Richard D Smart

US Patent:

54064040, Apr 11, 1995

Filed:

Nov 2, 1993

Appl. No.:

8/146340

Inventors:

David J. DiGiovanni - Montclair NJ
Jonathan A. Nagel - Freehold NJ
Richard G. Smart - Naperville IL
James W. Sulhoff - Ocean NJ
John L. Zyskind - Shrewsbury NJ

Assignee:

AT&T Corp. - Murray Hill NJ

International Classification:

H04B 1000

US Classification:

359161

Abstract:

The present invention relates to a method of mitigating gain peaking in a chain of fiber amplifiers by pumping the amplifiers at a predetermined wavelength to produce gain over a specified wavelength range.

US Patent:

54305721, Jul 4, 1995

Filed:

Sep 30, 1993

Appl. No.:

8/129825

Inventors:

David J. DiGiovanni - Montclair NJ
Joseph D. Evankow - Colts Neck NJ
Jonathan A. Nagel - Freehold NJ
Richard G. Smart - Naperville IL
James W. Sulhoff - Ocean NJ
John L. Zyskind - Shrewsbury NJ

Assignee:

AT&T Corp. - Murray Hill NJ

International Classification:

G02B 626

US Classification:

359341

Abstract:

High output power, high gain, and low noise are achieved in a two-stage optical amplifier, suitable for use as a repeater for a long haul lightwave communication system, in accordance with the principles of the invention, by employing a first amplifying stage having a signal gain sufficiently small to prevent self-saturation by amplified stimulated emission (ASE) that uses counter-propagating pump light to cause maximum inversion of the first stage amplifying medium. In an illustrative embodiment of the invention, EDFAs are used in each of two amplifying stages. The length of the EDFA in the first stage is short enough to ensure nearly complete inversion of the EDFA from pump light that counter-propagates with the signal. The counter-propagating pump light allows the invention to advantageously avoid the significant noise figure penalty from the input loss associated with co-propagating pump light. And, noise figure is improved because complete inversion is achieved throughout the EDFA, and, at the input where the noise figure is most sensitive to inversion.

US Patent:

52237052, Jun 29, 1993

Filed:

Aug 12, 1992

Appl. No.:

7/929660

Inventors:

Jennifer Aspell - Tinton Falls NJ
Neal S. Bergano - Lincroft NJ
Bruce M. Nyman - Manalapan NJ
Richard G. Smart - Holmdel NJ
James W. Sulhoff - Ocean NJ
John L. Zyskind - Shrewsbury NJ

Assignee:

AT&T Bell Laboratories - Murray Hill NJ

International Classification:

G02F 101
H01S 330

US Classification:

250225

Abstract:

In an embodiment for obtaining accurate noise figure measurements for any degree of saturation of an optical amplifier, a polarizer is located at the output of the optical amplifier. The amplified spontaneous noise (ASE) produced by an optical amplifier is not polarized, whereas the amplified signal has a well defined state of polarization which is preferably linear. If the amplified signal is not linearly polarized, it can be rendered linearly polarized in one direction by means of a polarization controller located downstream of the polarizer. By setting the polarizer to have its state of polarization orthogonal to that of the linearly polarized amplified signal, the spectral density of the ASE from the polarizer can be measured without associated distortion due to the signal. By sequentially adjusting the polarization controller to minimize and then maximize the signal which it passes, sequential measurements of the ASE spectral density and gain of the optical amplifier can be obtained. Continuous measurements of the ASE can be obtained by placing a splitter such as a 3dB coupler between the polarizer and the optical amplifier and setting the state of polarization of the polarizer to be continuously orthogonal to the state of polarization of the amplified signal from one leg of the splitter.