Small-diameter polarization maintaining optical fiber

Abstract

Disclosed is a small-diameter polarization maintaining optical fiber, which relates to the field of special optical fibers. The small-diameter polarization maintaining optical fiber comprises a quartz optical fiber (5); the periphery thereof is provided with an inner coating (6) and an outer coating (8); the interior of the quartz optical fiber (5) is provided with an optical fiber core layer (1) and a quartz cladding (2); two stress zones (4) are arranged between the optical fiber core layer (1) and the quartz cladding (2); a buffer coating (7) is arranged between the inner coating (6) and the outer coating (8); the periphery of each stress zone (4) is provided with a buffer layer (3) which is concentric with the stress zone (4); when a working wavelength of a small-diameter polarization maintaining optical fiber is 1310 nm, the attenuation thereof reaches less than 0.5 dB/km, and the crosstalk reaches 35 dB/km; and when the working wavelength of the small-diameter polarization maintaining optical fiber is 1550 nm, the attenuation thereof reaches less than 0.4 dB/km, and the crosstalk reaches 30 dB/km. The optical fiber not only has excellent stability characteristics of attenuation and crosstalk, but also has the excellent stability characteristic of long-term operation, and can provide a better optical fiber ring for research on a high-precision optical fiber gyroscope, thereby laying the foundation for the development directions of miniaturization and high precision of the optical fiber gyroscope.

Claims

1. A small-diameter polarization maintaining optical fiber, comprising quartz optical fiber (5), the periphery of the quartz optical fiber (5) is provided with an inner coating (6) and an outer coating (8), the inner of the quartz optical fiber (5) is provided with an optical fiber core layer (1) and a quartz cladding (2), the quartz cladding (2) is located at the periphery of the optical fiber core layer (1); two stress zones (4) are provided between the optical fiber core layer (1) and the quartz cladding (2), the two stress zones (4) are symmetrically distributed along the center of the optical fiber core layer (1); characterized in that: a buffer coating (7) is provided between the inner coating (6) and the outer coating (8), the periphery of each stress zone (4) is provided with a buffer layer (3) which is concentric with the stress zone (4); the refractive index of the optical fiber core layer (1) is n.sub.O (optical fiber core layer), the refractive index of the buffer layer (3) is n.sub.B (Buffer layer), the refractive index of the quartz cladding (2) is n.sub.Q (Quartz cladding); the refractive index of the stress zone (4) is n.sub.SZ (stress zone), the refractive index of the periphery of stress zone (4) is n.sub.SZP (periphery of stress zone), the refractive index of the center of the stress zone (4) is n.sub.SZC (center of the stress zone); the relative refractive index difference n.sub.O of n.sub.O and n.sub.Q is 0.5%-1.3%, the relative refractive index difference n.sub.B of n.sub.B and n.sub.Q is 0.1%-0.4%; the relative refractive index difference n.sub.SZP of n.sub.SZP and n.sub.Q is 0.1%-0.4%, the relative refractive index difference n.sub.SZC of n.sub.SZC and n.sub.Q is 1.2%-0.8%; when working wavelength of the small-diameter polarization maintaining optical fiber is 1310 nm, its attenuation is below 0.5 dB/km, and its crosstalk reaches 35 dB/km; when working wavelength of the small-diameter polarization maintaining optical fiber is 1550 nm, its attenuation is below 0.4 dB/km, and its crosstalk reaches 30 dB/km.

2. The small-diameter polarization maintaining optical fiber according to claim 1, characterized in that: the diameter of the optical fiber core layer (1) is d.sub.O (optical fiber core layer), the diameter of the buffer layer (3) is d.sub.B (buffer layer), the diameter of the quartz optical fiber (5) is d.sub.Q (quartz optical fiber), the diameter of the stress zone (4) is d.sub.SZ (stress zone); the ratio of d.sub.O and d.sub.Q is 0.05-0.08, the ratio of d.sub.B and d.sub.SZ is 1.0-1.2, the ratio of d.sub.SZ and d.sub.Q is 0.2-0.4.

3. The small-diameter polarization maintaining optical fiber according to claim 1, characterized in that: the diameter of the inner coating (6) is d.sub.IC (inner coating), the diameter of the buffer coating (7) is d.sub.BC (buffer coating), the diameter of the outer coating (8) is d.sub.OC (outer coating), the ratio of d.sub.IC and d.sub.OC is 0.65-0.85, the ratio of d.sub.BC and d.sub.OC is 0.75-0.9.

4. The small-diameter polarization maintaining optical fiber according to claim 3, characterized in that: the diameter d.sub.Q of the quartz optical fiber (5) is 50 um or 80 um, and the d.sub.OC is 90 um-140 um.

5. The small-diameter polarization maintaining optical fiber according to claim 3, characterized in that: the Young's modulus of the inner coating (6) is 0.05 Mpa-20 Mpa, and the Young's modulus of the outer coating (8) is 0.5 Gpa-1.5 Gpa; the Young's modulus of the buffer coating (7) is 0.1 Mpa-600 MPa, and the Young's modulus of the buffer coating (7) is between the inner coating (6) and the outer coating (8).

6. The small-diameter polarization maintaining optical fiber according to claim 1, characterized in that: when producing the inner coating (6), the buffer coating (7) and the outer coating (8), the inner coating (6) is coated with a single mold and cured by ultraviolet rays, then the buffer coating (7) and the outer coating (8) are simultaneously coated with a double molds, and finally the buffer coating (7) and the outer coating (8) are simultaneously cured by ultraviolet rays.

7. The small-diameter polarization maintaining optical fiber according to claim 1, characterized in that: the formula for calculating the relative refractive index difference is: =(n.sub.R (refractive index)n.sub.Q)/(n.sub.R+n.sub.Q.Math.100%, wherein is the relative refractive index difference; when calculating the relative refractive index difference of the optical fiber core layer (1) and the quartz cladding (2), n.sub.R in the above formula is n.sub.O; when calculating the relative refractive index difference of the buffer layer (3) and the quartz cladding (2), n.sub.R in the above formula is n.sub.B; when calculating the relative refractive index difference of the periphery of stress zone (4) and the quartz cladding (2), n.sub.R in the above formula is n.sub.SZP; and when calculating the relative refractive index difference of the center of stress zone (4) and the quartz cladding (2), n.sub.R in the above formula is n.sub.SZC.

8. The small-diameter polarization maintaining optical fiber according to claim 1, characterized in that: the optical fiber core layer (1) is prepared through germanium doping, and the buffer layer (3) is prepared through shallow boron doping, and the stress zone (4) is prepared through deep boron doping.

9. The small-diameter polarization maintaining optical fiber according to claim 2, characterized in that: when producing the inner coating (6), the buffer coating (7) and the outer coating (8), the inner coating (6) is coated with a single mold and cured by ultraviolet rays, then the buffer coating (7) and the outer coating (8) are simultaneously coated with a double molds, and finally the buffer coating (7) and the outer coating (8) are simultaneously cured by ultraviolet rays.

10. The small-diameter polarization maintaining optical fiber according to claim 3, characterized in that: when producing the inner coating (6), the buffer coating (7) and the outer coating (8), the inner coating (6) is coated with a single mold and cured by ultraviolet rays, then the buffer coating (7) and the outer coating (8) are simultaneously coated with a double molds, and finally the buffer coating (7) and the outer coating (8) are simultaneously cured by ultraviolet rays.

11. The small-diameter polarization maintaining optical fiber according to claim 4, characterized in that: when producing the inner coating (6), the buffer coating (7) and the outer coating (8), the inner coating (6) is coated with a single mold and cured by ultraviolet rays, then the buffer coating (7) and the outer coating (8) are simultaneously coated with a double molds, and finally the buffer coating (7) and the outer coating (8) are simultaneously cured by ultraviolet rays.

12. The small-diameter polarization maintaining optical fiber according to claim 5, characterized in that: when producing the inner coating (6), the buffer coating (7) and the outer coating (8), the inner coating (6) is coated with a single mold and cured by ultraviolet rays, then the buffer coating (7) and the outer coating (8) are simultaneously coated with a double molds, and finally the buffer coating (7) and the outer coating (8) are simultaneously cured by ultraviolet rays.

13. The small-diameter polarization maintaining optical fiber according to claim 2, characterized in that: the formula for calculating the relative refractive index difference is: =(n.sub.R (refractive index)n.sub.Q)/(n.sub.R+n.sub.Q).Math.100%, wherein is the relative refractive index difference; when calculating the relative refractive index difference of the optical fiber core layer (1) and the quartz cladding (2), n.sub.R in the above formula is n.sub.O; when calculating the relative refractive index difference of the buffer layer (3) and the quartz cladding (2), n.sub.R in the above formula is n.sub.B; when calculating the relative refractive index difference of the periphery of stress zone (4) and the quartz cladding (2), n.sub.R in the above formula is n.sub.SZP; and when calculating the relative refractive index difference of the center of stress zone (4) and the quartz cladding (2), n.sub.R in the above formula is n.sub.SZC.

14. The small-diameter polarization maintaining optical fiber according to claim 3, characterized in that: the formula for calculating the relative refractive index difference is: =(n.sub.R (refractive index)n.sub.Q)/(n.sub.R+n.sub.Q).Math.100%, wherein is the relative refractive index difference; when calculating the relative refractive index difference of the optical fiber core layer (1) and the quartz cladding (2), n.sub.R in the above formula is n.sub.O; when calculating the relative refractive index difference of the buffer layer (3) and the quartz cladding (2), n.sub.R in the above formula is n.sub.B; when calculating the relative refractive index difference of the periphery of stress zone (4) and the quartz cladding (2), n.sub.R in the above formula is n.sub.SZP; and when calculating the relative refractive index difference of the center of stress zone (4) and the quartz cladding (2), n.sub.R in the above formula is n.sub.SZC.

15. The small-diameter polarization maintaining optical fiber according to claim 4, characterized in that: the formula for calculating the relative refractive index difference is: =(n.sub.R (refractive index)n.sub.Q)/(n.sub.R+n.sub.Q).Math.100%, wherein is the relative refractive index difference; when calculating the relative refractive index difference of the optical fiber core layer (1) and the quartz cladding (2), n.sub.R in the above formula is n.sub.O; when calculating the relative refractive index difference of the buffer layer (3) and the quartz cladding (2), n.sub.R in the above formula is n.sub.B; when calculating the relative refractive index difference of the periphery of stress zone (4) and the quartz cladding (2), n.sub.R in the above formula is n.sub.SZP; and when calculating the relative refractive index difference of the center of stress zone (4) and the quartz cladding (2), n.sub.R in the above formula is n.sub.SZC.

16. The small-diameter polarization maintaining optical fiber according to claim 5, characterized in that: the formula for calculating the relative refractive index difference is: =(n.sub.R (refractive index)n.sub.Q)/(n.sub.R+n.sub.Q).Math.100%, wherein is the relative refractive index difference; when calculating the relative refractive index difference of the optical fiber core layer (1) and the quartz cladding (2), n.sub.R in the above formula is n.sub.O; when calculating the relative refractive index difference of the buffer layer (3) and the quartz cladding (2), n.sub.R in the above formula is n.sub.B; when calculating the relative refractive index difference of the periphery of stress zone (4) and the quartz cladding (2), n.sub.R in the above formula is n.sub.SZP; and when calculating the relative refractive index difference of the center of stress zone (4) and the quartz cladding (2), n.sub.R in the above formula is n.sub.SZC.

17. The small-diameter polarization maintaining optical fiber according to claim 2, characterized in that: the optical fiber core layer (1) is prepared through germanium doping, and the buffer layer (3) is prepared through shallow boron doping, and the stress zone (4) is prepared through deep boron doping.

18. The small-diameter polarization maintaining optical fiber according to claim 3, characterized in that: the optical fiber core layer (1) is prepared through germanium doping, and the buffer layer (3) is prepared through shallow boron doping, and the stress zone (4) is prepared through deep boron doping.

19. The small-diameter polarization maintaining optical fiber according to claim 4, characterized in that: the optical fiber core layer (1) is prepared through germanium doping, and the buffer layer (3) is prepared through shallow boron doping, and the stress zone (4) is prepared through deep boron doping.

20. The small-diameter polarization maintaining optical fiber according to claim 5, characterized in that: the optical fiber core layer (1) is prepared through germanium doping, and the buffer layer (3) is prepared through shallow boron doping, and the stress zone (4) is prepared through deep boron doping.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic structural view of quartz end face of the small-diameter polarization maintaining optical fiber in an embodiment of the present invention;

(2) FIG. 2 is a schematic structural view of coating end face of the small-diameter polarization maintaining optical fiber in an embodiment of the present invention;

(3) FIG. 3 is the schematic view of the waveguide structure with the stress zone of the small-diameter polarization maintaining optical fiber in an embodiment of the present invention;

(4) FIG. 4 is a trend graph showing the stability characteristic curve of the optical fiber attenuation under the long-term aging condition of the small-diameter polarization maintaining optical fiber in an embodiment of the present invention;

(5) FIG. 5 is a trend graph showing the stability characteristic curve of the optical fiber crosstalk under the long-term aging condition of the small-diameter polarization maintaining optical fiber in an embodiment of the present invention.

(6) In figures: 1optical fiber core layer, 2quartz cladding, 3buffer layer, 4stress zone, 5quartz optical fiber, 6inner coating, 7buffer coating, and 8outer coating.

DETAILED DESCRIPTION OF THE INVENTION

(7) The invention will now be described in further detail with reference to the accompanying drawings and examples.

(8) Referring to FIGS. 1 and 2, the small-diameter polarization maintaining optical fiber of an embodiment of the present invention comprises quartz optical fiber 5, the inner of the quartz optical fiber 5 is provided with an optical fiber core layer 1 and a quartz cladding 2, and the quartz cladding 2 is located at the periphery of the optical fiber core layer 1. Two stress zones 4 are provided between the optical fiber core layer 1 and the quartz cladding 2, the two stress zones 4 are symmetrically distributed along the center of the optical fiber core layer 1, the periphery of each stress zone 4 is provided with a buffer layer 3 which is concentric with the stress zone 4. The periphery of the quartz optical fiber 5 is provided with an inner coating 6 and an outer coating 8, the buffer coating 7 is provided between the inner coating 6 and the outer coating 8.

(9) The refractive index of the optical fiber core layer 1 is n.sub.O, the refractive index of the buffer layer 3 is n.sub.B, the refractive index of the quartz cladding 2 is n.sub.Q; the refractive index of the stress zone 4 is n.sub.SZ, the refractive index of the periphery of stress zone 4 is n.sub.SZP, the refractive index of the center of the stress zone 4 is n.sub.SZC.

(10) In the embodiments of the present invention, the formula for calculating the relative refractive index difference of the small-diameter polarization maintaining optical fiber is: =(n.sub.Rn.sub.Q)/(n.sub.R+n.sub.Q).Math.100%, wherein is the relative refractive index difference; when calculating the relative refractive index difference of the optical fiber core layer 1 and the quartz cladding 2, n.sub.R in the above formula is n.sub.O; when calculating the relative refractive index difference of the buffer layer 3 and the quartz cladding 2, n.sub.R in the above formula is n.sub.B; when calculating the relative refractive index difference of the periphery of stress zone 4 and the quartz cladding 2, n.sub.R in the above formula is n.sub.SZP; when calculating the relative refractive index difference of the center of stress zone 4 and the quartz cladding 2, n.sub.R in the above formula is n.sub.SZC.

(11) Referring to FIG. 3, the waveguide structure of optical fiber core layer 1 is a stepped waveguide structure, the optical fiber core layer 1 is prepared through germanium doping, and the relative refractive index difference n.sub.O of n.sub.O and n.sub.Q is 0.5%-1.3%. The buffer layer 3 is prepared through shallow boron doping, and the relative refractive index difference n.sub.B of n.sub.B and n.sub.Q is 0.1%-0.4%. The stress zone 4 is prepared through deep boron doping, the relative refractive index difference n.sub.SZP of n.sub.SZP and n.sub.Q is 0.1%-0.4%, the relative refractive index difference n.sub.SZC of n.sub.SZC and n.sub.Q is 1.2%-0.8%.

(12) The diameter of the optical fiber core layer 1 is d.sub.O, the diameter of the buffer layer 3 is d.sub.B, the diameter of the quartz optical fiber 5 (ie quartz cladding 2) is d.sub.Q, the diameter of the stress zone 4 is d.sub.SZ; the ratio of d.sub.O and d.sub.Q is 0.05-0.08, the ratio of d.sub.B and d.sub.SZ is 1.0-1.2, the ratio of d.sub.SZ and d.sub.Q is 0.2-0.4.

(13) In the embodiments of the present invention, the diameter d.sub.Q of the quartz optical fiber 5 is 50 um or 80 um, the diameter of the inner coating 6 is d.sub.IC, the diameter of the buffer coating 7 is d.sub.BC, the diameter d.sub.OC of the outer coating 8 is 90 um-140 um. The ratio of d.sub.IC and d.sub.OC is 0.65-0.85, and the ratio of d.sub.BC and d.sub.OC is 0.75-0.9.

(14) The Young's modulus of the buffer coating 7 is between the inner coating 6 and the outer coating 8, the Young's modulus of the inner coating 6 is 0.05 Mpa-20 Mpa, and the Young's modulus of the outer coating 8 is 0.5 Gpa-1.5 Gpa, the Young's modulus of the buffer coating 7 is 0.1 Mpa-600 MPa.

(15) The inner coating 6, the buffer coating 7 and the outer coating 8 are each formed by ultraviolet curing, specifically: the inner coating 6 is coated with a single mold and cured by ultraviolet rays, then the buffer coating 7 and the outer coating 8 are simultaneously coated with a double molds, and finally the buffer coating 7 and the outer coating 8 are simultaneously cured by ultraviolet rays, thereby achieving a special dry plus wet plus wet coating curing.

(16) In the embodiments of the present invention, when working wavelength of the small-diameter polarization maintaining optical fiber is 1310 nm, its attenuation is below 0.5 dB/km, and its crosstalk reaches 35 dB/km; when working wavelength of the small-diameter polarization maintaining optical fiber is 1550 nm, its attenuation is below 0.4 dB/km, and its crosstalk reaches 30 dB/km.

(17) The manufacturing principle of the small-diameter polarization maintaining optical fiber in the embodiments of the present invention is as follows:

(18) when n.sub.O is larger, the mode field diameter can be controlled smaller, the bending resistance of the polarization maintaining optical fiber will be stronger, when n.sub.O is smaller, the attenuation of the polarization maintaining optical fiber will be better, while the mode field diameter will become larger, the bending resistance of the polarization maintaining optical fiber will be weaker.

(19) The n.sub.B, n.sub.O and n.sub.SZC should be matched, when the n.sub.O is higher, and the n.sub.SZC is larger, the value of n.sub.B can be larger, at this point the polarization maintaining optical fiber should be provided with lower buffering capacity; when the larger value of n.sub.O is smaller, and the lower value of n4 is smaller, the value of n3 can be smaller, at this point the polarization maintaining optical fiber should be provided with higher buffering capacity.

(20) The n.sub.SZP and n.sub.SZC can control refractive index range, thereby achieving good crosstalk and beat length control under the condition of the small-diameter polarization maintaining optical fiber.

(21) The specific diameter ratio of the present invention can realize the good mode field diameter, the cut-off wavelength and the optical fiber's performance control of crosstalk and beat length of the polarization maintaining optical fiber.

(22) The detailed description of the small-diameter polarization maintaining optical fiber of the present invention is carried out by 2 embodiments below.

Embodiment 1

(23) Four kinds of small-diameter polarization maintaining optical fiber with the diameter d.sub.Q of the quartz optical fiber 5 is 80 um: optical fiber 1, optical fiber 2, optical fiber 3, optical fiber 4, the specific parameters of optical fiber 1, optical fiber 2, optical fiber 3 and optical fiber 4 are shown in Table 1.

(24) TABLE-US-00001 TABLE 1 parameters table of four kinds of small-diameter polarization maintaining optical fiber when d.sub.Q is 80 um optical optical optical optical Parameter name fiber 1 fiber 2 fiber 3 fiber 4 d.sub.O/d.sub.Q 0.05 0.06 0.07 0.08 n.sub.O 1.2% 0.8% 1.3% 0.50% d.sub.B/d.sub.SZ 1.0 1.1 1.2 1.05 n.sub.B 0.3% 0.85% 0.4% 0.1% d.sub.SZ/d.sub.Q 0.2 0.35 0.4 0.25 n.sub.SZC 0.9% 1.05% 1.2% 0.8% n.sub.SZP 0.3% 0.85% 0.4% 0.1% d.sub.OC (um) 120 135 140 125 d.sub.IC/d.sub.OC 0.65 0.85 0.75 0.7 d.sub.BC/d.sub.OC 0.75 0.8 0.9 0.85 Young's modulus of inner 0.05 0.1 0.5 20 coating 6 (Mpa) Young's modulus of buffer 250 0.1 10 600 coating 7 (Mpa) Young's modulus of outer 1.5 0.8 0.5 1.0 coating 8 (Mpa) working wavelength 1310 1310 1550 1550 attenuation dB/km 0.43 0.32 0.28 0.35 crosstalk dB/km 32 35 30 27

Embodiment 2

(25) Four kinds of small-diameter polarization maintaining optical fiber with the diameter d.sub.Q of the quartz optical fiber 5 is 50 um: optical fiber 5, optical fiber 6, optical fiber 7, optical fiber 8, the specific parameters of optical fiber 5, optical fiber 6, optical fiber 7 and optical fiber 8 are shown in Table 2.

(26) TABLE-US-00002 TABLE 2 parameters table of four kinds of small-diameter polarization maintaining optical fiber when d.sub.Q is 50 um optical optical optical optical Parameter name fiber 5 fiber 6 fiber 7 fiber 8 D.sub.O/d.sub.Q 0.06 0.05 0.07 0.08 n.sub.O 1.3% 0.5% 0.8% 1.2 d.sub.B/d.sub.SZ 1.1 1.0 1.05 1.2 n.sub.B 0.3% 0.85% 0.4% 0.1% d.sub.SZ/d.sub.Q 0.25 0.4 0.35 0.2 n.sub.SZC 0.8% 1.05% 1.2% 0.9% n.sub.SZP 0.1% 0.85% 0.4% 0.3% d.sub.OC (um) 90 105 135 110 d.sub.IC/d.sub.OC 0.65 0.75 0.8 0.7 d.sub.BC/d.sub.OC 0.75 0.9 0.8 0.85 Young's modulus of inner 20 0.5 0.2 0.05 coating 6 (Mpa) Young's modulus of buffer 250 10 0.2 600 coating 7 (Mpa) Young's modulus of outer 1 0.8 0.5 1.5 coating 8 (Mpa) working wavelength 1310 1310 1550 1550 attenuation dB/km 0.46 0.42 0.36 0.39 crosstalk dB/km 39 35 30 25

(27) The optical fibers obtained in embodiments 1 and 2 are subjected to a long-term aging test at 85 degrees high temperature and 85% humidity in the present invention. Through the repeated test of many samples in the past one month, the theoretical value of stable operating characteristics of optical fiber attenuation and crosstalk is obtained under the condition of the optical fiber working 5 years after a lot of data analysis. Referring to FIG. 4, the increase in attenuation coefficient will not exceed 1.6% of its intrinsic additional attenuation for 5 years under conditions of 85 C. and 85% humidity. For the polarization maintaining optical fiber with an additional loss of less than 0.05 dB when leaving the factory, the attenuation coefficient of the polarization maintaining optical fiber is increased by about 0.0008 dB in the 5 year. Referring to FIG. 5, under the conditions of temperature 85 degree and humidity 85%, after 5 years, the birefringence of the optical fiber will be reduced by about 2.6% under the same external stress condition, and will keep the balance.

(28) The present invention is not limited to the embodiments described above, and modifications and improvements may be made to those skilled in the art without departing from the principles of the present invention, which are also regarded as the protection of the present invention. What is not described in detail in this specification belongs to the prior art known to those skilled in the art.