Michael J Freeman

US Patent:

6532101, Mar 11, 2003

Filed:

Mar 16, 2001

Appl. No.:

09/811103

Inventors:

Mohammed N. Islam - Allen TX
Carl A. Dewilde - Richardson TX
Michael J. Freeman - Canton MI

Assignee:

Xtera Communications, Inc. - Allen TX

International Classification:

H01S 300

US Classification:

359334, 3593374, 3593413

Abstract:

A multi-stage Raman amplifier includes a first Raman amplifier stage having a first sloped gain profile operable to amplify a plurality of signal wavelengths, and a second Raman amplifier stage having a second sloped gain profile operable to amplify at least most of the plurality of signal wavelengths after those wavelengths have been amplified by the first stage. The second sloped gain profile is approximately complementary slope to the slope of the first sloped gain profile. The combined effect of the first and second Raman stages contributes to an approximately flat overall gain profile over the plurality of signal wavelengths.

US Patent:

6574037, Jun 3, 2003

Filed:

Jan 22, 2001

Appl. No.:

09/768367

Inventors:

Mohammed N. Islam - Allen TX
Carl Dewilde - Richardson TX
Michael Freeman - Canton MI

Assignee:

Xtera Communications, Inc. - Allen TX

International Classification:

H01S 300

US Classification:

359334

Abstract:

A Raman amplifier apparatus includes an optical transmission line with an input to receive an optical signal, an output that passes the optical signal, a first Raman gain fiber and a second Raman gain fiber. A first WDM is positioned between the second Raman gain fiber and the output. A first set of pump wavelengths is input to the first WDM. A second WDM is positioned between the first and second Raman gain fibers. A second set of pump wavelengths is input to the second WDM. At least a portion of the first set of pump wavelengths are different than the second set of pump wavelengths. The first and second set of pump wavelengths propagate in the same direction.

US Patent:

6587259, Jul 1, 2003

Filed:

Jul 27, 2001

Appl. No.:

09/916454

Inventors:

Mohammed N. Islam - Allen TX
Carl A. DeWilde - Richardson TX
Michael J. Freeman - Canton MI

Assignee:

Xtera Communications, Inc. - Allen TX

International Classification:

H04B 1000

US Classification:

359334, 359161

Abstract:

One aspect of the invention includes an optical amplifier operable to amplify a plurality of optical wavelength signals at least in part through Raman amplification. The amplifier includes an input operable to receive a plurality of wavelength signals and an output operable to communicate an amplified version of at least some of the plurality of wavelength signals. The amplifier further includes a pump assembly operable to generate one or more pump signals and a gain medium operable to receive the plurality of wavelength signals and the one or more pump signals and to facilitate amplification of at least some of the plurality of wavelength signals. The amplifier has associated with it a noise figure having a shape varying as a function of wavelength. At least one of the one or more pump signals is operable to have its power varied to selectively control the shape of the noise figure.

US Patent:

6631025, Oct 7, 2003

Filed:

Jan 12, 2001

Appl. No.:

09/760201

Inventors:

Mohammed N. Islam - Allen TX
Michael Freeman - Canton MI

Assignee:

Xtera Communications, Inc. - Allen TX

International Classification:

H01S 3091

US Classification:

359334, 35934132, 372 3, 372 6, 372 20

Abstract:

A Raman amplifier assembly includes a Raman amplifier configured to receive a signal from a signal source. The signal travels in an upstream direction in the Raman amplifier. A first pump source is coupled to the Raman amplifier. The first pump source produces a first pump beam that travels in a downstream direction and is counter-propagating relative to the signal. A second pump source is coupled to the Raman amplifier and produces a second pump beam that travels in the upstream direction. The second pump source has an average relative intensity noise of less than -80 dB/Hz.

US Patent:

6714342, Mar 30, 2004

Filed:

Jan 2, 2003

Appl. No.:

10/335808

Inventors:

Mohammed N. Islam - Allen TX
Michael Freeman - Canton MI

Assignee:

Xtera Communications, Inc. - Allen TX

International Classification:

H01S 330

US Classification:

359334, 3593413, 35934131, 359341

Abstract:

A Raman amplifier assembly includes a Raman amplifier configured to receive a signal from a signal source. The signal travels in an upstream direction in the Raman amplifier. A first pump source is coupled to the Raman amplifier. The first pump source produces a first pump beam that travels in a downstream direction and is counter-propagating relative to the signal. A second pump source is coupled to the Raman amplifier and produces a second pump beam that travels in the upstream direction. The second pump source has an average relative intensity noise of less than -80 dB/Hz.

US Patent:

6819479, Nov 16, 2004

Filed:

Dec 20, 2001

Appl. No.:

10/028576

Inventors:

Mohammed N. Islam - Allen TX
Michael J. Freeman - Northville MI
Pavle Gavrilovic - Allen TX
Andrzej Kaminski - Allen TX

Assignee:

Xtera Communications, Inc. - Allen TX

International Classification:

H01S 300

US Classification:

359337, 3593413

Abstract:

In one embodiment, an optical amplifier includes a gain medium operable to receive a plurality of signals each having a center wavelength and a noise figure associated with at least a portion of the amplifier and varying as a function of wavelength. At least two of the plurality of signals have launch powers that are a function of a magnitude of the noise figure measured at or near the center wavelength of that signal.

US Patent:

6876489, Apr 5, 2005

Filed:

Apr 15, 2003

Appl. No.:

10/414890

Inventors:

Mohammed N. Islam - Allen TX, US
Carl Dewilde - Richardson TX, US
Michael Freeman - Canton MI, US

Assignee:

Xtera Communications, Inc. - Allen TX

International Classification:

H01S003/00

US Classification:

359334

Abstract:

A Raman amplifier apparatus includes an optical transmission line with an input to receive an optical signal, an output that passes the optical signal, a first Raman gain fiber and a second Raman gain fiber. A first WDM is positioned between the second Raman gain fiber and the output. A first set of pump wavelengths is input to the first WDM. A second WDM is positioned between the first and second Raman gain fibers. A second set of pump wavelengths is input to the second WDM. At least a portion of the first set of pump wavelengths are different than the second set of pump wavelengths. The first and second set of pump wavelengths propagate in the same direction.

US Patent:

6924926, Aug 2, 2005

Filed:

Aug 2, 2002

Appl. No.:

10/210987

Inventors:

Mohammed N. Islam - Allen TX, US
Michael J. Freeman - Northville MI, US

Assignee:

Xtera Communications, Inc. - Allen TX
The Regents of the University of Michigan - Ann Arbor MI

International Classification:

H01S003/00

US Classification:

359334

Abstract:

A laser diode pump includes a plurality of laser diodes each capable of generating a lasing wavelength. The laser diode pump further includes at least one wavelength combiner operable to combine the plurality of lasing wavelengths generated by the plurality of laser diodes into a multiple wavelength pump signal. In one particular embodiment, at least two of the plurality of lasing wavelengths generated by the plurality of laser diodes comprise a wavelength between 1270 nm and 1350 nm.