An optical coherence-domain reflectometry system provides an interferometer driven by a broadband incoherent light source with the device under test connected to one arm of the interferometer and a movable scanning mirror in the other arm providing a reference signal. The mirror moves at a controlled velocity to produce a Doppler shift in the reference signal frequency. The reference signal arm also includes a piezoelectric transducer which modulates the phase of the reference signal at a given frequency, causing a further shift in the reference signal frequency. The interference signal is detected and measured by a polarization diversity receiver. A linear polarizer in the reference signal arm is adjusted to produce equal reference signal powers in each arm of the polarization diversity receiver in the absence of a reflection signal from the test arm. The measured reflectometry signal is substantially independent of the state of polarization of the reflected signal from the device under test.

Polarization independent optical coherence-domain reflectometry

An imaging guidewire can include one or more optical fibers communicating light along the guidewire. At or near its distal end, one or more blazed or other fiber Bragg gratings (FBGs) directs light to a photoacoustic transducer material that provides ultrasonic imaging energy. Returned ultrasound is sensed by an FBG sensor. A responsive signal is optically communicated to the proximal end of the guidewire, and processed to develop a 2D or 3D image. In one example, the guidewire outer diameter is small enough such that an intravascular catheter can be passed over the guidewire. Techniques for improving ultrasound reception include using a high compliance material, resonating the ultrasound sensing transducer, using an attenuation-reducing coating and/or thickness, and/or using optical wavelength discrimination. Techniques for improving the ultrasound generating transducer include using a blazed FBG, designing the photoacoustic material thickness to enhance optical absorption. Techniques for distinguishing plaque or vulnerable plaque may be used to enhance the displayed image.

Systems and methods for minimally-invasive optical-acoustic imaging

A sensitive towed optical fiber sensor array 50, wherein the fiber sensors (60A-60N) are connected in parallel, and the optical fiber cable (34) is paid out from the towing ship at a velocity about equal to but opposite to the velocity of the towing ship. The fiber sensors (60A-60N) are immune to electromagnetic interference, and the output of the sensors can be isolated readily to the parallel hookup of the sensors. Turbulence and acceleration noise is greatly reduced due to the manner in which the fiber cable (34) is paid out, and crosstalk between sensors is eliminated.

Reduced noise fiber optic towed array and method of using same

The present invention is directed to providing an environmentally stable, ultra-short pulse source. Exemplary embodiments relate to passively modelocked ultra-short fiber lasers which are insensitive to temperature variations and which possess only negligible sensitivity to pressure variations. Further, exemplary embodiments can be implemented in a cost-effective manner which render them commercially practical in unlimited applications. Arbitrary fiber lengths (e.g., on the order of 1 millimeter to 1 kilometer, or greater) can be used to provide an ultra-short pulse with a cost-effective architecture which is commercially practical.

Environmentally stable passively modelocked fiber laser pulse source

A method and apparatus for drug product tracking (or other pharmaceutical, health care or cosmetics products, and/or the packages or containers they are supplied with) using diffraction grating-based encoded optical identification elements (8) includes an optical substrate (10) having at least one diffraction grating (12) disposed therein. The grating (12) has one or more colocated pitches A which represent a unique identification digital code that is detected when illuminated by incident light (24). The incident light (24) may be directed transversely from the side of the substrate (10) (or from an end) with a narrow band (single wavelength) or multiple wavelength source, and the code is represented by a spatial distribution of light or a wavelength spectrum, respectively, or a combination thereof. The encoded element (8) may be used to label any desired item, such as drugs or medicines, or other pharmaceutical or health care products or cosmetics. The label may be used for many different purposes, such as for sorting, tracking, identification, verification, authentication, anti-theft/anti-counterfeit, security/anti-terrorism, or for other purposes. In a manufacturing environment, the elements (8) may be used to track inventory for production information or sales of goods/products. Such labeling provides product identification at the pill or liquid medicine level, which provides traceability of these products to their manufacturer, thereby reducing counterfeit products in the marketplace. Also, the elements (8 )may be incorporated into a film, liquid, coating or adhesive tape at attached to the product package.

Method and apparatus for drug product tracking using encoded optical identification elements

A fiber optic sensor array has multiple segments, each capable of detecting a physical condition such as an acoustic wave. The segments are separated by weak reflectors such as fiber optic Bragg gratings. Light from a light source is input into the input end of the array. Light reflected by each of the reflectors has a phase shift representing the effects of the physical condition on all of the segments from the input end to that reflector. To address a specific reflector, the return light is demultiplexed. This demultiplexing is done by modulating the light input into the input end of the array with a pseudo-random bit sequence and correlating the output with a time-shifted version of the pseudo-random bit sequence to isolate the part of the output caused by that reflector. To address a specific segment, the phase shifts from two adjacent reflectors are determined. The return light can be strengthened by mixing it with a portion of the light picked off from the light source.

Coherent reflectometric fiber Bragg grating sensor array

A method and apparatus for overcoming polarization induced signal fading in both heterodyne communication and interferometric sensing. An adjustable birefringent element in series with a linear-polarization beam splitter forms an elliptical-polarization beam splitter. The birefringent element controllably evolves the states of polarization of two input signals thereby controlling the power contribution of each signal onto the orthogonal axes used by the linear beam splitter. When the states of polarization are evolved such that there are equal signal to reference power ratios on the beam splitter axes, subsequent detectors generate a constant, optimum amplitude signal without the need for weighting or decision circuits.

Adaptive polarization diversity detection scheme for coherent communications and interferometric fiber sensors

A new serial interferometric fiber-optic sensor array configuration is diosed In a preferred embodiment of the invention pulsed light from a laser source is transmitted into a long input fiber which forms a series of N sensor elements, each of optical path length L Each sensor element is responsive to any change in an associated predetermined physical parameter for changing its optical path length A small portion of the optical power in the input fiber is tapped-off to a long output fiber at tap points between adjacent sensor elements and at tap points before the first and after the last sensor elements in order to produce at the output of the last sensor element a series of N+1 pulses separated in the time domain This series of N+1 pulses from the output of the last sensor element is applied to each of two paths in a compensating interferometer of optical path imbalance L The compensating interferometer coherently mixes pulses obtained from each adjacent pair of tap points to obtain a series of interferometric signals respectively indicative of any change in the physical parameters to which the sensor elements are respectively responsive

Serial interferometric fiber-optic sensor array

A system and method for minimizing polarization-induced phase noise in an interferometric fiber sensor is disclosed. The system includes an optical source of light; a single mode input fiber; means coupled between the optical source and the input fiber for scrambling the polarization state of the light from the optical source at a first frequency to effectively produce and pass depolarized light to the input fiber; an interferometric fiber sensor responsive to light from the input fiber for producing at its output an interference pattern proportional to a phase shift produced by a field being sensed by the interferometric fiber sensor; detection means responsive to the interference pattern for developing a photocurrent signal averaged over a period of time longer than the period of the first frequency; and demodulation means responsive to the photocurrent signal for producing an electrical output signal substantially proportional to the phase shift produced by the field being sensed by the interferometric sensor.

System and method for minimizing input polarization-induced phase noise in an interferometric fiber-optic sensor depolarized input light

An improved inline fiber optic sensor array is achieved by packaging a pllity of fiber optic sensor units such that each fiber optic sensor unit incorporates a complete functional sensor and adjacent fiber optic sensor units are separated by a delay element connected in series between each pair of fiber optic sensor units. Delay elements temporally separate measureand signals received from the individual fiber optic sensor units and permit decoupling of signals produced in response to environmental stress on the non-sensor unit portions of the array.

Anthony Dandridge

Papers

Coherent reflectometric fiber Bragg grating sensor array

Adaptive polarization diversity detection scheme for coherent communications and interferometric fiber sensors

Serial interferometric fiber-optic sensor array

System and method for minimizing input polarization-induced phase noise in an interferometric fiber-optic sensor depolarized input light

Inline fiber optic sensor arrays with delay elements coupled between sensor units