CLAIMS

What is claimed is:

1. A method for selecting fibers meeting requirements of a second minimum bandwidth at a second wavelength based on differential mode delay data measured at a first wavelength different from the second wavelength, the method comprising:

measuring the differential mode delay (DMD) data for the multimode fiber at the first wavelength, wherein the DMD data comprises output laser pulse data as a function of the radial position of an input laser pulse having the first wavelength;

selecting the multimode fiber based on meeting requirements of the second minimum bandwidth at the second wavelength based on a second set of criteria, comprising a second criterion comprising:

the radial dependence of the differential mode delay data measured at the first wavelength being within a pre- determined tolerance of a pre-determined reference function constructed by concatenating two or more even-order polynomials having the form:

wherein:

a is a normalizing factor;

r is variable radial position on the fiber over at least two different ranges r_{l k} < r < r_{2 k} c_{0 ,k}, c_{l k}, and c_{2 k} are coefficients that are constant within each range of r;

r_{l k} and r_{2 k} are discrete radial positions on the fiber marking the boundary of each range of r;

k is an indexing variable with values k = {1 ...K} where K is 2 or 3.

2. The method of claim 1, wherein the radial dependence of the differential mode delay data measured at the first wavelength is determined using a centroid of the data measured for each value of r.

3. The method of claim 1, wherein the radial dependence of the differential mode delay data measured at the first wavelength is determined using a peak of the data for measured for each value of r.

4. The method of claim 1, wherein the radial dependence of the differential mode delay data measured at the first wavelength is determined by:

deconvolving the DMD data measured at the first wavelength to determine mode group delay data r_{g};

reconvolving the mode group delay data x with a theoretical Pxg matrix to determine smoothed differential mode delay data in radial space;

determining the radial dependence of the differential mode delay data measured at the first wavelength using a centroid of the data measured for each value of r.

5. The method of any of claims 1 through 4, wherein, for k = 1 :

microns and r_{2 1} = 7+ microns;

for a radial range defined by r_{1 ±} and r_{2 l}, the radial dependence of the differential mode delay data measured at the first wavelength is within a pre-determined tolerance of a pre determined reference function when a least-squares fit of the differential mode delay data to a function having the form:

has coefficients:

-0.02 ns/km < coi < 0.2 ns/km;

-1.5 ns/km < cn < 0.5 ns/km; and

-2.0 < ns/km < C2i < 8.0 ns/km.

6. The method of any of claims 1 through 5, wherein:

K = 3;

for k = 2 and k = 3, the pre-determined tolerance c^{2} is:

x(r)meas is measured delay at position r;

x(r)ref, k is reference delay at position r in interval k:

r is radial position in microns;

Wk is a weighting for each of the k regions (k= 2... K), where W2=W3=1 .

a is 25 microns;

r_{l 2} = 7 microns;

^{r}2_{,}2^{=} 15 microns;

r_{1 3} = 15 microns;

r_{2 3}= 25+ microns;

for k = 2:

Co, 2 = -0.02 to 0.02 ns/km;

ci, 2 = -0.2 to 0.01 ns/km;

C2,2 = -0.6 to 0.01 ns/km;

for k = 3 ;

Co, 3 = 0.01 to 0.1 ns/km;

ci_{, 3} = -0.35 to -0.1 ns/km;

C2,3 = 0.05 to 0.25 ns/km

7. The method of claim 6, wherein:

for k = 2:

Co, 2 = 0.0009 ns/km;

ci, 2 = 0.001 1 ns/km;

C2,2 = -0.206 ns/km;

for k = 3 ;

Co, 3 = 0.0391 ns/km;

ci_{, 3} = -0.233 ns/km;

C2,3 = 0.146 ns/km

8. The method of any of claims 1 through 5, wherein:

K = 3;

for k = 2 and k = 3, the pre-determined tolerance c^{2} is:

x(r)meas is measured delay at position r;

x(r)ref, k is reference delay at position r in interval k:

r is radial position in microns;

K = 3;

W_{k} is a weighting for each of the k regions (k= 2... K), where W_{2}=W_{3}=1.

a is 25 microns;

r_{1 2} = 7 microns;

^{r}2_{,}2^{=} 15 microns;

r_{1 3} = 15 microns;

r_{2 3}= 25+ microns;

for k = 2:

Co_{,} 2 = -0.02 to 0.02 ns/km;

ci, 2 = -0.2 to 0.01 ns/km;

C2,2 = -0.6 to 0.01 ns/km;

for k = 3 ;

Co_{,} 3 = 0.01 to 0.1 ns/km;

ci_{, 3} = -0.35 to -0.1 ns/km;

C2,3 = 0.05 to 0.25 ns/km

9. The method of claim 8, wherein:

for k = 2:

Co, 2 = 0.0009 ns/km;

ci, 2 = 0.001 1 ns/km;

C2,2 = -0.206 ns/km;

for k = 3 ;

Co, 3 = 0.0391 ns/km;

ci_{, 3} = -0.233 ns/km;

C2,3 = 0.146 ns/km

10. The method of any of claims 6 through 9, wherein the second set of criteria requires that c^{2} < 3 (ns/km)^{2}.

11. The method of claim 10, wherein the second set of criteria requires that c^{2} < 2.5 (ns/km)^{2}.

12. The method of claim 11, wherein the second set of criteria requires that c^{2} < 2 (ns/km)^{2}.

13. The method of any of claims 1 through 12, further comprising:

selecting the multimode fiber based on meeting requirements of the first minimum bandwidth at the first wavelength based on a first set of criteria comprising:

a first criterion using as input the measured differential mode delay (DMD) data for the multimode fiber measured at the first wavelength.

14. The method of claim 13, further comprising calculating an effective minimum

bandwidth at the first wavelength (minEMBci) from the DMD data measured at the first wavelength, and wherein the first criterion requires that minEMBci is greater than or equal to a first threshold value.

15. The method of any of claims 13 through 14, further comprising applying a first mask to the DMD data measured at the first wavelength, and wherein the first criterion requires that the DMD data measured at the first wavelength passes the first mask.

16. The method of any of claims 1 through 15, wherein the first wavelength is less than the second wavelength.

17. The method of any of claims 1 through 16, wherein the first wavelength is in the range 847 nm - 853 nm.

18. The method of claim 14, wherein the first wavelength is in the range 847 nm - 853 nm and the first threshold value is 4160 MHz-km.

19. The method of any of claims 13 through 18, further comprising calculating from the DMD data measured at the first wavelength an overfilled launch bandwidth at the first wavelength (OFLci), and wherein the first set of criteria further comprise a criterion requiring that OFLci is greater than or equal to 3500 MHz-km.

20. The method of any of claims 1 through 19, further comprising:

measuring differential mode delay (DMD) data for the multimode fiber at the second wavelength, wherein the DMD data comprises output laser pulse data as a function of the radial position of an input laser pulse having the second wavelength

selecting the multimode fiber based on meeting requirements of the second minimum bandwidth at the second wavelength based on a third set of criteria in addition to the second set of criteria, the third set of criteria comprising:

a third criterion using as input the measured differential mode delay (DMD) data for the multimode fiber measured at the second wavelength.

21. The method of claim 20, further comprising calculating an effective minimum

bandwidth at the second wavelength (minEMBc2) from the DMD data measured at the second wavelength, and wherein the third criterion comprises a requirement that minEMBc2 is greater than or equal to a second threshold value.

22. The method of any of claims 20 through 21, further comprising applying a third mask to the DMD data measured at the second wavelength, and wherein the third criterion comprises a requirement that the DMD data measured at the second wavelength passes the parameters of the third mask.

23. The method of any of claims 1 through 22, wherein the second wavelength is in the range 950 nm - 956 nm.

24. The method of claim 21, wherein the second wavelength is in the range 950 nm - 956 nm and the second threshold value is 2190 MHz-km.

25. The method of any of claims 20 through 24, further comprising calculating from the DMD data measured at the second wavelength an overfilled launch bandwidth at the second wavelength (OFLC2), and wherein the third set of criteria further comprise a criterion requiring that OFLc2 is greater than or equal to 1850 MHz-km.

26. The method of any of claims 20 through 25, wherein the second set of criterion are satisfied before measuring differential mode delay (DMD) data for the multimode fiber at the second wavelength.

27. A method of selecting, from a plurality of multimode fibers, a third subset of the

multimode fibers meeting requirements of a first minimum bandwidth at a first wavelength and a second minimum bandwidth at a second wavelength greater than the first wavelength, the method comprising:

measuring differential mode delay (DMD) data for the plurality of multimode fibers at the first wavelength, wherein the DMD data comprises output laser pulse data as a function of the radial position of an input laser pulse having the first wavelength;

selecting a first subset of the plurality of multimode fibers based on criteria comprising: passing a first mask applied directly to the DMD data measured at the first wavelength;

selecting a second subset of the plurality of multimode fibers based on criteria comprising:

the radial dependence of the differential mode delay data measured at the first wavelength being within a pre- determined tolerance of a pre-determined reference function constructed by concatenating two or more even-order polynomials having the form:

wherein:

a is a normalizing factor;

r is variable radial position on the fiber over at least two different ranges r_{l k} < r < r_{2 k} c_{0 ,k}, c_{l k}, and c_{2 k} are coefficients that are constant within each range of r;

r_{l k} and r_{2 k} are discrete radial positions on the fiber marking the boundary of each range of r;

k is an indexing variable with values k = {2 ...K} where K is 2 or 3;

selecting the third subset of the plurality of multimode fibers by applying further selection criteria;

wherein:

the first subset is a subset of the plurality of multimode fibers;

the second subset is a subset of the first subset;

the third subset is a subset of the second subset.

28. A system for selecting a multimode fiber meeting requirements of a first minimum bandwidth at a first wavelength and a second minimum bandwidth at a second wavelength greater than the first wavelength, the system comprising:

a measurement device configured to measure differential mode delay (DMD) data for the multimode fiber at the first wavelength, wherein the DMD data comprises output laser pulse data as a function of the radial position of an input laser pulse having the first wavelength;

a first selection device configured to select the multimode fiber if the multimode fiber passes a first mask applied to the DMD data for the multimode fiber at the first wavelength; and

a second selection device configured to select the multimode fiber if the multimode fiber passes a selection criteria comprising:

the radial dependence of the differential mode delay data measured at the first wavelength being within a pre- determined tolerance of a pre-determined reference function constructed by concatenating two or more even-order polynomials having the form:

wherein:

a is a normalizing factor;

r is variable radial position on the fiber over at least two different ranges r_{l k} < r < r_{2 k} c_{0 ,k}, c_{l k}, and c_{2 k} are coefficients that are constant within each range of r;

r_{l k} and r_{2 k} are discrete radial positions on the fiber marking the boundary of each range of r;

k is an indexing variable with values k = {2 ...K} where K is 2 or 3.

29. A method of selecting a multimode fiber meeting requirements of a first minimum bandwidth at a first wavelength and a second minimum bandwidth at a second wavelength different from the first wavelength, the method comprising:

selecting the multimode fiber based on meeting requirements of the first minimum bandwidth at the first wavelength based on a first set of criteria comprising:

a first criterion using as input differential mode delay (DMD) data for the multimode fiber measured at the first wavelength; and

selecting the multimode fiber based on meeting requirements of the second minimum bandwidth at the second wavelength based on a second set of criteria, comprising:

the radial or mode group number dependence of the differential mode delay data measured at the first wavelength being within a pre-determined tolerance of a pre determined reference function constructed by concatenating two or more even-order polynomials having the form:

wherein:

a is a normalizing factor;

r is variable radial position on the fiber over at least two different ranges r_{l k} < r < r_{2 k} c_{0 ,k}, c_{l k}, and c_{2 k} are coefficients that are constant within each range of r;

r_{l k} and r_{2 k} are discrete radial positions on the fiber marking the boundary of each range of r;

k is an indexing variable with values k = {2 ...K} where K is 2 or 3.

30. A method for selecting fibers meeting requirements of a second minimum bandwidth at a second wavelength based on differential mode delay data measured at a first wavelength different from the second wavelength, the method comprising:

measuring the differential mode delay (DMD) data for the multimode fiber at the first wavelength, wherein the DMD data comprises output laser pulse data as a function of the radial position of an input laser pulse having the first wavelength;

selecting the multimode fiber based on meeting requirements of the second minimum bandwidth at the second wavelength based on a second set of criteria, comprising a second criterion comprising:

the radial dependence of the differential mode delay data measured at the first wavelength being within a pre- determined tolerance of a pre-determined reference function having the form:

wherein:

a is a normalizing factor;

r is variable radial position on the fiber over at least one range r_{l k} < r < r_{2 k}:

c_{0 ,k}, c_{l k}, c_{2 k}, and c_{3 k} are coefficients that are constant within each range of r;

r_{l k} and r_{2 k} are discrete radial positions on the fiber marking the boundary of each range of r;

k is an indexing variable with values k = {1 ...K} where K is 1 or 2.

31. The method of claim 30, wherein:

K = 2;

for k = 1 :

^{r}i_{,i} ^{=} 0 microns and r_{2 l} = 7+ microns;

for a radial range defined by r_{1 ±} and r_{2 1}, the radial dependence of the differential mode delay data measured at the first wavelength is within a pre-determined tolerance of a pre determined reference function when a least-squares fit of the differential mode delay data to a function having the form:

has coefficients:

-0.02 ns/km < coi < 0.2 ns/km;

-1.5 ns/km < cn < 0.5 ns/km;

-2.0 < ns/km < C2i < 8.0 ns/km; and

wherein c_{3 k} is set to zero for the fit.

32. The method of any of claims 30 to 31, wherein:

K = 2;

for k = 2, the pre-determined tolerance c^{2} is:

x(r)meas is measured delay at position r;

x(r)ref, k is reference delay at position r in interval k:

r is radial position in microns;

W_{k} is a weighting for each of the k regions (k= 2... K), where W2= l .

a is 25 microns;

microns;

^{r}2,2^{=} 25+ microns;

for k = 2:

Co, 2 = -0.02 to 0.01 ns/km;

ci, 2 = -0.3 to 0.1 ns/km;

C2,2 = -0.5 to 0.3 ns/km; and

C2,3 = -0.1 to 0.4 ns/km.

33. The method of any of claims 1 through 22, wherein the second wavelength is in the range 950 nm - 1070 nm.