Abstract: A novel in-fiber polarizer is provided that is implemented in an optical fiber structure based on a polarization maintaining (“PM”) optical fiber, and that is configured to impart a predetermined desired polarization to a light signal transmission of a predetermined at least one wavelength transmitted therethrough.

Abstract: A novel in-fiber polarizer is provided that is implemented in an optical fiber structure based on a polarization maintaining (“PM”) optical fiber, and that is configured to impart a predetermined desired polarization to a light signal transmission of a predetermined at least one wavelength transmitted therethrough.

Abstract: The present invention is directed to an optical fiber grating having a core, that is capable of controlling the light signal transmission therethrough by causing at least one of: at least one spectral peak, and/or at least one spectral dip in its core light transmission spectrum, corresponding to at least one predetermined wavelength. The inventive optical fiber diffraction grating comprises at least one longitudinally positioned structural element of a predetermined geometric profile and that is configured for diffracting a portion of the transmitted light signal at at least one predefined wavelength thereof, from at least one core mode into at least one of: at least one cladding mode and/or at least one radiating mode. Various embodiments of a number of novel techniques for fabrication of the inventive optical fiber diffraction grating are provided, inclusive of a novel technique for fabricating the inventive grating from a single material.

Abstract: An optical fiber coupler array capable of providing multiple low loss, high coupling coefficient interfaces between a predetermined number of low numerical aperture optical fibers and an optical waveguide device with at least a corresponding number of waveguide interfaces. The novel coupler array includes a plurality of coupler inner cores and a plurality of corresponding coupler outer cores, within a medium surrounding each plural outer core, and also includes a first end for interfacing with plural optical fibers and a second end for interfacing with a plurality of waveguide interfaces of an optical waveguide device. The sizes of the inner and outer cores are gradually reduced from the first end to the second end in accordance with at least one predetermined reduction profile.

Abstract: An chiral optical fiber polarizer is provided that is capable of being fabricated in-line along a conventional polarization maintaining fiber, preferably one which includes at least one structure element that is external, and parallel, to the fiber's core. The novel chiral fiber polarizer is preferably positioned between two unmodified optical fiber portions, and includes a modified central portion with altered fiber cladding interface elements on each side thereof.

Abstract: A distributed elongated optical fiber detection system is provided, having at least one sensitive region, and being capable of detecting the occurrence and location(s) of one or more events along its length that cause one or more perturbations in the at least one sensitive region. In one embodiment of the invention, the novel detection system includes, at its first end, an optical signal source capable of launching a signal in a first signal mode through an optical fiber waveguide comprising at least one sensitive region along its length, and configured for transmitting at least two signal modes therethrough, toward its second end. A reflecting device, capable of reflecting only signals in a second signal mode, is positioned at the second end of the waveguide.

Abstract: A chiral fiber grating for reflecting, scattering or polarizing an optical signal, or for forming a fiber laser feedback structure is disclosed. The chiral fiber grating is fabricated by fusing and then twisting/drawing two tapered optical fibers in accordance with a predetermined fabrication protocol. In one embodiment of the invention, the chiral fiber grating includes two single helix structure end-regions, with a double helix structure therebetween, providing the grating with apodizing properties. In another embodiment of invention, the pitch profile along a portion of the grating is configured to produce desired chiral fiber grating properties. In yet another embodiment of the invention, the chiral fiber grating, comprising two single helix end regions and a middle double helix region, may be separated into two or more portions after fabrication, for example to provide one or more single helix chiral fiber gratings and one or more double helix chiral fiber gratings.

Abstract: The present invention provides process for fabricating an optical fiber assembly that includes two or more integral optical fiber elements having different interface characteristics, where at least one of the elements is a fiber optic device (fiber grating, in-fiber polarizer, coupler, mode filter, etc.), and where the length, and thus the cost, of each fiber optic device is advantageously optimized. The inventive process utilizes a two-stage approach, where at a first process stage, one or more optical fibers are spliced to one or more predetermined optical fiber device preforms (usable to fabricate one or more optical fiber devices), and where at a second process stage, one or more preform processing techniques (such as one or more of: drawing, twisting, etching, wrapping, etc.), are applied to the one or more preforms, to fabricate one or more corresponding optical fiber devices that are already integral with the optical fibers on one or both ends, thus forming the desirable optical fiber assembly.

Abstract: An optical fiber coupler capable of providing a low loss, high coupling coefficient interface between conventional optical fibers and optical waveguide devices is provided. The novel coupler, which may be polarization maintaining, if a polarization maintaining preform is used in its fabrication includes a core, a cladding, a first end for interfacing with an optical fiber and a second end for interfacing with an optical waveguide device. The sizes of the core and cladding are gradually reduced from the first end to the second end in accordance with a predetermined reduction profile. Various parameters, such as refractive indices and sizes of the core and cladding and the reduction profile are selected to produce a low numerical aperture at the first end and a high numerical aperture at the second end, while advantageously minimizing insertion loss and maximizing the coupling coefficient at each end.

Abstract: Lasing at the edge of the reflection band or at a defect state within the reflection band of a thin one-dimensional feedback structure is used to create a large-area, thin-film laser source with transverse dimensions that can be much greater than the film thickness. Angular confinement of radiation propagating perpendicular to the layers leads to a spreading of the beam inside the medium which is much greater than the diffraction divergence. This enhances the spatial extent of correlation at the output surface of the thin film. When a pump source induces gain at the lasing threshold in a wide region, a spatially coherent monochromatic light beam is emitted perpendicular to the film surface from the entire gain region. Alternate embodiments of the present invention include a passive spatial filter and an active amplifier.

Abstract: A chiral structure having an advantageous extended chiral defect that provides an enhanced energy distribution characteristic therein. This is accomplished by configuring a central portion of the chiral structure with a pitch different from the rest of the structure. This may be envisioned as a distributed chiral twist with a predefined angle over a portion of a chiral structure. With the distributed defect, the photonic stop band remains wide, allowing for the substantial increase in the lifetime of the mode in which lasing occurs, while the extent of the high intensity region of the mode is large. The extended chiral defect structure may also be implemented as a thin-film chiral structure, for example using cholesteric liquid crystal or sculptured thin films.

Abstract: A chiral in-fiber polarizer implemented in a chiral fiber structure having a core and a cladding surrounding the core, is provided. The chiral polarizer includes an entry end for receiving incident light and an exit end for outputting polarized light, as well as a pitch variation along its length between the entry and exit ends in accordance with a predetermined desirable pitch profile, wherein in one embodiment of the inventive polarizer, the inverse value of the chiral structure's pitch at the exit end is less than at the entry end, and preferably substantially equal to zero. The pitch profile may be advantageously selected to correspond to one or more predetermined pitch configurations, may be determined in accordance with one or more mathematical functions, or may be random.

Abstract: A chiral structure having an expanded adjustable reflection band to provide broadband tunability is provided. In the preferred embodiment, the chiral structure is implemented as a chiral fiber structure and comprises two or more sequential chiral fiber elements of different pitches, each having a tunable chiral defect generator. The pitches are selected such that the individual photonic band gaps of the elements are formed into one expanded reflection band such that at least one defect state can be formed and moved within the expanded reflection band by selectively activating and adjusting one or more of the tunable chiral defect generator. The tunable chiral defect generators may generate and control defect state(s) in the structure's spectral response by introducing chiral twists and/or spacing between the chiral elements, with the length of the spacings and angles of chiral twists being proportional to the position of the defect state(s) within the reflection band of the structure.

Abstract: A long period chiral fiber grating (“LPCFG”) that has a number of advantageous properties that can be readily utilized in a number of different applications is provided. The inventive LPCFG is a fiber grating having a pitch that exceeds the wavelength of light propagating therethrough. The LPCFG includes a number of dips in its transmission spectrum, but does not reflect any portion of the signal passing therethrough. The LPCFG is sensitive to changes in the refractive index of its external environment (or in the refractive index of a coating covering the LPCFG cladding). In response to changes in the external refractive index, the transmission dips shift proportionally to changes in the index, thus enabling the use of LPCFG as a fiber sensor element. In addition, the LPCFG is polarization sensitive—one circular polarized wave of one handedness is coupled to the cladding mode stronger than the wave of the other polarization handedness.

Abstract: An add-drop filter, utilizing chiral couplers, that enables a new signal to be added at a particular vacuum wavelength ??k to a fiber optic line carrying n signal channels over a band of wavelengths encompassing ?1 . . . ?k?1, ?k, ?k+1 . . . ?n, while an existing signal, ?k, is simultaneously dropped from the signal group.

Abstract: An apparatus and method for fabricating a thin layer periodic structure by successively depositing alternating uniform layers of two or more different dielectric materials on a substrate utilizing centrifugal force in a novel spin coating technique. In an alternate embodiment of the present invention, the novel spin-coating technique is configured for fabricating chiral media by successively depositing layers of one or more anisotropic materials, while rotating the substrate by a predetermined angle between deposition of each layer. In both embodiments of the inventive apparatus, a defect layer may be introduced by depositing a defect material in a desired position in the media.

Abstract: A a chiral fiber grating mimicking a cholesteric liquid crystal structure to achieve fiber Bragg grating properties, is provided. The chiral fiber grating includes a first and a second helical structures disposed along its central longitudinal axis, where the second helical structure is identical in orientation to the first helical structure but is shifted by one half of the structure's pitch forward. In another embodiment of the invention, only a single helical structure is disposed along the fiber to create an optically resonant chiral fiber.

Abstract: A chiral fiber sensor implemented in a chiral fiber is provided that mimics advantageous optical properties of a cholesteric liquid crystal structure. In a passive sensor embodiment the chiral fiber sensor of the present invention includes a chiral fiber element configured to shift its reflection band in response to a change in a particular external condition (such as temperature, pressure and axial twist). The chiral fiber element is subjected to a broadband emission while monitoring its refection or the transmission spectrum. Changes in the monitored spectrum indicate changes in the particular external condition. In an active sensor embodiment, the chiral fiber element is configured as an optically pumped chiral laser having a lasing wavelength that shifts in response to a change in a particular external condition (such as temperature, pressure and axial twist). The lasing wavelength is monitored and shifts in the wavelength indicate changes in the particular external condition.

Abstract: An add-drop filter, utilizing chiral elements, that enables a new signal to be added at a particular vacuum wavelength &lgr;′k to a fiber optic line carrying n signal channels over a band of wavelengths encompassing &lgr;1 . . . &lgr;k−1, &lgr;k, &lgr;k+1 . . . &lgr;n, while an existing signal, &lgr;k, is simultaneously dropped from the signal group.

Abstract: A apodized chiral fiber grating consists of a chiral fiber with a variable effective grating strength along different regions of its length, such that the effective grating strength gradually increases from one end of the chiral fiber until a peak effective grating strength is reached and then gradually decreases at the same rate towards the other end of the fiber. Optionally, the effective grating strength remains stable for a portion of the fiber before decreasing. Other forms of grating strength variations in different regions of the chiral fiber are also contemplated. The effective grating strength variation produces an apodized chiral fiber that possesses desirable characteristics that greatly reduce or eliminate the sidelobes in the fiber's spectral response.