Complexity, fractals, disease time, and cancer.

Despite many years of research, a method to precisely and quantitatively determine cancer disease state remains elusive. Current practice for characterizing solid tumors involves the use of varying systems of tumor grading and staging and thus leaves diagnosis and clinical staging dependent on the experience and skill of the physicians involved. Although numerous disease markers have been identified, no combination of them has yet been found that produces a quantifiable and reliable measure of disease state. Newly developed genomic markers and other measures based on the developing sciences of complexity offer promise that this situation may soon be changed for the better. In this paper, we examine the potential of two measures of complexity, fractal dimension and percolation, for use as components of a yet to be determined "disease time" vector that more accurately quantifies disease state. The measures are applied to a set of micrographs of progressive rat hepatoma and analyzed in terms of their correlation with cell differentiation, ratio of tumor weight to rat body weight and tumor growth time. The results provide some support for the idea that measures of complexity could be important elements of any future cancer "disease time" vector.

Statistical-mode sensor for fiber optic vibration sensing uses.

A method of sensing vibration using the detection of changes in the spatial distribution of energy in the output of a multimode optical fiber has been demonstrated. Two implementations of the sensor have been built and tested. The first implementation involved simple optical processing of the output fiber speckle pattern using spatial filtering. The second implementation involved projecting the pattern on a CCD array and digitally processing observed changes in the intensity distribution. A mathematical model has been developed which has shown good agreement with observed sensor behavior. The sensor technique has been used to detect induced structural vibration in laboratory test specimens. Simple field testing has also demonstrated the ability of the technique to detect personnel and vehicles passing over a buried and electrically undetectable sensing cable. The sensing technique is compatible with off-the-shelf components and fiber cable and even allows for simultaneous telecommunication and sensing using the same optical fiber cable. Near term application of this technology could provide significant benefits for vibration sensing, intrusion detection, and acoustic sensing.

Fiber optic linear displacement sensor based on a variable period diffraction grating.

A high accuracy wavelength encoding fiber optic sensor is shown to display surprisingly little sensitivity to temperature or optical source drift. Average measurement error of 0.1 % full scale has been demonstrated over a displacement range of 10 mm.

Fiber-optic rotary displacement sensor with wavelength encoding.

A fiber-optic sensor is described in which an optical retardation plate is used to encode rotary displacement information as a notched minimum in a broadband optical signal. As the waveplate is rotated, the optical beam experiences a variable linear retardation. The signal wavelength at which the retardation is exactly one-half wave exhibits a minimum intensity transmission. The wavelength of the intensity minimum is then a function of the rotation of the retardation plate. The theoretical prediction of the sensor's performance is developed and compared to experimental results.

Optical waveguides in LiTaO(3) formed by proton exchange.

We describe the fabrication of optical waveguides in LiTaO(3) using proton exchange in hot benzoic acid. All specimens analyzed were X cut. An increase in surface extraordinary index of ~0.14 has been observed for samples exchanged for 3 h at a melt temperature of 249 degrees C. No change was observed in the ordinary index. Waveguide fabrication was facilitated by further baking the samples for an extended period of time at a temperature hotter than the acid melt. The latter technique also served to minimize the surface damage that is characteristic of acid baths exceeding roughly 4 h. The depth of proton exchange in X-cut LiTaO(3) appears to be considerably less than would be the case for X-cut LiNbO(3) under the same conditions.

Multimode fiber-optic pressure sensor based on the photoelastic effect.

A multimode fiber-optic pressure sensor is described that is based on the photoelastic effect. The device was shown to be able to detect pressures as small as 95 Pa, to have a dynamic range of 86 dB, and to have hysteresis less than 0.01. Device sensitivity may easily be modified to coincide with required measurement sensitivity through careful choice of the active photoelastic material. The device is simple, rugged, electrically passive, and compatible with existing multimode technology.

Hybrid fiber-optic sensors using liquid-crystal light modulators and piezoceramic transducers.

A new technique is described for linking remote sensors by multimode optical fibers. It combines two well-known technologies and is compatible with multimode optical multiplexing. At the sensing location, the output of a transducer (such as a piezoceramic hydrophone) is connected directly to a low-voltage liquid-crystal light modulator that is coupled to fiber-optic transmission lines by graded-index rod lenses. Transducer voltages as low as 10 microV produce intensity modulation of the fiber light. An optical hydrophone based on the technique demonstrated a minimum detectable pressure of 39 dB re 1 [equiation] at 500 Hz. The device performance was evaluated over the 8-45 degrees C temperature range. Sensitivity was found to decrease linearly by 0.2 dB/ degrees C over that range. The technique provides a means by which rugged nonmechanical sensors can be constructed that are suitable for incorporation into practical fiber-optic sensor systems.

Multimode fiber-optic hydrophone based on the photoelastic effect.

A multimode fiber-optic hydrophone based on the photoelastic effect is described. The device offers the advantages that it is simple, low cost, sensitive, inherently solid state, rugged, and exploits a differential approach for amplitude noise reduction. A minimum detectable pressure of 47 dB re 1 microPa/Hz(1/2) has been demonstrated at 500 Hz, and calculations based on photoelastic material properties indicate that a minimum detectable pressure as low as 15 dB re 1 microPa/Hz(1/2) might be achieved. This device design, therefore, represents an attractive technique for making a practical multimode fiber-optic hydrophone.

Multimode fiber-optic hydrophone based on a schlieren technique.

A multimode fiber-optic hydrophone is described which is based upon a schlieren acoustooptic intensity modulation mechanism. Computer modeling of critical device parameters was experimentally verified and used to indicate ultimate attainable device performance. The device was shown to be able to detect the Knudsen noise level for frequencies up to 1 kHz, to have a dynamic range of 125 dB, to have an omnidirectional receiving response, and to be able to detect displacements as small as 3.4 x 10(-3) A. The device is not susceptible to phase noise, is relatively insensitive to static pressure head variations and is electrically passive.

Frustrated-total-internal-reflection multimode fiber-optic hydrophone.

A multimode fiber-optic hydrophone based upon the principle of frustrated total internal reflection has been constructed and tested. The sensitivity of the device to acoustic waves in water is in good agreement with predictions derived from its measured sensitivity to applied static displacements in air. The minimum detectable pressure for the device was 62 dB relative to 1 micro Pa at 500 Hz. Static displacements as small as 4.8 x 10(-3) A can be detected. The sensor is compatible with present multimode fiber-optic sources, detectors, and components.

Mechanical one-to-many fiber-optic switch.

A mechanical multimode fiber-optic switch has been developed which uses a spherical mirror mounted on a galvanometer scanner to switch multimode light from one to many other fibers located in a linear array in the one-to-one imaging plane of the mirror. Characteristics of the switch include (1) measured optical insertion loss less than 1.5 dB; (2) optical isolation greater than 37 dB; (3) switching rate of 300 Hz; (4) potential for greater than one-to-ten fiber switching; and (5) little degradation of device characteristics after 10(6) switchings between two output fibers spaced four fiber diameters apart.

Fail-safe fiber-optics data bus using active multimode mirror terminals.

A prototype fail-safe optical data bus utilizing active LiTaO(3) electrooptic mirror terminals has been constructed and tested. Features of the system include (1) a single optical source; (2) an optical insertion loss of less than 6 dB and a tapoff ratio of 13 dB for the mirror terminals in the fail-safe mode; (3) compatibility with commercially available LED sources, P-I-N photodiode detectors, and step-index multimode monofibers; (4) remote terminal modulation depth approaching 50% for 100 V applied; and (5) the use of a pulse transformer technique which allows the required electrooptic modulation voltages to be obtained from a 5-V electrical supply. The construction of a working prototype data bus using mirror terminals demonstrates the feasibility of such systems for use in optical communications at the present state of the art.