WO2020006462A1

WO2020006462A1 - Piezoelectric fiber optic ferrule

Info

Publication number: WO2020006462A1
Application number: PCT/US2019/039900
Authority: WO
Inventors: Samuel Taylor FINNEGAN
Original assignee: Commscope Technologies Llc
Priority date: 2018-06-29
Filing date: 2019-06-28
Publication date: 2020-01-02

Abstract

A fiber optic connector that includes an optical fiber with an outer surface defined by a first profile. The fiber optic connector also includes a ferrule defined by a tube geometry with an outer surface and an inner surface. The inner surface has a relaxed clearance state and a different compressed clearance state. The ferrule inner surface in the compressed clearance state is wider than the optical fiber outer surface first profile. The ferrule inner surface in the relaxed clearance state is narrower than the optical fiber outer surface first profile.

Description

PIEZOELECTRIC FIBER OPTIC FERRULE

Cross-Reference to Related Application

This application is being filed on June 28, 2019 as a PCT International Patent Application and claims the benefit of U.S. Patent Application Serial No. 62/692,319, filed on June 29, 2018, the disclosure of which is incorporated herein by reference in its entirety.

Background

When assembling fiber optic connectors, optical fibers are fixed in position within a ferrule, for example with adhesive. This method is often inexact, time consuming, and wastes material. There exists a need to improve the process for securing an optical fiber within the ferrule in a fiber optic connector.

Summary

The present disclosure uses piezoelectric ceramic material to make fiber optic connector ferrules that can expand or contract when a high electric voltage is applied to them. This mechanical expansion/contraction allows the ferrule to mechanically secure the optical fiber rather than using adhesive to fix the fiber in location. Of potential benefit, a fiber could be precision cleaved then inserted to the point in a ferrule it normally reaches after a polish step.

In another aspect, the present disclosure relates to a fiber optic connector that includes an optical fiber with an outer surface defined by a first profile. The fiber optic connector also includes a ferrule defined by a tube geometry with an outer surface and an inner surface. The inner surface has a relaxed clearance state and a different compressed clearance state. The ferrule inner surface in the compressed clearance state is wider than the optical fiber outer surface first profile. The ferrule inner surface in the relaxed clearance state is narrower than the optical fiber outer surface first profile.

Brief Description of the Drawings

FIG. 1 A is a schematic diagram of piezoelectric material having a defined polarity, and in a relaxed state under no application of an electric field or voltage. FIG. 1B is a schematic diagram of the piezoelectric material from FIG. 1 A, under application of an electric field with the same polarity.

FIG. 1C is a schematic diagram of the piezoelectric material from FIG. 1A, under application of an electric field with opposite polarity.

FIG. 2 is a schematic diagram of a cylindrical piezoelectric material that has a radial polarity arrangement.

FIG. 3 is a schematic diagram of an example piezoelectric actuator tube.

FIG. 4 is a cross sectional schematic diagram of the piezoelectric actuator tube shown in FIG. 3.

FIG. 5 is a schematic diagram of a piezoelectric actuator tube with segmented electrodes.

FIG. 6 is a schematic diagram of a piezoelectric actuator tube with a circular electrode collar.

FIG. 7 is a schematic diagram of an example fiber optic connector with a ferrule and an optical fiber.

FIG. 8 is a schematic diagram of the ferrule and optical fiber shown in FIG. 7, showing a cross-sectional side view relationship of the insertion of the optical fiber into the ferrule.

FIG. 9 is a schematic diagram of the ferrule shown in FIG. 8 in a relaxed state.

FIG. 10 is a schematic diagram of the ferrule shown in FIG. 9, shown in a compressed state under application of an electrical field.

FIG. 11 is a schematic diagram of the ferrule and optical fiber shown in FIG. 8, showing a cross-sectional end view.

FIGS. 12A - 12C are a series of schematic diagrams of a piezoelectric ferrule drawing a fiber therethrough through a stick-slip effect created by a saw tooth pattern of electric voltage.

FIG. 13 is a diagram of the movement between a ferrule and fiber during the stick- slip effect caused by a saw tooth pattern of electric voltage.

Detailed Description

Exposure to electrical fields can deform piezoelectric material 106 in what can be described as an "inverse piezoelectric effect". FIG. 1A illustrates piezoelectric material 106 having a defined polarity, and in a relaxed state under no application of an electric field or voltage. A strong electric field 100 of several kV/mm can be applied to create a relaxed state asymmetry of polarity in a previously unorganized compound. The electric field 100 reorients the spontaneous polarization. FIG. 1B illustrates that an applied electrical field 102 which has a voltage with the same polarity as the piezoelectric material 106 can cause the material to expand in all directions. FIG. 1C illustrates that an applied electrical field 104 which has a voltage with an opposite polarity as the piezoelectric material 106 can cause the material to contract in all directions. When the applied electrical field is removed, the piezoelectric material 106 returns to the original dimensions of the relaxed state, as shown in FIG. 1 A.

FIG. 2 illustrates an example cylindrical geometry 200 of piezoelectric material.

In this cylindrical geometry 200, the overall polarity 204 is radially aligned toward the centerline 202 of the cylinder, such that an application of electrical field can cause the cylindrical piezoelectric material to expand or contract radially.

Example piezoelectric materials can include polycrystalline ferroelectric ceramics such as barium titanate (BaTiO³) and lead zirconate titanate (PZT). These types of piezo- ceramic components can include a polycrystalline structure with numerous crystallites, each having elementary cells. Example elementary cells of these piezo-ceramic components can exhibit a perovskite crystal structure, generally described with the structural formula A²⁺B⁴⁺Ch²

Piezoelectric components for delivering an electrical field, such as metal electrodes including plates, disks or rings can deliver an electrical voltage into the ceramic material to cause the above described expansion or contraction. An internal electrode metal and the piezoelectric ceramic materials can be vapor deposited in alternating layers. Then, an electro-conductive paint can be applied to tie the layers of internal electrode together. The painted ceramic material can then be lapped to obtain the final dimensions. Effective voltage to perform the above described compression or expansion of the piezoelectric material can be between 75 V and about 150 V, more preferably 100 V. Example effective resonant frequencies delivered by the electrodes can be between 200 kHz and 10 MHz. In some examples, the ceramic material can take the form of tubes, also referred to as piezoelectric actuator tubes. FIGS. 3 and 4 illustrate an example piezoelectric actuator tube 300 that is defined by an outer surface 302, an inner surface 304 and an inner passageway or aperture 306 extending along a length L. The inner passageway 306 can be defined by a radius Rin extending between the center point and the inner surface 304. A radius Rou defines the dimensions of the outer surface 302 from the center point.

The example piezoelectric actuator tube 300 can include an amount of ceramic material 312, an inner electrode 308 positioned proximal to the inner surface 304, and an outer electrode 310 positioned proximal to the outer surface 302. In one example, the inner electrode 308 can cover the inner surface 304, and the outer electrode 310 can cover the outer surface 302. The thickness of the electrodes 308, 310 is negligible and thus does not affect the inner radius Rin or outer radius Rou. Having electrodes 308, 310 positioned proximal to the inner surface 304 and the outer surface 302 allows the electric field or voltage to be applied over the entire ceramic material 312 in the piezoelectric actuator tube 300.

The example piezoelectric actuator tube 300 can have a radial polarity defined by a positive charge +V towards the outer surface 302 and a negative charge -V toward the inner surface 304. However, this polarity can be reversed, as desired or preferred.

Applying an electrical field or voltage, for example through wire leads, through the electrodes 308, 310 can cause the ceramic material 312 to either expand or contract. The inner electrode 308 can receive a positive power voltage and the outer electrode 310 can receive a negative power voltage, and vice versa depending on the polarity of the piezoelectric actuator tube 300 and the desired mechanical action, expansion or contraction. An electric field or voltage that has the same polarity as the piezoelectric actuator tube 300 causes the ceramic material 312 to expand, and thus increases the length L and the radius Rou of the outer surface 302, and/or decreases the radius Rin of the inner surface 304, narrowing the inner passageway 306. Conversely, an electric field or voltage that has an opposite polarity as the piezoelectric actuator tube 300 causes the ceramic material 312 to contract, and thus decreases the length L and the radius Rin of the inner surface 304, narrowing the inner passageway 306, and/or reduces the radius Rou of the outer surface 302.

Other example piezoelectric actuator tubes can be provided with multi-segmented electrodes to influence the expansion and contraction characteristics. As illustrated in FIG. 5, example multi-segmented electrodes 502 extending lengthwise can segment a tube 500 into quarters. In another example illustrated in FIG. 6, the ceramic material can receive and cover wrap-around electrodes, such as a collar 602, so that electrical contacting can be established at a favorable position within the mechanical assembly.

An embodiment of a piezoelectric actuator tube, as described above, can be a ferrule in a fiber-optic connector. FIG. 7 illustrates an example fiber-optic connector 700 with an example ferrule 702. The outer surface of the ferrule 702 can have a circular geometry defined by a diameter. The example ferrule 702 includes an inner passageway for receiving an optical fiber 704. FIG. 8 illustrates the inner passageway 706 extending along the interior of the ferrule 702. The inner passageway 706 can have a circular geometry defined by a diameter. This diameter of the inner passageway 706 is defined between a center point and the inner surface of the ferrule 702. The optical fiber 704 is received along axis X within the inner passageway 706.

The ferrule 702 can be constructed of piezoelectric ceramic material, for example as described above. The ferrule 702 can further have a radial polarity between the outer surface and the inner surface, similarly to the embodiments described above. The ferrule 702 can also include electrodes, as described above, which can cover the outer surface and the inner surface defining the inner passageway 706.

The optical fiber 704 can have an outer diameter that is equal to or greater than the diameter of the inner passageway 706 of the ferrule 702 in the relaxed state. For example, the outer diameter of the optical fiber 704 can be between about 0.121 mm and about 0.129 mm, preferably between about 0.123 mm and about 0.127 mm, and more preferably about 0.125 mm. However, it is possible for the outer diameter of the optical fiber 704 to be greater or smaller depending on the desired use and the diameter of the inner passageway 706 of the ferrule 702.

FIG. 9 illustrates the ferrule 702 in a relaxed state, without being exposed to an electrical field or voltage. At rest, an outer surface 708 of the ferrule 702 has an outer diameter ODi. At rest, an inner surface 710 defines the inner passageway 706 with an inner diameter IDi that is smaller than the outer diameter of the optical fiber 704. For example, the inner diameter IDi of the inner surface 710 in a relaxed state can be between about 0.120 mm and about 0.128 mm, preferably between about 0.122 mm and about 0.126 mm, and more preferably about 0.124 mm.

FIGS. 10 and 11 illustrate the ferrule 702 in a compressed contracted state, being exposed to an electrical field with an opposite polarity to its own, as described above. The ferrule 702 in the compressed state has an outer diameter OD₂ that is smaller than the outer diameter ODi in the relaxed state. The inner surface 710 has an inner diameter ID₂ that defines the inner passageway 706. The inner diameter ID2 under exposure to an electrical field with an opposite polarity is at least equal to or larger than the outer diameter of the optical fiber 704, which is to be inserted through the inner passageway 706. For example, the inner diameter ID2 of the inner surface 710 under exposure to an electrical field with an opposite polarity can be between about 0.122 mm and about 0.130 mm, preferably between about 0.124 mm and about 0.128 mm, and more preferably about 0.126 mm. Preferably, the inner diameter ID2 under exposure to the electrical field with opposite polarity is between about 0.8% and about 1.6%, more preferably about 1.2% greater than the inner diameter IDi in the relaxed state. Preferably, the inner diameter ID2 under exposure to the electrical field with opposite polarity is about 0.8% greater than the outer diameter of the optical fiber 704, which is to be inserted into the inner passageway 706. Preferably, the inner diameter ID2 under exposure to the electrical field with opposite polarity creates a gap or clearance C from contact with the outer surface of the optical fiber 706.

When assembling the fiber optic connector 700, the ferrule 702 is exposed to an electrical field with a polarity that is opposite to the polarity of the ferrule. Electrodes along the outer surface 708 and inner surface 710 of the ferrule 702 cause the piezoelectric ceramic material of the ferrule 702 to contract and widen the diameter of the inner passageway 706 to an inner diameter ID2, as shown in FIG. 10. Since this widened inner diameter ID2 is at least the same as or greater than the outer diameter of a preferred optical fiber 704, the optical fiber 704 is then inserted through the inner passageway 706 to a position sufficient for use. When the optical fiber 704 is in a preferred position within the inner passageway 706, the electrical field is removed from contact with the electrodes, and the piezoelectric ceramic material returns to the relaxed state, as shown in FIG. 9. Since the inner diameter IDi of the inner surface 710 in the relaxed state is less than the outer diameter of the optical fiber 704, the ferrule 702 applies a natural tight gripping force against the optical fiber 704 to ensure that the optical fiber 704 remains in position within the inner passageway 706.

In an additional embodiment illustrated in FIGS. 12A - 12C, a ferrule 802 made of piezoelectric material, similarly to the example described above, can be actuated to pull a length of fiber 800 through the inner passageway to a preferred position using a friction- based stick-slip effect. The stick-slip effect is a cyclical alternation of static and sliding friction between a moving runner and a drive element. In this example, the runner is the fiber 800 and the drive element is the ferrule 802. In this example, the piezoelectric material is linearly polarized in parallel to the longitudinal axis of the ferrule 802. When the electric voltage is applied with the same polarity as the piezoelectric material, the piezoelectric material expands or elongates linearly (FIGS. 12 A, 12C) while maintaining a tight friction or interference fit with the fiber 800. In this action, the ferrule 802 slowly takes along the fiber 800 through the inner passageway. When the electric voltage is removed, the piezoelectric material contracts quickly (FIG. 12B) to the relaxed state, and the fiber 800 cannot follow due to its inertia and remains at its position. Through this mechanical stick-slip movement, the fiber 800 can be pulled through the ferrule 802 against friction, even while retaining a tight tolerance therebetween.

To generate this stick-slip effect, the electric voltage can be applied through a saw tooth sine wave pattern. When such a saw tooth pattern is applied, the stick-slip effect controls the movement of the fiber 800 with respect to the ferrule 802, as illustrated in FIG. 13. The vertical axis represents the position (pm), and the horizontal axis represents the time (s). As can be shown, when the electric voltage is applied (FIGS. 12A, 12C), the ferrule 802 expands slowly and does not significantly alter the relative position with respect to the fiber 800. This movement can be reflected in the less steep portions 804 of the saw tooth pattern. When the electric voltage is removed (FIG. 12B), the ferrule 802 quickly contracts, but the fiber 800 remains in position, having moved with respect to the ferrule. This movement can be reflected in the steeper portions 806 of the saw tooth pattern. As illustrated, this alternating pattern between the less steep 804 and steep 806 portions reflects that the fiber 800 can be pulled through the ferrule 802 by a saw tooth electric voltage pattern.

The above specification, examples and data provide a complete description of the manufacture and use of the composition of the invention. Since many embodiments of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended.

Claims

What is claimed is:

1. A fiber optic connector comprising:

an optical fiber comprising an outer surface defined by a first profile; and a ferrule defined by a tube geometry with an outer surface and an inner surface, the inner surface comprising a relaxed clearance state and a different compressed clearance state, the ferrule inner surface in the compressed clearance state being wider than the optical fiber outer surface first profile, and the ferrule inner surface in the relaxed clearance state being narrower than the optical fiber outer surface first profile.

2. The fiber optic connector of any of the previous claims, wherein there is a gap between the ferrule inner surface in the compressed clearance state and the optical fiber outer surface first profile.

3. The fiber optic connector of any of the previous claims, wherein the ferrule inner surface in the compressed clearance state is between about 0.8% and about 1.6% wider than the optical fiber outer surface first profile.

4. The fiber optic connector of any of the previous claims, wherein the ferrule inner surface in the relaxed clearance state clamps the optical fiber outer surface.

5. The fiber optic connector of any of the previous claims, wherein the ferrule inner surface in the relaxed clearance state is about 0.8% narrower than the optical fiber outer surface first profile.

6. The fiber optic connector of any of the previous claims, wherein the ferrule comprises a radial electric charge polarity between the inner surface and the outer surface.

7. The fiber optic connector of any of the previous claims, wherein the ferrule inner surface is configured to transition to the compressed clearance state under application of an electrical field with an opposite charge polarity to the ferrule radial electric charge polarity.

8. The fiber optic connector of any of the previous claims, wherein the ferrule comprises piezoelectric material.

9. The fiber optic connector of any of the previous claims, wherein the ferrule is a piezoelectric actuator tube made of piezoelectric material.

10. The fiber optic connector of any of the previous claims, wherein the ferrule piezoelectric material comprises titanate.

11. The fiber optic connector of any of the previous claims, wherein the ferrule piezoelectric material comprises zirconate.

12. The fiber optic connector of any of the previous claims, wherein the ferrule comprises a plurality of electrodes configured to apply the electric field to the piezoelectric material.

13. The fiber optic connector of any of the previous claims, wherein the plurality of electrodes cover the ferrule outer surface and the ferrule inner surface.

14. The fiber optic connector of any of the previous claims, wherein the electric field applies a voltage of between about 75 V and about 150 V.

15. The fiber optic connector of any of the previous claims, wherein the piezoelectric material comprises ceramic components with a polycrystalline structure.