Optical waveguides – With optical coupler – Particular coupling structure
Reexamination Certificate
1998-03-06
2001-06-19
Ullah, Akm E. (Department: 2874)
Optical waveguides
With optical coupler
Particular coupling structure
Reexamination Certificate
active
06249626
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to an optical power monitoring tap for use with bulk optic devices and, more particularly, to an optical tap that may be included within a conventional optical subassembly and advantageously utilize pre-existing optical reflections (and possibly enhanced) as the light source for the optical tap.
2. Description of the Prior Art
In many optical subassemblies it is necessary to include an optical tap to monitor the power level of the optical signals passing th rough the optical subassembly. In most cases, the tap introduces additional optical components into the subassembly. For example, a grating, prism or partially reflecting mirror is added to the subassembly and functions to optically “tap” a portion of the light signal passing through the subassembly. While such an arrangement is useful in extracting a portion of the light signal, the introduction of additional optics adds to the cost and complexity of the overall subassembly. Further, the introduction of additional optics results in attenuating the optical signal passing through the subassembly.
SUMMARY OF THE INVENTION
The need remaining in the prior art is addressed by the present invention which relates to an optical power monitoring tap for use with bulk optic devices and, more particularly, to the utilization of a multimode filter as an optical tap that may be included within a conventional optical subassembly to monitor both transmitted and received optical signals.
In accordance with the present invention, a multimode optical fiber is disposed so as to capture the light traveling in the reverse direction through the optical subassembly. The multimode fiber is coupled to a conventional photodetector. By virtue of using a multimode fiber to couple the reflected signal, the photodetector need not be integral with the transmitter, but may be remotely located at a more convenient location.
In an alternative embodiment of the present invention, an additional pair of multimode fibers may be disposed on either side of the transmission fiber. These fibers would be used to capture other optical signals traveling in the reverse direction. This embodiment is particularly useful for arrangements including an optical isolator to test normally attenuated signals passing backward through the isolator assembly.
It is an aspect of the present invention to monitor transmitted signals (by detecting their reflections) as well as signals travelling in the reverse direction through isolators (by detecting portions of the signal outside the region of the single mode fiber).
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Koba Esq. Wendy W.
Lucent Technologies - Inc.
Ullah Akm E.
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