University System of Maryland

The United States of America As Represented by the National Security Agency

The United States of America As Represented by the Director of the

Julius Goldhar

Daniel Mahgerefteh

Pak Shing Cho

Douglas Llewellyn Butler

Lance G Joneckis

Ehab Awad

Norman Moulton

Christopher Richardson

All-optical timing extraction and optical clock recovery for high-speed return-to-zero binary optical data streams using the timing difference between clock and data counter-propagating optical pulses in a non-linear optical waveguide where the first pulse to arrive at the non-linear optical waveguide partially saturates the transmission properties of the waveguide resulting in a change of the transmission properties seen by the lagging pulse. A balanced photo-detector makes delay-dependent comparisons of the clock and data pulses' peak power and generates an error signal used in a phase-locked loop configuration to synchronize the clock to the data stream.

Optical clock recovery device using non-linear optical waveguides

The present invention provides simultaneous all-optical regeneration (re-shape and re-amplify) and wavelength conversion using a reverse-biased electroabsorption modulator. The nonlinear optical transmission characteristic of the electroabsorption modulator reshapes the degraded input data by selective absorption of the optical noise and, therefore, increases the signal-to-noise ratio of the output. Reverse biasing the modulator allows fast recovery of the optical absorption for high data-rate operation without the detrimental bit-patterning effect. Error-free wavelength conversion and regeneration at 20 Gb/s was obtained with more than 3-dB improvement of the receiver sensitivity at a bit-error-rate of 10 . Embodiments and applications of the present invention include an all-optical SEAM regenerator, an all-optical distributed feedback laser SEAM (DFB-SEAM) regenerator, an all-optical SEAM with fiber Bragg grating (SEAM-FBG) regenerator, an all-optical SEAM with polarizing beam splitter (SEAM-PBS) regenerator, an all-optical Mach-Zehnder interferometric (MZI-SEAM) regenerator, an all-optical 3-port MZI-SEAM regenerator, and a SEAM-based optimized receiver.

All-optical regeneration at high bit rates using an electroabsorption modulator

An apparatus and method for measuring the spectral dependence of the Raman gain coefficient in optical fibers is presented. This approach measures the power level of Raman scattering in both a walk-off limited region and a physical fiber length limited region and, from these measurements, extracts the spectral dependence of the Raman gain coefficient. Access to these two regions is accomplished through control of the excitation pulse temporal width and relies on fiber dispersion to separate the excitation light from the Raman scattered light for short pulse widths. This approach measures the spectral dependence of the Raman gain without the necessity of absolute power measurement of the Raman scattered light, the need for a reference standard, or the need of a frequency tunable secondary optical source.

Measurement of Raman gain spectrum in optical fiber

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Silver Spring, MD, United States of America

Julius Goldhar