Optical: systems and elements – Deflection using a moving element – Using a periodically moving element
Reexamination Certificate
1999-08-27
2001-10-30
Chan, Jason (Department: 2633)
Optical: systems and elements
Deflection using a moving element
Using a periodically moving element
C359S199200, C359S199200
Reexamination Certificate
active
06310703
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method and apparatus for optical spectrum analysis in wavelength division multiplexed fiber optic systems.
BACKGROUND OF THE INVENTION
Wavelength division multiplexing is one way in which the information capacity, bandwidth, of an optical fiber can be substantially increased. This is accomplished by using several optical carriers within a narrow spectrum, typically around 1550 nm, which individually carry information in the optical fiber. In such systems, the information is encoded onto each carrier. The carriers are then combined through an optical multiplexer which then permits simultaneous transmission of all carriers into the optical fiber. At the receiving end, the optical signals are passed through an optical demultiplexer which subsequently routes the individual carriers to their appropriate channel. The present invention relates to the measurement of optical parameters for individual carriers in a wavelength division multiplexed fiber optic system. In such systems, measurement of optical parameters on a per carrier basis are critical as they provide vital information regarding both the heath of the optical networks over which such systems operate in addition to the performance of the system. Such information can then be used for diagnosis and repair or for performance optimization actions.
The optical information sought can usually be determined by the measurement of wavelength, power, and optical signal-to-noise ratio all measured on a per carrier basis. The measurement of such parameters must be accurate, have a wide range, and be performed in a timely manner so as to provide the necessary information in the shortest amount of time for the appropriate actions.
The conventional approach to analyzing the optical parameters of a spectrally dependent system is to use an optical spectrum analyzer. These systems are generally based on using an optical tool known as a monochromater. Monochromater based optical spectrum analyzers are typically slow, large in size for most embedded and field applications, and tend to drift with time, giving poor absolute accuracy. In fact, for most applications more than one instrument is typically used to obtain key optical parameters such as those described above.
Accordingly it would be advantageous to provide a ratiometric wavelength and power detection system that accurately provides wavelength, power, and signal-to-noise ratio measurements on a per carrier basis. Further, it would be advantageous if such a system could be provided in situ to provide these measurements so that the information could be monitored on a continual basis. Alternatively it would be advantageous if such a system could be used as a stand alone diagnostic tool.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a method and devices for analyzing an optical spectrum in wavelength division multiplexed fiber optic systems that provides wavelength, power, and signal-to-noise ratio measurements on a per carrier basis.
The present invention provides an apparatus for analyzing an optical spectrum in wavelength division multiplexed fiber optic systems, comprising:
a tunable channel selector having an input and an output;
a wavelength and power detection system optically connected to the output of the tunable channel selector; and
a controller connected to the tunable channel selector and the wavelength and power detection system.
The present invention also provides a ratiometric method of analyzing an optical spectrum in wavelength division multiplexed fiber optic systems, comprising:
receiving a spectrally encoded optical signal into a tunable channel selector;
dividing the spectrally encoded optical signal into at least two optical signals and passing a first optical signal through an optical filter;
detecting an output of the optical filter and converting the detected optical signal to a first electrical signal and detecting a second optical signal from the divided optical signal and converting it to a second electrical signal; and
dividing one of the electrical signals by the other electrical signal to give a power independent representation of an input wavelength.
The method and apparatus forming the present invention allows for rapid analysis of the optical spectrum and its content by controlling the spectral position of a channel select element and using a ratiometric wavelength and power determination technique to accurately analyze the transmitted or selected portion of the optical spectrum. The channel select element may be either a transmissive or reflective device which may be tuned by way of a control signal. The system can be operated in either scan and post process mode or in a continuous feedback mode where the position of the channel select element is determined by the ratiometric wavelength determination system and used to control the wavelength position of the channel select element. This ratiometric wavelength and power determination system, in its typical form, is based on dividing the spectrally encoded optical signal into two parts. One part of this signal passes through an optical filter with continuously increasing or decreasing transmission as a function of wavelength while the other part is unperturbed. The two parts are subsequently detected by optical to electrical detectors where the electrical signal is proportional to the optical signal. Ratioing the two signals reveals a unique number which is a power independent representation of the input wavelength. The present invention advantageously provides a method and device to measure simultaneously several carriers and not just one. Furthermore, in the present invention, a power measurement may be obtained by using the unfiltered part of the optical signal.
REFERENCES:
patent: 4852079 (1989-07-01), Kinney et al.
patent: 5387992 (1995-02-01), Miyazaki et al.
patent: 5696863 (1997-12-01), Kleinerman
patent: 5747791 (1998-05-01), Coroy
patent: 5861980 (1999-01-01), Ono
patent: 5995255 (1999-11-01), Giles
patent: 6067288 (2000-05-01), Miller et al.
patent: 0455461 (1991-11-01), None
patent: 07626672 (1997-03-01), None
Alavie A. Tino
Xu Ming Gang
Chan Jason
JDS Uniphase Corporation
Leung Christina Y.
Teitelbaum Neil
LandOfFree
Method and apparatus for optical performance monitoring in... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for optical performance monitoring in..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for optical performance monitoring in... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2559083