixed 2 meter length of fiber. Pre-exposure fiber attenuation measures 70 dB/km (@ 633 nm) making it possible to detect chlorine on a continuous length of fiber on the scale of one hundred meters or more using standard detection methods (e.g. laser and photodetectors). This will replace the need of having a collection of point-detectors to cover large areas.