Polarization mode dispersion emulation
First Claim
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1. A method of emulating the first and second order PMD (polarisation mode dispersion) properties of a length of low birefringence optical fibre installed in the field, in which method light is caused to propagate through a concatenation of n lengths of high birefringence optical waveguide, each having two guided modes, respectively a fast mode and a slow mode, and each length presenting a different value of differential group delay, τ
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r, for light propagating in those modes, where r is a positive integer between 1 and n, wherein the rth length of the concatenation is optically coupled with the (r+1)th length in a manner providing cross coupling of the modes so that only cos2 θ
r of the power propagating in each mode (fast or slow) of the rth length is launched into the same mode (fast or slow) of the (r+1)th length while the remaining sin2 θ
r of the power is launched into the opposite mode (slow or fast), wherein the values of θ
r for r=1 to r=(n−
1) have a substantially random distribution within the range 0 to π
/2, and wherein said lengths and their differential group delays satisfy the following five criteria (i) to (v);
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Abstract
A PMD (polarisation mode dispersion) emulator which provides at least first and second order emulation of PMD effects observed in fiber installed in the field consists of a small number of concatenated lengths of high birefringence fiber having an appropriate distribution of relative DGDs (differential group delays), and connected with random relative orientation. Varying some parameter, such as temperature distribution, allows the emulator to provide accelerated exploration of random fluctuations in PMD which, in the field, may require many weeks, or longer, to observe.
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Citations
26 Claims
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1. A method of emulating the first and second order PMD (polarisation mode dispersion) properties of a length of low birefringence optical fibre installed in the field, in which method light is caused to propagate through a concatenation of n lengths of high birefringence optical waveguide, each having two guided modes, respectively a fast mode and a slow mode, and each length presenting a different value of differential group delay, τ
-
r, for light propagating in those modes, where r is a positive integer between 1 and n, wherein the rth length of the concatenation is optically coupled with the (r+1)th length in a manner providing cross coupling of the modes so that only cos2 θ
r of the power propagating in each mode (fast or slow) of the rth length is launched into the same mode (fast or slow) of the (r+1)th length while the remaining sin2 θ
r of the power is launched into the opposite mode (slow or fast), wherein the values of θ
r for r=1 to r=(n−
1) have a substantially random distribution within the range 0 to π
/2, and wherein said lengths and their differential group delays satisfy the following five criteria (i) to (v);
- View Dependent Claims (2, 3, 4, 5)
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r, for light propagating in those modes, where r is a positive integer between 1 and n, wherein the rth length of the concatenation is optically coupled with the (r+1)th length in a manner providing cross coupling of the modes so that only cos2 θ
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6. A method of emulating the first and second order PMD (polarisation mode dispersion) properties of a length of low birefringence optical fibre installed in the field, in which method light is caused to propagate through a concatenation of n lengths of high birefringence optical waveguide, wherein 5≦
- n≦
30, each having two guided modes, respectively a fast mode and a slow mode, and each presenting a different value of differential group delay, τ
, for light propagating in those two modes, wherein the rth length of the concatenation, where r is a positive integer between 1 and n, is optically coupled with the (r+1)th length in a manner providing cross coupling of the modes so that only cos2 θ
r of the power propagating in each mode (fast or slow) of the rth length is launched into the same mode (fast or slow) of the (r+1)th length while the remaining sin2 θ
r of the power is launched into the opposite mode (slow or fast), wherein the values of θ
r for r=1 to r=(n−
1) have a substantially random distribution within the range 0 to π
/2, wherein said differential group delay values are substantially aligned with members of the series τ
=qs, where q is a constant common to all members of the series, and s is a different integer for each member of the series. - View Dependent Claims (7, 8, 9, 10)
- n≦
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11. A method of emulating the first and second order PMD (polarisation mode dispersion) properties of a length of low birefringence optical fibre installed in the field, in which method light is caused to propagate through a concatenation of n lengths of high birefringence fibre, each presenting a different value of differential group delay, τ
-
r, where r is a positive integer between 1 and n, and each connected with its adjacent lengths in the concatenation with birefringence axes unaligned relative orientation, wherein said lengths satisfy the following five criteria (i) to (v);
- View Dependent Claims (12)
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r, where r is a positive integer between 1 and n, and each connected with its adjacent lengths in the concatenation with birefringence axes unaligned relative orientation, wherein said lengths satisfy the following five criteria (i) to (v);
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13. A method of emulating the first and second order PMD (polarisation mode dispersion) properties of a length of low birefringence optical fibre installed in the field, in which method light is caused to propagate through a concatenation of n lengths of high birefringence optical waveguide, wherein 5≦
- n≦
30, each presenting a different value of differential group delay, τ
, and each connected with its adjacent lengths in the concatenation with birefringence axes unaligned substantially random relative orientation, wherein said differential group delay values are substantially aligned with members of the series τ
=qs, where q is a constant common to all members of the series, and s is a different integer for each member of the series.
- n≦
-
14. An emulator for emulating the first and second order PMD (polarisation mode dispersion) properties of a length of low birefringence optical fibre installed in the field, the emulator including a concatenation of n lengths of high birefringence optical waveguide through which light is caused to propagate, each length having two guided modes, respectively a fast mode and a slow mode, and each presenting a different value of differential group delay, τ
-
r, for light propagating in those modes, where r is a positive integer between 1 and n, wherein the rth length of the concatenation is optically coupled with the (r+1)th length in a manner providing cross coupling of the modes so that only cos2 θ
r of the power propagating in each mode (fast or slow) of the rth length is launched into the same mode (fast or slow) of the (r+1)th length while the remaining sin2 θ
r of the power is launched into the opposite mode (slow or fast), wherein the values of θ
r for r=1 to r=(n−
1) have a substantially random distribution within the range 0 to π
/2, and wherein said lengths and their differential group delays satisfy the following five criteria (i) to (v);
- View Dependent Claims (15, 16, 17, 18)
-
r, for light propagating in those modes, where r is a positive integer between 1 and n, wherein the rth length of the concatenation is optically coupled with the (r+1)th length in a manner providing cross coupling of the modes so that only cos2 θ
-
19. An emulator for emulating the first and second order PMD (polarisation mode dispersion) properties of a length of low birefringence optical fibre installed in the field, the emulator including a concatenation of n lengths of high birefringence optical waveguide through which light is caused to propagate, wherein 5≦
- n≦
30, each having two guided modes, respectively a fast mode and a slow mode, and each presenting a different value of differential group delay, τ
, for light propagating in those two modes, wherein the rth length of the concatenation, where r is a positive integer between 1 and n, is optically coupled with the (r+1)th length in a manner providing cross coupling of the modes so that only cos2 θ
r of the power propagating in each mode (fast or slow) of the rth length is launched into the same mode (fast or slow) of the (r+1)th length while the remaining sin2 θ
r of the power is launched into the opposite mode (slow or fast), wherein the values of θ
r for r=1 to r=(n−
1) have a substantially random distribution within the range 0 to π
/2, wherein said differential group delay values are substantially aligned with members of the series τ
=qs, where q is a constant common to all members of the series, and s is a different integer for each member of the series. - View Dependent Claims (20, 21, 22, 23)
- n≦
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24. An emulator for emulating the first and second order PMD (polarisation mode dispersion) properties of a length of low birefringence optical fibre installed in the field, the emulator including a concatenation of n lengths of high birefringence fibre through which light is caused to propagate, each length presenting a different value of differential group delay, τ
-
r, where r is a positive integer between 1 and n, and each connected with its adjacent lengths in the concatenation with birefringence axes unaligned relative orientation, wherein said lengths satisfy the following five criteria (i) to (v);
- View Dependent Claims (25)
-
r, where r is a positive integer between 1 and n, and each connected with its adjacent lengths in the concatenation with birefringence axes unaligned relative orientation, wherein said lengths satisfy the following five criteria (i) to (v);
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26. An emulator for emulating the first and second order PMD (polarisation mode dispersion) properties of a length of low birefringence optical fibre installed in the field, the emulator including a concatenation of n lengths of high birefringence optical waveguide through which light is caused to propagate, wherein 5≦
- n≦
30, each length presenting a different value of differential group delay, τ
, and each connected with its adjacent lengths in the concatenation with birefringence axes unaligned substantially random relative orientation, wherein said differential group delay values are substantially aligned with members of the series τ
=qs, where q is a constant common to all members of the series, and s is a different integer for each member of the series.
- n≦
Specification
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Current AssigneePopkin Family Assets LLC (Intellectual Ventures LLC)
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Original AssigneeNortel Networks Limited (Nortel Networks Corporation)
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InventorsRobinson, Alan, Epworth, Richard, Watley, Daniel A
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Primary Examiner(s)Schuberg, Darren
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Assistant Examiner(s)ASSAF, FAYEZ G
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Application NumberUS09/470,628Time in Patent Office860 DaysField of Search385/11, 385/29, 385/123, 385/95, 385/99, 385/28, 359/156, 359/161, 359/192US Class Current385/28CPC Class CodesG02B 6/02071 Mechanically induced gratin...G02B 6/105 having optical polarisation...G02B 6/274 based on light guide birefr...G02B 6/278 Controlling polarisation mo...H04B 10/2572 due to forms of polarisatio...
