David K Caplan

US Patent:

6694104, Feb 17, 2004

Filed:

Mar 3, 1999

Appl. No.:

09/261628

Inventors:

David O. Caplan - Concord MA
Mark L. Stevens - Pepperell MA
Don M. Boroson - Needham MA

Assignee:

Massachusetts Institute of Technology - Cambridge MA

International Classification:

H04B 1004

US Classification:

398197, 398140, 375300

Abstract:

A variable-bit-rate communication system is described. The communication system includes a variable-bit-rate transmitter that generates digital data at a first or a second bit rate and a variable-bit-rate receiver that receives the digital data. The digital data comprises a sequence of signaling waveforms having a first or a second duty cycle, respectively, wherein each signaling waveform has the same shape.

US Patent:

6831779, Dec 14, 2004

Filed:

Apr 27, 2001

Appl. No.:

09/845053

Inventors:

David O. Caplan - Bedford MA

Assignee:

Massachusetts Institute of Technology - Cambridge MA

International Classification:

H01S 300

US Classification:

359347, 359333

Abstract:

A high-gain, saturated output, double-pass, fault-tolerant optical amplifier has an extended range of stability, output power, and efficiency and fall back modes of operation. The optical amplifier is typically configured in a two-stage polarization maintaining configuration, employing erbium-doped fibers as the gain media in both of the stages. At least one optical element in a loss-insensitive region of the amplifier can have a loss substantially higher than optical elements in the gain paths outside of the loss-insensitive region without substantially reducing the overall output power and efficiency of the amplifier. These elements can influence the amplified signal waveform, spectrum, signal-to-noise ratio, or subsequent performance in an optical network, as well as amplifier characteristics, such as output power, stability, efficiency, and reliability. The optical amplifier is suitable for both free-space and fiber optic network applications.

US Patent:

7181097, Feb 20, 2007

Filed:

Mar 13, 2002

Appl. No.:

10/097187

Inventors:

David O. Caplan - Billerica MA, US
Walid A. Atia - Lexington MA, US

Assignee:

Massachusetts Institute of Technology - Cambridge MA

International Classification:

G02B 6/12

US Classification:

385 14, 385 24

Abstract:

A system includes an optical transmitter that outputs an optical signal having a substantially Gaussian waveform and an optical receiver that is optically coupled to the optical transmitter and has an impulse response essentially matching the waveform. The impulse response and waveform preferably match in the time domain. The transmitter and receiver may be average-power-limited, using, for example, an erbium-doped fiber amplifier. To achieve a high signal-to-noise ratio, the waveform may be designed to minimize jitter, sample duration, matching parasitics, and inter-symbol interference (ISI). Such a waveform may be a return-to-zero (RZ) Gaussian or Gaussian-like waveform and may be transmitted in a variety of modulation formats. Further, the system may be used in WDM or TDM systems. A method for characterizing the time domain impulse response of an optical element used in the optical receiver is provided, where the method is optionally optimized using deconvolution and/or cross-correlation techniques.

US Patent:

7233430, Jun 19, 2007

Filed:

Dec 23, 2004

Appl. No.:

11/022344

Inventors:

David O. Caplan - Westford MA, US

Assignee:

Massachusetts Institute of Technology - Cambridge MA

International Classification:

G02F 2/00
H04B 10/06
G02F 1/00
H01S 3/00
H04B 10/00
H04J 14/00
H04J 14/02

US Classification:

359325, 398 2, 398 79, 398208, 398209, 398210, 398211

Abstract:

An optical, multi-channel, Differential Phase Shift Keying (DPSK) receiver demodulates multiple Wavelength Division Multiplexed (WDM) channels using a single interferometer. This distributes expense of the interferometer over all channels of an optical signal, allowing for deployment of cost-effective, scalable, wideband, WDM DPSK systems. For example, for an 80 channel WDM link, the receiver uses a single interferometer instead of eighty interferometers and associated stabilization hardware, dramatically reducing size, weight, power, and cost. The receiver is architecturally compatible with existing interferometer technologies so previous development and qualification efforts can be leveraged. This allows for expedited technology insertion into existing optical communications networks, including terrestrial and space-based optical networks.

US Patent:

7313735, Dec 25, 2007

Filed:

Apr 30, 2004

Appl. No.:

10/836676

Inventors:

Thomas M. Levergood - Hopkinton MA, US
Peter R. Holland - Cambridge MA, US
David S. Caplan - Acton MA, US

Assignee:

Sun Microsystems, Inc. - Santa Clara CA

International Classification:

G06F 11/00

US Classification:

714 47

Abstract:

A system and method provide in-line server health checks to determine server health without having to wait for a next out-of-band polling interval as with conventional methods. By determining server health directly resulting from TCP and HTTP client requests, multiple connection retries on an unavailable server are prevented. The method for providing server health checking of a server in a network includes activating an in-line server health checking mechanism by monitoring a data path of a server as to health status. Results from the health status analysis are ultimately reported to an authority on server health.

US Patent:

7401355, Jul 15, 2008

Filed:

Apr 30, 2004

Appl. No.:

10/835794

Inventors:

Robert M. Supnik - Carlisle MA, US
David S. Caplan - Acton MA, US
Paul G. Phillips - Westboro MA, US
Michael Banatt - Cambridge MA, US

Assignee:

Sun Microsystems - Santa Clara CA

International Classification:

H04L 29/00

US Classification:

726 11

Abstract:

Methods and systems for load balancing a plurality of entities, such as firewalls, in a network environment are disclosed. In particular, the load balancing of firewalls on a bidirectional traffic path is performed using a single device that controls both incoming and outgoing traffic through the firewalls. The single device may include virtual routers for controlling the bidirectional traffic through the firewalls. A first virtual router may control incoming traffic to the firewalls and the other virtual router may control outgoing traffic to the firewalls. The virtual routers are logical partitions of the device layered on the physical resources of the device. The virtual routers share all or portions of the physical resources of the single device.

US Patent:

7411726, Aug 12, 2008

Filed:

Mar 8, 2007

Appl. No.:

11/715670

Inventors:

David O. Caplan - Westford MA, US

Assignee:

Massachusetts Institute of Technology - Cambridge MA

International Classification:

G02F 2/00
H04B 10/06
H04B 10/00
G02F 1/00
H01S 3/00
H04J 14/00
H04J 14/02

US Classification:

359325, 398 2, 398 79, 398208, 398209, 398210, 398211

Abstract:

An optical, multi-channel, Differential Phase Shift Keying (DPSK) receiver demodulates multiple Wavelength Division Multiplexed (WDM) channels using at least one interferometer. This distributes expense of the interferometer(s) over all channels of an optical signal, allowing for deployment of cost-effective, scalable, wideband, WDM DPSK systems. For example, for an 80 channel WDM link, the receiver uses a single interferometer instead of eighty interferometers and associated stabilization hardware, dramatically reducing size, weight, power, and cost. The receiver is architecturally compatible with existing interferometer technologies so previous development and qualification efforts can be leveraged. This allows for expedited technology insertion into existing optical communications networks, including terrestrial and space-based optical networks.

US Patent:

7414728, Aug 19, 2008

Filed:

Dec 23, 2005

Appl. No.:

11/318255

Inventors:

David O. Caplan - Westford MA, US

Assignee:

Massachusetts Institute of Technology - Cambridge MA

International Classification:

G01B 9/02

US Classification:

356477

Abstract:

A polarization independent (PI) interferometer design that can be built from standard optical components is described. Based upon a Michelson interferometer, the PI interferometer uses a 50/50 splitter and Faraday Rotator Mirrors (FM's). The interferometer achieves good optical characteristics, such as high extinction ratio (ER) and low insertion loss (IL). Lack of polarization sensitivity reduces interferometer construction tolerances and cost, enhances performance and utility, and expands the scope of interferometric based devices. Such characteristics can be used to construct flexible, high performance, polarization insensitive, multi-rate, self-calibrating, optical DPSK receivers, power combiners, optical filters and interleavers, all-optical switches, and cascaded interferometers. Since polarization is not maintained in standard fiber optic networks, a PI-DPSK receiver allows for use of more sensitive DPSK communications over fiber, without need for costly polarization control hardware. Other applications of PI interferometers include optical CDMA, secure communications, optical coherence tomography (OCT), and temporal gratings with ultra-precise timing.