Showing papers on "Optical fiber published in 2005"

Tunable all-optical delays via Brillouin slow light in an optical fiber.

Abstract: We demonstrate a technique for generating tunable all-optical delays in room temperature single-mode optical fibers at telecommunication wavelengths using the stimulated Brillouin scattering process. This technique makes use of the rapid variation of the refractive index that occurs in the vicinity of the Brillouin gain feature. The wavelength at which the induced delay occurs is broadly tunable by controlling the wavelength of the laser pumping the process, and the magnitude of the delay can be tuned continuously by as much as 25 ns by adjusting the intensity of the pump field. The technique can be applied to pulses as short as 15 ns. This scheme represents an important first step towards implementing slow-light techniques for various applications including buffering in telecommunication systems.

Fiber-optic fluorescence imaging.

Abstract: Optical fibers guide light between separate locations and enable new types of fluorescence imaging. Fiber-optic fluorescence imaging systems include portable handheld microscopes, flexible endoscopes well suited for imaging within hollow tissue cavities and microendoscopes that allow minimally invasive high-resolution imaging deep within tissue. A challenge in the creation of such devices is the design and integration of miniaturized optical and mechanical components. Until recently, fiber-based fluorescence imaging was mainly limited to epifluorescence and scanning confocal modalities. Two new classes of photonic crystal fiber facilitate ultrashort pulse delivery for fiber-optic two-photon fluorescence imaging. An upcoming generation of fluorescence imaging devices will be based on microfabricated device components.

Distributed fiber-optic intrusion sensor system

Abstract: A distributed sensor system for detecting and locating intruders based on the phase-sensitive optical-time-domain reflectometer (/spl phi/-OTDR) is described. The sensing element is a cabled single-mode telecommunications fiber buried along the monitored perimeter. Light pulses from a continuous-wave Er:fiber Fabry-Pe/spl acute/rot laser with a narrow (/spl ap/3 kHz) instantaneous linewidth and low (few kilohertz per second) frequency drift are injected into one end of the fiber, and the backscattered light is monitored with a photodetector. The effect of phase changes resulting from the pressure of the intruder on the ground immediately above the buried fiber are sensed by subtracting a /spl phi/-OTDR trace from an earlier stored trace. In laboratory tests with fiber on reels, the effects of localized phase perturbations induced by a piezoelectric fiber stretcher on /spl phi/-OTDR traces were observed. In field tests, people walking on the ground above a buried fiber cable induced phase shifts of several-/spl pi/ radians.

Highly sensitive fiber Bragg grating refractive index sensors

Abstract: We combine fiber Bragg grating (FBG) technology with a wet chemical etch-erosion procedure and demonstrate two types of refractive index sensors using single-mode optical fibers. The first index sensor device is an etch-eroded single FBG with a radius of 3 μm, which is used to measure the indices of four different liquids. The second index sensor device is an etch-eroded fiber Fabry-Perot interferometer (FFPI) with a radius of ~1.5 μm and is used to measure the refractive indices of isopropyl alcohol solutions of different concentrations. Due to its narrower resonance spectral feature, the FFPI sensor has a higher sensitivity than the FBG sensor and can detect an index variation of 1.4 X 10(-5). Since we can measure the reflection signal, these two types of sensors can be fabricated at the end of a fiber and used as point sensors.

Observation of pulse delaying and advancement in optical fibers using stimulated Brillouin scattering

Abstract: We demonstrate experimentally that it is possible to control optically the group velocity of an optical pulse as it travels along an optical fiber. To achieve this control we use the effect of Stimulated Brillouin Scattering. In our experiments we have achieved changes in the group index of 10-3 in several kilometer-length fibers, thus leading to pulse delaying and advancement in the range of tens of nanoseconds. We believe that this is the first evidence of such optically-controlled strong delay changes in optical fibers. In this paper we derive the basic theory behind these group-delay changes and we demonstrate the effect in two kinds of fibers which are conventionally used.

Compact, stable and efficient all-fibre gas cells using hollow-core photonic crystal fibres

Abstract: Gas-phase materials are used in a variety of laser-based applications--for example, in high-precision frequency measurement, quantum optics and nonlinear optics Their full potential has however not been realized because of the lack of a suitable technology for creating gas cells that can guide light over long lengths in a single transverse mode while still offering a high level of integration in a practical and compact set-up or device As a result, solid-phase materials are still often favoured, even when their performance compares unfavourably with gas-phase systems Here we report the development of all-fibre gas cells that meet these challenges Our structures are based on gas-filled hollow-core photonic crystal fibres, in which we have recently demonstrated substantially enhanced stimulated Raman scattering, and which exhibit high performance, excellent long-term pressure stability and ease of use To illustrate the practical potential of these structures, we report two different devices: a hydrogen-filled cell for efficient generation of rotational Raman scattering using only quasi-continuous-wave laser pulses; and acetylene-filled cells, which we use for absolute frequency-locking of diode lasers with very high signal-to-noise ratios The stable performance of these compact gas-phase devices could permit, for example, gas-phase laser devices incorporated in a 'credit card' or even in a laser pointer

Nonlinear response of silicon photonic crystal microresonators excited via an integrated waveguide and fiber taper

Abstract: A technique is demonstrated which efficiently transfers light between a tapered standard single-mode optical fiber and a high-Q, ultra-small mode volume, silicon photonic crystal resonant cavity. Cavity mode quality factors of 4.7×104 are measured, and a total fiber-to-cavity coupling efficiency of 44% is demonstrated. Using this efficient cavity input and output channel, the steady-state nonlinear absorption and dispersion of the photonic crystal cavity is studied. Optical bistability is observed for fiber input powers as low as 250 µW, corresponding to a dropped power of 100 µW and 3 fJ of stored cavity energy. A high-density effective free-carrier lifetime for these silicon photonic crystal resonators of ~ 0.5 ns is also estimated from power dependent loss and dispersion measurements.

Optical-Fiber Source of Polarization-Entangled Photons in the 1550 nm Telecom Band

Abstract: We present a fiber-based source of polarization-entangled photons that is well suited for quantum communication applications in the 1550 nm band of standard fiber-optic telecommunications. Polarization entanglement is created by pumping a nonlinear-fiber Sagnac interferometer with two time-delayed orthogonally polarized pump pulses and subsequently removing the time distinguishability by passing the parametrically scattered signal and idler photon pairs through a piece of birefringent fiber. Coincidence detection of the signal and idler photons yields biphoton interference with visibility greater than 90%, while no interference is observed in direct detection of either signal or idler photons. All four Bell states can be prepared with our setup and we demonstrate violations of the Clauser-Horne-Shimony-Holt form of Bell's inequality by up to 10 standard deviations of measurement uncertainty.

Experimental observation of temporal soliton molecules.

Abstract: A bound state of temporal solitons in optical fibers is predicted numerically and demonstrated experimentally. It is appropriately described as a pair of bright solitons, bound together by a dark soliton. This structure exists only in dispersion-managed fiber and is different from bound solitons in fiber lasers.

High-Power Thulium Fiber Laser Ablation of Urinary Tissues at 1.94 µm

Abstract: Purpose: This paper describes the preliminary testing of a new laser, the thulium fiber laser, as a potential replacement for the holmium:YAG laser for multiple applications in urology Materials and Methods: A 40 W thulium fiber laser operating at a wavelength of 194 µm delivered radiation in a continuous-wave or pulsed mode (10 msec) through either 300-µm- or 600-µm-core low-OH silica fibers for vaporization of canine prostate and incision of animal ureter and bladder-neck tissues Results: The thulium fiber laser vaporized prostate tissue at a rate of 021 ± 002 g/min The thermal-coagulation zone measured 500 to 2000 µm, demonstrating the potential for hemostasis Laser incisions were also made in bladder tissue and ureter, with coagulation zones of 400 to 600 µm Conclusions: The thulium fiber laser has several potential advantages over the holmium laser, including smaller size, more efficient operation, more precise incision of tissues, and operation in either the pulsed or the continuous-wave mod

Wide bandwidth slow light using a Raman fiber amplifier

Abstract: We demonstrate an all-optical tunable pulse delay scheme that utilizes the power-dependent variation of the refractive index that accompanies stimulated Raman scattering in an optical fiber. Using this technique, we delay 430-fs pulses by up to 85% of a pulse width. The ability to accommodate the bandwidth of pulses shorter than 1 ps in a fiber-based system makes this technique potentially viable for producing controllable delays in ultra-high bandwidth telecommunication systems.

Evanescent field-based optical fiber sensing device for measuring the refractive index of liquids in microfluidic channels

Abstract: We report a simple optical sensing device capable of measuring the refractive index of liquids propagating in microfluidic channels. The sensor is based on a single-mode optical fiber that is tapered to submicrometer dimensions and immersed in a transparent curable soft polymer. A channel for liquid analyte is created in the immediate vicinity of the taper waist. Light propagating through the tapered section of the fiber extends into the channel, making the optical loss in the system sensitive to the refractive-index difference between the polymer and the liquid. The fabrication process and testing of the prototype sensing devices are described. The sensor can operate both as a highly responsive on–off device and in the continuous measurement mode, with an estimated accuracy of refractive-index measurement of ?5×10?4.

Multistability and hysteresis phenomena in passively mode-locked fiber lasers

Abstract: A passively mode-locked fiber laser is theoretically investigated. The mode locking is achieved using the nonlinear polarization technique. We consider the practical case of the ytterbium-doped fiber laser operating in the normal dispersion regime. The effect of the phase plates is explicitly taken into account. The resulting model reduces to one iterative equation for the optical Kerr nonlinearity, the phase plates and the polarizer, and one partial differential equation for the gain and the dispersion. Numerical simulations allow us to describe several features observed in passively mode-locked fiber lasers such as bistability between the mode lock and the continuous regime, multiple pulse behavior, hysteresis phenomena. The dynamics of the number of pulses as a function of the pumping power is also reported. Pump power hysteresis is demonstrated.

Raman amplification in fiber optical communication systems

Abstract: Introduction Stimulated Raman Scattering in Optical Fibers Raman Pumping in Optical Fiber Communications Distributed Raman amplification along the transmission span Discrete Raman amplifiers Impairments and Limitations to Raman Amplification.

Tunable all optical delay via slow and fast light propagation in a Raman assisted fiber optical parametric amplifier: a route to all optical buffering.

Abstract: We propose and demonstrate the use of narrow band optical parametric amplification for tunable slow and fast light propagation in optical fibers. The parametric gain is coupled to the Raman process which changes the gain value moderately but modifies the gain spectral shape. Consequently, the delay is enhanced at short wavelengths while it is moderated at long wavelengths. The maximum delay and tuning range can be optimized with respect to each other considering saturation effects in long fibers. The proposed scheme offers tunable delay in the presence of gain and with a bandwidth which is sufficiently wide to process digital data streams at tens of Gbit/s rates as well as picoseconds pulses.

High-power rod-type photonic crystal fiber laser.

Abstract: We report on a novel ytterbium-doped fiber design that combines the advantages of rod and fiber gain media. The fiber design has outer dimensions of a rod laser, meaning a diameter in the range of a few millimeters and a length of just a few tens of centimeters, and includes two important waveguide structures, one for pump radiation and one for laser radiation. We obtained 120-W output power in single-mode beam quality from a 48-cm-long fiber cane that corresponds to an extracted power of 250 W/m. The fiber has significantly reduced nonlinearity, which therefore allows for scalability in the performance of a high-peak-power fiber laser and amplifier system.

Optical fiber scanner for performing multimodal optical imaging

Abstract: An optical fiber scanner is used for multiphoton excitation imaging, optical coherence tomography, or for confocal imaging in which transverse scans are carried out at a plurality of successively different depths within tissue The optical fiber scanner is implemented as a scanning endoscope using a cantilevered optical fiber that is driven into resonance or near resonance by an actuator The actuator is energized with drive signals that cause the optical fiber to scan in a desired pattern at successively different depths as the depth of the focal point is changed Various techniques can be employed for depth focus tracking at a rate that is much slower than the transverse scanning carried out by the vibrating optical fiber The optical fiber scanner can be used for confocal imaging, multiphoton fluorescence imaging, nonlinear harmonic generation imaging, or in an OCT system that includes a phase or frequency modulator and delay line

Assembly of silica nanowires on silica aerogels for microphotonic devices

Abstract: We report on the assembly of low-loss silica nanowires into functional microphotonics devices on a low-index nondissipative silica aerogel substrate. Using this all-silica technique, we fabricated linear waveguides, waveguide bends, and branch couplers. The devices are significantly smaller than existing comparable devices and have low optical loss, indicating that the all-silica technique presented here has great potential for future applications in optical communication, optical sensing, and high-density optical integration.

Erbium in silicon

Abstract: The overlap of the principal luminescence band of the erbium ion with the low-loss optical transmission window of silica optical fibres, along with the drive for integration of photonics and silicon technology, has generated intense interest in doping silicon with erbium to produce a silicon-based optical source Silicon is a poor photonic material due to its very short non-radiative lifetime and indirect band gap, but it has been hoped that the incorporation of optically active erbium ions into silicon will permit the development of silicon-based light sources that will interface with both CMOS technology and optical fibre communications Some years into this activity, there have now been a wide range of experimental studies of material growth techniques, optical, physical and electrical properties, along with a considerable body of theoretical work dealing with the site of the erbium ion in silicon, along with activation and deactivation processes This paper reviews the current state of what remains an active field, summarizing results from a range of studies conducted over the last few years, and points to further developments by considering the prospects for successful photonic integration of erbium and silicon

Fiber access terminal

Abstract: A fiber access terminal for mounting to the end of a fiber distribution cable and configured to be extended through a buried conduit. The fiber distribution cable may include a plurality of optical fibers and enters a housing of the terminal through a base. The terminal also includes a plurality of fiber optic connectors or adapters extending through the housing in generally the same direction as the fiber distribution cable for connecting to optical fiber customer drop cables. The terminal includes a cover and the housing defining an interior and the interior includes a cable slack storage arrangement providing bend radius protection for the optical fiber cables within the interior. A method of assembling a fiber access terminal. A fiber access terminal assembly including a pedestal mounting arrangement.

Fast detection of hydrogen with nano fiber tapers coated with ultra thin palladium layers

Abstract: We report a miniature hydrogen sensor that consists of a sub-wavelength diameter tapered optical fiber coated with an ultra thin palladium film. The optical properties of the palladium layer changes when the device is exposed to hydrogen. Consequently, the absorption of the evanescent waves also changes. The sensor was tested in a simple light transmission measurement setup that consisted of a 1550 nm laser diode and a photodetector. Our sensor is much smaller and faster than other optical hydrogen sensors reported so far. The sensor proposed here is suitable for detecting low concentrations of hydrogen at normal conditions.

Optical Waveguide Self-Assembled from Organic Dye Molecules in Solution

Abstract: Fiber-shaped H-aggregates with lengths of up to 300 μm are synthesized by self-assembly of thiacyanine (TC) dye molecules in solution. Photoluminescence (PL) images and spatially resolved PL spectra of the fibers that are transferred onto a glass substrate reveal that the fibers act as single-mode optical waveguides that propagate PL in the range of 520 to 560 nm over 250 μm without any loss.

Photonic crystal fiber source of correlated photon pairs.

Abstract: We generate correlated photon pairs at 839 nm and 1392 nm from a single-mode photonic crystal fiber pumped in the normal dispersion regime. This compact, bright, tunable, single-mode source of pair-photons will have wide application in quantum communications.

Fiber optic drop cables and preconnectorized assemblies having toning portions

Abstract: A preconnectorized outdoor cable streamlines the deployment of optical waveguides into the last mile of an optical network. The preconnectorized outdoor cable includes a cable and at least one plug connector. The plug connector is attached to a first end of the cable, thereby connectorizing at least one optical waveguide. The cable has at least one optical waveguide, at least one tensile element, and a cable jacket. Various cable designs such as figure-eight or flat cables may be used with the plug connector. In preferred embodiments, the plug connector includes a crimp assembly having a crimp housing and a crimp band. The crimp housing has two half-shells being held together by the crimp band for securing the at least one tensile element. When fully assembled, the crimp housing fits into a shroud of the preconnectorized cable. The shroud aides in mating the preconnectorized cable with a complimentary receptacle.

Numerical modeling of photonic crystal fibers

Abstract: Recent progress on numerical modeling methods for photonic crystal fibers (PCFs) such as the effective index approach, basis-function expansion approach, and numerical approach is described. An index-guiding PCF with an array of air holes surrounding the silica core region has special characteristics compared with conventional single-mode fibers (SMFs). Using a full modal vector model, the fundamental characteristics of PCFs such as cutoff wavelength, confinement loss, modal birefringence, and chromatic dispersion are numerically investigated.

Sensitivity evaluation of a multi-layered surface plasmon resonance-based fiber optic sensor: a theoretical study

Abstract: A multi-layered surface plasmon resonance (SPR)-based fiber optic absorption sensor has been studied theoretically. The sensitivity is evaluated for the p-polarized light launched in the fiber using ray approximation. Four-layers configuration is used to excite the surface plasmon wave. The first layer or the medium considered is the core of the fiber. Second and third layers are metallic (silver and gold). The fourth layer or medium is absorbing medium. The effect of the ratio of the thickness of the metallic layers (silver:gold) on the sensitivity of the sensor has been investigated. The sensitivity increases as the silver to gold thickness ratio increases. The gold should be used only to protect silver layer. In addition, the influences of various parameters like numerical aperture (NA), ratio of sensing region length to fiber core diameter, total bimetallic thickness, maximum absorption wavelength, and half maximum width of the sensing medium on the sensitivity of the sensor have been studied. It has been found that the sensitivity is better for the lower off-resonance excitation frequency. Replacing gold by self-assembled monolayers like thiol does not improve sensitivity much. Further, adding ZrO2 as the fourth layer does not improve the sensitivity of the four layers configuration.

Selective detection of antibodies in microstructured polymer optical fibers

Abstract: We demonstrate selective detection of fluorophore labeled antibodies from minute samples probed by a sensor layer of complementary biomolecules immobilized inside the air holes of microstructured Polymer Optical Fiber (mPOF). The fiber core is defined by a ring of 6 air holes and a simple procedure was applied to selectively capture either α-streptavidin or α-CRP antibodies inside these air holes. A sensitive and easy-to-use fluorescence method was used for the optical detection. Our results show that mPOF based biosensors can provide reliable and selective antibody detection in ultra small sample volumes.

Design concept for optical fibers with enhanced SBS threshold

Abstract: We propose a criterion to predict the relative value of the stimulated Brillouin scattering (SBS) threshold in single-mode optical fibers with different refractive index profiles. We confirm our results by several representative measurements. We show that with the proper profile design one can achieve more than 3 dB increase in the SBS threshold compared to the standard single-mode optical fiber.

Fiber-optic rotational device, optical system and method for imaging a sample

Abstract: A device, system and method for transmitting electro-magnetic radiation between at least two separate fibers (as well as for imaging a sample) are provided. For example, a first optical fiber and a second optical fiber may be provided, such that the first and/or second fibers is/are rotatable. At least one first optical arrangement may also be included which communicates with at least one end of the first optical fiber and/or the second optical fiber. Further, at least one second arrangement may be included which is configured to control a position of the optical arrangement to align longitudinal axes of the first and the second optical fibers at least at the ends thereof. In addition, at least one third arrangement can be provided which is adapted to rotate the first and/or second optical fibers at a rate that is greater than 40 revolutions per second. It is also possible to include at least one fourth arrangement which can be adapted for connecting the first optical fiber and/or the second optical fiber to a catheter arrangement, such that the fourth arrangement includes a protector provided at least at one end thereof, and wherein the protector is automatically removed upon a connection of the first and/or second optical fiber to the catheter arrangement via the fourth arrangement.

Fiber-taper seeded long-period grating pair as a highly sensitive refractive-index sensor

Abstract: We report the fabrication and characterization of a highly sensitive refractive-index sensor based on a long-period grating (LPG) pair with a fiber-taper section in between. Two LPGs with /spl sim/3-dB transmissivity form an in-fiber Mach-Zehnder interferometer. A fiber taper is made between the two LPGs to improve and tailor the sensitivity of the sensor. Enhanced sensitivity, which is about five times higher than that of a normal LPG pair, is achieved in the experiment.