1. A method in a computing system for performing enhanced electronic relationship searches on a corpus of documents, comprising:
receiving a designated query indicating one or more terms;
in response to the received designated query, determining a plurality of matching rules that correspond to at least one indicated term of the designated query, each rule including a term used to decide whether the designated query matches the rule and including a relationship search specification string that specifies syntax for a corresponding relationship search to be executed as a search against the corpus when the rule is matched, the relationship search indicating one or more terms and associated syntactic andor semantic information used to convey how the one or more terms are to be understood in relation to the corpus;
for each of the plurality of determined matching rules, determining and executing the corresponding relationship search specified by the relationship search specification string in parallel against the corpus to validate whether the corresponding relationship search produces a successful result, thereby causing multiple different relationship searches to be executed against the same corpus in response to a same designated query at the same time; and
for each of a plurality of the executed corresponding relationship searches that have been validated as producing a successful result, forwarding an indication of the corresponding relationship search as a suggested search tip, each suggested search tip indicative of a different relationship search applicable to the same designated query.
2. The method of claim 1 wherein the receiving the designated query further comprises receiving an indication of one or more components of a relationship query.
3. The method of claim 1 wherein the receiving the designated query further comprises receiving an indication of one or more keywords.
4. The method of claim 1 wherein the receiving the designated query comprises receiving an indication of an entity or an entity type.
5. The method of claim 4 wherein the entity or the entity type is a source for an action or for an action type.
6. The method of claim 4 wherein the entity or the entity type is a target for an action or for an action type.
7. The method of claim 1 wherein the receiving the designated query comprises receiving an indication of an action or an action type.
8. The method of claim 1, further comprising:
for the one or more corresponding executed relationship searches that have been validated as producing a successful result,
evaluating results of the corresponding executed relationship search that produced the successful result to determine a plurality of additional specific relationship queries to serve as additional suggested searches; and
forwarding indications of the plurality of additional specific relationship queries as additional suggested search tips.
9. The method of claim 1 wherein, for the one or more corresponding executed relationship searches that have been validated as producing a successful result, the forwarding the indication of the corresponding relationship search as a suggested search tip further comprises:
evaluating results of the corresponding executed relationship search to determine whether the results meet a set of criteria for presenting as a suggested search tip; and
when it is determined that the results meet the criteria, forwarding an indication of the corresponding relationship search as a suggested search tip.
10. The method of claim 1 wherein a corresponding executed relationship search that produces a successful result is determined by whether search results are produced from executing the corresponding relationship search against the corpus.
11. The method of claim 1 wherein the suggested search tip is presented as a navigation tip in a visual user interface.
12. The method of claim 1, further comprising:
caching search results of one or more corresponding executed relationship searches that have been validated as producing a successful result; and
when a suggested searched tip is indicated for execution, returning the cached results of the relationship search that corresponds to the suggested search tip.
13. The method of claim 1 wherein the rules are specified by a configuration file, and further comprising:
parsing the configuration file to determine, for each rule, a relationship search specification string that specifies a corresponding relationship query; and
for each determined relationship search specification string, storing the corresponding relationship query along with information for matching the corresponding relationship query to a received designated query.
14. The method of claim 1 wherein the rules are specified using a tag-based scripting language.
15. The method of claim 1, further comprising presenting indications of the corresponding relationship searches in a ranked order.
16. The method of claim 1 wherein the executing of the corresponding relationship searches is performed in parallel.
17. The method of claim 1 wherein the determining the plurality of matching rules that correspond to the designated query further comprises:
determining a set of matching ontology paths that correspond to an indicated entity or entity type of the designated query.
18. The method of claim 1, further comprising:
when a suggested search tip is indicated for execution, executing the corresponding relationship search; and
presenting search results of the executed relationship search with indications of the components of the relationship query performed by the executed relationship search.
19. The method of claim 18 wherein the indications of the components in the presented results are used to facilitate teaching syntax of a specific query language.
20. A computer-readable medium containing instructions that, when executed, control a computer processor to provide search navigation tips by performing a method comprising:
receiving a designated query indicating one or more terms;
in response to the received designated query, determining a plurality of matching rules that correspond to at least one indicated term of the designated query, each rule including a term used to decide whether the designated query matches the rule and including a relationship search specification string that specifies syntax for a corresponding relationship search to be executed as a search against the corpus when the rule is matched, the relationship search indicating one or more terms and associated syntactic andor semantic information used to convey how the one or more terms are to be understood in relation to the corpus;
for each of the plurality of determined matching rules, determining and executing the corresponding relationship search specified by the relationship search specification string asynchronously against the corpus to validate whether the corresponding relationship search produces a successful result, thereby causing multiple different relationship searches to be executed against the same corpus in response to a same designated query at the same time; and
for each of a plurality of the executed corresponding relationship searches that have been validated as producing a successful result, forwarding an indication of the corresponding relationship search as a suggested search tip, each suggested search tip indicative of a different relationship search applicable to the same designated query.
21. The computer readable medium of claim 20 comprising a computer memory.
22. The computer-readable medium of claim 20 wherein the receiving the designated query further comprises receiving an indication of one or more components of a relationship query.
23. The computer-readable medium of claim 22 wherein the one or more components of the relationship query are indicated using IQL.
24. The computer-readable medium of claim 20 wherein the receiving the designated query further comprises receiving an indication of more or more keywords.
25. The computer-readable medium of claim 20 wherein the receiving the designated query comprises receiving an indication of one or more of an entity, an entity type, an action, or an action type.
26. The computer-readable medium of claim 20, the method further comprising:
for the one or more executed corresponding relationship searches that have been validated as producing a successful result,
evaluating results of the executed corresponding relationship search that produced the successful result to determine a plurality of more specific relationship queries to serve as additional suggested searches; and
forwarding indications of the plurality of more specific relationship queries as additional suggested search tips.
27. The computer-readable medium of claim 20, the method further comprising:
caching search results of the one or more executed corresponding relationship searches that have been validated as producing a successful result; and
when a suggested searched tip is indicated for execution, returning the cached results of the executed relationship search that corresponds to the suggested search.
28. The computer-readable medium of claim 20 wherein the rules are specified in a file using a tag-based scripting language.
29. The computer-readable medium of claim 20, the method further comprising presenting the one or more suggested search tips in a ranked order.
30. The computer-readable medium of claim 20 wherein the executing of the corresponding relationship searches is performed in parallel.
31. A relationship search navigation tip engine comprising:
a computer processor;
a data repository configured to maintain rules that map between one or more relationship query components and corresponding relationship query specification strings that specify syntax for corresponding relationship queries to be executed as searches against a corpus when the corresponding rule is matched;
a storage medium comprising a tip search manager that, when executed on the computer processor, is configured to parse the rules stored in the data repository to generate rule mappings between potential input queries and corresponding relationship searches to be executed, each relationship search indicating one or more terms and associated syntactic andor semantic information used to convey how the one or more terms are to be understood in relation to the corpus; and
a storage medium comprising a tip searcher that, when executed on the computer processor, is configured to receive an input query, determine, using the tip search manager, a plurality of rule mappings that correspond to the input query by matching a term of the input query to a plurality of the stored rules, execute the plurality of different corresponding relationship search queries that are specified by the relationship search specification strings of the determined plurality of rule mappings to generate corresponding search results, and return indications to the executed relationship searches that generated successful corresponding search results.
32. The navigation tip engine of claim 31 wherein the indications to the executed relationship searches that generated successful corresponding search results are visual navigation tips.
33. The navigation tip engine of claim 31 wherein the tip searcher is further configured to provide additional indications to relationship searches that correspond to specific entities or specific actions discovered during the executed plurality of relationship searches.
34. The navigation tip engine of claim 33 wherein the additional indications comprise deep tips.
35. The navigation tip engine of claim 31 wherein the tip searcher is configured to execute the relationship searches that correspond to the determined plurality of mappings in parallel with each other.
36. The navigation tip engine of claim 31 wherein the tip searcher is configured to execute the relationship searches that correspond to the determined plurality of mappings asynchronously.
37. A computer-implemented method for performing a relationship search against a corpus of documents comprising:
receiving from a user a relationship query indicating one or more terms and semantic andor syntactic information associated with the one or more terms, the received relationship query including a separate document constraint portion, the terms and associated semantic andor syntactic information specifying what relationships in one or more documents of the corpus will match the query using, at least in part, the indicated semantic andor syntactic information, the document constraint portion specifying a document constraint operator symbol or phrase and a designated ontology path specification;
executing a relationship search against the corpus of documents for a designated entity andor designated action of the received relationship query to yield a plurality of indications of documents in the corpus, where each indicated document contains at least one relationship involving the designated entity andor designated action as specified by the indicated terms and associated semantic andor syntactic information indicated by the query;
as a filter of results obtained by executing the relationship search, determining whether each of the indicated documents also contains a term that matches the designated ontology path specification of the document constraint portion of the received indicated relationship query; and
for each determined document that satisfies the document constraint portion, returning an indication of the document as a successful result of the relationship search.
38. A computer-implemented method for performing a relationship search against a corpus of documents comprising:
receiving from a user a designated relationship query indicating one or more terms and semantic andor syntactic information associated with the one or more terms, the received designated relationship query including a separate context operator portion, the terms and associated semantic andor syntactic information specifying what relationships in one or more documents of the corpus will match the query using, at least in part, the indicated semantic andor syntactic information, the context portion specifying a context operator symbol or phrase and an entity andor an action;
executing a relationship search that corresponds to the designated relationship search query to yield one or more indications of documents in the corpus, where each document contains at least one sentence or clause that matches the relationship specified by the indicated terms and associated semantic andor syntactic information of the designated relationship query; and
predetermining a number of sentences or clauses for determining a surrounding context for use with the context operator portion of the designated relationship query;
for each indicated document, determining whether the context surrounding the at least one matching sentence or clause, within the predetermined number of sentences or clauses before or after the at least one matching sentence or clause, further matches the entity or the action specified by the context operator portion of the designated relationship query, wherein the context is a sentence or clause that is distinct from the at least one matching sentence or clause.
39. The method of claim 38 wherein the context includes a sentence before the at least one matching sentence.
40. The method of claim 38 wherein the context includes a sentence after the at least one matching sentence.
41. The method of claim 38 wherein the designated relationship query specifies at least one of a source entity, a target entity, or an action and specifies a context operator along with a corresponding entity or action.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
What is claimed is:
1. A coherent polarization mode dispersion (PMD) generator for generating a coherent PMD spectrum, wherein said generator comprises at least four birefringent stages in optical series, said stages forming at least three pairs of adjacent stages, and wherein each of said stages comprises a harmonic differential group delay (DGD) element and a phase-compensating element.
2. The generator of claim 1 wherein, for each stage, said phase-compensating element has an extraordinary axis and said DGD element has an extraordinary axis that are oriented to avoid polarization mode-mixing within said each stage.
3. The generator of claim 2 wherein, for said each stage, said extraordinary axes have an orientation that is selected from a group consisting of substantially perpendicular and substantially parallel.
4. The generator of claim 1 wherein each of said stages has a residual optical retardation that, when divided by a DGD value of its DGD element, is substantially the same for each of said stages.
5. The generator of claim 1 wherein each of said stages has a total retardation that is an integral multiple of .
6. The generator of claim 5 wherein, for each of said stages, said DGD element has a retardation error and said phase compensating element has a compensating retardation such that said total retardation is said integral multiple of .
7. The generator of claim 1 wherein said PMD spectrum comprises a DGD spectrum that has Fourier component frequencies that are in phase.
8. The generator of claim 1 wherein said Fourier component frequencies have a common Fourier-component frequency denominator.
9. The generator of claim 1 wherein said PMD spectrum comprises a DGD spectrum that has sinusoidal Fourier components that are all aligned in phase and share an optical frequency where all the sinusoidal components are either at a maximum or at a minimum.
10. The generator of claim 1 wherein each of said DGD elements has a DGD value that is substantially equal to an integral multiple of a unit DGD value.
11. The generator of claim 10 wherein each of said DGD elements has a DGD value is substantially the same.
12. The generator of claim 10 wherein each of said DGD elements has a different DGD value.
13. The generator of claim 10 wherein said unit DGD value is substantially equal to a multiplicative inverse of a WDM channel spacing.
14. The generator of claim 13 wherein said phase-compensating element is a locked phase-compensating element.
15. The generator of claim 7 wherein said DGD spectrum is aligned to a comb of WDM signals.
16. The generator of claim 1 wherein said generator is capable of inducing a degree of polarization mode-mixing between at least one of said pairs of stages.
17. The generator of claim 16 wherein each of said stages has a birefringent axis, such that when each of said stages is rotated, said birefringent axis is rotated.
18. The generator of claim 17 wherein each of said stages can be physically rotated about a beam propagation axis of said generator to induce polarization mode-mixing between at least one of said pairs of stages, but not within any of said stages.
19. The generator of claim 16 further comprising a polarization mode-mixing element located between at least one of said pairs of stages.
20. The generator of claim 19 wherein each of said stages has a birefringent axis, and each of said pairs of stages includes a first stage and a second stage, wherein said first stage birefringent axis and said second stage birefringent axis is either substantially parallel or substantially perpendicular.
21. The generator of claim 19 wherein said mode-mixing element comprises at least one waveplate.
22. The generator of claim 21 wherein said at least one waveplate comprises a half-wave waveplate.
23. The generator of claim 22 wherein said half-wave waveplate is rotatable about a beam propagation axis.
24. The generator of claim 19 further comprising at least one waveplate controller coupled to said at least one waveplate for controlling rotation of said at least one waveplate.
25. The generator of claim 19 wherein said mode-mixing element comprises an electro-optic element.
26. The generator of claim 25 wherein said electro-optic element is located between a first pair of said adjacent stages, said first pair comprising a first of said stages and a second of said stages, wherein said electro-optic element has a principal axis and each of said first and second stages has a birefringent axis, and wherein said principal axis is not substantially parallel nor substantially perpendicular to either of said birefringent axes of said first and second stages.
27. The generator of claim 26 wherein said principal axis and said birefringent axes of said first and second stages are at an angle that is about 45 degrees.
28. The generator of claim 16 further comprising at least one voltage source for driving said electro-optic element.
29. The generator of claim 16 wherein said at least one pair of adjacent stages comprises every pair of said adjacent stages.
30. The generator of claim 29 further comprising at least one mode-mixing element controller coupled to said at least one mode-mixing element for controlling said mode-mixing element.
31. The generator of claim 29 wherein at least one of said mode-mixing elements comprises an electro-optic element.
32. The generator of claim 1 wherein each of said DGD elements comprises a birefringent crystal selected from a group consisting of alpha barium borate, yttrium ortho-vanadate, rutile, lithium niobate, mica, crystalline quartz, and any combination thereof.
33. The generator of claim 1 wherein at least one of said DGD elements comprises a first birefringent crystal having an extraordinary axis and a second birefringent crystal having an extraordinary axis.
34. The generator of claim 33 wherein said extraordinary axes have an orientation that is selected from a group consisting of substantially parallel and substantially perpendicular.
35. The generator of claim 1 wherein at least one of said DGD elements comprises a plurality of birefringent elements.
36. The generator of claim 35 wherein said plurality of birefringent elements are chosen such that at least one physical attribute is optimized, said attribute being selected from a group consisting of a free-spectral range, an optical retardation temperature coefficient, a thermal expansion coefficient, and any combination thereof.
37. A coherent polarization mode dispersion (PMD) generator for generating a coherent PMD spectrum, wherein said generator comprises at least four birefringent stages in optical series, said stages forming at least three pairs of adjacent stages, and wherein each of said stages comprises a colorless differential group delay (DGD) element and a locked phase-compensating element.
38. The generator of claim 37 wherein, for each stage, said phase-compensating element has an extraordinary axis and said DGD element has an extraordinary axis that are oriented to avoid polarization mode-mixing within said each stage.
39. The generator of claim 38 wherein, for said each stage, said extraordinary axes have an orientation that is selected from a group consisting of substantially perpendicular and substantially parallel.
40. The generator of claim 37 wherein each of said stages has a residual optical retardation that, when divided by a DGD value of its DGD element, is substantially the same for each of said stages.
41. The generator of claim 37 wherein each of said stages has a total retardation that is an integral multiple of .
42. The generator of claim 41 wherein, for each of said stages, said DGD element has a retardation error and said phase compensating element has a compensating retardation such that said total retardation is said integral multiple of .
43. The generator of claim 37 wherein said PMD spectrum comprises a DGD spectrum that has Fourier component frequencies that are in phase and further phase aligned with the phase of Fourier component frequencies of a WDM comb spectrum.
44. The generator of claim 37 wherein said Fourier component frequencies have a common Fourier-component frequency denominator is the same as a WDM channel spacing.
45. The generator of claim 37 wherein said PMD spectrum comprises a DGD spectrum that has sinusoidal Fourier components that are all aligned in phase and share an optical frequency where all the sinusoidal components are either at a maximum or at a minimum.
46. The generator of claim 37 wherein each of said DGD elements has a DGD value that is substantially equal to an integral multiple of a unit DGD value.
47. The generator of claim 46 wherein each of said DGD elements has a DGD value is substantially the same.
48. The generator of claim 46 wherein each of said DGD elements has a different DGD value.
49. The generator of claim 46 wherein said unit DGD value is substantially equal to a multiplicative inverse of a WDM channel spacing.
50. The generator of claim 37 wherein said generator is capable of inducing a degree of polarization mode-mixing between at least one of said pairs of stages.
51. The generator of claim 50 wherein each of said stages has a birefringent axis, such that when each of said stages is rotated, said birefringent axis is rotated.
52. The generator of claim 51 wherein each of said stages can be physically rotated about a beam propagation axis of said generator to induce polarization mode-mixing between at least one of said pairs of stages, but not within any of said stages.
53. The generator of claim 50 further comprising a polarization mode-mixing element located between at least one of said pairs of stages.
54. The generator of claim 53 wherein each of said stages has a birefringent axis, and each of said pairs of stages includes a first stage and a second stage, wherein said first stage birefringent axis and said second stage birefringent axis is either substantially parallel or substantially perpendicular.
55. The generator of claim 53 wherein said mode-mixing element comprises at least one waveplate.
56. The generator of claim 55 wherein said at least one waveplate comprises a half-wave waveplate.
57. The generator of claim 56 wherein said half-wave waveplate is rotatable about a beam propagation axis.
58. The generator of claim 53 further comprising at least one waveplate controller coupled to said at least one waveplate for controlling rotation of said at least one waveplate.
59. The generator of claim 53 wherein said mode-mixing element comprises an electro-optic element.
60. The generator of claim 59 wherein said electro-optic element is located between a first pair of said adjacent stages, said first pair comprising a first of said stages and a second of said stages, wherein said electro-optic element has a principal axis and each of said first and second stages has a birefringent axis, and wherein said principal axis is not substantially parallel nor substantially perpendicular to either of said birefringent axes of said first and second stages.
61. The generator of claim 60 wherein said principal axis and said birefringent axes of said first and second stages are at an angle that is about 45 degrees.
62. The generator of claim 50 further comprising at least one voltage source for driving said electro-optic element.
63. The generator of claim 50 wherein said at least one pair of adjacent stages comprises every pair of said adjacent stages.
64. The generator of claim 63 further comprising at least one mode-mixing element controller coupled to said at least one mode-mixing element for controlling said mode-mixing element.
65. The generator of claim 63 wherein at least one of said mode-mixing elements comprises an electro-optic element.
66. The generator of claim 37 wherein each of said DGD elements comprises a birefringent crystal selected from a group consisting of alpha barium borate, yttrium ortho-vanadate, rutile, lithium niobate, mica, crystalline quartz, and any combination thereof.
67. The generator of claim 37 wherein at least one of said DGD elements comprises a first birefringent crystal having an extraordinary axis and a second birefringent crystal having an extraordinary axis.
68. The generator of claim 67 wherein said extraordinary axes have an orientation that is selected from a group consisting of substantially parallel and substantially perpendicular.
69. The generator of claim 37 wherein at least one of said DGD elements comprises a plurality of birefringent elements.
70. The generator of claim 69 wherein said plurality of birefringent elements are chosen such that at least one physical attribute is optimized, said attribute being selected from a group consisting of a free-spectral range, an optical retardation temperature coefficient, a thermal expansion coefficient, and any combination thereof.
71. The generator of claim 37 wherein said PMD spectrum comprises a DGD spectrum having substantially the same DGD value at any center frequency of a WDM comb spectrum.
72. The generator of claim 37 wherein each of said stages has a total optical retardation equal to a sum of a retardation of a DGD element and a retardation of a respective locked phase-compensating element, wherein each of said locked phase-compensating elements can be tuned such that a first predetermined frequency of said DGD spectrum is aligned with a second predetermined frequency of a WDM comb spectrum.
73. The generator of claim 72 wherein said first and second frequencies are either coincident or have a predetermined frequency difference.
74. The generator of claim 37 wherein a WDM spectrum has a plurality of center frequencies that are equally separated by a channel spacing, and wherein said DGD spectrum has a periodic substantially flattened middle portion that is substantially aligned with said center frequencies.
75. The generator of claim 37 wherein a WDM spectrum has a plurality of center frequencies, and wherein said PMD spectrum comprises a frequency-dependent DGD spectrum having periodic stationary points that are substantially coincident with said center frequencies.
76. A coherent polarization mode dispersion (PMD) generator for generating a coherent PMD spectrum, wherein said generator comprises at least four birefringent stages in optical series, said stages forming at least three pairs of adjacent stages, and wherein each of said stages comprises a harmonic differential group delay (DGD) element and a phase-compensating element, wherein said generator can be controlled to generate DGD and second order PMD (SOPMD) independently at at least one optical frequency by inducing polarization mode-mixing between said pairs of stages.
77. The generator of claim 76 wherein, for each stage, said phase-compensating element has an extraordinary axis and said DGD element has an extraordinary axis that are oriented to avoid polarization mode-mixing within said each stage.
78. The generator of claim 77 wherein, for said each stage, said extraordinary axes have an orientation that is selected from a group consisting of substantially perpendicular and substantially parallel.
79. The generator of claim 76 wherein each of said stages has a residual optical retardation that, when divided by a DGD value of its DGD element, is substantially the same for each of said stages.
80. The generator of claim 76 wherein each of said stages has a total retardation that is an integral multiple of .
81. The generator of claim 80 wherein, for each of said stages, said DGD element has a retardation error and said phase compensating element has a compensating retardation such that said total retardation is said integral multiple of .
82. The generator of claim 76 wherein said PMD spectrum comprises a DGD spectrum that has Fourier component frequencies that are in phase.
83. The generator of claim 76 wherein said Fourier component frequencies have a common Fourier-component frequency denominator.
84. The generator of claim 76 wherein said PMD spectrum comprises a DGD spectrum that has sinusoidal Fourier components that are all aligned in phase and share an optical frequency where all the sinusoidal components are either at a maximum or at a minimum.
85. The generator of claim 76 wherein each of said DGD elements has a DGD value that is substantially equal to an integral multiple of a unit DGD value.
86. The generator of claim 85 wherein each of said DGD elements has a DGD value is substantially the same.
87. The generator of claim 85 wherein each of said DGD elements has a different DGD value.
88. The generator of claim 85 wherein said unit DGD value is substantially equal to a multiplicative inverse of a WDM channel spacing.
89. The generator of claim 88 wherein said phase-compensating element is a locked phase-compensating element.
90. The generator of claim 82 wherein said DGD spectrum is aligned to a comb of WDM signals.
91. The generator of claim 76 wherein said generator is capable of inducing a degree of polarization mode-mixing between at least one of said pairs of stages.
92. The generator of claim 91 wherein each of said stages has a birefringent axis, such that when each of said stages is rotated, said birefringent axis is rotated.
93. The generator of claim 92 wherein each of said stages can be physically rotated about a beam propagation axis of said generator to induce polarization mode-mixing between at least one of said pairs of stages, but not within any of said stages.
94. The generator of claim 91 further comprising a polarization mode-mixing element located between at least one of said pairs of stages.
95. The generator of claim 94 wherein each of said stages has a birefringent axis, and each of said pairs of stages includes a first stage and a second stage, wherein said first stage birefringent axis and said second stage birefringent axis is either substantially parallel or substantially perpendicular.
96. The generator of claim 94 wherein said mode-mixing element comprises at least one waveplate.
97. The generator of claim 96 wherein said at least one waveplate comprises a half-wave waveplate.
98. The generator of claim 97 wherein said half-wave waveplate is rotatable about a beam propagation axis.
99. The generator of claim 94 further comprising at least one waveplate controller coupled to said at least one waveplate for controlling rotation of said at least one waveplate.
100. The generator of claim 94 wherein said mode-mixing element comprises an electro-optic element.
101. The generator of claim 100 wherein said electro-optic element is located between a first pair of said adjacent stages, said first pair comprising a first of said stages and a second of said stages, wherein said electro-optic element has a principal axis and each of said first and second stages has a birefringent axis, and wherein said principal axis is not substantially parallel nor substantially perpendicular to either of said birefringent axes of said first and second stages.
102. The generator of claim 101 wherein said principal axis and said birefringent axes of said first and second stages are at an angle that is about 45 degrees.
103. The generator of claim 91 further comprising at least one voltage source for driving said electro-optic element.
104. The generator of claim 91 wherein said at least one pair of adjacent stages comprises every pair of said adjacent stages.
105. The generator of claim 104 further comprising at least one mode-mixing element controller coupled to said at least one mode-mixing element for controlling said mode-mixing element.
106. The generator of claim 91 wherein at least one of said mode-mixing elements comprises an electro-optic element.
107. The generator of claim 76 wherein each of said DGD elements comprises a birefringent crystal selected from a group consisting of alpha barium borate, yttrium ortho-vanadate, rutile, lithium niobate, mica, crystalline quartz, and any combination thereof.
108. The generator of claim 76 wherein at least one of said DGD elements comprises a first birefringent crystal having an extraordinary axis and a second birefringent crystal having an extraordinary axis.
109. The generator of claim 108 wherein said extraordinary axes have an orientation that is selected from a group consisting of substantially parallel and substantially perpendicular.
110. The generator of claim 76 wherein at least one of said DGD elements comprises a plurality of birefringent elements.
111. The generator of claim 110 wherein said plurality of birefringent elements are chosen such that at least one physical attribute is optimized, said attribute being selected from a group consisting of a free-spectral range, an optical retardation temperature coefficient, a thermal expansion coefficient, and any combination thereof.
112. The generator of claim 76 wherein said generator can be controlled to generate differential group delay (DGD) and second order PMD (SOPMD) independently at at least one optical frequency by inducing polarization mode-mixing between said pairs of stages.
113. The generator of claim 112 wherein each of said DGD elements has a DGD value that is substantially the same.
114. The generator of claim 112 wherein said PMD generator is restricted to operate along a predetermined DGDSOPMD trajectory.
115. The generator of claim 114 wherein said predetermined trajectory is selected from a group consisting of a constant DGD trajectory, a constant SOPMD trajectory, a fixed rate of change of a DGD trajectory, a fixed rate of change of a SOPMD trajectory, and any combination thereof.
116. The generator of claim 115 wherein each of said DGD and SOPMD at said optical frequency can vary within a DGDSOPMD space in which said DGD and said SOPMD only vary monotonically between zero and a respective maximum.
117. The generator of claim 76 wherein said at least one optical frequency is a plurality of optical frequencies.
118. The generator of claim 117 wherein said independent control of DGD and second order PMD can be simultaneous.
119. The generator of claim 117 wherein said plurality of optical frequencies is a set of WDM channel frequencies, and wherein said first and second amounts are substantially the same at each of said channel frequencies.
120. The generator of claim 76 wherein said at least four stages comprises four stages.
121. The generator of claim 120 wherein said four stages comprises:
a first stage having an input and an output;
a second stage having an input and an output, wherein said second stage input is optically coupled to said first stage output;
a third stage having an input and an output, wherein said third stage input is optically coupled to said second stage output; and
a fourth stage having an input and an output, wherein said fourth stage input is optically coupled to said third stage output.
122. The generator of claim 121 further comprising:
a first polarization mode-mixing controller for controlling a first degree of mode-mixing between said first and second stages and between said third and fourth stages by physical rotation of at least one of said stages; and
a second polarization mode-mixing controller for controlling a second degree of mode-mixing between said second and third stages by physical rotation of at least one of said second and third stages.
123. The generator of claim 122 further comprising:
a first polarization mode-mixing element between said first stage and said second stage;
a second polarization mode-mixing element between said second stage and said third stage; and
a third polarization mode-mixing element between said third stage and said fourth stage.
124. The generator of claim 123 further comprising:
a first polarization mode-mixing element controller coupled to said first mode-mixing element and said third mode-mixing element for controlling a first degree of mode-mixing between said first and second stages and between said third and fourth stages; and
a second polarization mode-mixing element controller coupled to said second mode-mixing element for controlling a second degree of mode-mixing between said second and third stages.
125. The generator of claim 124 wherein said first controller and said second controller are programmed to coordinate mode-mixing between said adjacent pairs of stages to generate said first amount of DGD and said second amount of SOPMD within a free-spectral range of said PMD spectrum.
126. The generator of claim 125 wherein said controllers are programmed to vary said PMD spectrum by changing the first and second degrees of mode-mixing such that said first amount of DGD is substantially fixed while said second amount varies.
127. The generator of claim 125 wherein said controllers are programmed to vary said PMD spectrum by changing the first and second degrees of mode-mixing such that said first amount of DGD changes at a predetermined rate while said second amount varies.
128. The generator of claim 125 wherein said controllers are programmed to vary said PMD spectrum by changing the first and second degrees of mode-mixing such that said second amount of SOPMD is substantially fixed while said first amount varies.
129. The generator of claim 125 wherein said controllers are programmed to vary said PMD spectrum by changing the first and second degrees of mode-mixing such that said second amount of SOPMD changes at a predetermined rate while said first amount varies.
130. The generator of claim 125 wherein said controllers induce sufficient polarization mode-mixing between adjacent pairs of stages such that said second amount changes from a first SOPMD state to a second SOPMD state without varying said DGD value by moving along a constant DGD contour.
131. The generator of claim 130 wherein said constant DGD contour can be determined substantially as follows:
o4cos (PM1)cos (PM2PM1)
where o is the first amount of DGD, is a DGD value of a birefringent stage, PM1 is the first degree of mode-mixing, and PM2 is the second degree of mode-mixing.
132. The generator of claim 125 wherein said controllers induce sufficient polarization mode-mixing between adjacent pairs of stages such that said first amount changes from a first DGD state to a second DGD state without varying said second amount of SOPMD by moving along a constant SOPMD contour.
133. The generator of claim 132 wherein said constant SOPMD contour can be determined substantially as follows:
w.{square root}(1w22w 23w2),
where
1w(1cos (PM1))(1cos (PM2PM1)),2w(1cos (PM1))(sin 2(PM2PM1)sin (PM2PM1))2 sin (PM1), and3w0
and where 51 w is the second amount of SOPMD at said optical frequency, is a DGD value of a birefringent stage, PM1 is the first degree of mode-mixing, and PM2 is the second degree of mode-mixing.
134. The generator of claim 125 wherein said degrees of mode-mixing between stages can vary within certain limits such that all constant SOPMD contours change monotonically.
135. The generator of claim 125 wherein said degrees of mode-mixing between stages can vary within certain limits such that all said constant DGD value contours change monotonically.
136. A method for generating a coherent polarization mode dispersion (PMD) spectrum generator with a PMD generator, said generator comprising at least four birefringent stages in optical series, said stages forming at least three pairs of adjacent stages, and wherein each of said stages comprises a harmonic differential group delay (DGD) element and a phase-compensating element, said method comprising:
inducing a degree of polarization mode-mixing between at least one adjacent pair of said stages.
137. The method of claim 136 wherein said generator further comprises:
a polarization mode-mixing element located between at least one pair of adjacent stages; and
a mode-mixing element controller coupled to said mode-mixing element, and wherein said inducing comprises causing said controller to vary said degree of mode-mixing.
138. The method of claim 137 wherein said at least one pair of adjacent stages comprises all of said pairs of stages, and wherein said inducing comprises varying said degrees of mode-mixing between all of said pairs of stages.
139. The method of claim 138 wherein at least one of said mode-mixing elements comprises an electro-optic element, and wherein said varying said degree of mode-mixing comprises continuously varying a voltage applied to said electro-optic element.
140. The method of claim 136 wherein each of said stages has an extraordinary axis, and wherein said inducing comprises adjusting said extraordinary axes of adjacent stages until an angle between said axes is substantially 45 degree to induce maximal polarization mode-mixing.
141. The method of claim 136 wherein each of said stages has an extraordinary axis, and wherein said inducing comprises adjusting said extraordinary axes of adjacent stages until an angle between said axes is either substantially parallel or substantially perpendicular to induce substantially zero polarization mode-mixing.
142. The method of claim 136 wherein each of said DGD elements is a colorless DGD element, each of said phase-compensating elements is a locked phase-compensating element, each of said plurality of optical frequencies is an equally spaced channel of a WDM comb spectrum, and wherein said inducing comprises inducing a same amount of DGD at each of said channels.
143. The method of claim 136 wherein each of said DGD elements is a harmonic DGD element, and wherein said inducing comprises generating differential group delay (DGD) and second order PMD (SOPMD) independently at at least one optical frequency by inducing varying degrees of polarization mode-mixing between each of said pairs of stages.
144. The method of claim 143 wherein said at least four stages comprises four stages, and said at least three pairs of stages comprises three pairs of stages, and wherein said inducing comprises varying said degrees of mode-mixing between said stages such that DGD and said SOPMD vary according to a predetermined trajectory.
145. The method of claim 144 wherein said predetermined trajectory is selected from a group consisting of a constant DGD trajectory, a constant SOPMD trajectory, a fixed rate of change of a DGD trajectory, a fixed rate of change of a SOPMD trajectory, and any combination thereof.
146. The method of claim 143 wherein said inducing comprising varying said DGD and SOPMD within a DGDSOPMD space in which said DGD and said SOPMD only vary monotonically between zero and a respective maximum.
147. A method for generating coherent, colorless polarization mode dispersion (PMD) spectrum with a PMD generator comprising at least four birefringent stages in optical series, said stages forming at least three pairs of adjacent stages, wherein each of said stages comprises a colorless DGD element and a locked phase-compensating element, said method comprising:
inducing polarization mode-mixing between said stages such that a first amount of differential group delay (DGD) and a second amount of second order PMD (SOPMD) can be independently generated and controlled at a plurality of equally spaced optical frequencies in said PMD spectrum.
148. The method of claim 147 wherein inducing comprises controllably and simultaneously changing said DGD and said PMD.
149. The method of claim 147 wherein said generator further comprises at least one polarization mode-mixing element between each pair of adjacent stages.
150. The method of claim 149 wherein said at least four stages comprises: (1) a first stage having an input and an output, (2) a second stage having an input and an output, wherein said second stage output is optically coupled to said first stage input, (3) a third stage having an input and an output, wherein said third stage input is optically coupled to said second stage output, and (4) a fourth stage having an input and an output, wherein said fourth stage input is optically coupled to said third stage output, wherein said inducing comprises:
controlling a first degree of mode-mixing between said first and second stages and between said third and fourth stages; and
controlling a second degree of mode-mixing between said second and third stages.
151. The method of claim 150 wherein said controlling said first and second degrees occurs such that said first amount of DGD is substantially fixed while said second amount of SOPMD varies.
152. The method of claim 150 wherein said controlling said first and second degrees occurs such that said first amount of DGD changes at a predetermined rate while said second amount varies.
153. The method of claim 150 wherein said controlling said first and second degrees occurs such that said second amount of SOPMD is substantially fixed while said first amount varies.
154. The method of claim 150 wherein said controlling said first and second degrees occurs such that said second amount of SOPMD changes at a predetermined rate while said first amount varies.
155. The method of claim 150 wherein said controlling said first and second degrees occurs such that said second amount changes from a first SOPMD state to a second SOPMD state without varying said first amount of DGD by moving along a constant DGD contour.
156. The method of claim 155 wherein said constant DGD contour is defined substantially according to:
o4cos (PM1)cos (PM2PM1)
where o is the first amount of DGD, is a DGD value of a birefringent stage, PM1 is the first degree of mode-mixing, and PM2 is the second degree of mode-mixing.
157. The generator of claim 150 wherein said including comprises using said controllers to induce sufficient polarization mode-mixing between adjacent pairs of stages such that said first amount changes from a first DGD state to a second DGD state without varying said second amount of SOPMD by moving along a constant SOPMD contour.
158. The generator of claim 157 wherein said constant SOPMD contour is defined substantially according to:
w.{square root}(1w22w23w2),
where
1w(1cos (PM1))(1cos (PM2PM1)),2w(1cos (PM1))(sin 2(PM2PM1)sin (PM2PM1))2 sin (PM1), and3w0
and where w is the second amount of SOPMD at said optical frequency, is a DGD value of a birefringent stage, PM1 is the first degree of mode-mixing, and PM2 is the second degree of mode-mixing.
159. The generator of claim 149 wherein said inducing comprises varying said degrees of mode-mixing between stages within certain limits such that all constant SOPMD contours change monotonically.
160. The generator of claim 150 wherein said inducing comprises varying said degrees of mode-mixing between stages within certain limits such that all said constant DGD value contours change monotonically.