USA As Represented by Secretary of the Navy

Matthew N McLandrich

Donald J Albares

Richard J Orazi

Stephen A Pappert

A system is described which generates a wavelength stabilized output from a superluminescent diode. The system may be implemented whereby a superluminescent diode injects an optical signal into a conically tapered optical fiber fused to an optical fiber polarization independent wavelength division multiplexing (PINC WDM) coupler. The PINC WDM coupler transforms the optical signal into an optical signal which is wavelength stabilized with respect to temperature.

System for generating a wavelength stabilized output from a superluminescent diode

An optical system and method include a short coherence length edge, emitt LED, a fiber optic coupler probe, and a Michelson interferometer to measure the parameter of thickness of optical devices, such as thin silicon substrate samples and to characterize other parameters of optical waveguide devices such as absolute attenuation, effective refractive index, and changes in these parameters with the application of a modulation voltage or an external disturbance. The measurable thickness range from a few to hundreds of microns with a thickness precision exceeding 0.1 micron for a 10 micron sample. In situ localized measurements of samples in an etching chamber are obtainable to control processing and provide for thickness uniformity. Attenuation measurements for optical waveguides compare the values of interferogram maxima at the values of the reference arm path length to changes corresponding to one and two times the optical path length of the sample. Effective refractive index is determined by counting the number of fringes in the recorded interferogram between successive maxima. Changes in these parameters due to an external disturbance are measured by comparing the interferograms before and after. The sample stays in the system during all measurements which can also indicate the degree of coupling or interaction between simultaneous refractive index and absorption changes.

Method for characterization of optical waveguide devices using partial

The invention provides a method for fabricating a polarization independent narrow channel wavelength division multiplexing fiber optic coupler, comprising the steps of: holding two optical fibers in an abutting longitudinal relation along a predetermined length of the fibers; injecting light energy into one of the fibers; fusing the optical fibers together along the predetermined length to form a fused length of a fiber optic coupler; elongating the fused length of the fusing optical fibers; measuring the light energy output from the ends of the first and second fibers; ceasing the fusing and elongating when the measured light energy output from the ends of the first and second fibers indicates that a predetermined number, N.sub.S, of one-half power transfer cycles have occurred in the coupler, where the N.sub.S th one-half power transfer cycle occurs within a K.pi. phase region of a polarization envelope associated with the coupler, where K is a positive integer.

Polarization independent narrow channel wavelength division multiplexing

An apparatus and method of manufacturing optical couplers of at least two optical fibers make explicit use of computer control to assure automation and reproducibility. The method and apparatus are independent of human operation for the precise and timely control of the coupler fabrication procedure which is necessary for reliable and high yield production. The steps of the method performed by the apparatus call for the exact starting and stopping of the movement of motor driven translation stages at an exact translation speed after at least two juxtaposed optical fibers have had a heating source positioned and toggled at an exact rate relative to the fibers in order to control the temperatures of the fibers. A computer controls the timed removal of the heat source which had raised the temperatures of at least portions of the fibers to the fusion temperature and the timed termination of the fiber elongation translation stages which draw the fibers in the proper proximity for coupling. These and other functions are all controlled independently of an operator by a computer which has been preprogrammed and which has been interfaced to optical power monitoring detectors at outputs of the individual fibers and to a control unit which appropriately actuates the motorized translation stages connected to the heat source and the fibers. The coupling characteristics of the fibers can be specifically adjusted by appropriately monitoring the power outputs of the optical fibers so that the heating and elongation of the fibers are controlled to achieve the desired results.

Automated and computer controlled precision method of fused elongated

An apparatus and method of entering and extracting a discrete wavelength of optical data in a single-mode duplex optical data transmission system relies on a selective evanescent field coupling. A continuous single-mode fiber transmits the two wavelengths in opposite directions with respect to each other. A length of a like single-mode fiber is fused to the continuous single-mode fiber such that the product of the fused length and the coupling coefficient of the fiber pairs equals .pi./2 at one of the optical frequencies to effect one-hundred percent evanescent field coupling to and from the continuous fiber. The product of the coupling coefficient and the fused length equals .pi. at the other optical wavelength to effect a zero percent evanescent field coupling. The other wavelength travels the length of the continuous single-mode fiber uninterrupted while the first wavelength is selectively coupled and decoupled from the fiber as desired.

Method of wavelength multiplexing in fused single-mode fiber couplers

A hydrophone remotely senses impinging acoustic energy. Light output from a laser is split and launched into a single-mode fiber which transmits it to an optical resonator at its end. The resonator is made up of a fixed fiber end having a dielectric coating and a movable mirror which is displaced in response to an incident acoustic signal. The acoustic signal displaces the mirror so that mirror movement modulates the intensity of the reflected beam which is transmitted back through the single-mode fiber and received at a detector. The frequency and magnitude of the reflected beam yield acoustic signal information.

Optical resonator single-mode fiber hydrophone

An improvement for the coupling of optical energy in a single-mode fiber ures a stable bidirectional coupling. A method of fabricating a single-mode evanescent field coupler for optical data between two single-mode fibers calls for there first being an etching away of a substantial portion of the claddings about the cores of both single-mode fibers. This etching calls for the immersion of sections of the fibers in an etching solution for a predetermined time with the ends of the exposed sections being carefully masked to create smooth, unscored, tapered transitions. The etched sections of the single-mode fibers are placed in a side-by-side relationship, are longitudinally twisted about each other to assume a closely abutting helical disposition and are secured in place at their ends. A pair of tungsten electrodes are brought into the close proximity of the twisted etched fibers and an arc is initiated. Moving the electrodes along the length of the twisted etched fibers causes the arc to fuse them together to assure a stable configuration and, hence, stable evanescent field coupling. Once the fibers have been fused, a protective envelope encases the fused twisted fibers and it is filled with a liquid having the same index of refraction as the fibers' claddings. Thus, a stable coupler is created that is isolated from outside thermal and mechanical influences.

Method of fabricating a fused single-mode fiber bidirectional coupler

A fiber interferometer gyro employing a continuous, integral looped single-mode fiber is coupled to bidirectionally transmit clockwise and counterclockwise pulsed beams of light through a coiled continuous integral single-mode fiber from a laser to a pair of detectors. A suitably polarized piezoelectric cylinder is fitted about a portion of the continuous integral single-mode fiber to change the refractive index of that portion of the continuous integral single-mode fiber when appropriate electric fields are impressed across it. Changing the refractive index in only that portion of the continuous integral single-mode fiber results a selective phase biasing between the clockwise and counterclockwise traveling pulsed beams so that a rotation displacement of the interferometer gyro is more easily detected. This enhanced capability does not compromise the interferometer's effectiveness since its integral, continuous path is not broken nor are other elements introduced in the light pathway provided by the continuous single-mode fiber.

Method of providing phase biasing in a continuous single-mode fiber ring

Improved performance in a fiber interferometer gyro results from eliminat signals attributed to unwanted reflections from the fiber ends and the coupling lenses. A coiled single-mode fiber bidirectionally transmits beams radiating from a continuous wave laser to a detector. A fixed frequency oscillator amplitude modulates the laser output and provides a reference signal at the same frequency to enable synchronous detection of the detector output signals. Shifting the reference signal .pi./2 radians from the modulating signal eliminates the detector output signals which are attributed to reflections from the fiber ends and coupling lenses. By properly selecting the modulating frequency and reference phase, the information validity of beam signals passing through the coiled single-mode fiber is enhanced.

Method to eliminate fiber interferometer reflections

A method and apparatus for zero fringe shift referencing has unique appliion in an optical fiber interferometer gyroscope. Passive optical couplers introduce pulsed laser energy into the interferometer's main loop and a much smaller loop encircling a negligible area. An output signal from the smaller loop is representative of a zero rotation rate while the output signal from the much larger main interferometer loop is representative of an unknown rotation rate. The zero rotation rate and unknown rotation rate signals are compared and referenced so that there can be compensation for the response variation of the photodetectors or the source of laser energy to enable more accurate responsive readouts.

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San Diego, CA, United States of America

Matthew N McLandrich