Patent Description:
Today's increasing demand for more signal speed and bandwidth has stimulated the transition from copper to fiber as the preferred means for the data transfer. A common perception is that this transition can be solved by simply replacing the copper cables with a fiber system. However, such a conversion faces significant technical challenges. For example, not only must the fiber termini physically fit within the same form factor as the electrical contacts, but, when dealing with fibers, and, in particular, the nine (<NUM>) micron single mode (SM) fiber core, much tighter tolerances are required than those sufficient for copper contact operation. For instances, copper connectors allow the copper contacts to bend during the mating engagement whereas the fiber termini have limited allowance for such deformation. The reason is that copper contacts need to make only physical contact (anywhere over the wipe distance) to operate, while the fiber termini require precise axial alignment of the small fiber cores.

For optical operation in a vibrational and dusty environment, it is often preferred to use a non-contacting lensed expanded beam (EB) terminus rather than a physical contact (PC) fiber connection as an expanded beam provides more reliable performance under harsh conditions. However, the tight alignment requirements mentioned above still apply. For example, the circular MIL-<NUM> connector, which originally was designed for copper contacts and is standardized in MIL-DTL-<NUM>, is a widely used industrial connector. MIL-DTL-<NUM> allows a lateral misalignment of the plug to receptacle cavities of up to <NUM> [. <NUM> inch].

While this is acceptable for electrical contacts, such a misalignment will cause serious mating problems for fiber termini. This can result in termini damage due to stubbing and will usually result in unacceptable loss levels. Typically, the effect of mating fiber termini with lateral misalignment will translate into an angular tilt between the pin and the socket and is one of the largest loss contributors for optical fibers. The effects on single mode (SM) expanded beam (EB) connectors are particularly deleterious.

One approach for accommodating angular offset in SM connectors is disclosed in <CIT>. Referring to <FIG>, the connector <NUM> disclosed in this patent avoids the above-identified problem by disposing the sleeve <NUM> on the ferrule <NUM> forward of the connector housing and front wall <NUM> such that a gap <NUM> is defined between the ferrule <NUM> and the front wall <NUM> at the orifice <NUM> through which the ferrule extends from the connector housing. In one embodiment, the gap is roughly the size of the sleeve which conventionally is disposed around the ferrule in the orifice. The gap is sufficient to allow the ferrule to move within the orifice angularly and laterally with respect to the housing.

Although this connector configuration addresses the misalignment problem identified above, Applicant discovered unexpectedly that, when exposing the design to high levels of vibration or mechanical shock, signal discontinuities may occur. Typically, for optics, industrial standards specify a discontinuity as a signal loss increase of <NUM>. 5dB or more lasting for more than <NUM> micro-second.

<CIT> discloses a ferrule receptacle which can be received in a front face opening of a housing of a connector wherein the housing has a cavity, and a wall with an opening between the front face opening and the cavity. The housing also has a ferrule which extends from the cavity, through the wall opening and into the front face opening. The ferrule has a diameter less than that of the wall opening such that a gap is defined between the ferrule and the housing at the wall opening, and the ferrule receptacle includes elastic elements which surround and engage a portion of the ferrule.

<CIT> discloses an elongated connector in which a pair of fiber-optic cables can be connected. Each fiber-optic cable has a termination body and each cable is inserted into a respective end of the elongated connector so that the termination bodies engage each other inside the connector. Each cable is held by a respective grommet just inside the respective end of the connector.

<CIT> discloses a connector holding a ferrule wherein the ferrule extends through an annular seal held in a sleeve of the connector and beyond a front face of the sleeve.

What is needed is a connector suitable for accommodating angular and lateral misalignments, but also one in which continuity is maintained during vibration or mechanical shock. The present invention fulfills this need among others.

The above-identified problem is avoided by introducing a compliant member in the gap between the ferrule and the front wall at the orifice through which the ferrule extends. The gap functions to allow the ferrule to move within the orifice angularly and laterally with respect to the housing to accommodate misalignment as discussed in <CIT>. Moreover, the compliant member disposed in the gap absorbs vibration between the two components, thereby dampening vibration, and reducing discontinuity.

According to the present invention there is provided a connector as claimed in claim <NUM>.

Referring to <FIG>, one embodiment of a connector <NUM> of the present invention is shown. The connector <NUM> has a front and rear orientation or end and is configured to mate with a mating connector (not shown). The connector comprises a housing <NUM> having one or more cavities <NUM> defined therein, and a front wall <NUM> with one or more orifices <NUM> defined therein. Each of the cavities <NUM> has an axis 102a. Each of the orifices <NUM> corresponds to one of the cavities and has an inner first diameter. The connector <NUM> also comprises an optical contact <NUM> at least partially disposed in one of the cavities <NUM>. The optical contact <NUM> comprises at least a ferrule <NUM> extending from the cavity <NUM> through the orifice <NUM>. The ferrule has an outer second diameter and defines at least one borehole <NUM> for receiving a fiber (not shown). In one embodiment, the ferrule has a constant outer second diameter. The second diameter is less than the first diameter such that a gap <NUM> is defined at the orifice between the ferrule <NUM> and the front wall <NUM>, thereby allowing the ferrule to move within the orifice angularly and laterally with respect to the axis. A compliant member <NUM> is disposed at least partially in the gap and configured to suppress vibration between the housing and the optical contact.

These elements are considered in greater detail below in connection with selected alternative embodiments.

Throughout this description, a MIL-<NUM> connector is illustrated. However, it should be understood that the claims apply to any connector that accommodates a mateable pin and sockets style connection. For some of these connectors, the cavity dimensions and tolerances are defined and restricted by industrial Standards and for use with those connectors it is important that the contacts are designed to function in their respective cavities and orifices.

As described in <CIT>, an important aspect of the connector design is the tolerance between optical contact and the housing to accommodate angular and lateral misalignment of the optical contact with the housing. This tolerance can be provided in different ways. The angular and lateral accommodation of the optical contact and the housing <NUM> is achieved by a gap <NUM> between the outside of the orifice <NUM> as defined in the front wall <NUM>. The functionality of the gap <NUM> and its ability to accommodate misalignment between the contact <NUM> and the housing <NUM> is described in connection with <FIG> of <CIT>, and, accordingly, will not be repeated herein. Additionally, <CIT>, in connection with its <FIG> and 5a & 5b, describes the function of the wide shoulder <NUM> to accommodate lateral/angular offset, and thus will not be repeated herein. As discussed in <CIT>, the gap, either alone or in combination with the wide shoulder, effectively accommodates misalignment between the contact and the housing.

Applicant discovered that disposing a compliant member in the gap dampens vibrations between the contact and the housing yet allows movement between the two components as described above to accommodate misalignment. In other words, by filling the gap with a resilient compliant member, movement is allowed, but vibrations are not transmitted from one component to the other. Applicants has found that this configuration both accommodates misalignment while reducing signal discontinuity caused by vibration.

In one embodiment, the compliant member spans essentially the entire gap, while in a different embodiment, the compliant member spans only a portion of the gap thereby leaving a smaller gap either on its outside between it and the housing, or on its inside between it and the ferrule. The choice of whether to fill the entire gap or not is a function of the desired dampening required, and the compliance of the compliant member. Generally, although not necessarily, a compliant member having greater compliance is required if the entire gap is filled, while a stiffer compliant member may be used if the compliant member only fills a portion of the gap. In one embodiment, the compliant member is annular and has a wall thickness between <NUM> and <NUM> when mounted on a <NUM> diameter ferrule. (The term "mounted" is used because the compliant member could start out with a smaller inner diameter and then be stretched over the ferrule during assembly as mentioned above.

The physical configuration of the compliant member may also vary according to the application. For example, in one embodiment, the compliant member is attached to the contact. For example, referring to <FIG>, the compliant member <NUM> is disposed around the ferrule. In this embodiment, the compliant member is a compliant sleeve having a relaxed diameter which is slightly less than the outer diameter of the ferrule <NUM>, such that, during assembly, the compliant member <NUM> is stretched to slide over the ferrule, and then, when released, squeezes the ferrule to stay in place. Alternatively, the sleeve may be affixed to the ferrule using an adhesive.

An alternative connector <NUM> with an optical contact <NUM>, a housing <NUM> and a front wall <NUM> is shown in <FIG>. The compliant member <NUM> may be a compliant grommet that is inserted into the orifice <NUM> of the front wall <NUM>. In this embodiment, the outer diameter of the grommet may be slightly greater than that of the orifice diameter such that, during assembly, the grommet is compressed to be inserted in the orifice, and then, when released, it urges outward against the wall of orifice in the front wall to stay in place. Alternatively, the grommet may be affixed to the orifice using an adhesive or be held in place by the contact.

Still other embodiments will be obvious to those of skill in the art in light of this disclosure. For example, in yet another embodiment, the compliant member is discrete from both the housing and the contact.

The resiliency of the compliant member may be achieved in different ways. For example, referring to <FIG>, examples of different resilient members 350A, 350B and 350C are shown.

By way of background, stiffness describes the resistance of a material against elastic deformation caused by an external source, such as a force or torque. The more easily the structure moves as a result of an applied force, the lower is the stiffness (and the greater is the compliance). The stiffness again depends on the type of material, its geometry and the direction of the load. The mathematical description of stiffness is defined by the ratio between the stress and the strain also termed Young's modulus of elasticity. Compliance (flexibility) is the inverse of stiffness. Compliant materials have a low elastic modulus. Highly compliant materials are easily stretched or distended.

Stiffness is required for a body to transfer power (energy). There are certain types of power transmissions which are not desired, for example mechanical shock loads. To eliminate shock loads, the system must be dampened. Damping reduces the amplitude of oscillations or prevents oscillations in a system by a mechanism that opposes the changes in it. When an external oscillating force is applied to a material/structure, damping occurs by dissipation of mechanical energy, transformation of mechanical energy into other forms of energy such as heat. Hence, damping represents the capacity for energy absorption.

Thus, we are looking for materials with low stiffness and resiliency. These properties are found in polymers and rubbers.

Unlike metal springs, rubber has high hysteresis and does not release the absorbed compression energy completely on the rebound. The more resilient a rubber material is, the less damping it is. When rubber is deformed, its molecules are uncoiled and straightened. This happens only if its segments are sufficiently flexible.

In <FIG>, a compliant material is used to impart compliance in the compliant member. In this embodiment, the stiffness/modulus of the compliant material can be determined by one of skill in the art without undue experimentation. Suitable materials, include, for example, natural rubber, synthetic rubbers, synthetic fluoropolymers of tetrafluoroethylene (e.g., polytetrafluoroethylene (PTFE)). The elastic modulus will depend on type of material. For example, PTFE is about <NUM> to about <NUM> GPa, while rubber is lower, from about <NUM> to about <NUM>. In one embodiment, the compliant member comprises silicone rubber with a modulus of <NUM> to <NUM> GPa.

In another embodiment, the compliance of the compliant member is achieved either wholly or in part through its mechanical configuration. For example, in <FIG>, the compliant member comprises resilient ribs <NUM>, allowing the compliant member to have mechanically engineered compliance. That is, if greater compliance is desired, rather than altering the material, thinner/longer ribs may be defined on the periphery of the compliant member.

In one embodiment, the compliance of the compliant member is derived essentially entirely from its physical configuration. For example, referring to <FIG>, the compliant member 350C may comprise a non-elastic material, such as, for example, a metal (e.g. beryllium-copper, stainless steel) which is bowed, thereby allowing the compliant member to be flexed inwardly or otherwise allow for deformation to facilitate movement between the contact and the housing, yet dampen vibrations between them. Still other embodiments of the compliant member will be obvious to those of skill in the art in the light of this disclosure.

Claim 1:
A connector (<NUM>) having a front end and a rear end and configured to mate with a mating connector, said connector comprising:
a housing (<NUM>) having one or more cavities (<NUM>) defined therein;
a front wall (<NUM>) having one or more orifices (<NUM>) defined therein, wherein each of said orifices (<NUM>) corresponds to one of said cavities (<NUM>) and has an inner first diameter; and
an optical contact (<NUM>) at least partially disposed in one of said cavities (<NUM>), and comprising at least a ferrule (<NUM>) extending from said cavity (<NUM>), said ferrule (<NUM>) extending through the orifice (<NUM>) corresponding to said cavity (<NUM>), said ferrule (<NUM>) having a second diameter less than said first diameter such that a gap (<NUM>) is defined between said ferrule (<NUM>) and said front wall (<NUM>) at said orifice (<NUM>);
characterized by
a compliant member (<NUM>) disposed at least partially in said gap (<NUM>) and configured to suppress vibration between said housing (<NUM>) and said optical contact (<NUM>).