# US 2016/0252684 A1 · Systems and Techniques for Improving Insertion Loss Performance of Multicore Fiber Connectors

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- Number: US 2016/0252684 A1
- Document ID: US20160252684A1
- Status: Published application
- Kind: A1
- Application number: 15/152,275
- Filed: 2016-05-11
- Published: 2016-09-01
- Earliest claimed: 2010-03-16
- Assignees: OFS Fitel, LLC
- Applicants: OFS Fitel, LLC
- Inventors: Kelvin B. Bradley
- Web page: https://patentgrep.com/patent/US20160252684A1

## CPC

- G02B 6/3885: {Multicore or multichannel optical connectors, i.e. one single ferrule containing more than one fibre, e.g. ribbon type (optical ribbon cable G02B6/4403, G02B6/448)}
- G02B 6/02042: {Multicore optical fibres}
- G02B 6/245: Removing protective coverings of light guides before coupling
- G02B 6/3843: {with auxiliary facilities for movably aligning or adjusting the fibre within its ferrule, e.g. measuring position or eccentricity (testing the alignment of axes, including eccentricity, G01B11/27)}
- G02B 6/3851: {Ferrules having keying or coding means}
- G02B 6/3861: {Adhesive bonding (adhesives in general C09J)}
- G02B 6/3863: {fabricated by using polishing techniques (grinding of the fibre ends B24B19/226)}
- G02B 6/3893: {Push-pull type, e.g. snap-in, push-on}
- G02B: OPTICAL ELEMENTS, SYSTEMS OR APPARATUS

## Abstract

Structures and techniques are described for aligning multicore optical fibers in a multicore optical fiber cable having a plurality of optical fiber cores, at least one end portion and a protective coating. The protective coating is removed from the end portion of the multicore fiber cable to create an exposed end portion of the multicore fiber. The exposed end portion of the multicore fiber is inserted into a guide hole defined longitudinally through a ferrule subassembly. The cores of the fiber are aligned rotationally, in a predetermined orientation, relative to the ferrule. Each fiber is biased within its respective guide hole in a predetermined orientation relative to the ferrule. The multicore fiber is bonded within the ferrule. The fiber is trimmed at the ferrule tip and the ferrule and fiber end faces are polished, so that a selected alignment of the multicore fiber is achieved.

## Claims

### Claim 1

A method of aligning multicore optical fibers in a multicore optical fiber cable having a plurality of optical fiber cores, at least one end portion and a protective coating, the method comprising:
stripping an end portion of the multicore fiber cable, to create an exposed, bare end portion of the multicore fiber,
inserting the bare end portion of the multicore fiber into a guide hole defined longitudinally through a ferrule subassembly,
aligning the cores of the fiber rotationally, in a predetermined orientation, relative to the ferrule,
biasing each fiber within the fiber guide hole, in a predetermined orientation relative to the ferrule,
bonding the multicore fiber within the ferrule, and
trimming the fiber at the ferrule tip and polishing the ferrule end face, so that a selected alignment of the multicore fiber is achieved.

### Claim 2 (depends on 1)

The method of claim 1, wherein a selected rotational alignment of the multicore fiber is achieved with respect to a second multicore fiber mounted into a mating optical connector.

### Claim 3 (depends on 1)

The method of claim 1, wherein a selected rotational alignment of the multicore fiber is achieved with respect to an array of optical devices to which the multicore fiber is to be connected.

### Claim 4 (depends on 1)

The method claim 1, wherein the multicore fiber has a circular profile.

### Claim 5 (depends on 1)

The method of claim 1, wherein the multicore fiber has at least one flat side identifying a particular rotational orientation of the plurality of cores.

### Claim 6 (depends on 5)

The method of claim 5, wherein the multicore fiber has a D-shaped profile.

### Claim 7 (depends on 5)

The method of claim 5, wherein the multicore fiber has a double D-shaped profile.

### Claim 8 (depends on 5)

The method of claim 5, wherein the multicore fiber has a polygonal profile.

### Claim 9 (depends on 1)

The method of claim 1, wherein the step of biasing each fiber comprises biasing each fiber using a biasing fixture.

### Claim 10 (depends on 9)

The method of claim 9, wherein the multicore fiber is aligned using a fixture in which a flat side of the fiber is urged against a fiber alignment surface so as to cause the multicore fiber to have a selected rotational alignment.

### Claim 11 (depends on 9)

The method of claim 9, wherein the at least one multicore fiber is biased to one side of its respective guide hole using a fixture in which the fiber is urged to one side of its respective guide hole.

### Claim 12 (depends on 1)

The method of claim 1, wherein the step of bonding the multicore fiber comprises bonding using adhesive or epoxy.

### Claim 13

A curing fixture for biasing a multicore fiber against a selected surface within a ferrule capillary, comprising:
a tubular fixture body having a first end and a second end, with a hole extending therebetween,
wherein the first end is configured to receive a connector into which a multicore fiber is mounted, with a multicore fiber end extending out of the connector tip and through the fixture hole, and
a deflector pin extending across the fixture hole, wherein the deflector pin is configured such that when a connector is seated in the first end of the fixture, with a multicore fiber end extending out of the connector tip and through the fixture hole, contact between the fiber end and the deflector pin causes the fiber end to be biased in a selected direction within the ferrule capillary.

### Claim 14

A method for providing an aligned angled-physical contact (APC) connectorization for an optical cable containing a twisted core multicore optical fiber, the twisted core multicore optical fiber having a plurality of optical fiber cores arrayed substantially in a helical pattern, the method comprising:
stripping an end portion of the multicore optical cable to create an exposed, bare end of the multicore fiber,
inserting the exposed end portion of the multicore fiber into a capillary extending longitudinally through a ferrule subassembly of an optical connector,
bonding the exposed end of the multicore fiber within the ferrule,
trimming the fiber at the ferrule tip,
polishing the trimmed fiber, and
rotating the ferrule subassembly around its longitudinal axis, within the optical connector, until the fiber cores have a selected pre-polish angular offset relative to a selected post-polish rotational alignment, and
polishing the ferrule to a desired endface angle, such that the fiber cores have the selected post-polish rotational alignment.

### Claim 15 (depends on 14)

The method of claim 14, further comprising:
prior to bonding the exposed end of the multicore fiber within the ferrule, biasing the multicore fiber within the capillary, in a predetermined orientation relative to the ferrule, using a fixture.

### Claim 16 (depends on 15)

The method of claim 15, wherein prior to polishing the ferrule to a desired endface angle, a selected core of the twisted core fiber is aligned in a selected pre-polish angular offset, relative to a connector keying feature, based on fiber core twists rate, ferrule end-face angle, and ferrule pedestal diameter.

### Claim 17 (depends on 16)

The method of claim 16,
wherein the selected pre-polish angular offset is θpre-polish,
wherein θpre-polish is defined as:
θpre-polish=0.18 DT tan φ,
wherein D is pedestal diameter and T is twist rate in twists/meter.

### Claim 18 (depends on 16)

The method of claim 16, wherein the selected pre-polish angular offset is between 0.7 and 3.0 degrees for a twisted core fiber having a twist rate of between 47 and 78 twists per meter, terminated with an 8-degree angled connector.

### Claim 19 (depends on 16)

The method of claim 16, wherein performing an angle polish on a connector installed on the twisted core fiber results in a post-polish rotational alignment of a selected core within +/−1.5 degrees of the selected post-polish rotational alignment or of the connector keying feature.