Test and measurement system for detecting and monitoring faults and losses in passive optical networks (PONs)
First Claim
1. An apparatus for measuring transmission loss in a passive optical network (PON) transmitting optical signals from an optical fiber to each of N branches, said apparatus comprising:
- means for launching optical pulses into the PON, said optical pulses having different known states of polarization;
polarization markers deployed with each branch of the passive optical network for introducing a unique polarization dependent loss (PDL) in the corresponding branch of the PON;
means for measuring the backscatter of the optical pulses from the PON as a function of time, for each of the different known states of polarization; and
means for deriving the transmission loss based on the backscatter of the optical pulses for each of the different known states of polarization, wherein the unique PDL associated with each branch is used as the basis for distinguishing the branches of the PON from each other.
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Abstract
The present invention employs “polarization markers” deployed immediately after the branching portion of a passive optical network (PON) for measuring and monitoring transmission losses and faults. Each polarization marker is configured to produce a unique polarization dependent loss (PDL) within the corresponding branch of the PON. Since each polarization marker uniquely attenuates optical test pulse(s) launched into the PON, the back-scattering uniquely varies with the launched state of polarization. Losses within each branch of the PON are then monitored by measuring the back-scattered portion of the launched optical pulse(s) as a function of time for different known states of polarization, wherein the unique PDL associated with each polarization marker is used as the basis for distinguishing the branches from one another.
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Citations
34 Claims
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1. An apparatus for measuring transmission loss in a passive optical network (PON) transmitting optical signals from an optical fiber to each of N branches, said apparatus comprising:
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means for launching optical pulses into the PON, said optical pulses having different known states of polarization;
polarization markers deployed with each branch of the passive optical network for introducing a unique polarization dependent loss (PDL) in the corresponding branch of the PON;
means for measuring the backscatter of the optical pulses from the PON as a function of time, for each of the different known states of polarization; and
means for deriving the transmission loss based on the backscatter of the optical pulses for each of the different known states of polarization, wherein the unique PDL associated with each branch is used as the basis for distinguishing the branches of the PON from each other. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
where the subscript numeral i denotes the polarization state.
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14. The apparatus of claim 1 wherein said polarization markers include fiber coils.
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15. In a passive optical network (PON) having a feeder fiber carrying traffic signals, and a star coupler coupling the traffic signals from the feeder fiber to each of N optical network units (ONUs) through a corresponding distribution fiber, with each ONU, the corresponding distribution fiber and any intermediate network components lying between them referred to as a branch, an apparatus for measuring the transmission loss in each distribution fiber, comprising:
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an optical source generating optical pulses having N known polarization states;
an optical coupler coupling the optical pulses into the feeder fiber while simultaneously allowing the traffic signals to propagate along each of the N distribution fibers;
polarization markers deployed along each branch of the PON for introducing a unique polarization dependent loss (PDL) in the corresponding branch of the PON;
means for measuring the backscatter of the optical pulses from the distribution fibers as a function of time, for each of the different known states of polarization;
a signal processor for deriving the transmission loss of each distribution fiber from the backscatter of the optical pulses for each of the different known states of polarization, wherein the unique PDL associated with each branch is used as the basis for distinguishing the distribution fibers. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29)
where the subscript numeral i denotes the polarization state.
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29. The apparatus of claim 27 wherein said polarization markers include fiber coils.
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30. In a passive optical network (PON) having a feeder fiber carrying traffic signals, and a distribution node distributing the traffic signals from the feeder fiber to each of N optical network units (ONUs) along a corresponding distribution fiber, with each ONU, the corresponding distribution fiber and any intermediate network components lying between them referred to as a branch, a method for measuring the transmission loss in each distribution fiber, comprising the steps of:
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launching optical pulses into the feeder fiber having one of N known polarization states;
introducing a unique polarization dependent loss (PDL) in each branch of the PON;
measuring the backscatter of the optical pulses from the distribution fibers as a function of time, for each of the N known states of polarization; and
deriving the transmission loss of each distribution fiber from the backscatter of the optical pulses, with the unique PDL associated with each branch used as the basis for distinguishing the distribution fibers. - View Dependent Claims (31, 32, 33, 34)
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Specification