Patent Description:
Various techniques are known for cleaving or cutting optical fibers and achieving an optical-grade surface. Some techniques require mechanical scoring, followed by a torsional break, followed by a mechanical polish or lapping to rid the surface of hackle, chatter, and cracks brought on by the mechanical scoring. Other techniques, such as laser processing under controlled optical conditions (such as disclosed in <CIT>), are capable of achieving similar optical properties as the mechanical polishing techniques. There are advantages and disadvantages associated with these two techniques and, depending on the specific application, one method may be preferred over the other. Another device and method for cleaving optical fibers is also known from <CIT>. This latter relates to a device and method for cleaving optical fibers which yields cleaved optical fiber ends possessing high damage threshold surfaces. The device can be used to cleave optical fibers with core diameters greater than <NUM> microns.

Since the early <NUM>'s, laser processing of optical fiber has become an industryaccepted standard, though mechanical polishing remains the dominant method of processing optical fiber because of its low entry cost and versatility. Historically, one disadvantage of mechanical polishing optical fiber is that the surface deformations brought on by mechanical scribing need to be completely removed, often requiring lengthy and costly polishing steps. Additional disadvantages are the inability to polish the optical fibers to precise axial dimensions, the inability to align the stress members with polarization maintaining fibers relative to prescribed angles, and the increased tooling costs associated with achieving nonstandard surface angles (i.e., <NUM>° or <NUM>°).

Most recently, however, with the influx of high-power transmission needed for <NUM>, autonomous vehicle sensors, and military weapons, the silica deposits embedded in microabrasions found on the surface of optical fiber from conventional polishing techniques are found to be highly absorptive and disruptive to the optical transmissions, creating undesirable back reflections and beam scatter. When these detriments are present, ultimately device failure occurs (optical fiber or active devices). For this reason, laser processing of conventional optical fibers used in these applications is gaining significant momentum, however, there are still disadvantages of such laser processing of large diameter glass bodies.

Today's laser processing methods are well-suited for conventional optical fibers, specifically, optical fibers that are comprised of cores and claddings with total combined diameters of <NUM> or less. However, laser processing optical fibers or other glass bodies with combined core/clad diameters greater than <NUM> becomes problematic due to energy differentials of the entrance beam relative to the exit beam. Such entry/exit effects create undulating surfaces that impair optical transmission, creating uncontrollable back reflections and introducing beam skew and non-Gaussian energy distributions of the transmitted beam. The surface undulations are further exacerbated during angled cleaving of optical fibers, which heighten the entry/exit effects because of the increased cutting lengths along the hypotenuse.

The subject invention provides a cleaving assembly for cleaving a glass body having a face at a desired angle greater than <NUM> degrees and with reduced light-scattering or absorbing detriments. The assembly comprises a laser device for emitting a laser beam, a rotating device, and a positioning fixture. The rotating device has a head that rotates about a central axis that is orthogonal to the laser beam. The positioning fixture is operatively mounted to the head and centered axially along the central axis and is also rotatably driven by the rotating device. The positioning fixture has a tapered surface that is transverse to the central axis and that supports the glass body at a predetermined angle relative to the central axis. Rotation of the positioning fixture about the central axis when the glass body is exposed to the laser beam, cleaves the face of the glass body at the desired angle due to the glass body being supported transverse to the central axis.

The subject invention further provides a method of cleaving a glass body with a cleaving assembly. The cleaving assembly includes a laser device for emitting a laser beam, a rotating device, and a positioning fixture. The method includes the steps of positioning the rotating device and the positioning fixture centrally aligned along a central axis that is orthogonal to the laser beam and mounting the positioning fixture to a head of the rotating device, while supporting the glass body along a tapered surface of the positioning fixture. The tapered surface extends transverse to the central axis at a predetermined angle. Next, the positioning fixture and the head of the rotating device is rotated about the central axis while the glass body is supported at the predetermined angle such that the laser beam cleaves the face of the glass body at a desired angle corresponding to the predetermined angle.

The subject invention has numerous advantages over the prior art assemblies and methods. First ,the subject invention provides a face that is substantially free of surface undulations and detriments allowing the glass bodies to be processed free of the light-scattering or absorbing detriments of mechanical polishing. As a result, when cleaving according to the subject invention, the face of the glass body does not demonstrate undesirable entry/exit effects. Another advantage of the subject invention is that multiple different positioning fixtures of different predetermine angles can be quickly interchanged on the rotating device while maintaining precision of the laser cleaving and at the precise desired angle.

The present invention relates generally to an assembly <NUM> and method of cleaving a glass body <NUM> with a laser beam <NUM> to a desired angle. The glass bodies <NUM>, include, but are not limited to, glass rods, capillaries, ferrules, tubes, and optical fibers. Generally, the glass body <NUM> is cylindrical and are particularly useful in beveled surface applications and optical applications (high-power and other applications sensitive to back reflections, light scatter, beam skew and optical transmission). The assembly <NUM> can be used for angles greater than <NUM> degrees and will create the angle on a face <NUM> of the glass body <NUM> free of a lens or taper.

Referring to <FIG>, a perspective view of one embodiment of the cleaving assembly <NUM> for cleaving the glass body <NUM> is shown generally having a laser device <NUM> and a rotating device <NUM>. The glass body <NUM> may include a glass rod, a glass capillary, or an optical fiber. The glass body <NUM> has a diameter of at least <NUM> and would be considered by those of skill in the art as a large diameter when compared against a conventional, telecomgrade optical fiber. The glass body <NUM> extends along a longitudinal central axis C between a first end <NUM> and a second end <NUM>. The first end <NUM> of the glass body <NUM> presents the face <NUM> to be cleaved or finished. The glass body <NUM> may be any desired length depending upon the particular application. The glass body <NUM> may be hollow or solid. Referring to one embodiment of the glass body <NUM> as a glass rod, preferably the glass rod would be solid. In another embodiment, when the glass body <NUM> is a glass capillary, the glass capillary may be hollow. In yet another embodiment when the glass body <NUM> is an optical fiber, the optical fiber comprises at least one core, which is formed of a glass material. Optionally, the optical fiber may include a cladding (not shown) surrounding the core and an outer coating (not shown) surrounding the core. Further, the optical fiber may include a plurality of cores. The subject invention may be practiced with any of the various different types of glass bodies described herein, but is particularly useful with solid glass rods of large diameters above <NUM>.

The laser device <NUM> emits the laser beam <NUM>, preferably a carbon dioxide laser beam <NUM> with the wavelength of <NUM>. It is to be appreciated that other types of laser devices <NUM> having different types of beam shapes and different wavelengths may be used with the subject invention. For example, the laser device <NUM> may be quantum cascade laser, UV-excimer laser, semiconductor laser, or the like, and which may emit the laser beam <NUM> with a wavelength between <NUM> and <NUM>. The laser device <NUM> may include focusing systems <NUM> to direct and manipulate the laser beam <NUM> to the first end <NUM> of the glass body <NUM>.

Referring to <FIG>, the rotating device <NUM> includes a head <NUM> that rotates about the central axis C that is orthogonal to the laser beam <NUM> emitted by the laser device <NUM>. A positioning fixture <NUM> is operatively mounted to the head <NUM> and centered axially along the central axis C. The positioning fixture <NUM> is rotatably driven by the rotating device <NUM> about the central axis C. The positioning fixture <NUM> has a tapered surface <NUM> (best shown in <FIG>) that is transverse to the central axis C and that supports the glass body <NUM> at a predetermined angle θ relative to the central axis C. Rotation of the positioning fixture <NUM> about the central axis C while laser beam <NUM> is directed toward the glass body <NUM> cleaves the face <NUM> of the glass body <NUM> at the desired angle due to the glass body <NUM> being supported transverse to the central axis C.

With reference to <FIG>, the positioning fixture <NUM> has an outer surface <NUM>, a front face <NUM>, and a rear face <NUM>. The rear face <NUM> defines a mount <NUM> for operatively mounting to the head <NUM>. Referring to <FIG> and <FIG>, the mount <NUM> is further shown as being threaded. As one example, the mount <NUM> may a M6 or <NUM>-<NUM> thread.

Referring back to <FIG> and <FIG>, an extender <NUM> is operatively mounted between the positioning fixture <NUM> and the head <NUM>. The extender <NUM> secures the positioning fixture <NUM> operatively to the rotating device <NUM>. Additionally, the extender <NUM> may also serve as a secondary support for the glass body <NUM> for applications requiring the rotation of a large body around the center axis C, as discussed further discussed below. The extender <NUM> may also be threaded at one or both of the ends as either male or female connections. It is to be appreciated that the extender <NUM> may be used with certain types of glass bodies <NUM> and not used with other types of glass bodies <NUM>.

The subject invention may also include an adapter <NUM> operatively mounted between the extender <NUM> and the head <NUM>. The adapter <NUM> may also be threaded at one or both of the ends for mounting between the extender <NUM> and the head <NUM>. It is to be appreciated that the adapter <NUM> may be used with certain types of glass bodies <NUM> and not used with other types of glass bodies <NUM>. Further, in some embodiments, either the extender <NUM> or the adapter <NUM> may be omitted without deviating from the subject invention.

Referring to the glass body <NUM> shown in the Figures, the glass body <NUM> extends between the first end <NUM> and the second end <NUM>. The tapered surface <NUM> of the positioning fixture <NUM> supports the glass body <NUM> such that the first end <NUM> and the second end <NUM> may lie transverse to the central axis C of the rotating device <NUM>, and if present, the extender <NUM> and the adapter <NUM>. In the embodiment shown in <FIG> and <FIG>, the positioning apparatus, the extender <NUM>, and the adapter <NUM> are connected together and are centered axially along the central axis C.

<FIG> shows the central axis C along the extender <NUM>, the adapter <NUM>, and the positioning fixture <NUM>. The glass body <NUM> is presented at a predetermined angle drawn along axis L. The predetermined angle between C and L, defined as θ, is controllable per the tapered surface <NUM>.

Specifically, referring to <FIG>, a close-up perspective view of the cleaving apparatus is shown. In this embodiment, the positioning fixture <NUM> has the extender <NUM> integrated therein and the positioning fixture <NUM> rotates about the central axis C. The laser beam <NUM> cleaves the glass body <NUM> at its first end <NUM> point, resulting in a lost shard S that is then disposed. The face <NUM> of the glass body <NUM> is then transformed into an angled geometry that matches the desired angle.

<FIG> shows the positioning fixture <NUM> having an inner bore <NUM> extending between the front face <NUM> and the rear face <NUM> with the inner bore <NUM> centered axially along the central axis C. In various embodiments, the positioning fixture <NUM> may have a conical shape. The tapered surface <NUM> is defined as a channel <NUM> in the outer surface <NUM> that extends between the front face <NUM> and the rear face <NUM>. The tapered surface <NUM> has the predetermined angle of from greater than <NUM> degrees to <NUM> degrees. In this embodiment, the central axis C is the same as the axial center L of the glass body <NUM>. As such, the glass body <NUM> is rotating around both C and L, resulting in a flat, <NUM>° surface <NUM> geometry. Such a configuration allows the positioning fixture <NUM> to produce two different types of surface geometry on the face <NUM>, i.e. the face <NUM> having the desired angle and a flat geometry. One advantage of the subject invention is that various positioning fixtures <NUM> can be made having different predetermined angles. Thus, when a different angle is needed on a different glass body <NUM>, the positioning fixture <NUM> is selected with the appropriate tapered surface <NUM>. This allows for quick changes of the positioning fixture <NUM> while maintaining precise cleaving of the glass body <NUM>.

<FIG> is a perspective view of the positioning fixture <NUM> shown in <FIG> is a cross-sectional view and <FIG> is an end view of the positioning fixture <NUM> shown in <FIG>. The positioning fixture <NUM> has the channel <NUM> that runs down the outer surface <NUM> to define the tapered surface <NUM> at the predetermined angle θ. The channel <NUM> ensures that compound angles are eliminated during the cleaving operation. The predetermine angle controls the cleave during the rotation and cleaving operation.

<FIG> is a close-up schematic of the glass body <NUM> formed according to the invention using the positioning fixture <NUM> and having been exposed to the laser beam <NUM> while being rotated. The face <NUM> of the glass body <NUM> has the desired angle of <NUM> degrees.

Referring now to <FIG>, another embodiment of a positioning fixture <NUM>' is shown. The positioning fixture <NUM>' includes the front face <NUM>, the rear face <NUM>, the outer surface <NUM>, and the inner bore <NUM>, but with regard to this embodiment, the positioning fixture <NUM>' defines the tapered surface <NUM> within the inner bore <NUM>. An insert <NUM>, sized to be disposed within the inner bore <NUM>, is inserted into the inner bore <NUM>. The tapered surface <NUM> is defined between the insert <NUM> and the inner bore <NUM> and the glass body <NUM> is secured at the predetermined angle therebetween. Specifically, the insert <NUM> has an outer surface <NUM> that is inclined at the predetermined angle to define the tapered surface <NUM>. The outer surface <NUM> may also include a channel <NUM>'. In such an embodiment, multiple different inserts <NUM> can be used that have different predetermined angles, such as <NUM> degrees, <NUM> degrees, and so forth. Alternatively, the inner bore <NUM> has an inclined surface <NUM> at the predetermined angle to define the tapered surface <NUM>. The inclined surface <NUM> may also include the channel <NUM>'. In a similar fashion, different positioning fixtures <NUM> can be prepared having the inner bore <NUM> with different predetermined angles that can be easily changed while maintaining the precision of the cleave. The tapered surface <NUM> can define the predetermined angle of from greater than <NUM> degrees, or at least <NUM> degrees, to <NUM> degrees.

<FIG> is a cross-sectional view of the positioning fixture <NUM>' shown in <FIG> is an end view of the positioning fixture <NUM>' shown in <FIG>. In this embodiment, the glass body <NUM> is located within the inner bore <NUM> and is secured in place by the insert <NUM>. The glass body <NUM> is easily inserted and removed and requires no channeling as the glass body <NUM> is secured by the wedging dynamic of the tapered insert <NUM>. The insert <NUM> may be disposed within the fixture and mates with at least a portion of the inner bore <NUM> to secure the glass body <NUM>. In one embodiment, the inner bore <NUM> may include the channel <NUM>' to receive the glass body <NUM>. The insert <NUM> holds the glass body <NUM> in the channel <NUM>'. Alternatively, the channel <NUM> may be formed in the insert <NUM>. In yet another embodiment, the glass body <NUM> could be held in position by bonding or the like so that it could be removed after being cleaved. <FIG> shows the diameter and thicknesses of the positioning fixture <NUM>', the inner bore <NUM> and the insert <NUM>.

<FIG> illustrate the positioning fixture <NUM>' at two positions as it rotates about the central axis C. In <FIG>, one position of the glass body <NUM> is shown at - <NUM> degrees and, in <FIG>, another position of the glass body <NUM> is shown at +<NUM> degrees. <FIG> shows the glass rod at <NUM> degree intervals as the positioning fixture <NUM>' rotates with two of the positions shown in phantom. In this embodiment, the taper angle is <NUM> degrees.

<FIG> is a close-up of the glass body <NUM> in the -<NUM> degree and +<NUM> degree positions within the rotation of the positioning fixture <NUM>'. The ends <NUM>, <NUM>, of the glass body <NUM> are exact mirrors of one another during the rotation, allowing the laser beam <NUM> to cleave to the desired angle, φ. The predetermined angle θ corresponds to the desired angle φ.

<FIG> shows the versatility of glass rods that can be achieved with the cleaving assembly <NUM> of the subject invention that utilizes positioning fixtures <NUM>, <NUM>' with different predetermine angles such that an endless array of glass body <NUM> cleave angles can be obtained. <FIG> shows the glass body <NUM> having the first end <NUM> with the desired angles range from <NUM> degrees to any angle desirable. The angles illustrated in <FIG> are relative to the axial center L of the glass body <NUM>. The axial center L has the predetermined angle defined by the tapered surface <NUM>. The <NUM> degree angle would be denoted by those familiar with the art as a <NUM> degree cleave. The <NUM>, <NUM>, and <NUM> degree examples would represent a <NUM>, <NUM>, and <NUM> degree cleave by those familiar with the art.

With reference to <FIG>, one embodiment of the cleaving assembly <NUM> according to the subject invention is shown. Specifically, <FIG> shows a DC power supply <NUM> connected to and powering the rotating device <NUM>, as is well known to those skilled in the art. <FIG> shows the optical path of the laser head <NUM> and <FIG> shows a camera <NUM> and the laser device <NUM> and other optics.

With reference to <FIG>, close-up photographs of a <NUM> glass rod are shown that were effectively cleaved using the cleaving assembly <NUM> shown in <FIG> Specifically, in <FIG>, the tip of the glass rod has been cleaved to an angle of <NUM> degrees, with a targeted value of <NUM> degrees. In <FIG>, the tip of the glass rod has been cleaved to an angle of <NUM> degrees, with a targeted value of <NUM> degrees.

For illustrative purposes and to show the significance of the invention, rotating a glass body <NUM> during a laser cleaving process without the embodiment of this invention will create a conical or tapered surface <NUM> as shown in the photographs as <FIG>. These approaches generally are not able to create a flat angle greater than <NUM> degrees without these type of detriments and irregularities. While rotating a glass body <NUM> around its axial center L during laser processing of large diameter fibers can reduce the entry/exit effects and create surfaces suitable for optical-grade transmission, this method is only viable for flat (<NUM>°) cleaves. <FIG> show glass bodies <NUM> that were merely rotated its axial center L that was orthogonal to the laser beam <NUM> and an unacceptable conical or tapered surface geometry was obtained.

Claim 1:
A cleaving assembly (<NUM>) for cleaving a glass body (<NUM>) having a face (<NUM>) at a desired angle greater than <NUM> degrees and with reduced light-scattering or absorbing detriments, said assembly comprising
a laser device (<NUM>) for emitting a laser beam (<NUM>);
a rotating device (<NUM>) comprising a head (<NUM>) that rotates about a central axis (C) that is orthogonal to said laser beam (<NUM>);
a positioning fixture (<NUM>) operatively mounted to said head (<NUM>) and centered axially along said central axis (C), said positioning fixture (<NUM>) rotatably driven by said rotating device (<NUM>); and
wherein said positioning fixture (<NUM>) has a tapered surface (<NUM>) that is transverse to said central axis (C) and that supports the glass body (<NUM>) at a predetermined angle relative to said central axis (C), and wherein rotation of said positioning fixture (<NUM>) about said central axis (C) cleaves the face (<NUM>) of the glass body (<NUM>) at the desired angle due to the glass body (<NUM>) being supported transverse to said central axis (C).