Fiber optic cable breakout configuration with excess fiber length

• US 7,422,378 B2
• Filed: 07/21/2006
• Issued: 09/09/2008
• Est. Priority Date: 03/09/2006
• Status: Expired due to Fees

• Current Assignee: CommScope Technologies, LLC (CommScope Holding Company, Inc.)
• Original Assignee: ADC Telecommunications Incorporated (TE Connectivity Limited)
• Inventors: Lu, Yu, Millea, Keith, Gniadek, Jeff
• Primary Examiner(s): Bovernick; Rodney
• Assistant Examiner(s): ROJAS, OMAR R
• Application Number:
  US11/491,340
• Publication Number:
  US 20070212004A1
• Time in Patent Office: 781 Days
• Field of Search: None
• US Class Current: 385/95
• CPC Class Codes: G02B 6/4475 with provision for lateral branching G02B6/4431 takes precedence

Abstract

The present disclosure relates to a telecommunications cable including a distribution cable and a tether that braches from the distribution cable at a mid-span breakout location. A flexible closure covers the mid-span breakout location. Within the closure, fibers are broken out from the distribution cable and spliced to fibers of the tether. The lengths of broken out fibers within the flexible closure are provided with sufficient excess fiber length to allow the closure to be readily bent/flexed in any direction without damaging the fibers.

Claims

1. A telecommunications cable comprising:

a distribution cable including a cable jacket and a plurality of buffer tubes positioned within the cable jacket, the plurality of buffer tubes including a first buffer tube, the distribution cable including a mid-span location where a portion of the cable jacket has been removed and where at least the first buffer tube includes a fiber access location;

a flexible closure that surrounds the distribution cable and covers the mid-span location, the closure being factory installed, the closure being elongated along a length that extends along the distribution cable;

a tether that branches from the distribution cable at the closure, the tether including a tether jacket, a tether buffer tube positioned within the jacket and at least one strength member;

a tether retention block affixed to the distribution cable, the tether buffer tube passing through the retention block and at least the strength member of the tether being affixed to the retention block;

a first optical fiber that extends through the first buffer tube of the distribution cable, the first optical fiber being routed out of the first buffer tube through the fiber access location;

a second optical fiber that extends through the tether buffer tube, the second fiber being routed into the flexible closure;

the first optical fiber being spliced to the second optical fiber at a splice location located within the flexible closure; and

the first optical fiber including a breakout portion that extends from the fiber access location to the splice location and the second optical fiber including a breakout portion that extends from the tether retention block to the splice location, the breakout portions of the first and second fibers having an excess fiber length of at least π

α

R_dc/180°

, wherein R_dc equals a radius of the distribution cable measured from a centerline of the distribution cable to an outer surface of the cable jacket and α

equals a bend angle of the distribution cable.

2. The telecommunications cable of claim 1, wherein the excess fiber length is at least 3 percent of a combined length of the first and second optical fibers.

3. The telecommunications cable of claim 1, wherein the excess fiber length is in the range of 2-5 percent of a combined length of the first and second optical fibers.

4. The telecommunications cable of claim 1, wherein the telecommunications cable is sized to be pulled through a conduit having a 1.25 inch inner diameter.

5. The telecommunications cable of claim 1, wherein the tether is a stub cable or a drop cable.

6. The telecommunications cable of claim 1, wherein the flexible closure includes an overmold.

7. The telecommunications cable of claim 6, wherein the flexible closure includes an elongated protective sleeve through which the breakout portions of the first and second fibers pass, the protective sleeve being encased within the overmold.

8. The telecommunications cable of claim 7, further comprising stiffeners positioned within the protective sleeve, the stiffeners being spaced apart along a length of the protective sleeve, the stiffeners providing the protective sleeve with first regions of increased crush resistance separated by second regions having lesser degrees of crush resistance than the first regions.

9. The telecommunications cable of claim 8, wherein the stiffeners are separate pieces from the protective sleeve.

10. The telecommunications cable of claim 8, wherein at least some of the stiffeners nest within the protective sleeve and have shapes that engage and complement an interior of the protective sleeve.

11. The telecommunications cable of claim 8, wherein the breakout portions of the first and second fibers extend through openings defined by the stiffeners.

12. The telecommunications cable of claim 1, further comprising a splice sleeve for enclosing the splice location and a splice stiffener for holding the splice sleeve.

13. The telecommunications cable of claim 12, wherein the splice sleeve can slide back and forth along a length of the splice stiffener.

14. The telecommunications cable of claim 12, wherein the splice stiffener includes a base defining a channel having a concave curvature, the channel fitting over a plurality of the buffer tubes.

15. The telecommunications cable of claim 1, wherein the retention block defines a first portion configured to mate with a second portion.

16. The telecommunications cable of claim 15, wherein each portion of the retention block defines at least one half-channel configured to cooperate with the half-channel of the other portion to receive the strength member of the tether.

17. The telecommunications cable of claim 16, wherein each portion of the retention block defines at least three half-channels configured to cooperate with the half-channels of the other portion to receive the second optical fiber and two strength members of the tether.

18. The telecommunications cable of claim 1, wherein the retention block defines a reduced diameter portion configured to protrude within an elongated protective sleeve.