Salim Nicolas Jabr

US Patent:

59698349, Oct 19, 1999

Filed:

Sep 3, 1997

Appl. No.:

8/922295

Inventors:

Gennady I. Farber - Palo Alto CA
Salim N. Jabr - Mountain View CA
Edward A. Vetter - Santa Clara CA
Victor A. Zeyliger - Milpitas CA

Assignee:

Ditech Corporation - Sunnyvale CA

International Classification:

H04B 1008

US Classification:

359110

Abstract:

One method of determining the signal to noise ratio of an optical signal models the noise floor based on amplified spontaneous emission (ASE) which is accumulated along the link. The ASE wavelength dependence is represented by a known mathematical function with a limited number of parameters. The parameters of this function are derived from measurements of the noise floor at a limited number of points by computational best fit means. A number of fiber grating filters at wavelengths between ITU allocated wavelengths are used to sample the optical noise and reflect the light back. An optical circulator is used to direct the reflected ASE light to an optical switch which allows the detector to select between transmitted and reflected light. The signal transmitted through the switch is monitored by a scanning filter with the appropriate resolution to resolve the signal or noise peaks. A first scan of the transmitted peaks is carried out and the signal is digitized and stored.

US Patent:

58619810, Jan 19, 1999

Filed:

Aug 20, 1997

Appl. No.:

8/915129

Inventors:

Salim N. Jabr - Mountain View CA

Assignee:

Ditech Corporation - Sunnyvale CA

International Classification:

H01S 322
H01S 3091
G02B 626

US Classification:

359341

Abstract:

A system and method are disclosed for adjusting the gain profile of an optical amplifier including a pump laser and an active gain element by selectively controlling the electron populations of at least one Stark sublevel of the electronic energy levels of the optical amplifier's active gain element. By dynamically controlling the electron populations of selected Stark sublevels the gain profile of the active gain element can be flattened. In a first method for controlling electron populations two-photon transitions are initiated between a pair of Stark sublevels of the same energy manifold of the active gain element. Two-photon transitions are stimulated by two additional pump lasers operating at wavelengths whose difference approximates the energy difference in the pair of Stark sublevels between which electrons are to be moved. In a second method for controlling electron populations single-photon transitions are initiated between a pair of Stark sublevels of different energy manifolds of the active gain element. Single-photon transitions are stimulated by an additional pump laser operating at a frequency difference that approximates the difference in the pair of energy levels.

US Patent:

53733606, Dec 13, 1994

Filed:

Nov 9, 1990

Appl. No.:

7/619703

Inventors:

Graham Martin - Woodland Hills CA
Salim Jabr - Mountain View CA

Assignee:

Litton Systems, Inc. - Woodland Hills CA

International Classification:

G01B 902
H01S 308

US Classification:

356350

Abstract:

Method and apparatus for reducing rotational bias error in a ring laser. The method includes the steps of varying a portion of an optical path for laser beams that emerge from a ring laser cavity along divergent paths and are subsequently combined along a common path to a detector. The apparatus of one embodiment includes a movable mirror positioned to intercept the laser beams emerging from the ring laser cavity before combination along a common path. The movable mirror may be piezo-electric transducive elements configured to bend on application of a voltage. The piezo-electric elements are provided with a reflective region that is positioned to redirect the laser beams from the ring laser back to an output coupling mirror so that re-reflection from the output mirror redirects the laser beams back into a beam combining optical element. In an alternative embodiment the detector is periodically displaced along an access parallel to the common path of the laser beam. In this embodiment piezo-electric elements are disposed between the beam combining optic and the detector to periodically displace the detector.

US Patent:

48377740, Jun 6, 1989

Filed:

Apr 19, 1988

Appl. No.:

7/183580

Inventors:

Salim N. Jabr - Woodland Hills CA
Thomas J. Hutchings - West Hills CA
Nicholas Koumvakalis - Thousand Oaks CA

Assignee:

Litton Systems, Inc. - Beverly Hills CA

International Classification:

H01S 3083

US Classification:

372 94

Abstract:

A compact three axis ring laser gyroscope having six laser corner mirrors which are positioned on the faces of a parallelopiped laser block, and method for making. Preferably the laser block is a cube. The laser block has a plurality of conduits therein for defining a plurality of closed laser beam-paths for guiding counterpropagating laser waves. Each laser beam-path has a gain medium therein and is formed to define a sensing axis for detection of rotations of the laser block. A single cathode is positioned inside the laser block, preferably substantially at its geometric center, and a plurality of anodes are mounted to the laser block and spaced apart from the cathode. A ion flow path is formed between each anode and the cathode such that application of a suitable electrical potential difference between the anodes and the cathode produces counterpropagating laser beams in each laser beam-path. The anodes are arranged to eliminate undesired Fresnel-Fizeau phase shifts by ensuring that each of the three ring gyros has two opposing ion flows.

US Patent:

60162139, Jan 18, 2000

Filed:

Jul 8, 1996

Appl. No.:

8/676561

Inventors:

Gennady Farber - Palo Alto CA
Salim Jabr - Mountain View CA

Assignee:

Ditech Corporation - Mountain View CA

International Classification:

H04B 1002

US Classification:

359177

Abstract:

An improved method of measurement of noise figure and gain of optical amplifiers is based on transforming the amplifier into an oscillator by applying optical feedback with known loss. The feedback consists of a tunable filter for wavelength control and of a variable attenuator for gain control. Measuring the output power at a given wavelength and the noise characteristics of the output signal, either with an optical spectrum analyzer or with a set of tunable filters and a power meter, provides data for full characterization of the optical amplifier. Another method is disclosed that utilizes the self-heterodyne setup and electrical spectrum analyzer to measure the spectral line width of the lasing amplifier, from which the noise figure is derived.

US Patent:

54714559, Nov 28, 1995

Filed:

May 17, 1994

Appl. No.:

8/245023

Inventors:

Salim N. Jabr - Mountain View CA

International Classification:

G11B 700

US Classification:

369107

Abstract:

Digital information is represented by surface steps orthogonal to the surface of a record carrier, said steps having a plurality of values between one tenth and 10,000 nanometers. The steps are read out by an optical differential interference method that is capable of resolving one tenth of a nanometer. The steps are written by a repeated masking and etching technique to form a master record carrier on glass from which a stamper is formed by molding and used to stamp replicate record carriers in polymeric material. In a different embodiment of the record carrier the surface steps are created by a modulated laser beam that ablates an integral number of layers from a pre-coated multilayer structure. In a third embodiment the data is represented by modulating the index of refraction between spots on a thin material film. The index difference is written optically.

US Patent:

51969050, Mar 23, 1993

Filed:

Apr 6, 1990

Appl. No.:

7/517644

Inventors:

Tae W. Hahn - North Hollywood CA
Salim N. Jabr - Woodland Hills CA

Assignee:

Litton Systems, Inc. - Beverly Hills CA

International Classification:

H01S 305
G01C 1964
G01B 902
G01P 900

US Classification:

356350

Abstract:

A radio frequency excitation system is disclosed for use in conjunction with a ring laser gyroscope. The radio frequency excitation system is comprised of a closed resonant cavity which surrounds a helical coil driven at a high radio frequency at a range of 5 to 550 megahertz. This closed resonant coil surrounds one leg of a ring laser gyroscope which is carved out and exposed so that it may be surrounded by the resonant cavity. Using such a radio frequency excitation system eliminates the need for high power DC discharge components such as cathodes and anodes, as well as problems inherent with properly sealing the cathodes and anodes to the monolithic frame of the ring laser gyroscope.

US Patent:

62296329, May 8, 2001

Filed:

May 12, 1997

Appl. No.:

8/854536

Inventors:

Salim Jabr - Mountain View CA

Assignee:

Ditech Corporation - Mountain View CA

International Classification:

H04B 1008
G02B 602

US Classification:

359124

Abstract:

A differential method of improving the carrier to noise ratio of optically transmitted amplitude modulated signals without affecting the fidelity of the transmitted signals is disclosed. The disclosed method improves over prior art methods by utilizing a single transmission fiber transmitting two wavelengths that are modulated out of phase by a single Mach Zehnder type modulator. The received light is separated into two components at two wavelengths and each wavelength is received by a photodetector. The two photodetector outputs are differentially combined to produce an output with improved signal to noise ratio resulting in improved bit error rates in digital transmissions. The invention is also useful in fiber optic analog transmission systems such as those used to distribute AM-VSB Cable Television programming, wherein the differential method improves the carrier to noise ratio without increasing the nonlinear components in the signal.