Patent Description:
Light-fidelity (Li-Fi) and other free space optical communications rely on direct paths between a source and a target to provide wireless optical communication. Often the source and target are mounted or otherwise secured to an elevated structure to prevent objects, vehicles, or people from interfering with the signal path. Especially in these elevated positions, each unit, i.e., the source and the target are prone to movement or drift with respect to each other due to a variety of factors including, for example, weather, sway caused by wind, and bending due to uneven thermal expansion of the materials used to construct the elevated structures. These environmental conditions may be so severe as to cause a misalignment between the source and target resulting in data loss within the communication.

<CIT> discloses a free space optical communication system providing alignment between transmitter and receiver.

The present disclosure is related to methods and systems for preemptively correcting a potential future misalignment of an optical communication beam between a plurality of free space optical (FSO) units or Light Fidelity (Li-Fi) units by intentionally generating predetermined and repetitive motions of the beam path between the units using an adjustment mechanism. For example, inducing small, known, repeating movements to a transmission unit while aligned with a detector portion of a receiving unit such that significant movements or drifts that would ultimately cause a future misalignment can be corrected prior to losing a significant amount of data. In some examples the predetermined motion is a circular motion or a reciprocating and/or translating motion. The predetermined motions can be implemented by an adjustment mechanism which can include a plurality of piezoelectric actuators or one or more MEMS controlled mirrors or micro-lenses.

In one example, a method according to claim <NUM> is provided.

In one aspect, the predetermined motion is a circular motion or a reciprocating motion.

In one aspect, the alignment mechanism comprises a plurality of piezoelectric actuators and wherein the plurality of piezoelectric actuators are radially spaced about an external surface of a body of the transmission unit, where each piezoelectric actuator of the plurality of piezoelectric actuators is configured to connect with a portion of the body of the transmission unit and wherein the plurality of piezoelectric actuators are arranged about a rear portion of the transmission unit.

In one aspect, the transmission unit comprises an inertial navigation system to obtain movement information of the transmission unit.

In one aspect, the alignment mechanism comprises at least one micro-electromechanical machine (MEMS) that comprises a mirror or micro-lens; or wherein the alignment mechanism comprises a rotating mass.

In one aspect, the at least one detector portion has a first diameter and the optical communication beam has a second diameter, wherein the first diameter is less than or equal to the second diameter.

In one aspect, the receiving unit further comprises a center reflector portion.

In another example, an optical system according to claim <NUM> is provided.

In one aspect, the alignment mechanism comprises a plurality of piezoelectric actuators and wherein the plurality of piezoelectric actuators are radially spaced about an external surface of a rear portion of a body of the transmission unit, where each piezoelectric actuator of the plurality of piezoelectric actuators is configured to engage with a portion of the body of the transmission unit.

In one aspect, the transmission unit is a Light Fidelity (Li-Fi) transmitter and the receiving unit is a Li-Fi receiver.

These and other aspects of the various embodiments will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.

Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the various embodiments.

The present disclosure is related to preemptively correcting a potential future misalignment of an optical communication beam between a plurality of free space optical (FSO) units or plurality of Li-Fi units by intentionally generating predetermined and repetitive motions of the beam path between the units using an adjustment mechanism. In some examples the predetermined motion is a circular motion or a reciprocating and/or translating motion. The predetermined motions can be implemented by an adjustment mechanism which can include a plurality of piezoelectric actuators or one or more MEMS controlled mirrors or micro-lenses.

The following description should be read in view of <FIG>. <FIG> illustrates a schematic perspective view of optical system <NUM> according to the present disclosure. As illustrated, optical system <NUM> includes a transmission unit <NUM> and a receiving unit <NUM>. Transmission unit <NUM> is intended to be a first free space optical (FSO) unit (discussed below) or a transmitter for Li-Fi based communication systems and receiving unit <NUM> is intended to be a second FSO unit (discussed below) or a receiver for Li-Fi based communication systems. Although transmission unit <NUM> and receiving unit <NUM> are illustrated and described herein as a first free space optical (FSO) unit <NUM> and a second FSO unit <NUM>, it should be appreciated the following techniques and principles can be utilized between units of a Li-Fi system as well, e.g., between a Li-Fi transmitter and a Li-Fi receiver. As will be discussed below, during operation of optical system <NUM>, first FSO unit <NUM> and second FSO unit <NUM> are intended to be mounted or otherwise affixed to a streetlamp, building, tower, or other elevated outdoor structure and separated by open air such that optical communication between each unit is possible. First FSO unit <NUM> includes an electromagnetic source <NUM> configured to produce focused electromagnetic radiation along imaginary alignment axis A (hereinafter "alignment axis A"). Electromagnetic source <NUM> can be selected from a Light-Emitting Diode (LED), Organic LED (OLED), a solid state laser, a gas laser, a liquid laser, a semiconductor laser or any other source of electromagnetic radiation (e.g., electromagnetic radiation in the visible and/or non-visible spectrums) capable of producing focused radiation along alignment axis A. In one example, the electromagnetic radiation produced is radio frequency (RF) radiation In the examples illustrated, electromagnetic source <NUM> is a semiconductor laser comprising a one or two-dimensional array of optical transmitters configured to produce optical communication beam <NUM> along beam path BP and/or along alignment axis A. It should be appreciated that electromagnetic source <NUM> can utilize one or more lenses or one or more micro-lenses to focus the electromagnetic radiation as it leaves first FSO unit <NUM> and travels along beam path BP. First FSO unit <NUM> further includes a unit detector <NUM> configured to receive at least a portion of optical communication beam <NUM> that has been reflected of second FSO unit <NUM>, as will be discussed below. As will be discussed below in detail, and as illustrated in <FIG>, <FIG>, and <FIG>, alignment axis A represents the trajectory of beam path BP when no predetermined motion (e.g., predetermined motion <NUM> discussed below) is applied to first FSO unit <NUM> and/or second FSU unit <NUM>. In other words, in the absence of a predetermined motion alignment axis A will be substantially parallel with beam path BP.

Optical communication beam <NUM>, once focused along beam path BP, has a first diameter D1 (shown in <FIG>) and an intensity I. It should be appreciated that in some examples, as will be discussed below, first diameter D1 can be substantially equal to or greater than the diameter of detector portion <NUM>, i.e.. , second diameter D2 (discussed below and shown in <FIG>). However, in some examples, as shown in <FIG>, diameter D1 is substantially smaller than detector portion <NUM> (discussed below). Optical communication beam <NUM> can be configured and/or focused such that intensity I decreases as a function of radius or distance from the center of optical communication beam <NUM>, e.g., the optical communication beam <NUM> may have its highest intensity or peak intensity I at the center and have the intensity I decrease or degrade toward the outside of the beam's diameter, i.e., the outside perimeter of D1.

It should be appreciated that any technology or protocol for transmitting data in optical communication beams may be utilized by the first FSO unit <NUM>. For example, optical communication beam <NUM> may be encoded with information by modulating a carrier signal with a modulating signal that contains the information desired to be transmitted, e.g., information related to predetermined motion <NUM> (discussed below). Additionally, or in the alternative to signal modulation, the wavelength of optical communication beam <NUM> can be set outside the visual spectrum if desired, which may enable the second FSO unit <NUM> (discussed in detail below) to more easily differentiate the optical communication beam <NUM> from ambient light, and therefore detect the optical communication beam <NUM>. In some example embodiments, optical communication beam <NUM> is generated having known and measurable characteristics, e.g., a known wavelength outside the visual spectrum and/or modulated with a carrier signal having a set base frequency. In some example embodiments, the wavelength and/or polarization of optical communication beam <NUM> is altered depending on the time of day to account for changing ambient conditions, e.g., due to the changing light spectrum from the sun or other light sources throughout the day. Furthermore, optical communication beam <NUM> may be transmitted in a collimated or parallel manner, with little or no divergence, e.g., to facilitate accurate long-range transmission. For example, the emitted optical communication beam <NUM> can be collimated by optics, e.g., an aspheric lens, to form a collimated light beam or beams that are pointed towards the second FSO unit <NUM>. In other example embodiments, a light torch can be included to focus optical communication beam <NUM>.

As will be discussed below, and as illustrated in <FIG>, <FIG> and <FIG>, first FSO unit <NUM> can include a body <NUM> configured to at least partially enclose electromagnetic source <NUM>. Body <NUM> includes an external surface <NUM> and has a front portion <NUM> and a rear portion <NUM>. In one example, as illustrated in <FIG> and <FIG>, external surface <NUM> is a circumferential surface; however, it should be appreciated that external surface <NUM> can have any cross-sectional shape including but not limited to: triangular, square, rectangular, hexagonal, octagonal, etc. Front portion <NUM> is intended to be the portion of body <NUM> proximate the opening, aperture, or surface of body <NUM> from which optical communication beam <NUM> is emitted. In other words, front portion <NUM> is intended to be the portion of body <NUM> closest to second FSO unit <NUM> during operation of optical system <NUM>. Conversely, rear portion <NUM> is intended to be the portion of body <NUM> that is farthest from second FSO unit <NUM> during operation. It should also be appreciated that, although not illustrated, first FSO unit <NUM> can include first circuitry electrically connecting a first processor and first memory, the first processor and the first memory configured to execute and store, respectively, a first plurality of non-transitory computer-readable instructions to perform the functions of first FSO unit <NUM> as will be discussed herein. Furthermore, as illustrated and described below in detail with respect to <FIG>, first FSO unit <NUM> can further comprise alignment mechanism <NUM>.

Second FSO unit <NUM> is configured to receive optical communication <NUM> from first FSO unit <NUM>. As illustrated in <FIG>, second FSO unit <NUM> includes at least one portion configured to receive optical communication beam <NUM>, i.e., detector portion <NUM>, and at least one portion configured to reflect optical communication beam <NUM>, i.e., reflector portion <NUM>. Detector portion <NUM> is intended to be a photodiode, a plurality of photodiodes, or any other detector or sensor capable of receiving and detecting the modulations in optical communication beam <NUM>. In one example, detector portion <NUM> can include at least one avalanche photodiode or at least one single-photon avalanche diode. Reflector portion <NUM> includes a passive reflective component or material or a plurality of passive reflective components or materials, e.g., mirrors or smooth coated surfaces with highly reflective properties. In the examples illustrated in <FIG>, both detector portion <NUM> and reflector portion <NUM> are circular shaped; however, it should be appreciated that other shapes and combinations of shapes may be utilized. Although reflector portion <NUM> is reflective or includes reflective parts or materials, it should be understood that the detector portion <NUM> may reflect a very small portion of the electromagnetic radiation of optical communication beam <NUM>, depending on the chosen wavelength, but is initially intended to be optimized to absorb all light and therefore be non-reflective. For example, reflector portion <NUM> can reflect radiation at the exact same angle as the incoming light beam, which is useful in situations where the communications are aligned (as will be discussed below) but not exactly at an angle perpendicular to the surface of the second FSO unit <NUM>. It should also be appreciated that, although not illustrated, second FSO unit <NUM> can include second circuitry electrically connecting a second processor and second memory, the second processor and the second memory configured to execute and store, respectively, a second plurality of non-transitory computer-readable instructions to perform the functions of second FSO unit <NUM> as will be discussed herein. The second circuitry of second FSO unit <NUM> can be configured to sense, detect, or otherwise receive optical communication beam <NUM> and decode optical communication beam <NUM> into information or data.

In example embodiments, the first and second FSO units <NUM> and <NUM> can be mounted at elevated positions in any suitable outdoor structure, e.g., a streetlamp, to avoid the obstructions or interference between optical communication beam <NUM> and people, vehicles, etc. The term "streetlamp" or "streetlight" as used herein refers to any outdoor lighting infrastructure that includes a light fixture, e.g., a light fixture extending from a support such as a pole, in order to illuminate an area proximate to the streetlamp. The pole may be built specifically for the streetlamp, or may be used for some other purpose, e.g., a utility pole. It is to be appreciated that in other examples, one or more of the streetlamps may include or extend from other types of infrastructure, such as signage, buildings, bridges, towers or the like.

Advantageously, streetlamps, and buildings which are already electrically wired, can provide electrical power for building systems and/or light fixtures. These electrically wired buildings or fixtures can provide electrical connections for the first and second FSO units <NUM> and <NUM>. Furthermore, streetlamps are commonly installed at regular intervals along a road, street, sidewalk, or other path, which extend to and/or between various locations where people reside, work, or otherwise desire high data rate communication. In this way, first and second FSO units <NUM> and <NUM> can be installed at streetlamps and a plurality of additional FSO units can form a connected network of FSO units, e.g., extending in any desired direction throughout all or part of a city, town, or other locations. Additionally, it is to be appreciated that existing streetlamp infrastructure can be leveraged by retrofitting the FSO units on existing streetlamps. It is also to be appreciated that one FSO unit can be mounted on a streetlight or streetlamp and the other can be mounted on a building, tower or other elevated structure.

As discussed above, one issue faced by free space optical systems is maintaining optical alignment or a direct optical path (e.g., the shortest straight path) between the first FSO unit <NUM> and the second FSO unit <NUM>. In operation, the first FSO unit <NUM> and second FSO unit <NUM> are capable of moving relative to each other based on weather and other factors, e.g., wind sway, thermal expansion, and vibration. Because of the diameter D1 of the transmitted optical communication beam <NUM> and the limited field of view of the detector portion <NUM> at the second FSO unit <NUM>, any slight movement due to any of these environmental conditions can affect beam alignment and interrupt communication. In some examples first FSO unit <NUM> and second FSO unit <NUM> are mounted on structures that are separated by significant distances, e.g., hundreds or thousands of meters, and any slight angular displacement in the beam path BP of optical communication beam <NUM> at first FSO unit <NUM> can cause significant misalignment proximate second FSO unit <NUM>. Other environmental conditions, such as, fog can also interrupt communication even when the first and second FSO units <NUM> and <NUM> are not moving.

Thus, in one example, an object of the present disclosure to provide an optical system <NUM> that is configured to preemptively alter the beam path BP of optical communication beam <NUM> relative to alignment axis A in a repeatable predetermined motion <NUM> to detect the potential for future misalignment and correct for the potential future misalignment before any significant data is lost occurs. To that end, optical system <NUM> includes an alignment mechanism <NUM> configured to generate predetermined motion <NUM> on beam path BP of optical communication beam <NUM> relative to alignment axis A.

As illustrated in <FIG>, predetermined motion <NUM> can be a circular motion. <FIG> illustrates a series of beam path BP positions located on detector portion <NUM> of second FSO unit <NUM>, and are illustrated as a series of dotted circles having diameter D1. It should be appreciated that although illustrated by a series of dotted circles, the circular predetermined motion <NUM> is intended to be a fluid circular motion and the dotted circles represent positions of optical communication beam <NUM> at different positions within the circular motion, e.g., every <NUM> degrees about alignment axis A. In other words, each dotted circle represents a snap shot of optical communication beam <NUM> at different points in time within the circular motion. Additionally, in one example, the circular predetermined motion <NUM> has a small radius, i.e., a radius that is less than half of diameter of detector portion <NUM>, i.e., second diameter D2, such that all of the dotted circles, i.e., the entire circular path of optical communication beam <NUM>, contacts detector portion <NUM> of second FSO unit <NUM> during the entire circular predetermined motion <NUM>. As shown in <FIG>, should first FSO unit <NUM> and/or second FSO unit <NUM> experience and motion or vibration due to, e.g., environmental conditions, uneven heating of its support structure, etc., alignment axis A may begin to drift or become misaligned with respect to center C of detector portion <NUM>.

As illustrated in <FIG>, first FSO unit <NUM> and/or second FSO unit <NUM> may begin to drift with respect to each other causing alignment axis A to drift, e.g., upward toward the top of detector portion <NUM>. As illustrated, the drift may continue until at least a portion of optical communication beam <NUM> overlaps with and is reflected off reflector portion <NUM> of second FSO unit <NUM>, and detected by unit detector <NUM> on first FSO unit <NUM> (illustrated by a dotted circle with cross-hatching). Due to the circular repeating pattern of predetermined motion <NUM> relative to alignment axis A, beam path BP will only momentarily overlap with reflective portion <NUM> of second FSO unit <NUM> and will automatically return to full contact with detector portion <NUM> as a part of its circular path. Thus, only a small or insignificant amount of data, i.e., the data contained in the communications reflected back to detecting unit <NUM> may be lost. As at least a portion of optical communication beam <NUM> was reflected back and detected by unit detector <NUM> of first FSO unit <NUM>, first FSO unit <NUM> can correct its potential future misalignment with second FSO unit <NUM> based on the trajectory of the reflected data and correct for the misalignment before the next complete circular motion. In other words, first FSO unit <NUM> may adjust (e.g., using alignment mechanism <NUM> discussed below) its position to offset for the drift experienced by optical system <NUM> such that alignment axis A is substantially in line with center C of detector portion <NUM>.

<FIG> illustrate a circular predetermined motion <NUM> with a larger radius, i.e., a radius that is slightly less than half of second diameter D2 (shown in <FIG>). In other words, when alignment axis A is lined up with center C of detector portion (shown in <FIG>), the circular path of optical communication beam <NUM> substantially traces the shape of the perimeter of detector portion <NUM> while maintaining that all portions of optical communication beam <NUM> are in contact with detector portion <NUM>. In these examples, given the geometry of the circular motion illustrated, any drift between first FSO unit <NUM> and second FSO unit <NUM> will result in at least a portion of optical communication beam <NUM> overlapping with reflector portion <NUM> of second FSO unit <NUM> indicating a potential future misalignment as shown in <FIG>. Once the portion of the optical communication beam <NUM> is reflected back to unit detector <NUM> of first FSO unit <NUM>, a preemptive correction can be made (e.g., using alignment mechanism <NUM> discussed below), to bring alignment axis A back into line with center C of detector portion <NUM> of second FSO unit <NUM> (shown by a deviation in the circular path in <FIG>).

It should be appreciated that predetermined motion <NUM> can be any repeating motion, e.g., a translational reciprocating motion (discussed below), a circular motion (discussed above), a square-shaped motion (i.e., where the projected path of optical communication beam <NUM> on any portion of second FSO unit <NUM> is substantially square shaped), a triangular motion, rectangular motion, hexagonal motion, octagonal motion, or any other repeating motion. For example, as shown in <FIG>, predetermined motion <NUM> is a reciprocating motion, i.e., a back-and-forth translational motion. It should be appreciated that the reciprocating motion can be a vertical translational motion, i.e., up and down with respect to alignment axis A; a horizontal translational motion, i.e., left-to-right or right-to-left motion with respect to alignment axis A; or any reciprocating translational motion between those motions, e.g., a diagonal motion with respect to alignment axis A. It should also be appreciated that compound motions of any of the motions discussed herein are possible, e.g., where a first part of the reciprocating predetermined motion <NUM> is a vertical translational motion and a second part of the reciprocating predetermined motion <NUM> is a horizontal translational motion. Additionally, predetermined motion <NUM> can be adapted in real-time to the misalignment detected by optical system <NUM>. For example, when the system detects misalignment of beam path BP as a substantially horizontal misalignment, the predetermined motion <NUM> can be selected as an elliptical motion with its longest axis in the horizontal plane. It should be appreciated that the misalignment experienced can be caused by a combination of motions occurring at the first FSO unit <NUM> and the second FSO unit <NUM>. In these examples, motion of either the first FSO unit <NUM> and the second FSO unit <NUM> could be determined by an inertial measurement unit, which can include an accelerometer, gyroscope, and/or a magnetometer.

Similarly to the example described above using a circular motion, first FSO unit <NUM> and/or second FSO unit <NUM> may begin to drift with respect to each other causing alignment axis A to drift, e.g., upward and to the right side of detector portion <NUM> (shown in <FIG>). As illustrated, the drift may continue until at least a portion of optical communication beam <NUM> overlaps with and is reflected off reflector portion <NUM> of second FSO unit <NUM> and detected by unit detector <NUM> on first FSO unit <NUM> (illustrated by a dotted circle with cross-hatching). Due to the reciprocating pattern of predetermined motion <NUM> relative to alignment axis A, beam path BP will only momentarily overlap with reflective portion <NUM> of second FSO unit <NUM> and will automatically return to full contact with detector portion <NUM> as a part of its reciprocating motion. Thus, in some extreme cases, only a small or insignificant amount of data, i.e., the data contained in the communications reflected back to unit detector <NUM> may be lost. As at least a portion of optical communication beam <NUM> was reflected back and detected by unit detector <NUM> of first FSO unit <NUM>, first FSO unit <NUM> can correct its potential future misalignment with second FSO unit <NUM> based on the trajectory of the reflected data and correct for the misalignment before the next complete reciprocating motion. In other words, first FSO unit <NUM> may adjust (e.g., using alignment mechanism <NUM> discussed below) its position to offset for the drift experienced by optical system <NUM> such that alignment axis A is substantially in line with center C of detector portion <NUM>.

As illustrated in <FIG>, first diameter D1 of optical communication beam <NUM> can be larger than second diameter D2 of detector portion <NUM> of second FSO unit <NUM>. In this example, rather than measure misalignment due to any portion of optical communication beam <NUM> contacting and being reflected off of reflector portion <NUM> of second FSO unit <NUM>, misalignment can be determined as a function of intensity I of optical communication beam <NUM>. For example, as discussed above, optical communication beam <NUM> can have an intensity I that degrades radially from the center of the beam to the outer edges of the beam. In some examples, the luminous intensity I across the width of a cross-section of optical communication beam <NUM> resembles a Gaussian distribution curve, Gaussian intensity profile (i.e.. , an intensity profile with a Gaussian distribution), with peak intensity located at the center of the beam and where intensity I degrades or decreases as <NUM>/distance as you approach the outer edges of the beam. Given this intensity distribution, the alignment axis A, when no predetermined motion <NUM> is applied to beam path BP, will be coincident with the area of highest intensity, I as detected by detector portion <NUM> of second FSO unit <NUM>. Inversely, misalignment can be determined from the intensity of the reflected portions of optical communication beam <NUM> that reflect off of reflector portion <NUM> of second FSO unit <NUM> and are detected by unit detector <NUM> of first FSO unit <NUM>. For example, after predetermined motion <NUM> is applied to beam path BP relative to alignment axis A, any drift between first FSO unit <NUM> and second FSO unit <NUM> can be determined if any portion of optical communication beam <NUM> that is reflected off reflector portion <NUM> has an intensity I that meets a predetermined threshold. In one example, this threshold is <NUM>% of the peak intensity I of optical communication beam <NUM>; however it should be appreciated that other intensity thresholds are contemplated, e.g., <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>%, <NUM>% etc..

Additionally, as illustrated in <FIG>, detector portion <NUM> of second FSO unit <NUM> can further include a center reflector portion <NUM> centered within detector portion <NUM>. Similarly to reflector portion <NUM> discussed above, center reflector portion <NUM> can include a passive reflective component or material or a plurality of passive reflective components or materials, e.g., mirrors or smooth coated surfaces with highly reflective properties. In the examples illustrated in <FIG>, center reflector portion <NUM> is circular shaped; however, it should be appreciated that other shapes, e.g., triangular, square, rectangular, hexagonal, octagonal, etc., may be utilized. In an aligned position, i.e., where alignment axis A is coincident with center C of detector portion <NUM>, a predetermined motion <NUM>, e.g., a circular motion, can be applied to beam path BP. In the example illustrated in <FIG>, the diameter of the center reflector portion <NUM>, i.e., third diameter D3, is smaller than the diameter of the predetermined circular motion <NUM>, such that, when in the aligned position, no portion of optical communication beam <NUM> overlaps any portion of center reflector portion <NUM>. However, similarly to the drift corrections discussed above, in example embodiments where second FSO unit <NUM> includes center reflector portion <NUM>, the contact position of alignment axis A as well as the contact portion of beam path BP can drift with respect to the center C of detector portion <NUM>. As illustrated in <FIG>, an upward drift, i.e., a drift of alignment axis A toward the upper portion of detector portion <NUM>, will cause a portion of optical communication beam <NUM> (illustrated as one or more dotted circles with cross-hatchings) to overlap with center reflector portion <NUM> which will be reflected back to unit detector <NUM> of first FSO unit <NUM> to signal that a potential future misalignment is imminent. As at least a portion of optical communication beam <NUM> was reflected back and detected by unit detector <NUM> of first FSO unit <NUM>, first FSO unit <NUM> can correct its potential future misalignment with second FSO unit <NUM> based on the trajectory of the reflected data and correct for the misalignment before the next complete circular motion. In other words, first FSO unit <NUM> may adjust (e.g., using alignment mechanism <NUM> discussed below) its position to offset for the drift experienced by optical system <NUM> such that alignment axis A is substantially in line with center C of detector portion <NUM>. It should be appreciated that the use of center reflector portion <NUM> can be used in isolation to create this effect, i.e., only center reflector portion <NUM> may be necessary, and optical system <NUM> may employ the measurements, predetermined motions, and detect misalignment without the need to reflector portion <NUM> and only rely on center reflector portion <NUM> to determine any misalignment.

As illustrated in <FIG>, predetermined motion <NUM> can be imparted by an alignment mechanism, i.e., alignment mechanism <NUM>. As illustrated, at least a portion of alignment mechanism <NUM> is configured to secure to and/or encompass at least a portion of body <NUM> and/or external surface <NUM> of first FSO unit <NUM>. In one example, alignment mechanism <NUM> includes a front support structure <NUM> and a rear support structure <NUM>. Front support structure <NUM> may be a frame-type structure configured to at least partially encompass front portion <NUM> of body <NUM> of first FSO unit <NUM>. Front support structure <NUM> may include a plurality of front support arms extending radially inward toward body <NUM> of first FSO unit <NUM> which are configured to attach to front portion <NUM> of body <NUM> to suspend front portion <NUM> in free space and potentially allow front portion <NUM> to pivot. Similarly, rear support structure <NUM> may be a frame-type structure configured to at least partially encompass rear portion <NUM> of body <NUM> of first FSO unit <NUM>. Rear support structure <NUM> may include a plurality of rear support arms extending radially inward toward body <NUM> which are configured to attach to rear portion <NUM> of body <NUM> of first FSO unit <NUM> to suspend rear portion <NUM> in free space.

In some examples, each rear support arm can include a piezoelectric element, i.e., at least one piezoelectric actuator of a plurality of piezoelectric actuators 134A-134D. Each actuator, operating individually, can push or pull on each respective rear support arm and cause the rear portion <NUM> of body <NUM> to move proportionately, thus by activating one or more piezoelectric actuators of the plurality of piezoelectric actuators 134A-134D, each predetermined motion <NUM> discussed above can be realized. For example, activation of first piezoelectric actuator 134A can operate to push or displace rear portion <NUM> of first FSO unit <NUM> in a downward direction, i.e., toward third piezoelectric actuator 134C while first support structure <NUM> is configured to maintain the suspended position of first portion <NUM> of FSO unit. Thus, the downward motion of rear portion <NUM> and pivoting of body <NUM> about front support structure <NUM> will cause beam path BP to be emitted at an upward trajectory or angle and contact second FSO unit <NUM> at a position above alignment axis A. Conversely, first piezoelectric actuator 134A can also be configured to pull or displace rear portion <NUM> in an upward direction causing beam path BP to be emitted at a downward trajectory or angle and contact second FSO unit <NUM> at a position below alignment axis A. It should be appreciated that all of the piezoelectric actuators 134A-134D may operate in a similar manner to push or pull rear portion to alter the trajectory of beam path BP horizontally or vertically relative to alignment axis A. Additionally, one or more piezoelectric actuators of the plurality of piezoelectric actuator 134A-134D can operate in concert to achieve one dimensional motion, e.g., an upward or downward motion. For example, downward displacement of rear portion <NUM> may be accomplished by a concerted activation of both first piezoelectric actuator 134A to push down on rear portion and third piezoelectric actuator 134C to pull down on rear portion <NUM>. Furthermore, it should be appreciated that one or more piezoelectric actuators of the plurality of piezoelectric actuator 134A-134D can operate in concert to create more complex motions, e.g., circular motions, diagonally motions, or any of the other motions discussed herein. For example, each piezoelectric actuator of plurality of piezoelectric actuators 134A-134D can be remotely activated sequentially, i.e., starting with activation of first piezoelectric actuator 134A and proceeding to second piezoelectric actuator 134B, then third piezoelectric actuator 134C, and finally to fourth piezoelectric actuator 134D to induce a synchronized clockwise circular motion to rear portion <NUM> which in turn induces a clockwise circular motion to beam path BP. It should also be appreciated that although four piezoelectric actuators are shown and described herein, more or less piezoelectric actuators may be utilized to generate more complex motions, e.g., hexagonal, octagonal, etc. It should be appreciated that only the rear support structure <NUM> may be necessary to impart predetermined motion <NUM> and that front portion <NUM> may simply rest on or other otherwise engage a surface that allows body <NUM> to pivot about front portion <NUM>. Moreover, in some examples, the front support structure <NUM> of front portion <NUM> can include the plurality of piezoelectric actuators 134A-134D to impart the predetermined motion <NUM> discussed herein and rear support structure <NUM> can be passive.

Furthermore, predetermined motion <NUM> can be imparted on beam path BP using one or more lenses or micro lenses, for example, as illustrated in <FIG> (which illustrates a partial cross-sectional view of first FSO unit <NUM>), first FSO unit <NUM> may include a controller <NUM> and a miniature laser scanning module which includes at least one micro-electromechanical system (MEMS) device <NUM> to operate one or more mirrors or micro-lenses <NUM>. Controller <NUM> can include a dedicated processor and memory configured to execute and store, respectively, a plurality of non-transitory computer-readable instructions to perform the functions of first FSO unit and/or alignment mechanism <NUM> as discussed herein. Controller <NUM> may be or may include one or more application specific integrated circuits or chips (ASIC) to direct MEMS device <NUM> to operate the mirror or micro-lens <NUM> to cause optical communication beam <NUM> to move in any of the motions discussed above relative to alignment axis A. In some examples, the MEMS mirrors are millimeter sized mirrors that perform laser scanning or in the transmitting portion of the solid state laser. Moreover, as illustrated in <FIG>, first FSO unit <NUM> and/or second FSO unit <NUM> can include an inertial navigation system INS which can contain one or more processors, one or more motion sensors, and one or more rotation sensors, e.g., accelerometers, gyroscopes, magnetometers, that are configured to obtain each respective device's position, orientation, or movement velocity, if any. The inertial navigation system INS can be used by the devices within optical system <NUM> to determine the absolute or relative motion of first FSO unit <NUM> with respect to second FSO unit <NUM> and optical system <NUM> can adapt the predetermined motion <NUM> that is selected according to the known motion data provided by the inertial navigation system INS.

Additionally, as illustrated in <FIG>, it should be appreciated that alignment mechanism <NUM>, in addition to, or in the alternative to, the piezoelectric actuators and/or MEMS machines discussed herein, can include a movable or rotating mass RM positioned within first FSO unit <NUM> and connected to or attached directly to electromagnetic source <NUM> or positioned with second FSO unit <NUM> to produce predetermined motion <NUM>. For example, a rotating shaft S may be provided within first FSO unit <NUM> which is non-rotationally secured to a mass RM that can take the shape of a half-cylinder, e.g., a cylindrical mass that has been cut parallel to the cylinder's long axis or its height axis. As the partial cylindrical mass RM rotates with the rotating shaft S, the uneven distribution of the mass in its rotation causes the shaft and structures attached to it to move slightly due to the impulse created. Given that the uneven distribution of mass caused by the partial cylindrical mass rotating about an axis, the impulse driven motions created will be circular motions, and therefore, the present application could utilize a rotating partial cylindrical mass RM to impart predetermined motion <NUM> in the form of a circular motion. It should be appreciated that this rotating mass can be provided within first FSO unit <NUM> and/or second FSU unit <NUM> to create the predetermined motion as will be discussed below.

Alternatively, or in addition to the foregoing, and although not illustrated, in some examples the functionality imparted by alignment mechanism <NUM> can be implemented on second FSO unit <NUM> rather than first FSO unit <NUM>. For example, rather than generating a circular or translational predetermined motion <NUM> of optical communication beam <NUM> by imparting motion on body <NUM> of first FSO unit <NUM>, FSO unit <NUM> may remain spatially fixed, while second FSO unit is displaced in a circular or translational pattern of motion. To that end, second FSO unit <NUM> may include a separate adjusting mechanism having, e.g., a plurality of piezoelectrical actuators to generate any of the predetermined motions <NUM> discussed herein relative to alignment axis A.

<FIG> is a flow chart illustrating the steps of method <NUM> according to the present disclosure. Method <NUM> can include, for example, generating, via a transmission unit <NUM>, an optical communication beam <NUM> along an imaginary alignment axis A, the transmission unit <NUM> comprising at least one unit detector <NUM>, the optical communication beam <NUM> having a beam path BP between the transmission unit <NUM> and a receiving unit <NUM>, the receiving unit <NUM> comprising at least one detector portion <NUM> and at least one reflector portion <NUM> (step <NUM>); receiving at the at least one detector portion <NUM> of the receiving unit <NUM>, the optical communication beam <NUM> (step <NUM>); preemptively altering the beam path BP relative to the imaginary alignment axis A, using a predetermined motion <NUM> (step <NUM>); detecting a potential misalignment of the imaginary alignment axis A when at least a portion of the optical communication beam <NUM> is received by the at least one unit detector <NUM> of the transmission unit <NUM> (step <NUM>); and aligning, using an alignment mechanism <NUM>, the imaginary alignment axis A relative to the center C of the at least one detector portion <NUM> based on the detected misalignment (step <NUM>).

Claim 1:
A method of maintaining alignment of an optical communication beam <NUM>, the method comprising:
generating, via a transmission unit (<NUM>), an optical communication beam (<NUM>) along an imaginary alignment axis (A), the transmission unit (<NUM>) comprising at least one unit detector (<NUM>), the optical communication beam (<NUM>) having a beam path (BP) between the transmission unit (<NUM>) and a receiving unit (<NUM>), the receiving unit (<NUM>) comprising at least one detector portion (<NUM>) and at least one reflector portion (<NUM>);
receiving at the at least one detector portion (<NUM>) of the receiving unit (<NUM>), the optical communication beam (<NUM>);
preemptively altering the beam path (BP) relative to the imaginary alignment axis (A), using a predetermined motion (<NUM>);
detecting a potential misalignment of the imaginary alignment axis (A) when at least a portion of the optical communication beam (<NUM>) is received by the at least one unit detector (<NUM>) of the transmission unit (<NUM>); and
aligning, using an alignment mechanism (<NUM>), the imaginary alignment axis (A) relative to the center (C) of the at least one detector portion (<NUM>) based on the detected misalignment;
characterized in that the at least one reflector portion (<NUM>) is surrounding the at least one detector portion (<NUM>).