USA As Represented by Secretary of the Navy

Sowilo Networks, Inc.

Michael L Dennis

Irl N Duling, Iii

William K Burns

Brian A Cole

Ishwar Dayal Aggarwal

Martin A Putnam

Lew Goldberg

Jin Ung Kang

Bo Pedersen

Robert P Moeller

Ronald D Esman

Keith J Williams

Carl A Villarruel

M Imran Hayee

William Shieh

Thomas F Carruthers

Nandakumar Ramanujam

Cathal Mahon

E Joseph Friebele

Irt N Duling, Iii

Brian J Cole

A device amplifies light at wavelengths in the vicinity of 1420-1530 nm, using thulium doped silica-based optical fiber. This wavelength band is of interest as it falls in the low-loss optical fiber telecommunications window, and is somewhat shorter in wavelength than the currently standard erbium doped silica fiber amplifier. The device thus extends the band of wavelengths which can be supported for long-distance telecommunications. The additional wavelength band allows the data transmission rate to be substantially increased via wavelength division multiplexing (WDM), with minimal modification to the standard equipment currently used for WDM systems. The host glass is directly compatible with standard silica-based telecommunications fiber. The invention also enables modified silicate based amplifiers and lasers on a variety of alternative transitions. Specifically, an S-band thulium doped fiber amplifier (TDFA) using a true silicate fiber host is described.

Amplification device utilizing thulium doped modified silicate optical fiber

Heavy metal modified silica glass fibers doped with thulium, holmium, and thulium-sensitized-holmium high quantum efficiencies

A system and method of providing a transmission span that compensates for signal attenuation, dispersion, and nonlinearity of an optical signal communicated between two line units of a transmission link includes dividing the transmission span into a plurality of fiber segments and selecting a particular fiber for each of the segments. The fiber selection and arrangement of fibers within the span can be selected in accordance with the nonlinearity, dispersion conditions, and distributed gain conditions of the constituent fibers. In a three segment map, the first segment can provide low non linearity, the third segment can provide distributed gain, and the second segment can compensate for the dispersion of the first and third segments. The span can be used, e.g., for distributed Raman amplification. The span can alternatively include a two segment map, a four segment map, or a map with additional segments.

Method and system for dispersion maps and enhanced distributed gain effect in long haul telecommunications

A method and apparatus for increasing the upper frequency range of an optical communication system, particularly one designed to communicate over, repeaterless, distances. A series of temporally interleaved optical solitons of different frequencies are generated, and transmitted and detected by wavelength division multiplexing. An adiabatic transmission line forms part of the transmission link, and serves to narrow the bandwidth of the pulses during propagation. As a result, one can generate the solitons with substantially overlapping spectra, thus increasing the rate at which they are produced, but, because of the narrowed spectra, still resolve them in frequency at the system's receiver.

Apparatus and method for high repetition rate optical communication over long unrepeated spans

An optical receiver for receiving a signal from an optical fiber in a fiber-optic digital transmission system that includes a first low noise optical amplifier to amplify an input optical signal. The first low noise optical amplifier has an input 3 dB compression point lower than the desired system input sensitivity at a desired bit rate. A high power optical amplifier further amplifies the amplified optical signal, and has an automatic gain control for output signal leveling at a desired operation point of the transmission system. A high current photodetector converts the further amplified optical signal from the high power optical amplifier to an electrical signal that drives a retiming circuit without requiring further amplification of the electric signal.

High-sensitivity, high-speed digital optical photoreceiver

In accordance with one aspect of the invention, a ring laser configuration having a polarizer, and whose cavity loop has substantially no net dispersion, permitting mode locked pulsing of high intensity and large bandwidth. In accordance with another aspect of the invention, a system using this laser to interrogate a plurality of arrays of Bragg gratings by use of both time and wavelength division multiplexing, increasing the total number of interrogatable gratings. In accordance with a third aspect of the invention, a system for interrogating one or more fiber Bragg gratings separated from the optical source by a dispersive optical fiber. As such a grating distends responsive to some measurand, its reflection frequency changes, and the traversal time of the reflection over the dispersive fiber changes, permitting inference of the measurand.

Broadband mode-locked fiber laser, particularly for fiber Bragg grating

An optical method and apparatus particularly useful as an intensity modulation system, in which two phase modulators are placed in the loop of a Sagnac interferometer. Selective placement of the modulators, and the amplitude of any modulation signal input to the modulators, varies the bandwidth and frequency response of the system. In a preferred embodiment, the ratio of the optical distances of the modulators from interferometric midpoint, and the ratio of modulation signal amplitudes, is about 3:1, which serves to broaden and flatten the frequency response of the system.

Apparatus and method for improving the frequency response of modulators

This invention is a demultuplexer consisting on a sequential division of the data stream in a series of Sagnac interferometer amplitude modulators (SIAMs), wherein each modulator in the series is driven by a single microwave frequency derived directly from a radio frequency (RF) data rate clock, with the RF phase properly adjusted to extract a channel of interest.

Sagnac interferometer amplitude modulator based demultiplexer

An optical intensity modulator which uses a Sagnac interferometer having an electro-optic phase modulator therein. An electric modulation signal is delivered to the modulator, and the latter is selected so that the phase velocity of optical and electrical signals are comparable in it. This causes the optical signal from one interferometer arm to copropagate through the modulator with the electrical signal, increasing interaction time with it, and causes the optical signal from the other arm to counterpropagate with the electric signal, reducing interaction time. In addition to phase modulating the optical signals by the electrical signal, the electro-optic effect in the modulator phase shifts the optical signals with respect to one another, permitting them to form a non-zero interference pattern, whose intensity corresponds to the electrical signal. In one embodiment, the interferometer has a non-reciprocal device to impose a constant phase difference between the counterpropagating optical signals, which permits one to place the system's setpoint to any arbitrary point on the system's transmissivity versus phase response, e.g. large signal and/or linear response.

Electro-optic modulator and method

A blue laser source outputting a beam having a wavelength of approximately 460 nm. A first laser cavity is formed around a Nd:YAG gain medium generating a first light beam having a wavelength of approximately 1064 nm. A second laser cavity, at least partially coextensive with the first laser cavity is formed around a Tm:ZBLAN gain medium generating a second light beam having a wavelength of approximately 810 nm. A non-linear KTP crystal is provided intracavity to both the first and second laser cavities to mix the first light beam and the second light beam and output a third light beam having a wavelength of approximately 460 nm. One of the mirrors forming the first or second laser cavity is coated to output a laser beam having a wavelength of approximately 460 nm.

Solid-state blue laser source

A pulsed laser includes a polarization section having a port, the polarization section being for receiving light at the port in a selected state of polarization and for outputting light at the port having a state of polarization orthogonal to the selected state of polarization. The laser also includes an amplifying section having a port, a bidirectional amplifier, and a rotator-reflector, the amplifying section being for receiving light at the amplifying section port and for outputting light at the amplifying section port amplified with respect thereto, the bidirectional amplifier being operatively coupled to the amplifying section port at a first end and operatively coupled to the rotator-reflector at a second end. The pulsed laser further includes means for transmitting light in both directions between the polarization section port and the amplifying section port, an amplitude modulator responsive to a modulation signal for actively mode-locking light internal to the pulsed laser, and means responsive to light internal to the polarization section for outputting coherent light.

Polarization-stable pulsed laser

The present invention is a fluorozirconate laser host doped with a suffict amount of Tm.sup.3+ ions to permit significant emission at a wavelength between about 790 nm and about 830 nm when pumped at a wavelength or wavelengths to excite Tm.sup.3+ ions from the .sup.3 H.sub.6 ground state to the .sup.3 F.sub.4 excited state, and then from the .sup.3 F.sub.4 excited state to the .sup.3 H.sub.4 excited state.

Upconversion pumped thulium fiber amplifier and laser operating at 790

An optical pulse generator for producing mode-locked optical pulses comprises: a beam splitter; first and second optical loops coupled together by the beam splitter so as to define a figure eight optical path in which a light beam propagating toward the beam splitter in one of the first and second optical loops is split by the beam splitter to form two light beams propagating in opposite directions around the other one of the first and second optical loops; a direction dependent loss element disposed in the first optical loop for reducing the intensity of light propagating in a predetermined direction around the first optical loop; a nonlinear element disposed in the second optical loop and having an intensity dependent nonlinear optical transmission characteristic; an optical gain medium disposed in a selected one of the first and second optical loops; coupling apparatus for coupling pump light into the selected one of said first and second optical loops having the gain medium, and for coupling mode-locked optical pulses out of the optical pulse generator; and a feedback structure, coupled to the coupling apparatus, being responsive to light propagating therethrough for controlling the repetition rate of the mode-locked optical pulses.

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Alexandria, VA, United States of America

Michael L Dennis