Dispersion-balanced optical cable

• US 5,611,016 A
• Filed: 06/07/1996
• Issued: 03/11/1997
• Est. Priority Date: 06/07/1996
• Status: Expired due to Term

• Current Assignee: Furukawa Electric North America Incorporated (Furukawa Electric Company Limited)
• Original Assignee: Lucent Technologies, Inc. (Nokia Corporation)
• Inventors: Fangmann, Robert E., Refi, James J., Judy, Arthur F.
• Primary Examiner(s): Ullah, Akm E.
• Application Number:
  US08/660,639
• Time in Patent Office: 277 Days
• Field of Search: 385/100-113, 385/147, 385/27, 385/28, 385/123, 385/128, 385/24, 385/31, 359/115, 359/124, 359/127, 359/161, 359/173, 359/188, 359/900, 372/26
• US Class Current: 385/100
• CPC Class Codes: G02B 6/02247 Dispersion varying along the longitudinal direction, e.g. dispersion managed fibre
• CPC Class Codes: G02B 6/02257 Non-zero dispersion shifted fibres, i.e. having a small negative dispersion at 1550 nm, e.g. ITU-T G.655 dispersion between - 1.0 to - 10 ps/nm.km for avoiding nonlinear effects
• CPC Class Codes: G02B 6/02271 Non-zero dispersion shifted fibres, i.e. having a small positive dispersion at 1550 nm, e.g. ITU-T G.655 dispersion between 1.0 to 10 ps/nm.km for avoiding nonlinear effects
• CPC Class Codes: G02B 6/0228 Characterised by the wavelength dispersion slope properties around 1550 nm G02B6/02228 takes precedence
• CPC Class Codes: G02B 6/29374 in an optical light guide G02B6/02214 takes precedence
• CPC Class Codes: G02B 6/4401 Optical cables glass fibres with a protective coating G02B6/02395
• CPC Class Codes: G02B 6/441 built up from sub-bundles G02B6/4429, G02B6/4439, G02B6/4479 take precedence
• CPC Class Codes: G02B 6/4432 with fibre reinforcements
• CPC Class Codes: G02B 6/4433 Double reinforcement laying in straight line with optical transmission element

Abstract

A dispersion-balanced optical cable 90 reduces four-photon mixing in Wave Division Multiplexing (WDM) systems and is effective to reduce cumulative dispersion D substantially to zero. The dispersion-balanced optical cable 90 includes one or more optical fibers 90-1 having positive dispersion D₁, and one or more optical fibers 90-2 having negative dispersion D₂. The fibers are singlemode and are suitable for the transmission of optical signals in the 1550 nm region. At this wavelength, the positive-dispersion fibers have a chromatic dispersion of about +2.3 ps/nm.km, and the negative-dispersion fibers have a chromatic dispersion of about -1.6 ps/nm.km. The dispersion-balance optical cable preferably includes an equal number of positive- and negative-dispersion fibers in the same cable. Various cable configurations 60, 80, 90 can be used including: a ribbon 60 which comprises a planar array of optical fibers bound together by a matrix material 65; groups of positive- and negative-dispersion fibers enclosed within a plastic tube 81; or other known configurations. An improved WDM system 100 interconnects two dispersion-balanced cables 90-90, and a crossover connection 105 is made between the positive-dispersion fibers 90-1 of one cable 90 and the negative-dispersion fibers 90-2 of the other cable 90.

Claims

1. A dispersion-balanced optical cable comprising one or more optical fibers of a first type and one or more optical fibers of a second type, both types of optical fiber being suitable for transmitting optical signals at a source wavelength λ

_s,

CHARACTERIZED IN THAT;

the first type of optical fiber has positive chromatic dispersion, the average of the absolute magnitudes of the dispersions of the positive dispersion fibers exceeding 0.8 ps/nm.km at λ

_s ; and

the second type of optical fiber has negative chromatic dispersion, the average of the absolute magnitudes of the dispersions of the negative dispersion fibers exceeding 0.8 ps/nm.km at λ

_s.

2. The dispersion-balanced optical cable of claim 1 wherein the source wavelength λ

_s resides in the range 1530 nm<

λ

_s <

1565 nm.

3. The dispersion-balanced optical cable of claim 2 wherein the first and second types of optical fiber are singlemode and have:

(i) an attenuation that is less than 0.26 dB/km at 1550 nm;

(ii) a cutoff wavelength that is less than 1450 nm; and

(iii) a dispersion slope that is less than 0.1 ps/(nm².km), the absolute magnitude of the average chromatic dispersion at 1550 nm being in the range 0.8-4.6 ps/nm.

4. The dispersion-balanced optical cable of claim 3 wherein the first type of optical fiber has an average chromatic dispersion D₁ and wherein the second type of optical fiber has an average chromatic dispersion D₂, the absolute magnitude of D₂ being 65-80% the absolute magnitude of D₁.

5. The dispersion-balanced optical cable of claim 3 wherein the first type of optical fiber has an average chromatic dispersion of approximately+2.3 ps/nm.km at 1550 nm.

6. The dispersion-balanced optical cable of claim 3 wherein the second type of optical fiber has an average negative chromatic dispersion of approximately -1.6 ps/nm.km at 1550 nm.

7. The dispersion-balanced optical cable of claim 1 wherein the cable further comprises:

a plastic tubular member that encloses the optical fibers of the first and second types;

a plastic jacket that encloses the tubular member; and

one or more strength members disposed within the cable.

8. The dispersion-balanced optical cable of claim 1 wherein the first and second types of optical fibers are bonded together in a planar array, said optical fibers having longitudinal axes that are substantially parallel to one another.

9. The dispersion-balanced optical cable of claim 8 wherein the optical fibers of the first type and the optical fibers of the second type are equal in number to each other.

10. The dispersion-balanced optical cable of claim 8 wherein the cable further comprises:

a plastic tubular member that encloses the planar array;

a plastic jacket that encloses the tubular member; and

one or more strength members disposed within the cable.

11. The dispersion-balanced optical cable of claim 1 wherein the first type of optical fibers are bonded together in a first planar array and the second type of optical fibers are bonded together in a second planar array, each planar array comprising optical fibers having longitudinal axes that are substantially parallel to one another.

12. The dispersion-balanced optical cable of claim 11 wherein the cable further comprises:

a plastic tubular member that encloses the first and second planar arrays;

a plastic jacket that encloses the tubular member; and

one or more strength members disposed within the cable.

13. The optical cable of claim 1 wherein optical fibers of the first type are assembled together into a first unit and wrapped with a binder, and wherein optical fibers of the second type are assembled together into a second unit and wrapped with a binder.

14. The dispersion-balanced optical cable of claim 13 wherein the cable further comprises:

a plastic tubular member that encloses the first and second units;

a plastic jacket that encloses the tubular member; and

one or more strength members disposed within the cable.

15. A wave division multiplexed system comprising:

a source of optical signals having a nominal wavelength λ

_s ;

first and second dispersion-balanced cables having predetermined lengths L₁, L₂ respectively, each cable including optical fibers having positive chromatic dispersion D₁ --the average of the absolute magnitudes of D₁ being greater than 0.8 ps/nm.km at λ

_s, and each cable including optical fibers having negative chromatic dispersion D₂ --the average of the absolute magnitudes of D₂ being greater than 0.8 ps/nm.km at λ

_s.

means interconnecting an optical fiber having positive chromatic dispersion within the first cable to an optical fiber having negative chromatic dispersion within the second cable.

16. The wave division multiplexed system of claim 15 wherein λ

_s resides in the wavelength range 1530 nm-1565 nm.

17. The wave division multiplexed system of claim 15 wherein the absolute magnitude of each of D₁ and D₂ resides in the range 0.8-4.6 ps/nm.km at λ

_s.

18. The wave division multiplexed system of claim 17 wherein the absolute magnitude of D₂ is about 65-80% of the absolute magnitude of D₁.

19. The wave division multiplexed system of claim 18 wherein D₁ is approximately equal to +2.3 ps/nm.km at λ

_s, and D₂ is approximately equal to -1.6 ps/nm.km at λ

_s.

20. The wave division multiplexed system of claim 15 wherein L₁ is approximately equal to L₂.

21. An optical cable including a plurality of glass fibers, some of the glass fibers having positive chromatic dispersions D₁ at a predetermined wavelength and others of the glass fibers having negative chromatic dispersions D₂ at the predetermined wavelength, the average of the absolute magnitudes of D₁ being greater than 0.8 ps/nm.km at the predetermined wavelength, and the average of the absolute magnitudes of the dispersions D₂ exceeding 0.8 ps/nm.km at the predetermined wavelength.

22. The optical cable of claim 21 wherein the absolute magnitudes of D₁ and D₂ are less than 4.6 ps/nm.km at the predetermined wavelength.

23. The optical cable of claim 21 wherein the predetermined wavelength resides in the range 1530 nm-1565 nm.