The disclosure is directed to optical connectors and, more particularly, to optical components and optical connectors having optical fiber stubs or optical fiber pigtails bonded to a lens substrate.
Optical fiber is increasingly being used for a variety of applications, including but not limited to broadband voice, video, and data transmission. As bandwidth demands increase optical fiber is migrating deeper into communication networks such as in fiber to the premises applications such as FTTx, 5G, and the like. As optical fiber extends deeper into communication networks there exists a need for building more complex and flexible fiber optic networks in a quick and easy manner.
Optical connectors are used to connect optical cables and optical components. For single and multi-fiber connectors, physical contact connectors like LC, MPO/MTP are widely used for different applications (telecom, datacom). Particularly for single-mode with fiber core diameter of approximately 10 microns, the cleanliness of the optical path is very important to achieve low loss (e.g., <0.35 dB insertion loss). Physical contact is achieved by applying mechanical force (e.g., 10N-20N) to overcome the dimensional variations to achieve low return loss of <−55 dB. With increasing number of fibers for high-density connectors with more than 24 fibers providing 24 optical channels, the mechanical force has to be increased to 20N or above to achieve physical contact. For very low loss, very precise fiber ferrules are required, which need to be assembled to the cable. This multi-step assembly process that includes adhesive bonding and fiber end-face polishing is mostly done manually because it is difficult to automate. For some application, like trunk cables, many of the same connectors need to be attached to the same cable. Then, the cable has to be moved from one assembly step to the next.
Lensed connectors for single-mode are a potential alternative to relax required mating force and cleanliness requirements. Current lensed connectors use a polymer injection molded ferrule, which makes them less reliable for high-power applications like external laser modules for co-packaged optics. Additionally, fiber orientation for polarization maintaining fibers is difficult to achieve.
Thus, alternative optical connectors having a large number of optical channels may be desired.
In one embodiment, an optical component includes a substrate having a lens surface, a fiber coupling surface, and an array of lenses at the lens surface. The optical component further includes an array of optical fibers bonded to the fiber coupling surface such that the array of optical fibers is aligned with the array of lenses in a plane defined by the fiber coupling surface, and an optical beam has an expanded beam diameter that is less than 100 μm at a surface of each lens of the array of lenses.
In another embodiment, an optical connector includes at least one optical component and ferrule. The at least one optical component a substrate includes a lens surface, a fiber coupling surface, an array of lenses at the lens surface, and an array of optical fibers bonded to the fiber coupling surface such that the array of optical fibers is aligned with the array of lenses in a plane defined by the fiber coupling surface, and an optical beam has an expanded beam diameter that is less than 100 μm at a surface of each lens of the array of lenses. The ferrule includes a front face having an opening, a substrate slot, and a fiber channel. The substrate is disposed within the substrate slot such that the lens surface is exposed by the opening. The array of optical fibers is disposed within the fiber channel.
In yet another embodiment, a method a fabricating an optical component includes placing an end of at least one optical fiber proximate a fiber coupling surface of a substrate. The substrate further includes a lens surface opposite from the fiber coupling surface, wherein the lens surface has at least one lens. The method also includes propagating an optical signal through the at least one optical fiber and into the substrate, and actively aligning the substrate with respect to the at least one optical fiber to an alignment position by detecting an optical power of the optical signal passed through the at least one lens. The alignment position is indicated by a position providing a maximum detected optical power of the optical signal. The method also includes bonding the at least one optical fiber to the fiber coupling surface at the alignment position.
In yet another embodiment, a method of fabricating an optical connector includes fabricating at least one optical component by placing an end of at least one optical fiber proximate a fiber coupling surface of a substrate. The substrate further includes a lens surface opposite from the fiber coupling surface, wherein the lens surface has at least one lens. Fabricating the at least one optical component further includes propagating an optical signal through the optical fiber and into the substrate, and actively aligning the substrate with respect to the at least one optical fiber to an alignment position by detecting the optical beam of the optical signal passed through the at least one lens. The alignment position is indicated by a position provided by detector feedback of the optical signal. Fabricating the at least one optical component also includes bonding the at least one optical fiber to the fiber coupling surface at the alignment position. The method further includes positioning the substrate within a substrate slot of a ferrule and the at least one optical fiber within a fiber channel of the ferrule.
Additional features and advantages will be set forth in the detailed description which follows, and in part will be readily apparent to those skilled in the art from that description or recognized by practicing the same as described herein, including the detailed description that follows, the claims, as well as the appended drawings.
It is to be understood that both the foregoing general description and the following detailed description present embodiments that are intended to provide an overview or framework for understanding the nature and character of the claims. The accompanying drawings are included to provide a further understanding of the disclosure and are incorporated into and constitute a part of this specification. The drawings illustrate various embodiments and together with the description serve to explain the principles and operation.
References will now be made in detail to the embodiments of the disclosure, examples of which are illustrated in the accompanying drawings. Whenever possible, like reference numbers will be used to refer to like components or parts.
The concepts disclosed are related to optical components and optical connectors configured as splice-on connectors with beam collimation for fabrication of low-loss one-dimensional or two dimensional fiber array connectors. Optical fiber end-faces are permanently attached to an optical substrate on one surface. The optical substrate is a transparent substrate with lenses or a metasurface on the opposite surface. Each optical fiber is individually aligned (e.g., by active alignment) to the optical component (e.g. lens), for best position of each optical channel avoiding tolerance stacks which lead to higher loss. Each optical channel has optimized alignment independent of fiber geometry resulting in lowest optical loss independent on number of optical fibers.
Various embodiments optical components, optical connectors, and methods of fabricating the same are described in detail below.
Referring now to
The first optical component includes a substrate 120 having fiber coupling surface 122 and a lens surface 124. The substrate 120 has a thickness t, which may be, without limitation, 0.3 mm to 1.2 mm, including endpoints. The material chosen for the substrate 120 should be transparent to the wavelength of an optical signal OS being propagated. As used herein, “transparent” means that less than 10% of an optical power of the optical signal OS is absorbed by the substrate 120.
Embodiments are not limited by any particular type of material for the substrate 120. It may be preferable to choose the material of the substrate 120 such that it matches the material of the optical fibers 130 (described in more detail below) For example, both the optical fibers 130 and the substrate 120 may be fused silica. The matching fused silica material provides very low loss coupling and very low back reflection due to the same refractive index. Further, having both the optical fibers 130 and substrate 120 be fused silica provides for an interface with a matching of coefficient of thermal expansion (CTE), which reduces the mechanical stress and increases the long-term reliability. Fused silica has a low CTE=0.55 ppm/C, with reduced expansion over wide range of temperature (T=−45 C to +125° C.).
The lens surface 124 has at least one lens 126. In the illustrated embodiment, the substrate 120 has an array of lenses 126, such as a one dimensional or two-dimensional array of lenses 126. The at least one lens 126 may be fabricated into the lens surface 124 by any method. As non-limited examples the at least one lens 126 may be formed by lithography and reactive ion etching (RIE), polymer photoresist, deposition and re-melting, embossing, ink-jet printing, dispensing of very small optical adhesive volumes, and/or the like. The shape of the at least one lens may be spherical, non-spherical, Fresnel, or any other shape or configuration. The at least one lens 126 can be made on a wafer or panel level. Lens arrays can be diced, or laser cut before the fiber bonding process described below or after the fiber bonding process.
The dimensions of the at least one lens 126 are not limited by this disclosure. As a non-limiting example, the radius of curvature of the at least one lens 126 may be within a range of 0.05 mm and 0.5 mm, including endpoints. As a further non-limiting example, the diameter of the at least one lens 126 may be about 240 μm for a 250 μm pitch P between optical fibers 130 or smaller dependent on optical fiber diameter. For example, reduced cladding optical fibers (e.g., 80 μm diameter or less) enables high-density lens arrays. An another example, the lens diameter may be 100 μm to 250 μm, including endpoints. In some embodiments, the lens surface 124 is coated with an anti-reflection coating 128 for a specific wavelength range depending on the application. Any other optical features for beam shaping are possible, as well as meta-surfaces, filters, or combinations thereof. Aside from single-mode, few-mode and multi-mode are also possible as well as polarization maintaining fibers or any special fiber designs.
The at least one optical fiber 130 is bonded to the fiber coupling surface 122. Embodiments are not limited by the type of optical fiber 130. As stated above, the optical fiber 130 may be made of fused silica. The optical fiber 130 can be any single-mode, multimode, polarization maintaining, or other specialty optical fiber. The optical fiber 130 can be provided from a spool with hundreds of meters of optical fiber length, for example. One end of the optical fiber 130 can be connectorized and coupled to a light source, for example. As described in more detail below, the at least one optical fiber 130 is two-dimensionally aligned (e.g., in x- and y-direction) with the at least one optical lens 126 on a plane defined by the fiber coupling surface 122. In other words, the at least one optical fiber is bonded to the fiber coupling surface 122 at an alignment position that provides the lowest optical loss of the optical signal OS passing through the at least one lens 126. In some cases, a center of the at least one optical fiber 130 (i.e., a center of the core of the optical fiber) is aligned with a center the at least one lens 126. The alignment may be within ±1 μm, for example. However, in some embodiments it may be desirable for there to be a slight misalignment between the center of the at least one optical fiber 130 and the center of the at least one lens 126 to prevent back reflections of the optical beam. As a non-limiting example, the center of the at least one optical fiber 130 and the center of the at least one lens 126 may be intentionally mis-aligned by 100 μm or less with the center of the at least one lens 126 to angle the expanded optical beam by 15 degrees or less.
As shown in
Referring now to
After the optical fibers 130 are prepared, they are ready to be bonded to the fiber coupling surface 122 of the substrate 120.
An active alignment process may be utilized to find the alignment position of the optical fiber 130, which is the position of the optical fiber on the fiber coupling surface 122 that provides the lowest optical loss. An end of the optical fiber 130 that is opposite end 136 is coupled to a light source 110, such as a laser light source, that injects an optical signal OS (e.g., an optical beam) into the optical fiber 130. The optical signal OS passes through the interface between the end 136 of the optical fiber 130 and the fiber coupling surface 122 of the substrate 120, where it then diverges. The corresponding lens 126 that is aligned with the optical fiber 130 collimates the optical signal OS. A detector 112, such as a beam analyzer, receives the optical signal OS (i.e., the expanded optical beam) exiting the lens 126 and measures its mode-field or optical power. The substrate 120 is moved in two directions (e.g., by a translation table) while the detector 112 measures the mode-field or optical power of the optical signal OS according to an active alignment routine. The position of the substrate 120 with respect to the end 136 of the optical fiber 130 providing the specified mode-field of the received beam or greatest optical power of the optical signal OS as detected by the detector (i.e., the detector feedback) is the alignment position.
Once the optical fiber 130 is aligned, the end 136 of the optical fiber 130 is permanently bonded to the fiber coupling surface 122 of the substrate 120. As shown in
In some embodiments, no matter the bonding method, additional adhesive 140 may be locally applied near the bonding region to increase the strength (i.e., pull force) of the optical fiber 130 to the fiber coupling surface 122. However, in other embodiments, no additional adhesive 140 is provided.
Referring now to
The optical component 100 may be incorporated into an optical connector.
The ends 159 of the ribbon optical fibers 151 may be spliced to the tips 139 of the fiber stubs 135 to couple the fiber stubs 135 to the ribbon optical fibers 151. Any known or yet-to-be-developed method of forming a splice S between the fiber stubs 135 and the ribbon optical fibers 151 may be used. For example, splice equipment can be utilized which aligns the respective fiber cores and fusion bonds the fiber stub 135 to the ribbon optical fiber 151, which can be part of a single ribbon or high fiber count cable. This process can be repeated for all optical fibers of a ribbon cable. The splice S may provide a very low loss (e.g., 0.05 dB) between the fiber stubs 135 and the ribbon optical fibers 151.
Referring now to
The front face 181 also has alignment bores 187 on opposite sides of the opening 188 for receiving alignment pins of a mated optical connector. The fiber channel 186 is sized and configured to receive the fiber stubs 135 and/or the stripped ribbon optical fibers 151. The substrate 120 and/or the ribbon optical fibers 151 may be secured within the ferrule 180 by an adhesive, for example.
An optical connector having a two-dimensional array of lenses may be fabricated by stacking multiple optical connector sub-assemblies 160 on top of one another.
Adhesive may be applied to fill all gaps inside of the ferrule 180 to protect the splice and the fiber-to-substrate interface. It is noted that the form factor of the ferrule 180 can be adjusted to fit more optical channels in each row or increase the number of rows, e.g., to make optical connectors with 144 channels, for example.
The splice S between the fiber stub 135 and the ribbon optical fiber 151 may be within the ferrule 180 or connector housing, or outside of the ferrule 180 or connector housing.
A combination of two splice-on fiber stub optical connectors as described above may be used to make a jumper cable. In some embodiments, one splice may be skipped by using a splice-on fiber pigtail connector (e.g., as shown by optical connector 170′ of
The optical connectors described herein may also be employed in optical cables (e.g. trunk cables) having multiple optical fiber ribbons.
It is noted that recitations herein of a component of the embodiments being “configured” in a particular way, “configured” to embody a particular property, or function in a particular manner, are structural recitations as opposed to recitations of intended use. More specifically, the references herein to the manner in which a component is “configured” denotes an existing physical condition of the component and, as such, is to be taken as a definite recitation of the structural characteristics of the component.
It is noted that one or more of the following claims utilize the term “wherein” as a transitional phrase. For the purposes of defining the embodiments of the present disclosure, it is noted that this term is introduced in the claims as an open-ended transitional phrase that is used to introduce a recitation of a series of characteristics of the structure and should be interpreted in like manner as the more commonly used open-ended preamble term “comprising.”
Although the disclosure has been illustrated and described herein with reference to explanatory embodiments and specific examples thereof, it will be readily apparent to those of ordinary skill in the art that other embodiments and examples can perform similar functions and/or achieve like results. All such equivalent embodiments and examples are within the spirit and scope of the disclosure and are intended to be covered by the appended claims. It will also be apparent to those skilled in the art that various modifications and variations can be made to the concepts disclosed without departing from the spirit and scope of the same. Thus, it is intended that the present application cover the modifications and variations provided they come within the scope of the appended claims and their equivalents.
This application claims the benefit of priority of U.S. Provisional Application Ser. No. 63/286,706, filed on Dec. 7, 2021, the content of which is relied upon and incorporated herein by reference in its entirety.
Number | Date | Country | |
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63286706 | Dec 2021 | US |