Optical bit rate detector

Details Optical bit rate detector Optical bit rate detector

2002-10-21

2004-07-20

Pham, Hoa Q. (Department: 2877)

Optics: measuring and testing

Photometers

C356S229000, C398S009000

Reexamination Certificate

active

06765665

ABSTRACT:

TECHNICAL FIELD
The present invention relates to, an optical bit rate detector, and in particular to an optical bit rate detector that differentiates between known modulation rates.
BACKGROUND OF THE INVENTION
Optical networks currently support signals with various modulation rates, e.g. 10 GB/s (OC192), 5 GB/s (OC96), 2.5 GB/s (OC48) and 1.25 GB/s (OC 24). Accordingly, there exists a need for a device with the ability to detect the bit rate of a received signal. To determine the absolute modulation rate would require a very high-resolution optical spectrum analyzer or the combination of a high-speed-receiver and an electrical spectrum analyzer. Both of these options require large and expensive equipment. U.S. Pat. No. 6,266,172 issued Jul. 24, 2001 in the name of Martin Zirngibl discloses an optical bit rate measurement device that alleviates the need for expensive spectrum analyzers. However, the Zirngibl device requires complicated electrical circuitry for separating, delaying, multiplying, and integrating electrical signals to generate an autocorrelation function.
An object of the present invention is to overcome the shortcomings of the prior art by providing a simple inexpensive optical bit rate detector that determines the optical bit rate of a signal by the amount of the signal passed through a narrow band optical filter.
SUMMARY OF THE INVENTION
Accordingly, the present invention relates to an optical bit rate detector device for determining the optical bit rate of an input optical signal comprising:
a beam splitter for dividing the input optical beam into first and second sub-beams;
an optical filter disposed to receive the first sub-beam;
a first photo-detector for measuring the optical power of the first sub-beam after passing through the optical filter;
a second photo-detector for measuring the optical power of the second sub-beam; and
circuit means for comparing the optical power of the first and second sub-beams to determine the bit rate of the input optical signal.
Another aspect of the present invention relates to a method of determining the optical bit rate of an optical signal comprising the steps of:
a) determining an initial power measurement of the optical signal;
b) passing at least a portion of the optical signal through an optical filter;
c) determining a secondary power measurement of the optical signal passing through the optical filter; and
d) comparing the initial power measurement with the secondary power measurement and determining the optical bit rate of the signal based of the comparison.
Another feature of the present invention provides A device for determining the optical bit rate of an optical signal comprising:
first power measuring means for obtaining a measure of the optical signal's initial power;
an optical filter for filtering at least a portion of the optical signal resulting in a filtered signal;
second power measuring means for obtaining a measure of the filtered signal's power; and
bit rate determining means for determining the bit rate of the optical signal based on the measure of the initial power and the filtered signal's power.


REFERENCES:
patent: 4989201 (1991-01-01), Glance
patent: 5513029 (1996-04-01), Roberts
patent: 6266172 (2001-07-01), Zirngibl
patent: 6580531 (2003-06-01), Swanson et al.

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