USA As Represented by Secretary of the Navy

Dorsal Networks, Inc.

Ronald D Esman

Irl N Duling, Iii

Alan D Kersey

Ronald E Johnson

Lew Goldberg

Bo Pedersen

Keith J Williams

M Imran Hayee

Lee Daniel Feinberg

Michael J Marrone

John G Hagopian

Nandakumar Ramanujam

Cathal Mahon

Brent Ashley Miller

Michael Y Frankel

Michael L Dennis

Carl A Villarruel

David G Cooper

Edward M Alexander

James L Dexter

Lee T Nichols

Jose E Roman

Michael J Monsma

A collapsed ring fiber optic system includes a service path and a protection path provides at a shallow water portion of the fiber optic system, to deal with any fiber cuts that may occur at the shallow water portion without loss of main trunk bandwidth. The service and protection paths meet at a branch point, which is preferably located at a deep water portion of the fiber optic system. A passive combiner or a 1&#xd7;2 switch is provided at the branch unit, along with a detector and a processor, to determine whether any signals are being received from the service path, and if not, to reconfigure the system to accept signals from the protection path. At another shallow water portion of the fiber optic system, nearby where a destination is located, the signal provided on the optical path over the deep water portion is split into a service path and a protection path, to provide redundancy to deal with any fiber cuts that may occur. The fiber optic system may also be utilized for a land-based system, having high probability of fiber cut regions and low probability of fiber cut regions.

Split redundant trunk architecture using passive splitters and path switching

A collapsed ring fiber optic system includes a service path and a protection path provides at a shallow water portion of the fiber optic system, to deal with any fiber cuts that may occur at the shallow water portion without loss of main trunk bandwidth. The service and protection paths meet at a branch point, which is preferably located at a deep water portion of the fiber optic system. A passive combiner or a 1&times;2 switch is provided at the branch unit, along with a detector and a processor, to determine whether any signals are being received from the service path, and if not, to reconfigure the system to accept signals from the protection path. At another shallow water portion of the fiber optic system, nearby where a destination is located, the signal provided on the optical path over the deep water portion is split into a service path and a protection path, to provide redundancy to deal with any fiber cuts that may occur. The fiber optic system may also be utilized for a land-based system, having high probability of fiber cut regions and low probability of fiber cut regions.

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

The fiber-optic true time-delay array antenna feed is a device for dynamically generating a plurality of identical electromagnetic radiation (EMR) signals with continuously variable time-delay separations. The EMR signal to be transmitted modulates a continuous-wave optical signal from a laser source which is applied to a plurality of high dispersion single-mode optical fibers acting as synchronized true time-delay modulators forming an array antenna feed system. Each fiber is chosen to have the same nominal time delay but a different net dispersion. Photodetectors convert the optical intensity back into an EMR electrical signal to feed each of the elements of the array antenna.

Fiber optic true time-delay array antenna feed system

The wideband single-sideband modulator generates single-sideband (SSB) modulation with suppressed carrier utilizing traveling-wave LiNbO,modulators in a Sagnac loop. In the wideband single-sideband modulator, optical light from a linearly-polarized source is injected into polarization-maintaining fiber (PolMF) where it is split equally via a polarization-maintaining (PolM) directional fiber coupler, resulting in counterpropagating lightwaves in a Sagnac loop. These counterpropagating waves are &pgr;/2 out of phase due to the action of the coupler and remain so when they return to the coupler because they travel equal distances around the loop. Because the coupler is a reciprocal device, if the waves return to the coupler with equal amplitudes, they will recombine and exit the original port toward the polarized light source. The technique achieves true carrier cancellation over a range of radio frequency (RF) power levels, thereby serving as an enabling architecture for photonically-remoted ultrawide-band single-sideband suppressed-carrier (SSB-SC) modulated links.

Wideband single sideband modulation of optical carriers

A new fiber optic based beamforming architecture for a time steered phased rray antenna based on chirped fiber gratings. All of the gratings are identical in length and period chirp so that they all have the same dispersion, thus at a given optical wavelength they have the same time delay. In a preferred embodiment an optical signal is modulated with an RF signal. The RF modulated optical is split and a portion propagates through a length of fiber to a photodetector feeding an antenna array. The second portion of the optical signal is routed through a circulator, which feeds the optical signal to a chirped fiber grating. The grating reflects and delays the optical signal back to the circulator which routes the reflected optical signal to a second coupler. The amount of delay incurred is determined by the grating dispersion and the wavelength of the optical source. The second splits the time delayed optical signal, passing a portion of the time delayed optical signal to the second antenna element and the other portion to other circulators and ultimately to other antenna elements comprising the antenna array. The time delay imposed on the optical signal through the use of chirped fiber gratings controls the relative timing between the antenna elements, thus allowing one to steer the antenna by changing the wavelength of the optical signal.

Chirped fiber grating beamformer for phased array antennas

A system that uses all optical elements for transmission, regeneration and reception of solitons in point-to-point, broadcast, ring and multi-user trunk type communication systems. Soliton pulses from an optical clock source are modulated by optical data pulses in an optical modulator producing a modulated channel of data pulses. Several channels are combined by an optical multiplexer into a network optical bit stream. This stream is carried by an optical fiber and one or more of optical regenerators which recover the system clock and regenerate the signal with the recovered system clock rather than just amplifying the signal. Each of the regenerators can, in addition to regenerating the data, act as part of a data drop or insert node in a ring network where the node can synchronously remove data from or insert data into the stream. Intermediate nodes can include packet drop/replace nodes if the network is a packet type network. The destination can include an optical demultiplexer which demultiplexes the network stream into the individual channels, an optical clock recovery system that recovers the clock of the system and a receiver that receives the pulses of one of the demultiplexed channels. The system can also include optical logic for decoding and routing optical packets.

Ultra high bit rate all optical communication system

An optical device includes a polarization section having a port, the polarization section being for receiving light at the port and for outputting light at the port with a state of polarization orthoconjugate to the light received at the port. The polarization section includes a reflector, a bidirectional nonreciprocal rotator and a bidirectional polarizer. The bidirectional nonreciprocal rotator has first and second ends, the first end being operatively coupled to the port. The bidirectional polarizer has first and second ends, the first polarizer end being operatively coupled to the reflector and the second polarizer end being operatively coupled to the second rotator end. The optical device further includes an amplifying section having a port 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 with a state of polarization orthoconjugate to the light received at the amplifying section port and being amplified with respect thereto. The optical device includes means for transmitting light in both directions between the polarization section port and the amplifying section port, and means responsive to light internal to the polarization section for outputting coherent light having a stable and known state of polarization.

Polarization-stable laser

In the transmission electrical signals using an optical carrier the signal power carried by an optical carrier is proportional to the optical power. High optical power levels are desired for optical carriers that are modulated by weak electrical signals, however, significant unmodulated power is left in the original carrier after processing. To maximize the radio frequency (RF) signal power generated by a given (maximized) photodetector current (for a given input power), in this invention, the optical carrier power is reduced. This is accomplished by the addition of a narrowband optical filter, such as a Fabry-Perot filter, to reduce the average optical carrier power without reducing the modulation sidebands, which results in an increased modulation depth. Therefore, greater RF and microwave power is generated by a photodetector with the same photocurrent. With a laser source exhibiting a beam whose linewidth is narrow compared to the filter bandwidth, the filter is tuned, or frequency locked, to match the filtering resonance with the optical carrier wavelength. With the high finesse filter and narrow-linewidth laser beam, the frequency range of operation is extended from the filter half-bandwidth to the next resonance of the filter. Thus, broadband effective gain results without introducing additional noise.

Wideband fiber-optic signal processor

An intracavity-modulated laser includes a gain element, an electro-optic modulator (EOM), a frequency selective coupler (FSOC), and an optical isolator coupled in such a way that a ring laser cavity is formed. The EOM selectively affects the optical input in intensity, phase, or frequency according the radio frequency (RF) input signal applied. The FSOC is a three-port device that receives light at a first port and passes narrowbands of light out a second port and directs the remaining optical spectrum out a third port. The optical isolator assures single direction lasing. When the gain is sufficient to overcome the ring losses, the laser cavity will oscillate with longitudinal modes corresponding to the pass bands of the FSOC. The light exiting the second port of the FSOC is amplified by the laser gain element and is directed to the EOM. The EOM modulates each carrier (longitudinal mode) of the laser cavity thereby creating optical modulation sidebands associated with each carrier. The FSOC selectively couples the modulation sidebands out of the laser cavity. Since the FSOC contains no active elements, the frequency selective coupling operation is essentially noise-free. In this way an optical source is formed which can be modulated to frequencies limited only by the EOM bandwidths, reduces the RF input voltages required to produce a given modulation depth, effectively couples out only the modulation of the longitudinal modes allowing efficient use of optical components, and improves system performance without adding noise.

Method and apparatus for improving the sensitivity of optical modulators

The fiber optic true time delay modulator generates a continuously variable true time-delay (i.e., phase shift) by utilizing the dispersion characteristic of a single mode optical fiber. The signal to be variably delayed modulates a continuous wave optical signal from a tunable laser source which is applied to a dispersive optical fiber wherein the phase shift occurs. The optical intensity output of the dispersive optical fiber is converted back into electrical energy by a photodetector for use in radio frequency, microwave and millimeter wave electronic devices. The invention can be used to generate multiple synchronized output signals by using a multiple wavelength laser or by combining outputs from several independently tuned lasers. Also. frequency and phase shifting is inherently provided by modulating the time delay.

Fiber optic continuous true time-delay modulator

An apparatus and method for converting a signal of arbitrary polarization one of preselected polarization, e.g. for use by a sensor, transducer, etc. A signal splitter divides the input signal into its orthogonal linearly polarized components, and launches the components from a pair of output ports. The signals counterpropagate to the opposite port, and, while counterpropagating, are rotated into the same linear polarization state. In one embodiment, the rotation is done by a pair of complementary 45.degree. Faraday rotators; in another, by one 90.degree. rotator. In the former, the signal is recombined at the splitter in the initial state of polarization that in which the signal initially entered the splitter; in the latter, the recombined signal is of orthoconjugate polarization to the input signal.

Apparatus and method for eliminating polarization sensitivity in

A sensor system includes a sensor head, an optical source, and a measurement apparatus. The sensor head includes a beamsplitter having first, second, third, and fourth ports, the beamsplitter being responsive to light selectively applied to the first, second and third ports for passing light of a first input polarization state from the first port to the second port, for passing light of a second input polarization state orthogonal to the first input polarization state from the first port to the third port, and for collectively passing light of a first output polarization state and light of a second output polarization state orthogonal to the first output polarization state from the third port to the fourth port. The optical source means provides light to the first port. The sensor head further includes a bidirectional polarimetric sensor responsive to polarized light output by the beamsplitter at the second and third ports and to an electromagnetic field applied to the polarimetric sensor for producing first polarized light at said third port and for producing second polarized light at said second port. The first and second polarized light have polarization states each of which varies as a function of the electromagnetic field and the polarization state of the light output by the beamsplitter at the other one of the second and third ports. The measurement means is responsive to light from the fourth port for producing an output signal indicative of the electromagnetic field strength.

Polarization insensitive current and magnetic field optic sensor

A sensor system includes a sensor head, an optical source, and a measurement apparatus. The sensor head includes a beamsplitter having first, second, third, and fourth ports, the beamsplitter being responsive to light selectively applied to the first, second and third ports for passing light of a first polarization state from the first port to the second port, for passing light of a second polarization state from the first port to the third port, for passing light of the second polarization state from the second port to the fourth port, and for passing light of the first polarization state from the third port to the fourth port. The optical source means provides light to the first port. The sensor head further includes a bidirectional polarimetric sensor responsive to polarized light output by the beamsplitter at the second and third ports and to an electromagnetic field applied to the polarimetric sensor for producing first polarized light at said third port and for producing second polarized light at said second port. The first and second polarized light have polarization states each of which varies as a function of the electromagnetic field and the polarization state of the light output by the beamsplitter at the other one of the second and third ports. The measurement means is responsive to light from the fourth port for producing an output signal indicative of the electromagnetic field strength.

A single-polarization fiber optical amplifier and corresponding method is provided capable of amplifying an optical input signal by a fiber optic amplifier constructed of fiber which may be non-polarization-maintaining. The single-polarization fiber optical amplifier provides a direction-selective coupler which receives an optical input at a first port and outputs an optical output at a second port. A fiber optic amplifier is operatively connected to the direction-selective coupler at a bidirectional port for amplifying the optical input. A retro-reflecting orthogonal polarization converter is operatively connected to the fiber optic amplifier, reflecting the amplified optical input from the fiber optic amplifier in a return direction through the fiber optic amplifier and in an orthogonal polarization to the amplified optical input. The direction-selective coupler outputs the reflected amplified orthogonal optical input at the second port as the optical output of the direction-selective coupler. Further configurations adapting the input and output ports to transmit the optical signal through cavity or other structures may be provided to produce, for example, an ultrashort pulse optical source; a single-wavelength, single-polarization, widely-tunable laser source; or an amplified spontaneous emission source.

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Burke, VA, United States of America

Ronald D Esman