Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1998-11-25
2002-05-14
Pascal, Leslie (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C359S199200
Reexamination Certificate
active
06388781
ABSTRACT:
FIELD OF THE INVENTION
The invention pertains to the field of multiplexing and demultiplexing optical signals between the time and wavelength domains. The invention addresses the problem of enabling the use of optical fiber data transmission at rates that exceed the maximum bit rate of conventional photodetectors.
BACKGROUND OF THE INVENTION
Optical fiber data transmission is widely employed because of its high bandwidth and low cost of operation. Optical fibers are presently capable of carrying data at bit rates in excess of 100 Gb/s. However, the maximum practical rate of data transmission over optical fibers is limited by the maximum bit rate of conventional photodetectors and the associated electronic components used to convert the optical signals to electrical signals. To support a bit rate of 100 Gb/s, a photodetector would need an operating frequency of approximately 50 Ghz. This rate is far in excess of what is available in conventional devices. Accordingly, optical fiber data transmission using conventional devices and methods is currently limited to time division multiplexed (TDM) data rates of approximately 10 Gb/s.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a multiplexer for demultiplexing optical data from a serial bit stream having a bit rate in excess of that of conventional photodetection devices to multiple bit streams at a bit rate that may be serviced using conventional photodetection devices. This object of the invention is accomplished, in general terms, through the use of four-wave mixing in a wavelength conversion element to produce from a single high rate data stream multiple intermodulation products which together represent the input data stream in wavelength division multiplexed (WDM) form.
A preferred embodiment of the invention in accordance with this object is an apparatus for converting a time division multiplexed signal to multiple wave division multiplexed signals. The apparatus includes a clocked pump for producing clocked signals having unique wavelengths at successive intervals corresponding to the bit rate of an input return-to-zero TDM signal. A wavelength conversion element produces intermodulation products of the TDM signal and clocked signals that represent a logical AND of the clocked signals and the TDM signal.
It is a further object of the invention to provide a multiplexer for multiplexing multiple data streams provided at conventional bit rates to a serial bit stream having a bit rate in excess of that of conventional photodetection devices. This object of the invention is accomplished, in general terms, through the use of four-wave mixing in a wavelength conversion element to produce from multiple data streams at differing wavelengths a single high rate data stream which represents the input data streams in time division multiplexed (TDM) form.
A preferred embodiment of the invention in accordance with this object is an apparatus for converting multiple wave division multiplexed (WDM) signals to a time division multiplexed (TDM) signal. The apparatus includes a clocked pump for producing clocked signals having unique wavelengths at successive intervals corresponding to the bit rate of an input WDM signal divided by the number of clocked signal. A wavelength conversion element produces intermodulation products of the WDM signal and clocked signals that represent a logical AND of the clocked signals and the WDM signal.
REFERENCES:
patent: 5737106 (1998-04-01), Sansonetti
patent: 5953138 (1999-09-01), Ellis
patent: 5953142 (1999-09-01), Chiaroni et al.
patent: 6023360 (2000-02-01), Morioka et al.
patent: 6204944 (2001-03-01), Uchiyama et al.
Lacey, J.P.R. et al. “All-optical WDM to TDM transmultiplexer.” Sep. 15, 1994. Electronics Letters, vol. 30, No. 19, pp. 1612-1613.*
Summerfield, M.A. et al. “All-optical TDM to WDM conversion in a semiconductor optical amplifier.” Feb. 3, 1994. Electronics Letters, vol. 30, No. 3, pp. 255-256.
Foley & Lardner
Leung Christina Y
Nortel Networks Limited
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