Coded data generation or conversion – Analog to or from digital conversion – Using optical device
Reexamination Certificate
1999-02-16
2001-09-11
Williams, Howard L. (Department: 2819)
Coded data generation or conversion
Analog to or from digital conversion
Using optical device,
C359S331000, C359S336000
Reexamination Certificate
active
06288659
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates in general to data conversion systems, and more particularly, to a method and apparatus for data conversion systems using time manipulation.
2. Description of Related Art
Signal speeds for electronics have dramatically increased over the past decade. Clocking speeds for computers are routinely in the hundreds of megahertz (MHz) region, and communications systems commonly use multi-gigahertz (GHz) carrier signals. Building high-speed receivers to capture and analyze such signals has become increasingly more difficult.
Time manipulation of signals has been proposed as a possible technique to match data rates of signals to the receiver or to observe phenomena that last for only a few nanoseconds (ns), e.g., signal transients, clock edges, and nuclear explosions. Considering the time/space equivalence of dispersion and diffraction, and in direct analogy to a spatial lens, an electrical signal may be stretched (or, alternatively, contracted) in time by subjecting the electrical signal to a dispersion-quadratic phase modulation-dispersion sequence. This concept remains mostly theoretical, however, because of the difficulty of obtaining high quadratic phase modulation rates and/or large bandwidth dispersion elements.
Some prior attempts at time stretching include an all-electrical time stretch system. In the electrical domain, highly dispersive elements are available; however, the small bandwidth of these elements limits the capability and performance of an all-electrical system.
All-optical systems have large bandwidth dispersive elements, but the all-optical system has difficulty producing a high quadratic phase modulation rate. Although resonant optical phase modulation has been used to attain high modulation rates, such systems are useful for very short periods of time. Compression of electrical signals is also difficult within electrical or optical conversion systems because of the reasons listed above relating to dispersion.
It can be seen, then, that there is a need for a system that can stretch or compress a signal in time. It can also be seen then that such a system must be able to be produced with standard components to increase usage times of the compression or dispersion system.
SUMMARY OF THE INVENTION
To overcome the limitations in the prior art described above, and to overcome other limitations that will become apparent upon reading and understanding the present specification, the present invention discloses a method and apparatus for altering the time base of an electrical signal. The time base can be altered in discrete or piecewise continuous fashion. A laser, typically an erbium-doped fiber laser, is chirped by frequency spreading the laser output. The chirped output is then modulated with the electrical signal, and then frequency spread again. The output of the modulated signal is detected with a photodetector to convert the optical signal back to an electrical signal.
The present invention overcomes the limitations of prior art solutions by using an optoelectronic time magnification system with electrical inputs and outputs. The linear chirp (quadratic phase modulation) is provided by a dispersed optical pulse from a mode-locked Erbium Doped Fiber Laser (EDFL). In addition to the ultra high bandwidth (~7.5 THz) and chirp rate, the present invention differs from others in that the bandwidth of the input signal is negligible compared to the chirp bandwidth. With this property available in the present invention, an approximation to an ideal time lens can be obtained without the need to disperse the input signal. By eliminating the initial dispersion of the input signal, less complicated designs can be used for the remainder of the system.
REFERENCES:
patent: 4928316 (1990-05-01), Heritage et al.
patent: 5010346 (1991-04-01), Hamilton et al.
patent: 5521703 (1996-05-01), Mitchell
patent: 5714954 (1998-02-01), Chung et al.
patent: 5793907 (1998-08-01), Jalai et al.
patent: 5862287 (1999-01-01), Stock et al.
Frankel et al.,High-performance photonic analogue-digital converter, Electronics Letters vol. 33, No. 25, Dec. 4, 1997, pp. 2096-2097.*
W.J. Caputi, “Stretch: A Time-Transformation Technique”,IEEE Transactions on Aerospace. and Electronic Systems., 1971, vol. AES-7, pp. 269-278.
B.H. Kolner and M. Nazarathy, “Temporal Imaging with a Time Lens”,Optical Society of America, 1989, vol. 14, No. 12, pp. 630-632.
A.A. Godil, B.A. Auld, and D.M. Bloom, “Time-Lens Producing 1.9 ps Optical Pulses”,Applied Physics Letters, 1993, vol. 62, No. 10, pp. 1047-1049.
C.V. Bennet, E.P. Scott and B.H. Kolner, “Temporal Magnification and Reversal of 100Gb/s Optical Data with an Up-conversion Time Microscope”,Applied Physics Letters, 1994, vol. 65, No. 20, pp. 2513-2515.
B.H. Kolner, “Generalization of the Concepts of Focal Length and f-number to Space and Time”,Optical Society of America, 1994, vol. 11, No. 12, pp. 3229-3234.
K. Mori, H. Takara, S. Kawanishi, M. Saruwatari, et al., “Flatly broadened Supercontinuum Spectrum Generated in a Dispersion Decreasing Fibre with Convex Dispersion Profile”,Electronic Letters, 1997, vol. 33, pp. 1806-1808.
S.T. Cundiff, W.H. Knox, and M.C. Nuss, “Active Feed-forward Channel Equalisation for Chirped Pulse Wavelength Division Multiplexing”,Electronic Letters, 1997, vol. 33, No. 1.
F. Coppinger, A.S. Bhushan and B. Jalai, “Time Magnification of Electrical Signals Using Chirped Optical Pulses”,Electronics Letters, Feb. 19, 1998, vol.. 34, No. 4, 399-400.
Coppinger Frederic Marie Alain
Jalali Bahram
Gates & Cooper LLP
The Regents of the University of California
Williams Howard L.
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