Showing papers on "Dispersion-shifted fiber published in 1993"

Multiplexed fiber Bragg grating strain-sensor system with a fiber Fabry–Perot wavelength filter

Abstract: The use of a fiber Fabry–Perot filter for detecting the wavelength shift of a fiber Bragg grating sensor or network of sensor elements along a commonfiber path is described. Results obtained by using a system with four sensor elements are presented.

Compensation of chromatic dispersion in a single-mode fiber by optical phase conjugation

Abstract: The effective compensation of waveform distortion due to chromatic dispersion in a single-mode fiber was demonstrated using an optical phase-conjugate wave generated by nondegenerate forward four-wave mixing in a zero-dispersion single-mode fiber. After transmission of 5- and 6-Gb/s continuous-phase FSK (CPFSK) signal through a dispersive single-mode fiber, distortion compensation was confirmed by measuring bit error rate characteristics and observing heterodyne-detected eye-patterns. >

Suppression of fiber nonlinearities by appropriate dispersion management

Abstract: A specific fiber dispersion management is proposed allowing the simultaneous suppression of linear dispersion penalties and of degradations arising from parametrical fiber nonlinearities. For the proposed dual dispersion configuration (DDCON) the number of optical channels that can be transmitted over 1000 km at a bit rate of 2.5 Gb/s is only limited by the available optical amplifier bandwidth. >

Stimulated Brillouin scattering suppression by means of applying strain distribution to fiber with cabling

Abstract: An optical fiber cable that can suppress stimulated Brillouin scattering (SBS) has been developed. Fiber cabling expanded the Brillouin gain bandwidth from 50 MHz to 400 MHz (9 dB). The expansion was caused by a sinusoidal fiber strain distribution of +or-0.35%, which was generated in fiber by a strainholding, double-stranded cable. This work explains the relationship between the cable structure and fiber strain, as well as with the Brillouin gain bandwidth expansion. Fiber loss caused by cabling was studied and found to be small; also, the strained fiber reliability of the cable is assured with the use of carbon-coated fiber. >

Effects of concentration and clusters in erbium-doped fiber lasers.

Abstract: We report a low-threshold, high-conversion-efficiency erbium-doped fiber laser in a 100-parts-in-106 fiber pumped at 1.48 μm. The threshold and efficiency are found to deteriorate noticeably as the erbium concentration is increased. We propose that this is due mostly to rapid cross relaxation between ion pairs or clusters, and through modeling we show that the cluster content increases with concentration.

In-line fiber étalon for strain measurement

Abstract: A description and demonstration of a fiber interferometer that uses a short segment of silica hollow-core fiber spliced between two sections of single-mode fiber to form a mechanically robust in-line cavity are presented. The hollow-core fiber is specifically manufactured to have an outer diameter that is equal to the outer diameter of the single-mode lead fibers, thereby combining the best qualities of existing intrinsic and extrinsic Fabry–Perot sensors. A dynamic strain resolution of ∼22n∊/Hz at frequencies of >5 Hz with a sensor gauge length of 137 μm is demonstrated.

Single-excimer-pulse writing of fiber gratings by use of a zero-order nulled phase mask: grating spectral response and visualization of index perturbations

Abstract: Optical fiber Bragg reflectors have been written by irradiating the fiber from the side through a phase mask with a single pulse of high-power 249-nm excimer-laser light. Efficient tapping of light to the radiation modes has been achieved for light at wavelengths shorter than the Bragg wavelength. The photoinduced periodic refractive-index perturbations have been observed directly with an optical microscope and are shown to have the same period as the phase mask and to be highly localized on one side, the irradiated side of the fiber core–cladding boundary.

A fiber chromatic dispersion compensation technique with an optical SSB transmission in optical homodyne detection systems

Abstract: A fiber chromatic dispersion compensation technique with optical single-sideband (SSB) transmission in optical homodyne detection systems is described. The chromatic dispersion compensation technique is demonstrated in a 6-Gb/s SSB phase-shift-keying (PSK) homodyne detection system equivalent experiment. A 270-km conventional single-mode fiber is used as a transmission medium at 1.55 mu m, and a microstrip line is used as a delay equalizer. The effect of compensating for the chromatic dispersion with the microstrip line is verified by improvement of eye-opening. >

8*10 Gb/s transmission through 280 km of dispersion-managed fiber

Abstract: Eight WDM channels each operating at 10 Gb/s were transmitted through 280 km of dispersion-shifted fiber concatenated with small amounts of conventional fiber. No degradations from optical nonlinearities were observed. >

Efficient diode-pumped single-frequency erbium:ytterbium fiber laser

Abstract: We report a 7.6-mW single-frequency fiber laser operating at 1545 nm, using for the first time an Er/sup 3+/:Yb/sup 3+/ doped fiber and a fiber grating output coupler. The laser did not exhibit self-pulsation, which is a typical problem in short three-level fiber lasers, and had a relative intensity noise (RIN) level below -145.5 dB/Hz at frequencies above 10 MHz. The linewidth of the laser was limited by the relaxation oscillation sidebands in the optical spectrum and was typically less than 1 MHz. >

Dispersion-compensating single-mode fibers: efficient designs for first- and second-order compensation.

Abstract: Single-mode dispersion compensating fiber designs with absolute dispersion values of greater than 100 ps/(nm km) are described. A multiclad fiber with a triangular refractive-index profile in the core gives a dispersion of −250 ps/(nm km), resulting in a 15:1 compensation scheme. All fiber designs use only the fundamental LP01 mode for dispersion compensation and can account for first- and second-order dispersion effects.

Compensation of pulse shape distortion due to chromatic dispersion and Kerr effect by optical phase conjugation

Abstract: Pulse shape distortion due to chromatic dispersion and self-phase modulation in a single-mode fiber was effectively compensated for by using an optical phase-conjugate wave generated by nondegenerate forward four-wave mixing in a zero-dispersion single-mode fiber. Using optical phase conjugation at the midpoint of a 100-km standard single-mode fiber compensates for the distortion of 10-Gb/s intensity-modulated NRZ pulse at an input power level exceeding +10 dBm with a resultant power penalty of less than 1.2 dB. >

Laser-diode-driven ultrafast all-optical switching by using highly nonlinear chalcogenide glass fiber

Abstract: Laser-diode-driven all-optical switching is demonstrated with an As2S3-based glass fiber only 2 m long and assistance from an erbium-doped fiber amplifier. The laser-diode operation makes it easy to control ultrafast pulse trains with low timing jitter. Ultrafast switching at as much as 80-GHz repetition rates is successfully demonstrated. The nonlinear refractive index of the fiber is estimated to be 9.3 × 10−15 (cm2/W) at a 1.55-μm wavelength.

Enhanced self-phase modulation in tapered fibers

Abstract: Fiber tapering reduces the effective area and increases the Kerr nonlinear phase shift of the fundamental mode. A significant nonlinear effect was observed in a micrometer-diameter centimeter-long section of tapered fiber at a wavelength of 1550 nm. The numerical simulation of a second-order soliton entering the taper gives a spectral widening that matches the observed spectrum.

10-Gb/s 360-km transmission over dispersive fiber using midsystem spectral inversion

Abstract: The use of multi-gigabit per second transmission speeds over the world's embedded fiber plant (normal dispersion fiber) is severely limited by the chromatic dispersion in systems operating at wavelengths within the gain bandwidth of erbium-doped fiber amplifiers. A dispersion-compensation technique utilizing a midsystem spectral inversion was used to overcome this limit, resulting in 1.55- mu m 10-Gb/s transmission through 360 km of normal-dispersion fiber. >

Interrogation and multiplexing techniques for fiber Bragg grating strain sensors

Abstract: Techniques for the detection of wavelength shifts of fiber Bragg grating sensors based on the use of a tunable bandpass filter, interferometric detection, and active laser configurations are described. The methods used to multiplex several sensors along a single fiber using these approaches are also discussed, and results presented.

Nonlinear wave mixing and induced gratings in erbium-doped fiber amplifiers.

Abstract: We present a study of nonlinear wave mixing in erbium-doped fiber amplifiers. Wave mixing is demonstrated in dynamic gain gratings induced by counterpropagating beams from a diode laser.

An optical communications system for transmitting information signals having different wavelengths over a same optical fiber

Abstract: An optical communications system provides optical signals of different wavelengths over an optical fiber (1, 2) having a zero dispersion wavelength. Electrical dispersion compensating elements (36-39) independently compensate optical signals having wavelengths different than the zero dispersion wavelength for dispersion in the optical fiber. Limiting radio frequency signals for modulating a light emitting device or laser (21-24) outputting signals at a wavelength different than the zero dispersion wavelength to less than one octave of frequency permits second order harmonic distortion resulting from dispersion in the fiber to be filtered at a receiving location. The optical communications system may include a reverse transmission path.

Polymer optical fiber amplifier

Abstract: Polymer optical fiber· amplifiers (POPA) of graded-index (GI) type were successfully prepared for the first time. The gain of 27 dB was observed at 591 ran signal wavelength in the GI POFA with a 0.5 m length.

Coupled-cavity erbium fiber lasers incorporating fiber grating reflectors.

Abstract: Narrow-linewidth erbium-doped fiber lasers of monolithic multiple linear cavity configurations that use intracore fiber grating reflectors are demonstrated. Robust single-frequency operation of a miniature coupled-cavity fiber laser with a linewidth of 30 kHz is reported. A novel multiple-cavity erbium fiber laser with simultaneous dual single-frequency lasing is also demonstrated. A 16-kHz linewidth and a frequency separation of 59 GHz with a stability of better than 3 MHz were achieved in this dual-frequency laser.

System for optically transmitting digital communications over an optical fiber with dispersion at the operating wavelength

Abstract: When digital signals are transmitted over optical fibers (3), which have a considerable chromatic dispersion at the wavelength being used, the length of the transmission path is very limited when the digital signal to be transmitted is converted into an optical signal by means of intensity modulation. If frequency modulation (also called FSK = Frequency Shift Keying) is used instead of the intensity modulation, the bridgeable path can be greatly increased, but requires a suitable optical receiver at the receiving end. The invention utilizes a simple optical receiver (4), which is not sensitive to frequency modulation, but to intensity modulation. This is possible, because an intensity variation is created, due to the chromatic dispersion of the optical fiber (3) and the resulting running time differences of signal portions at different wavelengths (.lambda.0, .lambda.1) from the initial frequency modulation during the transmission over the optical fiber (3), which process is contained in the digital signal.

Multiple channel optical coupling switch

Abstract: An optical coupling device for coupling light into a selected output fiber. The input fiber is optically aligned with one of a plurality of output fibers via a reflector. By rotating a reflector about an axis, the input light beam can be reflected to a selected output fiber. The input fiber and all the output fibers are in fixed position relative to each other.

Elliptical-core dual-mode fiber dispersion compensator

Abstract: Chromatic dispersion compensation is demonstrated in a 2.5-Gb/s system experiment using an elliptical-core dual-mode fiber operated in the LP/sub 11/ mode near cutoff. With a measured dispersion of -548 ps/nm-km for the LP/sub 11/ mode and a novel double-pass configuration, complete compensation of the dispersion in 50 km of conventional single-mode fiber at 1530 nm is achieved with 0.72 km of dual-mode fiber. System degradation due to remnant LP/sub 01/ mode power in the dual-mode fiber is investigated and found to be small for relative LP/sub 01/ power levels less than -20 dB. >

Technique to prepare high-reflectance optical fiber bragg gratings with single exposure in-line or fiber draw tower

Abstract: A process for making an optical reflection grating in a glass fiber includes exposing an unjacketed optic fiber to a single writing pulse from a pair of interfering light beams that form an interference pattern in the fiber. A novel optical fiber has at least one optical grating with a preselected Bragg spacing in at least one region of the fiber, with a periodic modulation in its index of refraction, with high thermal stability and narrow linewidth. A process for making an array of optical reflection gratings in a glass fiber includes exposing a fiber to a plurality of writing pulse from a pair of interfering light beams that form an interference pattern in the fiber, where these pulses are applied sequentially as the fiber is drawn from a draw furnace. A novel optical fiber has a plurality of unspliced gratings with high thermal stability and narrow linewidth.

High-power Q-switched erbium fiber laser using an all-fiber intensity modulator

Abstract: The authors report on the demonstration of a Q-switched erbium-doped fiber laser using a novel all-fiber intensity modulator acting as an efficient intracavity switching element. Switching speed and holdoff losses are compatible with the Q-switching dynamics of rare-earth-doped fiber lasers. The modulator is completely integrated in a spliceless erbium-doped fiber cavity. Pulses of less than 15 ns full width at half maximum (FWHM) and peak power close to 400 W were obtained for a launched pumping power of 100 mW at 980 nm. This compact source could find many uses in applications such as nonlinear optics, laser ranging and remote sensing, eyesafe free-space communication, time-gated fiber sensor systems, and long-distance optical time-domain reflectometry.

Optical fiber tree and branch network for AM signal distribution

Abstract: The use of a doped optical fiber amplifier enables the transmission of multi-channel AM-VSB television signals. An Erbium doped fiber amplifier is disclosed. The amplifier is also useful for reducing second order distortion products produced in an amplitude modulated subcarrier optical communication system. The amplifier may be used in a tree and branch structure optical fiber television network.

Lightwave transmission system using selected optical modes

Abstract: The capacity of a multi-mode optical fiber system, such as a local area network, is increased by selectively propagating only higher-order modes through the multi-mode fiber. Because only a small number of higher-order modes are propagated, pulse spreading induced by modal dispersion is minimized, and the bandwidth of the multi-mode fiber is increased. Because of the reduced modal dispersion, higher-order modes are recovered from the multi-mode fiber in accordance with the invention without filtering the output of the fiber. This renders the system less vulnerable to mechanical perturbations that are known to reduce the bit error rate of systems requiring filtering. Thus, by propagating only higher-order modes in this manner, the "bandwidth-distance" product of the multi-mode fiber is significantly increased.

Simultaneous compensation of laser chirp, Kerr effect, and dispersion in 10-Gb/s long-haul transmission systems

Abstract: The effects of chirp and fiber nonlinearity in a directly modulated 10-Gb/s intensity-modulated direct-detection (IM-DD) fiber transmission system are investigated by simulation, and a simple and flexible technique for compensating these effects is discussed. Self-phase-modulation (SPM) in optical fiber can be equalized by an anomalous dispersion fiber, whereas pulse broadening caused by laser transient chirp can be compensated by normal dispersion. Using these characteristics, laser transient chirp, SPM, and fiber dispersion can be simultaneously compensated by equalizing fibers inserted within certain intervals. Optimum compensation is always realizable for such fixed equalizing fibers, since the magnitude of SPM can be controlled by changing the optical power in the fiber. Simulation suggests that this technique enables 10-Gb/s, 100-km fiber transmission by direct modulation. >