1. In a process for the production of a high-purity diaryl carbonate in which a diaryl carbonate is produced by taking as a starting material a reaction mixture containing an alkyl aryl carbonate that has been obtained through a transesterification reaction between a dialkyl carbonate and an aromatic monohydroxy compound, continuously feeding the starting material into a reactive distillation column comprising a continuous multi-stage distillation column in which a homogeneous catalyst is present, carrying out a transesterification reaction and distillation simultaneously in said column, continuously withdrawing a low boiling point reaction mixture containing a produced dialkyl carbonate from an upper portion of the column in a gaseous form, and continuously withdrawing a high boiling point reaction mixture containing a diaryl carbonate from a lower portion of the column in a liquid form, wherein the improvement comprises:
(a) said high boiling point reaction mixture is continuously introduced into a high boiling point material separating column A, and continuously subjected to separation by distillation into a column top component AT containing the diaryl carbonate and a column bottom component AB containing the catalyst and a high boiling point material;
(b) said column top component AT is continuously introduced into a diaryl carbonate purifying column B having a side cut outlet, and continuously subjected to separation by distillation into a column top component BT, a side cut component BS and a column bottom component BB, the high-purity diaryl carbonate being continuously withdrawn as the side cut component BS; and
(c) said column top component BT is continuously introduced into an intermediate boiling point material separating column C having a side cut outlet, and continuously subjected to separation by distillation into a column top component CT having said alkyl aryl carbonate as a main component thereof, a side cut component CS having as a main component thereof an intermediate boiling point material having a boiling point between that of said alkyl aryl carbonate and that of said diaryl carbonate, and a column bottom component CB having said diaryl carbonate as a main component thereof.
2. The process according to claim 1, wherein said column top component CT from said intermediate boiling point material separating column C is continuously fed into said reactive distillation column.
3. The process according to claim 1 or 2, wherein said column bottom component CB from said intermediate boiling point material separating column C is continuously fed into said high boiling point material separating column A.
4. The process according to claim 1, wherein said reactive distillation column is a continuous multi-stage distillation column comprising an internal with a number of stages n thereinside, n satisfying 10\u2266n\u226680.
5. The process according to claim 1, wherein said high boiling point material separating column A is a continuous multistage distillation column comprising an internal with a number of stages nA thereinside, nA satisfying 20\u2266n\u2266100.
6. The process according to claim 1, wherein said diaryl carbonate purifying column B is a continuous multi-stage distillation column comprising an internal with a number of stages nB thereinside nB satisfying 20\u2266nB\u226670.
7. The process according to claim 1, wherein said intermediate boiling point material separating column C is a continuous multistage distillation column comprising an internal with a number of stages nC thereinside, nC satisfying 10\u2266nC\u226650.
8. The process according to claim 1, wherein a distillation operation of said high boiling point material separating column A is carried out at a column bottom temperature TA in a range of from 185 to 280\xb0 C., and a column top pressure PA in a range of from 1000 to 20000 Pa.
9. The process according to claim 1, wherein a distillation operation of said diaryl carbonate purifying column B is carried out at a column bottom temperature TB in a range of from 185 to 280\xb0 C., and a column top pressure PB in a range of from 1000 to 20000 Pa.
10. The process according to claim 1, wherein a distillation operation of said intermediate boiling point material separating column C is carried out at a column bottom temperature TC in a range of from 150 to 280\xb0 C., and a column top pressure PC in a range of from 500 to 18000 Pa.
11. The process according to claim 1, wherein a reflux ratio for said high boiling point material separating column A is in a range of from 0.01 to 10.
12. The process according to claim 1, wherein a reflux ratio for said diaryl carbonate purifying column B is in a range of from 0.01 to 10.
13. The process according to claim 1, wherein a reflux ratio for said intermediate boiling point material separating column C is in a range of from 0.01 to 10.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. An optical fiber comprising:
a first core located in a central portion of the optical fiber and having a first refractive index;
a second core located in an outer periphery of the first core and having a second refractive index lower than the first refractive index;
a third core located in an outer periphery of the second core and having a third refractive index lower than the first refractive index and higher than the second refractive index; and
a cladding located in an outer periphery of the third core and having a fourth refractive index lower than the third refractive index and higher than the second refractive index,
wherein an absolute value of dispersion at a wavelength of 1550 nm is equal to or less than 20 psnmkm, an effective area at the wavelength of 1550 nm is equal to or less than 15 \u03bcm2, and a nonlinear constant n2Aeff at the wavelength of 1550 nm is equal to or more than 25\xd710\u221210W.
2. The optical fiber according to claim 1,
wherein the effective area Aeff at the wavelength of 1550 nm is equal to or less than 12 \u03bcm2, and the nonlinear constant n2Aeff at the wavelength of 1550 nm is equal to or more than 35\xd710\u221210W.
3. The optical fiber according to claim 1,
wherein a relative reflective index difference \u03941 of the first core with respect to the cladding ranges from 1.5% to 5.0% inclusive, a relative reflective index difference \u03942 of the second core with respect to the cladding ranges from \u22121.4% to \u22120.1% inclusive, and a relative reflective index difference \u03943 of the third core with respect to the cladding ranges from 0.1% to 1.0% inclusive.
4. The optical fiber according to claim 1,
wherein a relative reflective index difference \u03941 of the first core with respect to the cladding ranges from 2.4% to 4.0% inclusive, a relative reflective index difference \u03942 of the second core with respect to the cladding ranges from \u22121.4% to \u22120.7% inclusive, and a relative reflective index difference \u03943 of the third core with respect to the cladding ranges from 0.1% to 1.0% inclusive.
5. The optical fiber according to claim 1,
wherein the absolute value of dispersion at the wavelength of 1550 nm is equal to or less than 10 psnmkm.
6. The optical fiber according to claim 1,
wherein the absolute value of dispersion at the wavelength of 1550 nm is equal to or less than 5 psnmkm.
7. The optical fiber according to claim 1,
wherein an absolute value of dispersion slope at the wavelength of 1550 nm is equal to or less than 0.03 psnm2km.
8. The optical fiber according to claim 1,
wherein an absolute value of dispersion slope at the wavelength of 1550 nm is equal to or less than 0.01 psnm2km.
9. The optical fiber according to claim 1,
wherein a difference between maximum and minimum values of dispersion along a longitudinal direction of the optical fiber at any one of wavelengths of 1550 nm to 1590 nm is equal to or less than 1 psnmkm.
10. The optical fiber according to claim 1,
wherein a difference between maximum and minimum values of dispersion along a longitudinal direction of the optical fiber at any one of wavelengths of 1510 nm to 1590 nm is equal to or less than 0.2 psnmkm.
11. The optical fiber according to claim 1,
wherein a cut-off wavelength \u03bbc of the optical fiber is equal to or less than 1500 nm.
12. The optical fiber according to claim 1,
wherein a ratio D1D2 between an outer diameter D1 of the first core and an outer diameter D2 of the second core ranges from 0.3 to 0.8 inclusive.
13. The optical fiber according to claim 1,
wherein a ratio D1D2 between an outer diameter D1 of the first core and an outer diameter D2 of the second core ranges from 0.4 to 0.7 inclusive.
14. The optical fiber according to claim 3,
wherein a ratio D2D3 between an outer diameter D2 of the second core and an outer diameter D3 of the third core ranges from 0.35 to 0.99 inclusive, and satisfies the following relation:
D2D3>\u03943+0.25 (0.1%\u2266\u03943\u22660.2%)
D2D3>(\xbd)\xb7\u03943+0.35(0.2%\u2266\u03943\u22660.6%)
D2D3>(\xbc)\xb7\u03943+0.5(0.6%\u2266\u03943\u22661.0%).
15. The optical fiber according to claim 1,
wherein a refractive index profile of the first core is an \u03b1-profile, where \u03b1-value is equal to or more than 3.0.
16. The optical fiber according to claim 1,
wherein a refractive index profile of the first core is an \u03b1-profile, where \u03b1-value is equal to or more than 6.0.
17. An optical signal processor using an optical fiber, the optical fiber comprising:
a first core located in a central portion of the optical fiber and having a first refractive index;
a second core located in an outer periphery of the first core and having a second refractive index lower than the first refractive index;
a third core located in an outer periphery of the second core and having a third refractive index lower than the first refractive index and higher than the second refractive index; and
a cladding located in an outer periphery of the third core and having a fourth refractive index lower than the third refractive index and higher than the second refractive index,
wherein an absolute value of dispersion at a wavelength of 1550 nm is equal to or less than 20 psnmkm, an effective area at the wavelength of 1550 nm is equal to or less than 15 \u03bcm2, and a nonlinear constant n2Aeff at the wavelength of 1550 nm is equal to or more than 25\xd710\u221210W.
18. The optical signal processor according to claim 17,
wherein the optical signal processor is an optical wavelength converter.
19. The optical signal processor according to claim 17,
wherein the optical signal processor is a pulse compressor.
20. An optical fiber comprising:
a first core located in a central portion of the optical fiber and having a first refractive index;
a second core located in an outer periphery of the first core and having a second refractive index lower than the first refractive index; and
a cladding located in an outer periphery of the second core and having a third refractive index lower than the first refractive index and higher than the second refractive index,
wherein an absolute value of dispersion at a wavelength of 1550 nm is equal to or less than 20 psnmkm, an effective area Aeff at the wavelength of 1550 nm is equal to or less than 15 \u03bcm2, and the nonlinear constant at the wavelength of 1550 nm is equal to or more than 25\xd710\u221210W, and
wherein the cladding is doped with germanium.
21. The optical fiber according to claim 20,
wherein the effective area Aeff at the wavelength of 1550 nm is equal to or less than 12 \u03bcm2 and the nonlinear constant n2Aeff at the wavelength of 1550 nm is equal to or more than 35\xd710\u221210W.
22. The optical fiber according to claim 20,
wherein a relative reflective index difference of the cladding with respect to pure silica glass ranges from 0.1% to 1.0% inclusive.
23. The optical fiber according to claim 20,
wherein a relative reflective index difference \u03941 of the first core with respect to the cladding ranges from 1.0% to 5.0% inclusive and a relative reflective index difference \u03942 of the second core with respect to the cladding ranges from \u22122.4% to \u22120.2% inclusive.
24. The optical fiber according to claim 20,
wherein a relative reflective index difference \u03941 of the first core with respect to the cladding ranges from 2.0% to 4.0% inclusive and a relative reflective index difference \u03942 of the second core with respect to the cladding ranges from \u22122.0% to \u22120.6% inclusive.
25. The optical fiber according to claim 20,
wherein the absolute value of dispersion at the wavelength of 1550 nm is equal to or less than 10 psnmkm.
26. The optical fiber according to claim 20,
wherein the absolute value of dispersion at the wavelength of 1550 nm is equal to or less than 5 psnmkm.
27. The optical fiber according to claim 20,
wherein an absolute value of dispersion slope at the wavelength of 1550 nm is equal to or less than 0.03 psnm2km.
28. The optical fiber according to claim 20,
wherein an absolute value of dispersion slope at the wavelength of 1550 nm is equal to or less than 0.01 psnm2km.
29. The optical fiber according to claim 20,
wherein a difference between maximum and minimum values of dispersion along a longitudinal direction of the optical fiber at any one of wavelengths of 1510 nm to 1590 nm is equal to or less than 1 psnmkm.
30. The optical fiber according to claim 20,
wherein a difference between maximum and-minimum values of dispersion along a longitudinal direction of the optical fiber at any one of wavelengths of 1510 nm to 1590 nm is equal to or less than 0.2 psnmkm.
31. The optical fiber according to claim 20,
wherein a cut-off wavelength \u03bbc of the optical fiber is equal to or less than 1500 nm.
32. The optical fiber according to claim 20,
wherein a cut-off wavelength \u03bbc of the optical fiber is equal to or less than 1200 nm.
33. The optical fiber according to claim 20,
wherein a ratio D1D2 between an outer diameter D1 of the first core and an outer diameter D2 of the second core ranges from 0.1 to 0.8 inclusive.
34. The optical fiber according to claim 20,
wherein a ratio D1D2 between an outer diameter D1 of the first core and an outer diameter D2 of the second core ranges from 0.4 to 0.7 inclusive.
35. The optical fiber according to claim 20, further comprising a third core located in an outer periphery of the second core and having a fourth refractive index lower than the first refractive index and higher than the third refractive index.
36. The optical fiber according to claim 35,
wherein a relative reflective index difference \u03943 of the third core with respect to the cladding ranges from 0.1% to 0.9% inclusive.
37. The optical fiber according to claim 35,
wherein a ratio D2D3 between an outer diameter D2 of the second core and an outer diameter D3 of the third core ranges from 0.35 to 0.99 inclusive.
38. The optical fiber according to claim 20,
wherein a refractive index profile of the first core is an \u03b1-profile, where \u03b1-value is equal to or more than 3.0.
39. The optical fiber according to claim 20,
wherein a refractive index profile of the first core is the \u03b1-profile, where \u03b1-value is equal to or more than 6.0.
40. An optical signal processor using an optical fiber, the optical fiber comprising:
a first core located in a central portion of the optical fiber and having a first refractive index;
a second core located in an outer periphery of the first core and having a second refractive index lower than the first refractive index; and
a cladding located in an outer periphery of the second core and having a third refractive index lower than the first refractive index and higher than the second refractive index,
wherein an absolute value of dispersion at a wavelength of 1550 nm is equal to or less than 20 psnmkm, an effective area Aeff at the wavelength of 1550 nm is equal to or less than 15 \u03bcm2, and the nonlinear constant at the wavelength of 1550 nm is equal to or more than 25\xd710\u221210W, and
wherein the cladding is doped with germanium.
41. The optical signal processor according to claim 40,
wherein the optical signal processor is an optical wavelength converter.
42. The optical signal processor according to claim 40,
wherein the optical signal processor is a pulse compressor.