Optics: measuring and testing – Lens or reflective image former testing
Reexamination Certificate
1999-09-24
2002-03-19
Font, Frank G. (Department: 2877)
Optics: measuring and testing
Lens or reflective image former testing
C372S028000, C250S228000
Reexamination Certificate
active
06359685
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to providing a laser system having a laser signal with information encoded therein related to its wavelength at a given instant in time.
There are several ways of testing an optical component for loss and other characteristics. For example, a single optical signal of known wavelength and amplitude can be launched into a component, and losses can be deduced from a signal measured at the output of the device. Alternatively, a plurality of signals can be launched into the device sequentially and similar measurements made for each wavelength. In a manufacturing and production environment, it is preferable to test devices over a range of wavelengths of interest as quickly as possible. Generally, a testing station for testing optical components requires a very costly tunable laser. In operation, these lasers are tuned to a plurality of wavelengths, one at a time, and have their output signal fed into a device under test (DUT). The purpose of providing a signal to a DUT at various wavelengths within a predetermined range of wavelengths, is to detect losses through the DUT at each or at several wavelengths of interest. Of course it would be possible to provide signals from several discrete lasers to a DUT, however, in a production environment, such a scheme would likely not be practicable. When using a tunable laser as mentioned above, it is preferred if electronic circuitry is provided to correlate an output response for the DUT with a particular wavelength of light propagating through the device at a particular instant in time.
Systems are currently known that employ a tunable laser in which the tuning mechanism stops at each wavelength to be tested. However, this process takes several minutes when a large number (i.e.>100) of wavelengths are to be measured. The wavelength accuracy is limited by the mechanical tolerances of the tuning mechanism.
It is an object of this invention to provide a laser system having means for encoding the wavelength of an optical signal within that signal.
It is an object of this invention to provide an apparatus for determining the wavelength of a tunable laser signal while it is tuning, so that the tuning mechanism does not have to stop at each wavelength, thus speeding up the measurement. The wavelength accuracy is not affected by the mechanical tolerances of the tuning mechanism.
It is an object of this invention, to provide a central system, which generates signals for testing optical devices at a plurality of testing stations, remote from the central system.
It is a further object of the invention to provide a system having one tunable laser for generating a plurality of signals to a plurality of test stations simultaneously.
It is a further object of the invention to provide a system for testing a plurality of devices simultaneously.
It is a further object of the invention to provide an apparatus responsive to an input signal of varying wavelengths, for testing a plurality of devices at a plurality of locations.
It is yet a further object to provide an optical signal that can be distributed to a plurality of remote test locations and wherein wavelength information is encoded within the optical signal and providing remote testing stations with means to decode the signal dynamically to determine its wavelength and to correlate a particular test with a particular wavelength.
STATEMENT OF THE INVENTION
In accordance with the invention, there is provided, an apparatus for testing an optical component, comprising:
a) means for encoding a first optical signal having a wavelength that changes in time, from a higher wavelength to a lower wavelength or from a lower wavelength to a higher wavelength with timing information that corresponds to the first optical signal being at a predetermined wavelength at a particular instant in time;
b) a test station including:
means for deriving from the encoded first optical signal, information relating to the wavelength of the first optical signal at a particular instant in time;
means for correlating test information with the derived wavelength information to determine an output response for the optical component to the first optical signal and to determine the wavelength of the first optical signal that produced the output response.
In accordance with the invention, there is provided, an apparatus for testing an optical component, comprising:
means for encoding a first optical signal that varies in wavelength with information relating to its wavelength.
In accordance with another aspect of the invention, there is provided, a method of generating a test signal for broadcast to a plurality of locations for testing optical devices, comprising the steps of:
a) generating a first laser signal that varies in wavelength from a first lower wavelength to a higher upper wavelength or vice versa sweeping through a plurality of wavelengths therebetween;
providing a synchronization signal for indicating when the first laser signal is at a predetermined frequency;
modulating the first laser signal that varies in wavelength to encode information therein corresponding to a plurality wavelengths of the first optical signal at a plurality of instants in time;
providing the modulated first laser signal to a test station; providing the first laser signal to an optical device for testing said device;
deriving wavelength information relating to the first laser signal from the modulated first laser signal;
and, correlating test information with the derived wavelength information.
In accordance with the invention, there is provided, a method of generating a test signal for broadcast to a plurality of locations for testing optical devices, comprising the steps of:
a) generating a first laser signal that varies in wavelength from a first lower wavelength to a higher upper wavelength sweeping through a plurality of wavelengths therebetween;
providing a synchronization signal for indicating when the first laser signal is at a predetermined frequency;
modulating the first laser signal that varies in wavelength to encode information therein corresponding to a plurality wavelengths of the first optical signal at a plurality of instants in time;
providing the modulated first laser signal to a test station;
providing the modulated first laser signal to an optical device for testing said device;
deriving wavelength information relating to the first laser signal from the modulated first laser signal;
and, correlating test information with the derived wavelength information.
In accordance with yet another aspect of the invention, there is provided, tunable laser signal for use in an optical system, the tunable laser signal having a wavelength that is controllably variable within predetermined limits, comprising:
a decodable signature encoded within the tunable laser signal that corresponds to its particular wavelength at a different instants in time as the its wavelength varies.
REFERENCES:
patent: 4905253 (1990-02-01), Chraplyvy et al.
patent: 5548433 (1996-08-01), Smith
patent: 5724166 (1998-03-01), Nakata
Colbourne Paul
Duck Gary
Nyman Bruce
Zimmerman Donald R.
Font Frank G.
Greene Kevin E.
JDS Uniphase Corporation
Lacasse Randy W.
Lacasse & Associates
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