Ofs Fitel, LLC

Fitel USA Corporation

Dfs Fitel LLC

Mikhail Sumetsky

David John DiGiovanni

Paul S Westbrook

Siddharth Ramachandran

Benjamin John Eggleton

Mikio Ogai

David J Digiovanni

A broadband fiber optic sensor array is formed along a length of single mode optical fiber, with the individual sensing elements formed by introducing local perturbations (e.g., changes in diameter) along the length of the optical fiber. The sensor array requires only a single light source input and a single (conventional) optical spectrum analyzer output and is capable of providing individual measurements (such as local temperature or pressure) for each sensing element disposed along the length of fiber. The individual transmission spectra of the sensing elements forming the array are smooth and strongly overlap, and a method has been developed for determining the characteristics of the individual elements from the variations in the total (combined) transmission spectrum.

Broadband fiber sensor array

A method of characterizing and correcting effective radius variations in a surface nanoscale axial photonic (SNAP) device that comprises a plurality of separate optical microdevices includes the steps of characterizing an as-fabricated SNAP device to determine local effective radius values of the plurality of separate optical microdevices, calibrating the as-fabricated SNAP device to determine a correction factor defined as a change in effective radius associated with a predetermined corrective treatment and then correcting individual microdevices by the application of a number of refractive index-changing treatments, the number of treatments applied to individual microdevices determined by the amount of correction required and the correction factor determined in the calibrating step. A number of iterations of the characterizing and correcting operations can be performed, achieving less than an Angstrom variation in effective radius variation. An apparatus for performing the method is also disclosed.

Method of fabricating surface nanoscale axial photonic devices

A conically tapered optical fiber with a small half-angle &#x3b3; (e.g., less than 10) has been found able to support whispering gallery mode (WGM) resonances and can therefore be used to form a high-Q cavity. This finding has led to the ability to measure angstrom-level variations in the radius of an optical fiber by viewing the resonance spectrum at various locations where a sensor contacts an optical fiber being measured. An evaluation process is proposed where a microfiber sensor is brought into contact with a target fiber and the created WGM resonance is measured so that location radius variation can be characterized. The sensor is then removed from the target fiber and re-positioned to contact the fiber to another location to repeat the evaluation.

High Q-factor conical optical microresonator and utilization in the location characterization of optical fibers

An optical microresonator is configured as an optical microbubble formed along a section of an optical microcapillary. The curvature of the outer surface of the microbubble creates an optical resonator with a geometry that encourages the circulating WGMs to remain confined in the central region of the bubble, creating a high Q optical resonator. The resonator may be tuned by modifying the physical properties of the microbubble, allowing the resonator to be used as an optical filter. The resonator may also be used as a sensor or laser by introducing the material to be sensed (or the active laser material) into the microcapillary along which the microbubble is formed.

Microbubble optical resonator

Complex, coupled photonic microdevices are formed to include sub-wavelength-sized radial perturbations sufficient to create resonant cavities, where these devices may be formed along the length of a single optical fiber and coupled together to form relatively complex photonic devices. By carefully selecting the placement and separation of these local radius variations, and using microfibers (or other suitable arrangements) to couple optical signals into and out of the device fiber, resonances in the form of whispering gallery modes (WGMs) are created in the device fiber such that a number of coupled microstructures (such as ring resonators) may be formed.

Fiber-based photonic microdevices with sub-wavelength scale variations in fiber radius

An optical fiber coupler is formed of a section of optical fiber that is positioned between a conventional input fiber (for example, a single mode fiber) or waveguide and a coiled optical fiber device. The adiabatic coupler is coiled (or, at least, curved) to assist in transforming a conventional fundamental mode optical signal propagating along the longitudinal axis of the input fiber to an optical signal that is shifted into a peripheral region of the coiled optical fiber. Moreover, the pitch of an inventive coiled optical fiber coupler can be controlled to assist in the adiabatic transformation process.

Adiabatic coupler for coiled optical fiber devices

An evanescent optical sensor is formed as a coil of either optical fiber or microfiber. By coiling the fiber/microfiber, the overall size of the sensor is significantly reduced when compared to 'straight path' fiber sensors, yet exhibits a similar degree of sensitivity. An optical signal is coupled into a fiber coil that has been immersed in an ambient to be analyzed. The use of a coil configuration results in creating a plurality of whispering gallery modes (WGMs) that will propagate along the coil by reflecting from the surface of the curved fiber/microfiber forming the coil. The interference between these modes will be modified as a function of the properties of the ambient environment. Environmental changes cause variations in the optical length of the coil as 'seen' by the various modes, and the interference of the modes is analyzed by studying the transmission spectrum at the output of the coil.

Coiled evanescent optical sensor

To date, the probes of scanning near-field optical microscopes were aimed at creating electromagnetic field characteristics that are maximally localized near a nano-sized point (miniature apertures and tips, fluorescent nano-particles and molecules, dielectric and metal corners). Alternatively, the probe field, which is distributed within a larger area, can ensure the super-resolution as well. For this purpose, the field spectrum should be enriched with high spatial frequencies corresponding to small sample dimensions. As examples of such near-field probes, we propose and theoretically study the models of optical fibers with end-faces containing sharp linear edges and randomly distributed nanoparticles. These probes are more robust than the conventional probes and their fabrication is not concerned with nanoscale precision. The probes enable waveguiding of light to and from the sample with marginal losses distributing and utilizing the incident light more completely. Numerical modeling shows that, even with substantial measurement noise, the suggested probes can resolve objects that are significantly smaller than the probe size and, in certain cases, can perform better than miniature nanoprobes.

Near-field scanning optical microscopy with nanoscale resolution from microscale probes

An optical delay line is formed from a coil of optical fiber (in many cases microfiber), where the radius of the optical fiber is greater than the wavelength &#x3bb; of the propagating signal and the radius R of the coil is selected, in consideration with the optical fiber radius, to limit propagation loss by minimizing coupling between adjacent turns of the coil. The difference in dimension between the fiber diameter and wavelength prevents the mode propagating along one turn from coupling into an adjacent turn. It has been discovered that the modal intensity at the interface between the central rod and the coil will be minimized when the radius of the fiber satisfies the following condition: where &#x3b2;=(2&#x3c0;n)/&#x3bb;, and n is the refractive index of the fiber.

Low loss optical delay line using a microfiber coil

The specification describes optical devices and related methods wherein an input mode is converted by multiple LPG mode transformers to produce an output with multiple predetermined modes.

Locally perturbed optical fibers for mode transformers

An optical resonator is configured for optimized performance as a sensor by maximizing the slope and/or sharpness of the resonance peak, instead of maximizing the Q-factor of the resonator. These characteristics of the resonance peak are controlled, in accordance with the present invention, by modifying the physical parameters of the resonator structure (e.g., dimensions, spacing between waveguides, ring diameter, materials and associated refractive indices, etc.) until the desired peak attributes are achieved, regardless of the Q-factor associated with these optimum attributes.

Optimized optical resonator device for sensing applications

An optical fiber coil of sub-micron diameter is shown to exhibit self-coupling between adjacent turns so as to form a three-dimensional optical resonator of relatively low loss and high Q. As long as the pitch of the coil and propagating wavelength remain on the same order (or less than) the fiber diameter, resonance may occur. Resonances can be induced by allowing adjacent turns of the coil to touch each other. Optical devices such as resonators and interferometers may then be formed from such 'microcoils' that exhibit superior characteristics to conventional planar devices. A method of forming such a microfiber using indirect laser heating is also disclosed.

Optical fiber microcoil, resonant structure and method of making the same

An apparatus and method for performing surface microscopy of an optical device uses an optical fiber taper including a microsphere endpoint as a near field probe. A transmission fiber is disposed adjacent to the microsphere so as to evanescently couple an optical test signal into the microsphere. A series of extremely narrow whispering gallery mode (WGM) resonances are created within the microsphere, with an associated electromagnetic field radiating outward therefrom. The microsphere probe may then be moved over the surface of an optical device being analyzed (or the device translated underneath the microsphere), where any abnormalities in the surface (such as defects, scratches and the like) will perturb the electromagnetic field pattern and be reflected in changes in the measured output power from the microsphere.

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Bridgewater, NJ, United States of America

Mikhail Sumetsky