Showing papers on "Photonic-crystal fiber published in 1994"

Chirped in-fiber Bragg gratings for compensation of optical-fiber dispersion.

Abstract: A linearly chirped in-fiber Bragg grating is reported that can compensate at 1549 nm for the dispersion [ approximately -19 ps/(nmkm)] of standard telecommunications optical fiber optimized for 1300-nm operation.

Characterization of UV-induced birefringence in photosensitive Ge-doped silica optical fibers

Abstract: The anisotropic nature of the UV-induced index change achieved in photosensitive optical fibers is characterized by a direct measurement of the induced birefringence in three different fibers. The birefringence, which grows with UV exposure proportionally to the total induced index change, is measured to be as small as 0.2% and as large as 8% of the total index change, depending on the fiber type and the exposure geometry. Such large values of birefringence are especially notable, since they can lead to substantial resonant effects such as polarization-dependent reflectivity in a fiber Bragg grating. The birefringence is predominantly determined by the polarization of the UV irradiation. We demonstrate an order-of-magnitude reduction of birefringence in an actual fiber phase grating by rotating the UV polarization to lie in the plane of the irradiating beams and the fiber axis.

Soliton versus nonsoliton operation of fiber ring lasers

Abstract: To date most passively mode‐locked erbium‐doped fiber laser systems have employed solitons for short pulse generation, and ultrashort high energy pulses have been difficult to achieve. We show that by reducing the system nonlinearity via pulse stretching and employing net positive dispersion cavities, pulses of sub‐100‐fs duration and ≳100 pJ energy are readily generated. Data are presented for varying net dispersion in a fiber ring.

Graded-index polymer optical fiber for high-speed data communication

Abstract: We successfully obtained a high-bandwidth (1 GHz km) and low-loss (90 dB/km at 0.572 μm of wavelength) graded-index polymer optical fiber by using the interfacial-gel polymerization technique, in which we used an unreactive component to obtain the quadratic refractive-index distribution. This high-bandwidth graded-index polymer optical fiber makes it possible to transmit a high-speed optical signal in a short-range network, which is not possible when we use the step-index type of polymer optical fiber commercially available.

Multiwavelength fiber laser using a spatial mode beating filter.

Abstract: A multiwavelength comb is obtained from Er(3+) - and Nd(3+)-doped fiber lasers by incorporation of a section of multimode optical fiber into an otherwise single-mode fiber ring cavity. This combination of fiber types acts as a wavelength-dependent filter in the laser through spatial mode beating between the LP(01) and LP(11) modes in the multimode fiber.

Grating-frustrated coupler: a novel channel-dropping filter in single-mode optical fiber.

Abstract: A low-insertion-loss, all-single-mode fiber, wavelength-division-multiplexing filter comprising a four-port polished coupler and a strong fiber grating is demonstrated. The device operated in a novel way by a process we call grating-frustrated directional coupling. A fiber grating, present in only one half of the coupler, frustrates the transference of power to the other half within a narrow wavelength range. The performance of a prototype device - a 1535-nm channel-dropping filter with 0.7-nm bandwidth, 70% peak transmission, and 13-dB isolation-shows great promise for wavelength-division-multiplexing and line-filtering applications.

The Golden Age of Optical Fiber Amplifiers

Abstract: After nearly two decades of research in fiber‐optics technology, what could possibly remain to be discovered? Clearly, the design of optical fibers cannot be improved forever. With current technology, fibers can transmit infrared (1.5‐micron wavelength) light pulses in a single electromagnetic mode with a minimal power loss of 5% per kilometer and without dispersion; such performance is forever fixed by Maxwell's equations and the physics of silica glass waveguides. Yet the field of fiber optics still reserves some surprises. Indeed, the past few years have seen stunning developments in reaction to advances in rare‐earth‐doped fiber amplifiers and nonlinear (or soliton) pulse propagation in fibers.

Role of third-order dispersion on soliton instabilities and interactions in optical fibers.

Abstract: We analyze the role of third-order dispersion on the propagation, stability, and interactions of solitons in optical fiber transmission links and fiber lasers.

Selective mode excitation in graded-index multimode fiber by a computer-generated optical mask.

Abstract: We report on the generation of optical masks that permit the spatial shaping of a laser beam so that one can selectively excite single modes of a multimode parabolic graded-index optical fiber. The amplitude masks are determined by the analytical radial function of the fiber mode in the weakly guiding approximation. Phase reversal is encoded on the transparency through a shifted-grating technique. Effective injection and propagation of a single mode in a largely multimode fiber are shown as examples.

Arrangement of fiber pieces for a wide wavelength conversion range by fiber four-wave mixing

Abstract: A new technique is reported for obtaining a wide wavelength conversion range in fiber four-wave mixing. One fiber is cut into short fiber pieces and rearranged, considering the zero-dispersion wavelength of each fiber piece. With this rearrangement, the wavelength conversion range is expanded, compared with that in the original fiber. An experiment using a 6-km fiber confirms the technique.

Optical waveguide including singlemode waveguide channels coupled to a multimode fiber

Abstract: An intrusion-alarmed optical fiber communication system, where light from two or more sources are launched with a planar channel waveguide launcher into two or more modes of a multimode graded-index transmission fiber, is disclosed. Input fibers containing the source light waves and the output fibers are in direct contact with the waveguide channels. Waveguide channels redistribute the light from input channels to output channels by rerouting, crossing, merging, or splitting channels. Waveguide launcher precisely launches data light into the fundamental mode and intrusion monitor light into high order modes of a multimode graded-index fiber. Fiber intrusion attenuates light in high order modes, but much less of the data in the fundamental mode, thereby forming a basis for the intrusion-alarmed system. Waveguide launcher permits light from a plurality of sources to be launched selectively into several types of fibers: singlemode fibers, multimode fibers, multicore fibers, multimode fibers having high refractive-index ring profile within the fiber core boundary. Waveguide channel configuration permit other versatile functions to be performed; these include optical time domain reflectometry, channel feedback stabilization of the diodes, launching light from more than one light source into the fundamental mode of a multimode graded-index fiber, and other functions. Means for launching and propagating the fundamental mode in multimode graded-index fiber in order to increase bandwidth capacity of said fiber are disclosed. Optical-electronic intrusion-alarmed systems with synchronous phase sensitive detection of intrusion are described, including reference recovery means. In order to decrease false alarm rates, information on transmitter light source variations are transmitted to the receiver via digital bit stream. A precise fiber optic sensor system based on the waveguide launcher is disclosed.

Method of building up an optical fiber preform by plasma deposition, and an optical fiber obtained from the preform built up by the method

Abstract: A method of using a plasma to build up an optical fiber preform consists in injecting hydroxyl ions in a controlled manner into the build-up silica that is deposited on the preform. The invention is applicable to the manufacture of optical fibers, in particular monomode fibers.

Single-frequency fiber Fabry-Perot micro lasers

Abstract: Compact, fixed-wavelength and tunable fiber optic lasers combine a sub-millimeter length of high-gain rare-earth-doped, sensitized glass fiber within a fiber Fabry-Perot (FFP) cavity. Tunable, single-frequency fiber lasers at 1535 nm employing high-gain erbium:ytterbium phosphate glass fiber are specifically provided. Single-frequency and/or single-polarization mode erbium:ytterbium glass fiber lasers, having cavity lengths less than about 200 μm with continuous wavelength tuning range over several nanometers are provided. Amplified single-frequency lasers incorporating fiber rare-earth ion optical amplifiers are also provided. Single-frequency lasing employing sub-millimeter lengths of rare-earth doped sensitized fiber in a 3 mirror laser design is also demonstrated.

High power semiconductor laser system

Abstract: A high power optical system (10) includes an array of a plurality of semiconductor laser diodes (14) each having a light emitting surface. A plurality of optical fibers (22), each has one end adjacent the light emitting surface of a separate one of the semiconductor laser diodes. A cylindrical lens (32) extends transversely across the one end of each of the optical fibers to direct the light beam from the semiconductor laser diode into the optical fiber. The other ends of the optical fibers are bundled together so as to effectively emit a single beam of a power equal to the combined beams from each of the optical fibers. A delivery optical fiber (30) has an end adjacent the bundled ends of the optical fibers. A lens system (26, 28), which is between the bondled ends of the optical fibers and the delivery optical fiber, directs the large beam of light emitted from the bundled ends of the optical fibers into the delivery optical fiber. Each of the optical fibers has a numerical aperture less than the numerical aperture of the delivery optical fiber, and preferably a numerical aperture of between about 0.12 and 0.14.

Light scattering with single-mode fiber collimators

Abstract: The recent development and availability of fiber-optic components including graded-index (GRIN) microlenses and the unique optical properties of single-mode optical fibers make it possible to build ideal detector systems for light-scattering measurements. We show that the simple coupling of a 0.25-pitch GRIN lens and a single-mode optical fiber to form a collimator makes a nonimaging detector system with properties that are superior to conventional setups based on pinholes and that approaches the theoretical limit of a perfectly coherent detector.

Thermal-stress-induced birefringence in bow-tie optical fibers.

Abstract: Birefringence induced by thermal stress in bow-tie optical fibers is studied in detail by the use of the finite-element method. Results of computer modeling show that a higher degree of birefringence can be obtained with the use of a larger cladding and larger stress-applying zones in the fiber.

Achromatic overclad fiber optic coupler

Abstract: An achromatic fiber optic coupler of the type wherein a plurality of single-mode optical fibers, each having a core and a cladding, are fused together along a portion of the lengths thereof to form a coupling region. The propagation constants of the fibers are preferably equal; however if the fiber claddings have different refractive indices, the lowest cladding refractive index is n 2 . A matrix glass body of refractive index n 3 surrounds the coupling region, n 3 being lower than n 2 by such an amount that the value of Δ 2-3 is less than 0.125%, wherein Δ 2-3 equals (n 2 2- n 3 2 )2n 2 2 .

Polarized wave holding optical fiber, production method therefor, connection method therefor, optical amplifier, laser oscillator and polarized wave holding optical fiber coupler

Abstract: A polarized wave holding optical fiber (10) of the present invention includes a plurality of core portions (12a, 12b) in a high refractive index region that are juxtaposed in a radial direction of an optical fiber, and three core portions (12a, 12b) integrally propagate one fundamental mode A method of producing a polarized wave holding optical fiber according to the present invention comprises forming a plurality of holes (22) in parallel with one another on a diameter of a glass rod (21) having a low refractive index as a clad, inserting glass rods (23) having a high refractive index as core portions into these holes (22), heating and integrating them together to form a base material, and melt-spinning the base material A polarized wave holding optical fiber containing a rare earth element according to the present invention is formed by adding a rare earth element to a waveguide portion of the polarized wave holding optical fiber, and an optical amplifier and a laser oscillator utilize this polarized wave holding optical fiber A polarized wave holding optical fiber coupler according to the present invention connects at least two polarized wave holding optical fibers, and heats, fuses and stretches them The connection method comprises heating portions near the coupling point before and after connection

Compound fiber ring resonator: theory

Abstract: A compound fiber ring resonator is made with a Fabry–Perot etalon built inside a fiber ring that is fed through a 2 × 2 directional single-mode fiber coupler. It is theoretically analyzed by an unfolded equivalent model and a transfer-matrix method. The output intensities are presented, and four cases are discussed. The results may be useful in applications such as fiber spectrum analyzers, sensors, and lasers.

Large core fiber optic cleaver

Abstract: The present invention relates to a device and method for cleaving optical fibers which yields cleaved optical fiber ends possessing high damage threshold surfaces. The device can be used to cleave optical fibers with core diameters greater than 400 μm.

Fiber Bragg grating high-magnetic-field probe

Abstract: We describe a novel fiber probe for monitoring a.c. high magnetic fields which is based on detecting the shift in the Bragg condition of a fiber Bragg grating due to magnetically induced circular birefringence. The technique should be usable over a wide range for fields above 1 Gauss.

Optical fiber interconnections using self-aligned core-extensions

Abstract: An optical fiber interconnecting structure connects an optical fiber (5) to an optical channel waveguide (1), in which a channel waveguide (1) is extended collinearly by a hollow channel (2) with sectional area and shape substantially identical to those for the channel waveguide (1). An optical fiber (5) is laid collinearly with the channel (1), and a core-extension (6) is formed at the end facet of the optical fiber (5) to form a gradual and smooth optical transition to the channel waveguide (1). The channel waveguide may be tapered out to have a substantially larger sectional area at the far end so as to ease the optical interconnection.

Fiber optic Bragg grating array for shape and vibration mode sensing

Abstract: Fiber Bragg gratings are of particular interest for distributed sensor applications such as embedded sensors for structural strain monitoring. This paper discusses the use of a wavelength division multiplexed fiber Bragg grating array for structural shape sensing and vibrational mode analysis. The gratings are surface attached to a cantilever beam and demodulated by a scanning fiber Fabry Perot filter to obtain strain information at different locations along the structure. A PC is used to read the strain information and perform static shape modeling of the beam.

Selective multi-chemical fiber optic sensor

Abstract: A fiber optic sensor for detecting at least one chemical by evanescent wave spectroscopy comprises a generator of a light signal, a mirror for introducing the light signal into a fiber, a clad optical chalcogenide glass fiber, a mirror for directing the light signal from the fiber into a detector, and a detector for detecting chemicals by the fiber. The fiber comprises a core and a clad having lower refractive index than the core enveloping and being in continuous contact with the core, at least one region on the fiber completely or partially devoid of the clad, and a polymer disposed in the region having affinity for the chemical(s). There being a different polymer in each region if there is more than one region.

Observation of mode selection in a radially anisotropic cylindrical waveguide with liquid‐crystal cladding

Abstract: Observation of mode selection in an optical fiber with nematic liquid‐crystal cladding is reported. The TE01 mode is guided, while the TM01 mode leaks out. This behavior is achieved by radially oriented liquid‐crystal directors in the cladding of an optical fiber with isotropic core. A theory which quantitatively accounts for the results is given.

Precision fabrication of D-shaped single-mode optical fibers by in situ monitoring

Abstract: A technique has been developed to locally remove, over a distance of several millimeters of fiber length, the cladding layer of single-mode (at the 1300 nm wavelength) optical fibers with 1 /spl mu/m depth precision by use of mechanical lapping and in situ optical transmission monitoring. A cylinder lap dressed with diamond is used to perform high-pressure mechanical lapping. The in situ monitoring technique is based on the specific different attenuations exhibited by higher order propagating modes (for 633 nm light) as the cylinder penetrates into the fiber. Advantages include relatively rapid overall processing, high lapping rate, good optical surface quality, and 1 /spl mu/m precision. Experimental results are presented and analyzed by an approximate geometrical-optics model. >