Zero clearance receptacle design for single mode optical fiber connectors

A zero-clearance receptacle for single mode optical fiber couplers. The zero-clearance receptacle includes an internally fluted V-groove formed by internally extending legs. The zero-clearance receptacle uses the fundamental action of the V-groove to accurately locate an optical fiber ferrule inserted into the zero-clearance receptacle in the radial direction. The zero-clearance receptacle further includes a slot that receives a biasing element, such as a spring, that biases the optical ferrule against the V-groove legs. This enables accurate positioning of an optical fiber in the optical ferrule relation to an optical element such as a VCSEL or a photoreceptor. The zero-clearance receptacle beneficially fits into an optical coupler, which may have a lens.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to optical connectors.

2. Discussion of the Related Art

Coupling optical elements, such as Vertical Cavity Surface Emitting Lasers (VCSELs), with optical fibers is a relatively difficult, time consuming, and expensive task. One reason for this is that optical coupling requires precise physical alignment between the optical fiber and the optical element. Complicating the problem is that the physical alignment must remain accurate over both time and temperature. For example, when coupling an optical element to a single mode optical fiber a physical alignment that is accurate within a micron or so radially, and between 10 and 15 microns axially, over the full temperature range and over the life of the product can be required.

Optical connectors are used to couple optical fibers to optical elements. A primary task of an optical connector is to couple optical signals between elements with minimal signal loss. As previously noted, an optical connector must provide for precise physical alignment in the axial and radial directions. Various physical alignment techniques have been tried with varying degrees of success. Prior art approaches include molded lens coupling, butt coupling, and butt coupling with V-groove alignment. While generally successful, such prior art methods are, as stated, relatively difficult and expensive to implement.

Compounding physical alignment problems is the need for plug-in connectors that can be made and unmade numerous times, all while meeting the required alignment precision. In practice, to minimize signal losses stemming from imprecise radial alignment, most plug-in type optical connectors relay light from a first optical element, such as a VCSEL light source, into a single mode fiber (SMF) stub. That SMF stub is terminated, polished, and inserted into a split sleeve. The SMF stub is usually comprised of a ceramic material having a coefficient of thermal expansion that closely matches the coefficient of thermal expansion of the optical fiber. The SMF stub is often captured by a split sleeve assembly within an optical connector such that the plugged-in optical fiber is accurately positioned relative to the end of an optical fiber that is fixed within the SMF stub within the optical connector. Conventionally, any radial movement during plug-in is taken up by the flexibility of the split sleeve. In practice, the split sleeve is optically coupled to the optical element via a conventional butt or lens-coupling technique.

While the SMF stub is amenable to batch ferrule assembly and polishing, it is a small and relatively delicate part that can be difficult to handle in automated machinery. Thus, the SMF stub approach does not provide an economical solution to precision optical alignment of an optical element with an optical fiber.

Therefore, a new optical coupler would be beneficial. Even more beneficial would be a new optical coupler that enables accurate alignment of optical elements. Still more beneficial would be a new optical coupler having an optical receptacle that enables plug-in connections that accurately align an optical element relative to an optical fiber. Beneficially, such a plug-in optical coupler would include an optical receptacle that provides zero clearance tolerance for the radial alignment of an optical element relative to an optical fiber over time and temperature. Preferably, such an optical coupler would be low-cost and useable by relatively untrained assembly workers.

SUMMARY OF THE INVENTION

Accordingly, the principles of the present invention provide for zero-clearance optical receptacles that enable plugable optical couplers that provide highly accurate coupling of single mode optical fibers with optical elements, plug-in after plug-in, and that substantially obviate one or more of the problems due to limitations and disadvantages of the related art. Such a zero-clearance optical receptacle is beneficially spring loaded to enable consistent, accurate alignment. Furthermore, the zero-clearance optical receptacle beneficially is part of an optical coupler that couples an optical element (such as a VCSEL or a photo-sensor) to a single mode optical fiber that is retained by an optical ferrule.

A zero-clearance optical receptacle according to the principles of the present invention includes an internally fluted V-groove. Such zero-clearance optical receptacles are beneficially dimensioned to receive an optical fiber ferrule on two surfaces that define the V-groove. The V-groove positions the center of the optical fiber ferrule at a defined, rigidly fixed, consistent position, plug-in after plug-in. Beneficially, the zero-clearance optical receptacle further includes a slot that receives a biasing element, such as a spring, that biases the optical fiber ferrule toward the V-groove. Suitable biasing elements include a leaf spring and a roll-pin tubular spring. Also beneficially, the zero-clearance optical receptacle includes a front end that accurately positions the optical fiber ferrule in the zero-clearance receptacle. Beneficially, the zero-clearance optical receptacle is fabricated from the same material (typically a ceramic such as Zirconia) that the optical fiber ferrule is comprised of.

An optical coupler according to the principles of the present invention includes a body having a channel that receives a zero-clearance optical receptacle. Beneficially, the zero-clearance optical receptacle itself is dimensioned to receive an optical fiber ferrule on an internally fluted V-groove formed by two surfaces. The zero-clearance optical receptacle beneficially includes a biasing feature for biasing the optical fiber ferrule toward the V-groove. The optical coupler body further includes an opening for enabling light to pass between an optical element (such as a VCSEL or a photo-receptor) and a single mode optical fiber retained in the optical fiber ferrule. Beneficially, the optical coupler further includes a lens for focusing light to or from the optical element to the single mode optical fiber. The optical coupler can also include a housing for retaining an optical element.

A zero-clearance optical receptacle according to the principles of the present invention can be implemented by extruding a tube through a die so that an inner channel is formed with two surfaces that define a V-groove. Additionally, a slot is beneficially formed for a biasing element. Preferably, the zero-clearance optical receptacle is dimensioned to receive a 1.25 or a 2.5 mm nominal diameter Zirconia optical fiber ferrule. Preferably, the zero-clearance optical receptacle is fabricated from the same material (typically a ceramic such as Zirconia) that the optical fiber ferrule is comprised of. This is important since the V groove design is inherently rotational asymmetric, thus without close temperature coefficient of thermal expansion matching radial drift of a retained optical fiber could result.

Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from that description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Reference will now be made in detail to various embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

FIG. 1illustrates an optical coupler200that is in accord with the principles of the present invention. That optical coupler includes a body209that has a central channel208. The central channel208is dimensioned to receive a zero-clearance optical receptacle300, which is described in more detail subsequently. In turn, the zero-clearance optical receptacle300receives an optical fiber ferrule203that retains an optical fiber205.

Still referring toFIG. 1, the optical coupler200includes an opening211that is axially aligned with the central channel208. One end of the opening211is dimensioned to receive a lens215. The optical coupler200further includes a base213that receives an optical element217having electrical leads219. The optical element217can be a light emitter, such as a VCSEL, or an optical sensor, such as a photo-diode. The base213attaches to the body209such that the relative positions of the optical element217and the lens215are fixed. To that end, the elements that affect alignment have similar, beneficially identical, coefficients of thermal expansion.

Still referring toFIG. 1, in operation, the optical fiber205is rigidly connected to the optical fiber ferrule203, beneficially using a suitable epoxy or other type of adhesive. The optical fiber ferrule203is then inserted into the zero-clearance optical receptacle300. The positions of the zero-clearance optical receptacle300and/or the base213are then adjusted such that the focal point of the lens211is properly positioned relative to the optical fiber205. Thus, the lens215couples light to or from the optical element217with the optical fiber205. Once the position of the zero-clearance optical receptacle300and/or the base213are fixed in the central channel208(such as by epoxy bonding or laser weld joining), the optical fiber ferrule203can be repeatedly removed from and plugged into the zero-clearance optical receptacle300.

FIG. 2illustrates one embodiment of the zero-clearance optical receptacle300. As shown, the zero-clearance optical receptacle300includes a cylindrically shaped body301having a central, generally cylindrically shaped inner opening323. The inner opening323defines a first inwardly protruding leg327having a first top surface, a second inwardly protruding leg329having a second top surface, and a slot325. The slot325and the legs327and329beneficially extend along the full length of the inner opening323. In operation, the legs327and329form a V-groove that contacts the optical fiber ferrule203when the optical fiber ferrule203is inserted into the zero-clearance receptacle300.

By V-groove what is meant is not a V-shape, rather what is referred to is the physical action of a V, top surfaces with a relieved section between the top surfaces. Thus, the top surfaces contact the inserted element, while the relieved middle section enables the inserted element to rest on the top surfaces. Thus the V is defined by the top surface contact points and by either the bottom of the relieved mid section or by the bottom of the inserted element. The slot325enables the insertion of a slotted wedge or a thin, spring element such as a round spring rod. Such elements bias the optical fiber ferrule203toward the legs327and329.

The zero-clearance optical receptacle300uses the fundamental mechanical action of a V groove to consistently align the end of the optical fiber205held within the optical ferrule203with the optical element217, plug-in after plug-in. The key or spring (such as a thin, round spring rod) inserted into the slot325biases the optical fiber ferrule203into position to avoid or eliminate positional errors.

While the foregoing zero-clearance optical receptacle300is highly advantageous, another zero-clearance optical receptacle suitable for use in the optical coupler200is the zero-clearance optical receptacle401illustrated inFIGS. 3 and 4. It should be understood that the zero-clearance optical receptacle401could be used in place of the zero-clearance optical receptacle300shown in FIG.1.

As shown inFIGS. 3 and 4, the zero-clearance optical receptacle401includes a generally cylindrically shaped body407that includes a central, generally cylindrically shaped inner opening411. The inner opening411defines a first inwardly protruding leg408having a first surface, a second inwardly protruding leg409having a second surface, and an inner slot412.

Still referring toFIGS. 3 and 4, the body407includes two openings425that pass through body and the slot412. The body407also includes two flat surfaces427that are adjacent the openings425and that are depressed below the outermost surface of the body407. The zero-clearance optical receptacle401further includes a spring403that fits into the slot412, that passes on each end through an opening425, and that rests on the flat surfaces427. The spring403is dimensioned such that at least part of the spring403extends out of the slot412toward the center of the inner opening411when an optical fiber ferrule203is not inserted into the inner opening411. However, the spring403is further dimensioned such that the optical fiber ferrule203can be inserted into the inner opening411. The spring403biases the optical fiber ferrule203against the legs408and409.

The particular implementations shown in the Figures may be adapted to many different connector designs to enable economical and flexible optical connectors and a wide range of assembly/joining techniques, specifically including laser welding.

Optical receptacles according to the principles of the present invention are beneficially comprised of the same material (preferably the ceramic material Zirconia) that the optical fiber ferrule is comprised of. This will provide highly accurate matching of the coefficients of thermal expansion of the materials that significantly impact on alignment of the optical fiber205with the optical element217. Thus, a zero-clearance optical receptacle is fabricated to form a channel with two surfaces that define a V-groove and with a slot. Preferably, the zero-clearance optical receptacle is dimensioned to receive either a 1.25 or a 2.5 mm nominal diameter Zirconia optical fiber ferrule.

The embodiments and examples set forth herein are presented to explain the present invention and its practical application and to thereby enable those skilled in the art to make and utilize the invention. Those skilled in the art, however, will recognize that the foregoing description and examples have been presented for the purpose of illustration and example only. Other variations and modifications of the present invention will be apparent to those of skill in the art, and it is the intent of the appended claims that such variations and modifications be covered. The description as set forth is not intended to be exhaustive or to limit the scope of the invention. Many modifications and variations are possible in light of the above teaching without departing from the spirit and scope of the following claims. It is contemplated that the use of the present invention can involve components having different characteristics. It is intended that the scope of the present invention be defined by the claims appended hereto, giving full cognizance to equivalents in all respects.