Channel wavelength assignment with transient reduction
View Patent ↗In an automatically switched optical network operating according to a wavelength plan, the wavelengths are assigned to an optical path based on availability, performance and SRS wavelength coupling reduction. First, the wavelengths are grouped in static bins based on their reach versus cost performance, and each bin assumes a ΔQ of a middle wavelength. Then, the bins are moved into subsets of dynamic bins, constructed using bin constraints that account for the particulars of the respective optical path. The path is characterized taking into account the wavelength currently accessing at the end nodes, and the wavelength tandeming through the end nodes. Wavelength selection starts with the bins that satisfy the maximum number of constraints, and the wavelengths are checked sequentially against wavelength constraints; relaxed constraints are also applied when it is not possible to exactly satisfy one or more constraints.
1. In automatically switched optical network operating according to a wavelength plan, a computer-implemented method of selecting a wavelength for an optical path with reduced wavelength SRS transients, comprising:
providing a plurality of configurable global variables, configured according to the performance requirements of said network;
grouping all wavelengths provided by said wavelength plan into static bins and, based on a plurality of bin constraints, organizing said static bins into subsets of dynamic bins which include all wavelengths available for said optical path; and
searching within said subsets of dynamic bins for a wavelength (Lam) that has an individual performance parameter ΔQ (λ) estimated for said optical path above a threshold (Th) and satisfies a maximum number of wavelength constraints,
wherein said bin constraints and said wavelength constraints are designed for offering various degrees of SRS transient reduction.
2. A computer-implemented method as claimed in claim 1 , wherein said step of grouping comprises:
selecting from said static bins a set S 0 of dynamic bins B S0 based on said threshold and a bin performance parameter ΔQ.
defining a range of consecutive wavelength within said wavelength plan and moving a bin from S 0 into a first subset of bins S 1 if it contains a wavelength (Lam) within said range.
3. A computer-implemented as claimed in claim 2 , wherein said step of grouping further comprises, for each end node of said optical path:
defining an access function (Facc) using said respective global variables, and calculating a current value Facc for said access function for quantifying the position of all wavelengths currently accessing said network at said end nodes;
for each wavelength in all bins of said first subset S 1 , calculating a respective new value for said access function based on said current valueFacc; and
moving a bin from said first subset S 1 into said a second subset S 2 if it contains a wavelength (Lam) for which said respective new value Facc is less than a limit (Limit 2 ).
4. A computer-implemented method as claimed in claim 2 , wherein said step of grouping further comprises, for each end node of said optical path:
defining an access and tandem function (Facc&tan) using said respective global variables, and calculating a current value Facc&tan for said access and tandem function which quantifies the position of all wavelengths currently present at said end nodes;
for each wavelength of all bins of said second subset S 2 , calculating a new value Facc&tan for said access and tandem function based on said current value; and
moving a bin from said second subset S 2 into a third subset S 3 if it contains a wavelength (Lam) for which said respective new value Facc&tan is less than a limit (Limit 3 ).
5. A computer-implemented method as claimed in claim 2 , wherein said step of searching comprises identifying within a subset S 3 a wavelength that satisfies a wavelength constraint and assigning said wavelength (Lam) to said optical path.
6. A computer-implemented method as claimed in claim 5 , wherein said step of searching further comprises, if no wavelength satisfies said wavelength constraint, increasing a code violation with a CV value, and continuing the search into a subset S 2 .
7. A computer-implemented method as claimed in claim 6 , wherein said step of searching further comprises identifying within said subset S 2 a wavelength that satisfies a second wavelength constraint and assigning said wavelength (Lam) to said optical path.
8. A computer-implemented method as claimed in claim 7 , wherein said step of searching further comprises, if no wavelength satisfies said second wavelength constraint, increasing said code violation with a second CV value, and continuing the search into said first subset S 1 .
9. A computer-implemented method as claimed in claim 8 , wherein said step of searching further comprises identifying within said first subset S 1 a wavelength that satisfies a first wavelength constraint and assigning said wavelength (Lam) to said optical path.
10. A computer-implemented method as claimed in claim 9 , wherein said step of searching further comprises, if no wavelength satisfies said first wavelength constraint, increasing said code violation with a first CV value, and continuing the search into said subset S 0 .
11. A computer-implemented method as claimed in claim 10 , wherein said step of searching further comprises identifying within said subset S 0 a wavelength that has an individual performance parameter above a threshold.
12. A computer-implemented method as claimed in claim 11 , wherein said wavelength selection is steered towards a wavelength that has a minimum code violation value.