Karen W Liu

US Patent:

50392018, Aug 13, 1991

Filed:

Apr 30, 1990

Appl. No.:

7/516893

Inventors:

Karen Liu - Montclair NJ

Assignee:

International Business Machines Corporation - Armonk NY

International Classification:

G02B 528
G01B 902

US Classification:

359589

Abstract:

This invention describes a double-pass optical filter having a pair of reflective surfaces with a pair of optical media of different indices of refraction inserted between the surfaces. Light is then passed through the surfaces and through each of the optical media to obtain selected frequencies. This invention also includes a means for varying the distance between the reflective surfaces so as to tune the filer over a continuous range of frequencies. The continuous simultaneous turning of two resonant can be achieved by merely displacing one reflective surface relative to another.

US Patent:

57456127, Apr 28, 1998

Filed:

Dec 18, 1995

Appl. No.:

8/574474

Inventors:

Franklin Fuk-Kay Tong - Stamford CT
Karen Liu - Montclair NJ

Assignee:

International Business Machines Corporation - Armonk NY

International Classification:

G02B 628

US Classification:

385 24

Abstract:

This invention provides methods and apparatus for achieving wavelength sorting multiplexer/demultiplexer and its application to the implementation of planarized dynamic wavelength routing. Using integrated arrayed-waveguide gratings, sorting can be achieved by two configurations. In the first configuration channel wavelengths are properly selected and launched into prearranged input waveguides of an arrayed-waveguide grating such that channels at the same wavelength and from all inputs will be demultiplexed and routed to adjacent outputs. Operated in the reverse direction, the same device becomes a sorting multiplexer. The second configuration achieves wavelength sorting by using the cascade of multiple arrayed-waveguide gratings and can also be operated as a demultiplexer or a multiplexer. Combined with space switches, the wavelength sorting multi/demultiplexer are utilized to implement the planarized channel-selective dynamic wavelength router. The function of wavelength sorting eliminates on-chip waveguide crossings and therefore reduces losses and crosstalks.

US Patent:

59531410, Sep 14, 1999

Filed:

Aug 18, 1998

Appl. No.:

9/135585

Inventors:

Karen Liu - Montclair NJ
Chaoyu Yue - North Tarrytown NY

Assignee:

International Business Machines Corporation

International Classification:

H04J 1402

US Classification:

359124

Abstract:

A method and apparatus for constructing an optical wavelength-routing network in which each network node is a dynamic add-drop multiplexer (OADM) with minimized spectral filtering effect on pass-through channels and survivability upon power failure. By using cascaded tunable reflection filters as the building blocks, strictly add-drop non-blocking OADMs for single input/output fibers, double input/output fibers, and 3 input/output fibers can be constructed for application to unidirectional and bidirectional ring networks and mesh networks of arbitrary degree. Methods and apparatus for minimizing various types of out-of-band and in-band crosstalk occurring within the dynamic OADMs are also described.

US Patent:

49641310, Oct 16, 1990

Filed:

Mar 9, 1989

Appl. No.:

7/319241

Inventors:

Karen Liu - Montclair NJ
Byoung Y. Kim - Menlo Park CA
Michel J. F. Digonnet - Palo Alto CA
Kenneth A. Fesler - Sunnyvale CA
Herbert J. Shaw - Stanford CA

Assignee:

The Board of Trustees of the Leland Standford Junior University - Stanford CA

International Classification:

H01S 330

US Classification:

372 6

Abstract:

An optical fiber laser includes a single-mode optical fiber doped with a lasing material such as Neodymium. The optical fiber is pumped with a pump optical signal having a pump wavelength selected to cause spontaneous emission of an optical signal at a second wavelength different from the pump wavelength. The optical fiber is formed into a laser cavity such as by including a suitable reflector at each of the two ends of a suitable length of the optical fiber so that the emitted optical signal oscillates therein. One of the reflectors has a reflectivity at the wavelength of the emitted light so that most (e. g. , approximately 95%) of the emitted light is reflected back into the laser cavity and a smaller portion (e. g, approximately 5%) is transmitted through the mirror as a laser output signal. Alternatively, the optical fiber can be formed into a ring laser structure using an optical coupler that couples a substantial portion (e. g.

US Patent:

59300167, Jul 27, 1999

Filed:

Oct 10, 1996

Appl. No.:

8/728871

Inventors:

Stuart Douglas Brorson - White Plains NY
Paul Eliot Green - Mount Kisco NY
Karen Liu - Montclair NJ

Assignee:

Tellabs Operations, Inc. - Lisle IL

International Classification:

H04J 1402

US Classification:

359127

Abstract:

A method and apparatus for constructing a modular and easily upgradable optical network node using the technique of wavelength-division multiplexing (WDM). According to the present invention, a WDM point-to-point link end node can be modularly upgraded in the number of wavelength channels or upgraded to a ring network node; both without requiring equipment internal rewiring.

US Patent:

62084437, Mar 27, 2001

Filed:

Aug 18, 1998

Appl. No.:

9/135957

Inventors:

Karen Liu - Montclair NJ
Chaoyu Yue - North Tarrytown NY

Assignee:

International Business Machines Corporation - Armonk NY

International Classification:

H04J14/02

US Classification:

359127

Abstract:

A method and apparatus for constructing an optical wavelength-routing network in which each network node is a dynamic add-drop multiplexer (OADM) with minimized spectral filtering effect on pass-through channels and survivability upon power failure. By using cascaded tunable reflection filters as the building blocks, strictly add-drop non-blocking OADMs for single input/output fibers, double input/output fibers, and 3 input/output fibers can be constructed for application to unidirectional and bidirectional ring networks and mesh networks of arbitrary degree. Methods and apparatus for minimizing various types of out-of-band and in-band crosstalk occurring within the dynamic OADMs are also described.