Optics: measuring and testing – By light interference – Using fiber or waveguide interferometer
Reexamination Certificate
2002-07-25
2004-11-02
Turner, Samuel A. (Department: 2877)
Optics: measuring and testing
By light interference
Using fiber or waveguide interferometer
Reexamination Certificate
active
06813028
ABSTRACT:
TECHNICAL FIELD
The present claimed invention relates to the field of optical network analysis. More specifically, the present claimed invention relates to calibration of an optical network analyzer.
BACKGROUND ART
Optical network analysis has been used to determine the optical characteristics of optical network components. For example, the optical characteristics of a fiber Bragg grating or series of fiber Bragg gratings can be determined using an optical network analyzer. More generally, optical network analyzers are used to determine the optical characteristics of various optical components, composite optical systems, and various other types of devices under test (DUTs).
Recently, advancements have been made in optical network analysis which enable extremely precise determination of the optical characteristics of an optical component. Specifically, interferometric optical analysis methods can now be used to precisely examine and measure the optical characteristics of an optical component. However, as the precision of such measurements improve, uncertainties or errors associated with the optical network analyzer itself become of greater concern. For example, an interferometric optical network analyzer may have an internal polarization dependent loss (PDL) of plus or minus several tenths of a dB. As a result, when attempting to determine the optical characteristic of an optical component (e.g. to plus or minus 50 milli-dB), the quantity of the PDL uncertainty associated with the optical network analyzer makes is difficult or impossible to measure the PDL of the optical component with the precision desired. Although the above discussion specifically refers to measurement of PDL, such an example is intended to be exemplary. That is, the uncertain intrinsic optical properties of conventional interferometric optical network analyzers also reduce the precision with which the measurement of various other optical characteristics can ultimately be made.
One approach to overcome the above-listed disadvantage is to attempt to reduce the uncertainties or errors associated with the intrinsic optical properties of the optical network analyzer itself. For example, an interferometric optical network analyzer may be constructed using optically inert components. For purposes of the present application, a component which is referred to as “optically inert” is an optical component which introduces no or very small degradation of measured optical characteristics. Typically, this means that such optically inert components possess low PDL and polarization mode dispersion (PMD). Such optically inert components, however, are typically quite expensive. As a result, the cost increase incurred by using such optically inert components can render a conventional interferometric optical network analyzer prohibitively expensive. Furthermore, even when optically inert components are used, the magnitude of the cumulative uncertainties may still be too great to enable measurement of the optical characteristic of the optical component with the precision desired.
Thus, a need exists for a method and system to readily determine the optical characteristics of an optical component. A further need exists for a method and system which meets the above need and can precisely determine the optical characteristics of an optical component. Another need exists for a method and system which meets the above needs and which does not require the use of an optical network analyzer comprised of optically inert components.
DISCLOSURE OF THE INVENTION
In accordance with the present invention, a method and system is provided to readily and precisely determine the optical characteristics of an optical component without requiring the use of an optical network analyzer comprised of optically inert components having very small measurement uncertainties.
In accordance with the present invention, a plurality of interferometric measurements for a control optical element using first polarized lightwaves of a first amplitude and second polarized lightwaves of a second amplitude are received in accordance with the invention. Next, a calibration result is derived using the plurality of interferometric measurements in accordance with the present invention. With this calibration result, the optical properties of a device under test (DUT) measured using the first polarized lightwaves of the first amplitude and the second polarized lightwaves of the second amplitude can be determined with reduced uncertainty due to intrinsic optical characteristics of the interferometric optical network analyzer.
These and other technical features of the present invention will no doubt become obvious to those skilled in the art after having read the following detailed description of the embodiments which are illustrated in the various drawing figures.
REFERENCES:
patent: 5619325 (1997-04-01), Yoshida
patent: 6259529 (2001-07-01), Sorin et al.
patent: 6606158 (2003-08-01), Rosenfeldt et al.
Agilent Technologie,s Inc.
Lyons Michael A.
Turner Samuel A.
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