Single-mode optical fiber

About: Single-mode optical fiber is a research topic. Over the lifetime, 24205 publications have been published within this topic receiving 347010 citations.

Method and apparatus for performing optical measurements using a fiber optic imaging guidewire, catheter or endoscope

Abstract: An imaging system for performing optical coherence tomography includes an optical radiation source; a reference optical reflector; a first optical path leading to the reference optical reflector; and a second optical path coupled to an endoscopic unit. The endoscopic unit preferably includes an elongated housing defining a bore; a rotatable single mode optical fiber having a proximal end and a distal end positioned within and extending the length of the bore of the elongated housing; and an optical system coupled to the distal end of the rotatable single mode optical fiber, positioned to transmit the optical radiation from the single mode optical fiber to the structure and to transmit reflected optical radiation from the structure to the single mode optical fiber. The system further includes a beam divider dividing the optical radiation from the optical radiation source along the first optical path to the reflector and along the second optical path; and a detector positioned to receive reflected optical radiation from the reflector transmitted along the first optical path and reflected optical radiation transmitted from the structure along the second optical path. The detector generates a signal in response to the reflected optical radiation from the reference reflector and the reflected optical radiation from the structure, and a processor generating an image of the structure in response to the signal from the detector. The system provides both rotational and longitudinal scanning of an image.

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.

Single-mode operation of a coiled multimode fiber amplifier

Abstract: The authors report a new approach to obtain single-transverse-mode operation of a multimode fiber amplifier, in which the gain fiber is coiled to induce significant bend loss for all but the lowest-order mode. They have demonstrated this method by constructing a coiled amplifier using Yb-doped, double-clad fiber with a core diameter of 25 {micro}m and NA of {minus}0.1 (V {approx} 7.4). When operated as an ASE source, the output beam had an M{sup 2} value of 1.09 {+-} 0.09; when seeded at 1,064 nm, the slope efficiency was similar to that of an uncoiled amplifier. This technique does not require exotic fiber designs or increase system complexity and is inexpensive to implement. It will allow scaling of pulsed fiber lasers and amplifiers to significantly higher pulse energies and peak powers and cw fiber sources to higher average powers while maintaining excellent beam quality.

Solitons in optical communications

Abstract: The history of the proposal that solitons be used for optical fiber communications and of the technical developments toward making soliton transmission practical is reviewed. The causes of bit errors in long-distance soliton transmission are presented and the methods for reducing them are described. A perturbation theory suited for soliton analysis is developed. Current status and future prospects of long-distance repeaterless fiber communications are stated.

Curvature loss formula for optical fibers

Abstract: The loss formula for optical fibers with constant radius of curvature of their axes is derived by expressing the field outside of the fiber in terms of a superposition of cylindrical outgoing waves. The expansion coefficients are determined by matching the superposition field to the field of the fiber along a cylindrical surface that is tangential to the outer perimeter of the curved fiber. This method is a direct extension of my derivation of the curvature-loss formula for slab guides.