Method for adjusting the optical link alignment of a first communication device with respect to a telecommunications device, and communication device therefor.
The method enhances tracking and pointing accuracy in FSOC systems by combining pre- and post-correction techniques, addressing errors in narrow beamwidth systems with long distances and reducing beacon beam reliance.
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- TAARA CONNECT INC
- Filing Date
- 2022-12-12
- Publication Date
- 2026-05-26
Smart Images
Figure 0007866070000001 
Figure 0007866070000002 
Figure 0007866070000003
Abstract
Description
Technical Field
[0001] Cross - reference to related applications
[0001] This application claims the benefit of the priority and filing date of U.S. Patent Application No. 17 / 709,544, filed Mar. 31, 2022, the entire disclosure of which is incorporated herein by reference.
Background Art
[0002] Background
[0001] A communication terminal can transmit and receive optical signals or optical beams via a free - space optical communication (FSOC) link. To achieve such transmission and reception, such a terminal generally uses a capture and tracking system to establish an optical link by directing optical beams in each other's directions. For example, a transmitting terminal irradiates a receiving terminal using a beacon beam, while the receiving terminal can use a position sensor to identify the position of the transmitting terminal and monitor the beacon beam. A steering mechanism can steer the terminals to point in each other's directions and track the pointing once capture is established. High - degree pointing accuracy may be required to ensure that optical signals are correctly received.
[0003]
[0002] Tracking performance and pointing accuracy are adversely affected by internal and external disturbances experienced by a communication system, which include vibrations of the pedestal, wind effects, or variations due to a bird landing on or departing from the device. In some free - space optical communication systems that employ a wide beamwidth, the adverse effects on tracking performance and pointing accuracy may not be so significant. However, in communication systems with a narrow beamwidth and a long transmission distance on the order of one kilometer or more, errors in tracking performance and pointing accuracy become more prominent, and precise correction is required to address them. That is, in a system with a narrow beamwidth, the system corrects tracking errors and alignment errors retrospectively, so the connection may be interrupted more frequently or the reliability of the connection may be more degraded due to disturbances. In addition, such a system may require additional beacon beam transmissions to assist tracking, which may consume excessive power.
Summary of the Invention
[0004] overview
[0003] This technology relates to an FSOC system that can effectively correct errors in tracking and directing accuracy in order to maintain connectivity integrity without using beacon beams or by reducing the frequency of beacon beam use. Aspects of this technology enable the FSOC system to correct errors in tracking performance and directing accuracy of terminals in the system both pre- and post-correction. Combining pre- and post-correction methods enables more accurate and efficient correction. Such methods are particularly beneficial for systems with narrow beamwidths and long transmission distances, such as on the order of 1 kilometer or more.
[0005]
[0004] According to one embodiment, a method is provided for adjusting the optical link alignment of a first communication device to a telecommunications device. The method includes receiving information indicating at least one external disturbance in the first communication device; determining from the information an expiry estimate indicating a first error related to the effect of at least one external disturbance in the current time step by one or more processors of the first communication device an expiry estimate indicating a second error related to the effect of at least one external disturbance in a previous time step by one or more processors of the first communication device an expiry estimate indicating a second error related to the effect of at least one external disturbance in a previous time step by one or more processors determining a final control signal based on the expiry and expiry estimates; and operating the optical assembly of the first communication device by a controller based on the determined final control signal.
[0006]
[0005] In one example, determining an advance estimate includes determining a first error, and determining an ex-post estimate includes determining a second error, where the final signal may be determined by summing the first and second errors. In another example, information indicating at least one external disturbance includes behavioral information of the telecommunications device from a previous time step. The behavioral information may include a set of elements related to the telecommunications device. The set of elements may include at least one of the following: the set point of the telecommunications device, the attitude of the telecommunications device, the angular velocity of the telecommunications device, the acceleration of the telecommunications device, or the target position of the telecommunications device. Alternatively, the behavioral information may be based on information about at least one external disturbance in a previous time step received from one or more sensors of the telecommunications device or one or more sensors of the first communication device. In a certain scenario, determining an advance estimate includes mapping information from the current time step to a first output by a feedforward gain scheduling technique, and determining an ex-post estimate includes mapping behavioral information from a previous time step to a second output by a feedback gain scheduling technique. Here, the first output is a prior estimate, and the second output is a posterior estimate. In this example, the feedforward gain scheduling method can be defined by u_FF(t)=G_FF(m), where u_FF(t) is the first output, t is time, G_FF is the feedforward function, and m is the information from the current time step. In another example, the feedback gain scheduling method is defined by u_FB(t)=G_FB(m), where u_FB(t) is the second output, t is time, G_FB is the feedback function, and m is the behavior information from the previous time step.
[0007]
[0006] In another example, the method further includes repeating the steps of receiving information, determining an prior estimate, determining an ex-post estimate, and determining a final control signal over a plurality of forward time steps. In this example, the method may include repeating the steps of receiving information, determining an ex-post estimate, and determining a final control signal over a plurality of forward time steps, wherein the prior estimate is not determined in at least one forward time step, and the final control signal in at least one forward time step is based solely on an ex-post estimate. Or, in addition, the method may include repeating the steps of receiving information, determining an prior estimate, and determining a final control signal over a plurality of forward time steps, wherein the ex-post estimate is not determined in at least one forward time step, and the final control signal in at least one forward time step is based solely on an prior estimate.
[0008]
[0007] In a further example, the operation of the optical assembly of the first communication device based on the determined final control signal includes adjusting the target position or setpoint position. In another example, the method further includes commanding the telecommunications device to adjust the target position or setpoint position based on the determined final control signal.
[0009]
[0008] In another embodiment, a communication device is provided. The communication device includes a transmitter configured to transmit an outbound optical signal to a telecommunications device, a receiver configured to receive an inbound optical signal from the telecommunications device, and one or more processors. The processors are configured to determine an expediency estimate showing a first error related to the effect of at least one external disturbance in the current time step, a posterior estimate showing a second error related to the effect of at least one external disturbance in a previous time step, and a final control signal based on the expediency and posterior estimates. The communication device also includes a steering mechanism configured to adjust the communication device based on the final control signal when instructed by one or more processors.
[0010]
[0009] In one example, the prior and subsequent estimates are determined based on information indicating at least one external disturbance. Here, the information indicating at least one external disturbance includes behavioral information of the telecommunications device from a previous time step. One or more processors may be further configured to map information from the current time step to a first output by a feedforward gain scheduling technique and behavioral information from the previous time step to a second output by a feedback gain scheduling technique. In this example, the first output is the prior estimate and the second output is the subsequent estimate. In one scenario here, the feedforward gain scheduling technique can be defined by u_FF(t) = G_FF(m), where u_FF(t) is the first output, t is time, G_FF is the feedforward function, and m is information from the current time step. Alternatively, the feedback gain scheduling method can be defined by u_FB(t) = G_FB(m), where u_FB(t) is the second output, t is time, G_FB is the feedback function, and m is the behavior information from the previous time step. In further examples of any of the above configurations, the communication device may be stationary or mobile. [Brief explanation of the drawing]
[0011] Brief explanation of the drawing [Figure 1]
[0010] This is a block diagram of a first communication device and a second communication according to an aspect of the present disclosure. [Figure 2A]
[0011] This is a diagram of the components of the first and second communication devices according to an aspect of the present disclosure. [Figure 2B]
[0011] This is a diagram of the components of the first and second communication devices according to an aspect of the present disclosure. [Figure 3]
[0012] A block diagram of an FSOC terminal according to this technology is shown. [Figure 4]
[0013] This is a diagram illustrating an example of a network according to the nature of this disclosure. [Figure 5]
[0014] This is a diagram showing the results of the corrections made according to the aspects of this disclosure. [Figure 6]
[0015] An example of a motion compensation method according to the aspects of this disclosure is shown. [Figure 7]
[0016] An example of a method according to the aspects of this disclosure is shown. [Modes for carrying out the invention]
[0012] Detailed explanation
[0017] Implementations of the Disclosure will be described in detail with reference to drawings in which similar reference numerals identify similar or identical elements. It should be understood that the disclosed implementations are merely examples of the Disclosure and can be embodied in various forms. The specific structural and functional details disclosed herein should not be constrained, but rather should be interpreted merely as the basis for the claims and as representative grounds to teach those skilled in the art to employ the Disclosure in various forms in virtually any appropriately detailed structure.
[0013] System example
[0018] Figure 1 is a block diagram 100 of a first communication device of a first communication terminal, configured to form one or more links with a second communication device 122 of a second communication terminal, for example, as part of a system such as an FSOC system. For example, the first communication device 102 includes, as components, one or more processors 104, memory 106, transmitter 112, receiver 114, steering mechanism 116, and one or more sensors 118. The first communication device 102 may include other components not shown in Figure 1.
[0014]
[0019] One or more processors 104 may be any hardware-based processor, such as a commercially available CPU. Alternatively, one or more processors may be dedicated devices, such as application-specific integrated circuits (ASICs) or other hardware-based processors, such as FPGAs. In one embodiment, processor 104 may be configured to perform estimations related to the tracking behavior of a remote device (e.g., a second communication device 130 or a client device). This estimation indicates where the remote terminal is located at a given forward time step. When performing tracking behavior estimation, processor 104 may implement various modules (e.g., a feedforward module 602 and a feedback module 606, described later in relation to Figure 6). Figure 1 functionally shows one or more processors 104 and memory 106 in the same block, but one or more processors 104 and memory 106 may actually include multiple processors and memories, which may or may not be housed in the same physical housing. Thus, references to processors or computers are understood to include references to a set of processors or computers or memories, which may or may not operate in parallel.
[0015]
[0020] Memory 106 may store information accessible by one or more processors 104, including data 108 and instructions 110 that can be executed by one or more processors 104. Memory can be any type of computer-readable medium capable of storing processor-accessible information, including hard drives, memory cards, ROMs, RAMs, DVDs, or other optical discs, as well as other writable and read-only memories. The system and method may include various combinations of the above, so that different parts of the data 108 and instructions 110 are stored on different types of media. Calibration information, such as one or more offsets determined for tracking signals, may be stored within the memory of each communication device, such as memory 106.
[0016]
[0021] Data 108 can be acquired, stored, or modified by one or more processors 104 according to instructions 110. For example, although the present technology is not limited by a particular data structure, data 108 can be stored in a relational database as a table with multiple different fields and records, an XML document, or a flat file within a computer register.
[0017]
[0022] Instructions 110 can be any set of instructions that are executed directly (such as machine code) or indirectly (such as a script) by one or more processors 104. For example, instructions 110 can be stored as computer code on a computer-readable medium. In that regard, the terms "instructions" and "program" can be used interchangeably herein. Instructions 110 may be stored in object code form for direct processing by one or more processors 104, or may be stored in any other computer language including scripts or a collection of independent source code modules that are interpreted on demand or pre-compiled. The functions, methods, and routines of instructions 110 will be described in more detail below.
[0018]
[0023] One or more processors 104 communicate with a transmitter 112 and a receiver 114. The transmitter 112 and the receiver 114 can be part of a transceiver configuration within the first communication device 102. Thus, one or more processors 104 can be configured to transmit data within a signal by the transmitter 112 and can also be configured to receive communications and data within a signal by the receiver 114. The received signal can be processed by one or more processors 104 to extract communication data and / or beacon information.
[0019]
[0024] As shown in Figure 1, the transmitter 112 of the first communication device 102 is configured to output the beacon beam 120 in order to establish a communication link 122 with the second communication device 130 which receives the beacon beam 120. The first communication device 102 can collinearly align the beacon beam 120 with an optical communication beam (not shown) that has a solid angle narrower than or the same angle as the beacon beam 120 and can carry the communication signal 124. Therefore, when the second communication device 130 receives the beacon beam 120, the second communication device 130 can establish a line-of-sight link with the first communication device 102 or align with the first communication device. As a result, a communication link 122 can be established that enables the transmission of the optical communication beam (not shown) from the first communication device 102 to the second communication device 130. Alternatively, the transmitter of the first communication device 102 may be configured to establish a communication link with the second communication device 130 without utilizing the beacon beam.
[0020]
[0025] In one embodiment, the transmitter 112 includes an optical transmitter, an amplifier, and an attenuator. As shown in the configuration example illustrated by the block diagrams and system diagrams of Figures 2A and 2B, the transmitter 112 includes a seed laser 202 configured to provide a certain amount of bandwidth for one or more output signals, an amplifier 204 such as an erbium-doped fiber amplifier (EDFA) configured to increase the amplitude of the output signal, and an attenuator 206 such as a single-mode variable optical attenuator (SMVOA) or a variable optical attenuator (VOA), which may be a multi-mode VOA (MMVOA), configured to decrease the amplitude of the output signal. As shown in Figure 2B, the output of the attenuator 206 is supplied into the amplifier 204 together with the seed laser output signal. This architecture allows the transmitter 112 to output a beacon beam 120 and one or more communication signals on one or more communication links 122, enabling one communication device to locate another communication device. In addition, as shown in Figure 1, the transmitter 112 is configured to output a beacon beam 120 and a communication signal on the communication link 122, enabling one communication device to locate another. Therefore, the output signal from the transmitter 112 may include the beacon beam 120, the communication signal, or both. The communication signal may be a signal configured to travel through free space, such as a radio frequency (RF) signal or an optical signal, as indicated by the propagation path 208. In some cases, the transmitter includes a separate beacon transmitter configured to transmit the beacon beam and one or more communication link transmitters configured to transmit the optical communication beam. Alternatively, the transmitter 112 may include a single transmitter configured to output both the beacon beam and the communication signal. The beacon beam 120 can illuminate a larger solid angle in space than the optical communication beam used on the communication link 122, allowing the communication device receiving the beacon beam to more accurately locate the beacon beam. For example, a beacon beam carrying a beacon signal can cover an angular region on the order of 1 square milliradian, while an optical communication beam carrying a communication signal can cover an angular region on the order of 1 / 100th of a square milliradian.Alternatively, if the first communication device 102, the second communication device 130, or both already know the location of the other, the beacon beam carrying the beacon signal may not be necessary. In such a scenario, the transmitter 112 of the first communication device 102 can transmit the communication link 122 without the beacon beam 120.
[0021]
[0026] The receiver 114 includes a tracking system configured to detect the optical signal. As shown in the example in Figures 2A and 2B, the receiver 114 of the optical communication system may include an attenuator 210, such as a multimode variable optical attenuator configured to adjust the amplitude of the received signal, a photodetector 212, and / or a photodiode 214. Using the photodetector 212, the receiver 114 can detect the signal position and convert the received optical signal from the propagation path 216 into an electrical signal using the photoelectric effect. The receiver 114 can track the received optical signal, which may be used to instruct the steering mechanism 116 to cancel out disturbances due to scintillation and / or platform movement. The system can process the signal output from the photodetector 212 by performing, for example, integration, low-pass filtering, and / or window-based sampling. In the example in Figure 2B, in block 218, the resulting signal is combined with the outputs from the attenuator 210 and the photodiode 214. The combined signal can then be processed by the controller 220, whose output controls the operation of the seed laser 202 and the attenuator 206. For example, each communication channel can be adjusted independently, for instance, by adjusting the seed laser output for each channel.
[0022]
[0027] Returning to Figure 1, one or more processors 104 communicate with the transmitter 112, the receiver 114, and / or a steering mechanism 116 for adjusting the direction of the optical signal. The steering mechanism 116 may include one or more mirrors that steer the optical signal through a fixed lens, and / or a gimbal configured to move the transmitter 112 and / or receiver 114 relative to the communication device. Specifically, the steering mechanism 116 may be a MEMS two-axis mirror, a two-axis voice coil mirror, or a piezoelectric two-axis mirror. The steering mechanism 116 may be configured to steer the transmitter, receiver, and / or the optical signal in at least two degrees of freedom, such as yaw and pitch. Directional adjustment may be performed to capture or align a communication link, such as the communication link 122 between the first communication device 102 and the second communication device 130. To perform a search for a communication link, one or more processors 104 may be configured to use a steering mechanism 116 to orient the transmitter 112 and / or receiver 114 in a series of changing directions until the communication link is acquired. In addition, the adjustment can optimize the transmission of light from the transmitter 112 and / or the reception of light in the receiver 114.
[0023]
[0028] One or more processors 104 also communicate with one or more sensors 118. One or more sensors 118 may be configured to monitor the status of the first communication device 102. In some implementations, one or more sensors may include standalone inertial measuring devices such as accelerometers and / or gyroscopes configured to measure or estimate selected forces. In some implementations, one or more sensors may be integrated into an inertial measuring unit (IMU) having one or more accelerometers, magnetometers, and / or gyroscopes configured to measure one or more of attitude, angle, velocity, angular velocity, etc., or into other sensors having one or more encoders or other components that can measure or estimate torque and other forces. In addition, sensors 118 may include one or more sensors configured to measure various environmental conditions such as temperature, wind, radiation, precipitation, humidity, etc. In this regard, one or more sensors 118 may include thermometers, barometers, hygrometers, etc. In Figure 1, one or more sensors 118 are shown in the same block as the other components of the first communication device 102; however, in some implementations, some or all of the one or more sensors may be separated and isolated from the first communication device 102.
[0024]
[0029] The second communication device 130 includes one or more processors 132, a memory 134 for storing data 136 and instructions 138, a transmitter 140, a receiver 142, a steering mechanism 144, and one or more sensors 146. The one or more processors 132 may be the same as the one or more processors 104 described above. The memory 134 may store information accessible by the one or more processors 132, including data 136 and instructions 138 that can be executed by the processor 124. The memory 134, data 136, and instructions 138 may be configured in the same way as the memory 106, data 108, and instructions 110 described above. In addition, the transmitter 140, receiver 142, steering mechanism 144, and sensors 146 of the second communication device 130 may be the same as the transmitter 112, receiver 114, and steering mechanism 116 described above.
[0025]
[0030] Similar to transmitter 112, transmitter 140 may include an optical transmitter, an amplifier, and an attenuator. As shown in Figure 2, transmitter 140 includes a seed laser 222 configured to provide a certain amount of bandwidth for the output signal, an amplifier 224 such as an EDFA configured to increase the amplitude of the output signal, and an attenuator 226, such as an SMVOA or MMVOA, configured to decrease the amplitude of the output signal. As shown in Figure 2, the amplifier 224 causes the output signal to be transmitted along the propagation path 216. As described above for communication device 102, each communication channel transmitted from communication device 130 can also be adjusted independently, for example, by adjusting the seed laser output for each channel. In addition, as shown in Figure 1, transmitter 140 may be configured to output both an optical communication beam and a beacon beam. For example, transmitter 140 of a second communication device 130 can establish a communication link 128 with a first communication device 102 that outputs a beacon 126 and receives the beacon beam 126. The second communication device 130 can collinearly align the beacon beam 126 with an optical communication beam (not shown) that has a narrower solid angle than the beacon beam and carries another communication signal. Therefore, when the first communication device 102 receives the beacon beam 126, the first communication device 102 can establish a line of sight with the second communication device 130 or align with the second communication device. As a result, a communication link 128 can be established that enables the transmission of the optical communication beam (not shown) from the second communication device 130 to the first communication device 102. Alternatively, if the first communication device 102, the second communication device 130, or both already know the position of the other, the beacon beam carrying the beacon signal may not be necessary. In such a scenario, the transmitter 140 of the second communication device 130 can transmit the communication link 128 without the beacon beam 126.
[0026]
[0031] Similar to receiver 114, receiver 142 includes a tracking system configured to detect the optical signal as described above with respect to receiver 114. As shown in Figure 2A, receiver 114 for the optical communication system may include an attenuator 228, such as a single-mode or multi-mode variable optical attenuator, configured to adjust the amplitude of the received signal, a photodetector 230, and / or a photodiode 232. Other components similar to those depicted in the first communication device 102 may be included in the second communication device 130. Using the photodetector 230, receiver 142 can detect the signal position and convert the received optical signal into an electrical signal using the photoelectric effect. Receiver 142 can track the received optical signal, which may be used to instruct the steering mechanism 144 to counteract disturbances caused by scintillation and / or platform movement.
[0027]
[0032] Returning to Figure 1, as described above with respect to the steering mechanism 116, one or more processors 124 communicate with the transmitter 140, the receiver 142, and / or the steering mechanism 144 for adjusting the direction of the optical signal. The adjustment of the direction of the signal may be performed to establish a capture and connection link between the first communication device 102 and the second communication device 130. In addition, as described above with respect to one or more sensors 118, one or more processors 132 communicate with one or more sensors 146. One or more sensors 146 may be configured to monitor the state of the second communication device 130 in the same or similar manner as one or more sensors 118 are configured to monitor the state of the first communication device 102.
[0028]
[0033] As shown in Figure 1, when the transmitters and receivers of the first communication device 102 and the second communication device 130 are aligned or in linked directional directions, communication links 122 and 128 can be formed between the first and second communication devices. Using communication link 122, one or more processors 104 can transmit communication signals to the second communication device 130. Using communication link 128, one or more processors 132 can transmit communication signals to the first communication device 102. In some examples, it is sufficient to establish one communication link between the first communication device 102 and the second communication device 130, thereby enabling bidirectional data transmission between the two devices. In these examples, the communication links are FSOC links. In other implementations, one or more of the communication links may be RF communication links or other types of communication links that can propagate in free space.
[0029] Example of device configuration
[0034] Figure 3 shows a block diagram of an example configuration 300 of an FSOC terminal for use with embodiments of this technology. While not intended to be limiting, this example may have a monostatic design with a single 75 mm open port for transmitting and receiving light. Here, the terminal can emit three (or more) laser wavelengths (e.g., two (or more) for 10 Gbps telecommunications signals and one beacon dedicated to tracking) and similarly receive three (or more) laser beams of different wavelengths (all of which may be within 100 nm of 1550 nm). Note that the signals transmitted at each wavelength may have different throughput and / or different modulation formats. The dashed lines in Figure 3 show the paths of the laser beams received by and emitted from the terminal.
[0030]
[0035] The receiver path is as follows: Three laser beams are incident on a terminal aperture window 302, which is preferably hydrophobic and anti-reflective coated, and then on a coarse pointing mirror (CPM) 304. The beams reflected by the CPM 304 pass through a telescope with a reduction ratio of approximately 40. The telescope in this example includes a first lens 306a and a second lens 306b. In the conjugate plane in the reduced space, the beams are incident on a fast steering mirror (FSM) 308.
[0031]
[0036] After being reflected by mirror 308, the beam is incident on dichroic beam splitter 310, which reflects the beacon wavelength and transmits two communication laser beams. The beacon laser reflected by the dichroic mirror is focused onto position detector (PSD) 313 by lens 312, from which the center of the focused spot on the sensor surface can be calculated by a pointing, acquisition, and tracking (PAT) module 314 such as a DSP. This input and information from one or more external sensors, indicated by the dotted arrow 316, are used by the PAT module 314 as feedback to adjust the pointing direction of the two mirrors (CPM 304 and FSM 308). The beacon laser may be modulated at a low frequency (e.g., on the order of 1-3 kHz or so) in the receiver processing chain to enable optical background and clutter removal by narrowband filtering near the modulation frequency before the center of the signal beam is calculated.
[0032]
[0037] The telecommunications beam (two wavelengths) transmitted through the dichroic beam splitter 310 is focused onto a fiber such as a multimode receiver fiber via a collimator lens 318 (dashed double arrow 320). The fiber-coupled beam is directed to the receiver photonics components through a circulator 322. Here, the beam can be initially tuned by an actively controlled multimode variable optical attenuator (VOA) 324 to ensure that the incident power to the downstream photodetector is at an optimal threshold. Next, the telecommunications wavelengths are multiplexed, separated, and filtered in block 326 and detected by high-bandwidth and high-sensitivity avalanche photodiodes in blocks 328a and 328b. After detection, the signal can be amplified, tuned, and converted into bits by clock and data recovery (not shown). In block 330, a high-speed modem processor is configured to extract data packets from the communication signal (e.g., an Ethernet-type telecommunications signal) and transmit those data packets over one or more optical fiber client ports 332.
[0033]
[0038] The transmitter's path is primarily the reverse of the receiver's path. For example, client-side Ethernet or other communication traffic enters the terminal through one or more optical fiber ports 334. In block 330, a modem processor is configured to structure packets into frames optimized for transmission over the wireless optical channel. Frames for each communication channel are processed independently and intensity-modulated to two seed lasers in blocks 336a and 336b. The beacon power can be adjusted relative to the communication beam by a variable optical attenuator (VOA) 340. The two laser beams are combined in a multiplexer 342 along with the beacon laser beam generated in block 338 prior to the VOA 340. The combined three wavelengths in a single-mode fiber (indicated by the dotted arrow 344) are amplified in an erbium-doped optical amplifier (EDFA) 346 and propagated into a third port of a circulator 322, thereby emitting the three wavelengths into free space through the terminal aperture window 302 from the same port that receives the light in the receiver's path.
[0034]
[0039] In this configuration example, the circulator 322 has three ports: a bidirectional port for dual single and multimode cores facing free space, a multimode receiver output port, and a single-mode transmitter input port. This circulator allows the system to operate in a monostatic configuration with single-mode transmission but multimode reception, which is advantageous for terrestrial communications where the atmosphere causes significant wavefront and radiation distortion. The three transmission beams cross the optical path in the terminal in opposite directions, are reflected by the FSM 308 and CPM 304, and then exit the terminal through the aperture 302. The dashed arrow 348 indicates that the PAT module 314 is configured to adjust the CPM 304, and the dotted arrow 350 indicates that the PAT module 314 is also configured to adjust the FSM 308.
[0035]
[0040] In one example, the line of sight between two terminals can be maintained by a two-stage active tracking system. The coarse-grabbing tracking mechanism (CPM304 in Figure 3) is primarily responsible for compensating for disturbances with large angles (e.g., on the order of a few degrees) but rather low frequencies (e.g., on the order of less than 1 Hz). Examples include movement of the mounting structure due to temperature changes during the day or low-frequency vibrations of the pole due to wind. The high-speed steering mirror (FSM308 in Figure 3) compensates for disturbances with high frequencies (approximately several tens of Hz) but small absolute angular ranges (e.g., on the order of several tens to several hundred μrads). Examples include vibrations from nearby equipment or high-frequency excitation of the mounting structure due to wind.
[0036]
[0041] An example block diagram 300 in Figure 3 illustrates the controller (e.g., PAT module 314) for a two-stage active tracking system. The inclination angle of the beam entering the terminal has a one-to-one correspondence with the center of the spot incident on the position detector (313 in Figure 3). The signal obtained by this detector is first subjected to a band-pass filter near the modulation frequency to remove out-of-band background and clutter, then demodulated to the baseband, and subsequently processed to estimate the center of the spot. These estimations inform the controller (PAT module 314) of changes in the incident angle of the beam arriving from the remote terminal due to platform movement (θp(t)) and beam wander in the atmosphere (θc(t)). Appropriate integration time is required to obtain estimations with a sufficient signal-to-noise ratio. In some scenarios, the beam center estimation may be updated at a rate of several hundred Hz or so.
[0037]
[0042] The difference between the estimated beam center and the target tracking position on the position detector (corresponding to the system's optical boresight) is the error signal input to the controller of the PAT module 314. This controller is configured to command the FSM308 and CPM304 of the pointing assembly to attempt to drive the error signal to zero (or as low as possible). The resulting operation of these two mirrors changes the arrival (and departure) angle of the laser beam (see the resulting pointing angle θ(t)) and closes the feedback loop.
[0038]
[0043] In one scenario, a terminal providing free-space optical communication can be deployed as a telecommunications device that passes traffic arriving through an optical fiber client Ethernet port. For example, there may be multiple communication channels, each independently running 10G-based Ethernet from input to output. To ensure robust communication across turbulent air, the modem core can employ forward error correction and hybrid automatic retransmission requests (ARQ). Note that there may be separate modem instances for each channel.
[0039] Example of a communication system configuration
[0044] As shown in Figure 4, a plurality of communication devices, such as the first communication device 102 and the second communication device 130, may be configured to form a network 400 by forming a plurality of communication links (indicated by arrows) between a plurality of communication terminals. The network 400 may include client devices 410 and 412, a server device 414, and communication devices 102, 130, 420, 422, and 424. Each of the client devices 410, 412, the server device 414, and the communication devices 420, 422, and 424 may include one or more processors, memory, transmitters, receivers, and steering mechanisms similar to those described above. Using transmitters and receivers, each communication device in the network 400 can form at least one communication link with another communication device, as indicated by arrows. The communication links may be for optical frequencies, radio frequencies, other frequencies, or a combination of various frequency bands. In Figure 4, it is shown that communication device 102 has communication links with client device 410 and communication devices 130, 420, and 422. It is shown that communication device 130 has communication links with communication devices 102, 420, 422, and 424. Each client device may be able to communicate with other client devices and / or server devices via one or more intermediate communication devices.
[0040]
[0045] The network 400 shown in Figure 4 is illustrative, and in some implementations, network 400 may include additional or different communication terminals. Network 400 may be a land network with multiple communication devices on multiple ground communication terminals. In other implementations, network 400 may include one or more high-altitude platforms (HAPs), which may be balloons, airships or other flying boats, airplanes, unmanned aerial vehicles (UAVs), or any other form of high-altitude platform configured to operate in the stratosphere, or other types of mobile or stationary communication terminals. In addition or otherwise, one or more communication devices may be satellites orbiting the Earth. In some implementations, network 400 may function as an access network for client devices such as mobile phones, laptop computers, desktop computers, wearable devices, or tablet computers. Network 400 may be connected to a larger network such as the Internet, and may be configured to provide client devices with access to resources stored on or provided by a larger computer network, such as a cloud computing network, which may include one or more remote server arrays.
[0041] Example of a method
[0046] In addition to the embodiments described and illustrated above, various operations will now be described. It should be understood that the following operations do not need to be performed in the exact order described below. While maintaining the communication link, one or more processors 104 of the first communication device 102 are configured to track a remote device (e.g., a second communication device 130 or a client device). Tracking the remote device involves adjusting the control inputs so that the mirror actuators effectively track the beam target position or setpoint in order to ensure the integrity of the communication link connection. The method described herein is configured to function whether the first communication device 102 is stationary or mobile.
[0042]
[0047] To track a remote device, one or more processors 104 of the first communication device 102 are configured to perform corrections or adjustments due to internal and external disturbances that cause errors related to the tracking behavior of the remote communication device. Correcting errors includes making an estimate of where the remote terminal is located in a given forward time step. Such estimations or other corrections may be both pre- and post-facto.
[0043]
[0048] One or more processors 104 can perform a pre-feedforward estimation based on information about external disturbances (e.g., wind speed measurement, mount motion measurement) received from one or more sensors 146 of the second communication device 130, one or more sensors 118 of the first communication device 102, or both. The information (e.g., measurement of disturbance or measurement of the effect of disturbance) may be obtained from an IMU such as those described above, including, for example, gyroscopes or accelerometers of one or more sensors 118, 146. This information may be from the current time step. The pre-estimate may include calculating the attitude or other positioning, angular velocity, acceleration, or any combination thereof of the second communication device 130 based on the obtained information. This information, attitude / positioning, angular velocity, acceleration, or any combination thereof may then be used to determine the estimated position of the second communication device 130 in the next time step. When determining the estimated position, one or more processors 104 can calculate a first error. The first error indicates the effect of disturbances on the position of the second communication device 130 in the preceding time step. In implementations where the first communication device is mobile, additional inputs such as linear velocity, acceleration, or GPS readings can be implemented in the feedforward estimation.
[0044]
[0049] In some implementations, one or more processors 104 utilize a gain scheduling method when determining the prior estimation. Utilizing a gain scheduling method involves modeling the behavior of the telecommunications device based on a mapping of input elements to an output by deterministic or dynamic mapping, where the output is a function of the input elements. The function may be a transfer function capable of modeling the behavior of a second communication device 130. For example, one or more processors 104 may, u_FF(t)=G_FF(m) The input elements can be mapped to the output u_FF by the feedforward function G_FF, where t is time and m is one or more input elements. The function G_FF is such that m is either a static or dynamic gain. * It can be a scaling of input elements such as G, and G_FF may be a general algebraic function such as f(m). G_FF is m * It can also take the form of T, where T is a transfer function related to approximations of system dynamics, sensor dynamics, etc. The input element function may include piecewise parts where certain parts of the function output zero or turn off for certain small input values. For example, the function can be a piecewise lookup table, where G_FF(m)=m * G is such that for an input of (0,1), G=2; for an input of (1,3), G=3; and for an input of <1, G=0 (it turns off for input values smaller than this), and so on.
[0045]
[0050] In such an implementation utilizing gain scheduling, the input element m used may include information about external disturbances. The mapping output shows the estimated position (e.g., attitude, angular velocity, acceleration, or any combination thereof) or the position itself and the first error of the second communication device 130 in the next time step.
[0046]
[0051] One or more processors 104 can perform retrospective feedback-based estimations based on the behavior of the remote terminal in the current time step and the previous time step, where the behavior indicates external disturbances. The behavior may include elements such as the remote terminal's position (e.g., setpoint), attitude, angular velocity, acceleration, and previous setpoint or target position. The behavior is based on information about external disturbances (e.g., wind speed measurement, mount motion measurement) received from one or more sensors 146 of the second communication device 130, one or more sensors 118 of the first communication device 102, or both, from at least one previous time step. The behavior information can then be used to determine the estimated position of the second communication device 130 in the next time step. When determining the estimated position, one or more processors 104 can calculate a second error, which indicates the effect of disturbances on the position of the second communication device 130 in the current time step. Similar to the prior prediction discussed above, post-hoc estimation can implement a gain scheduling technique when determining the post-hoc estimated position and the second error. In such an implementation, one or more processors, u_FB(t)=G_FB(m) The feedback function G_FB can be used to achieve the following, where u_FB is the output, t is time, and m is the input element. The input elements for gain scheduling may include, for example, behavioral information. Furthermore, in implementations where the first communication device is mobile, additional inputs such as linear velocity, acceleration, or GPS readings can be implemented in the feedback estimation.
[0047]
[0052] One or more processors 104 can determine the final control signal based on prior and subsequent estimations. The final control signal includes considering a first error and a second error. In some implementations, the final control signal may be determined, for example, by summing the first error and the second error. When the output functions u_FF and u_FB are the first error and the second error, respectively, the final control signal is: u_F = u_FF + u_FB This can be expressed as follows, where u_F is the final control signal. In some implementations, u_F, u_FF, and u_FB are control inputs that can be supplied to the controller of the communication device (e.g., the PAT module 314). Using the final control signal, one or more processors 104 of the first communication device 102 can adjust the control inputs of the actuator. In some implementations, one or more processors 104 may determine only the first error or only the second error. In such cases, the final control signal is the same as the first or second error, depending on which is determined. Either determination can be throttled on and off at any time step.
[0048]
[0053] Using control inputs from one or more processors 104, a controller (e.g., of the PAT module 314) can transmit control signals to the actuator of the steering mechanism 116 of the first communication device 102, enabling the actuator to effectively track a target position or setpoint position. For example, the control signals can cause the actuator to make adjustments. Adjustments may include the controller instructing the steering mechanism 116 to adjust the target position or setpoint of a sensor in the receiver 114, the transmitter 112, or both. This adjustment can be achieved by steering the mirror of the first communication device 102 or by shifting the setpoint by shifting the phase of the signal generated in the sensor. In some implementations, the first communication device 102 may, in addition to or instead of the adjustments performed by the first communication device 102, instruct the controller of the second communication device 130 or the client device to perform adjustments. In any scenario, the mirror of either communication device may be steered on multiple axes. One or more processors 104 can repeatedly determine the first error, the second error, and the final control signal for each consecutive time step. The time step may be every 0.1 or 1.0 seconds or less.
[0049]
[0054] Figure 5 shows an example 500 in which a setpoint or target position is adjusted based on control inputs from one or more processors 104. Position 502 represents the setpoint in the previous time step. One or more processors 104 may make a first adjustment 504 from position 502 to position 506 based on a first error. Then, one or more processors may make a second adjustment 508 from position 506 to position 510 based on a second error. Position 510 corresponds to the position considering both the first and second errors (i.e., the setpoint considering the final control signal in the current time step). Each adjustment is such that the final position 510 is closer to the zero-error position 512 than to position 502 from the previous time step. The actuators of the steering mechanisms 116 and / or 144 may or may not make separate first adjustments 504 and second adjustments 508 from position 502 to position 506 and position 510. The actuators of the steering mechanisms 116 and / or 144 may directly perform one adjustment corresponding to the first adjustment 502 and the second adjustment 508 from position 502 to position 480.
[0050]
[0055] Figure 6 shows an example of a motion compensation method 600 according to the methodology described above. At a specific time step, the feedforward module 602 receives sensor data 604 for use in determining a prior estimate. According to one aspect of this technique, the sensor data 604 is obtained by the device's IMU. The feedback module 606 receives behavioral information about the current and previous velocity, acceleration, and position (e.g., input setpoint 608) of the telecommunications device. The feedforward module outputs a first error, and the feedback module outputs a second error. The first and second errors are used to create a control input received by the controller 610 so that the controller 610 can send a control signal 612 indicating the tracking error to the steering mechanisms 116 and / or 144. In this technique, the tracking error may be added to the input information 608 at node 614 and supplied to the feedforward module 602 as indicated by the dashed arrow 616.
[0051]
[0056] Given that this pre- or predictive control system method is configured to compensate for errors before they are observed by the device's control system, it can result in a greater reduction in tracking errors than a purely post-facto system. In one embodiment, pre-control uses information from an IMU (including its gyroscope) that can predict the effects of rotational terminal motion caused by a land source (e.g., mount vibration) or an aerial source (e.g., wind, bird landing, etc.).
[0052]
[0057] This system can switch between predetermined and adaptive gains. The predetermined gain is a method for eliminating the effects of higher-than-desirable gyroscope noise, which can occur in inexpensive components and cause higher tracking noise during low-speed platform motion within the compensation capacity of the feedback system. When the platform's angular velocity begins to exceed the compensation capacity of the feedback system (e.g., feedback module 606), the obtained gyroscopic measurements can be multiplied by the output of a sliding scale algorithm (e.g., a linear or nonlinear equation) to reach the full gain when the platform's angular velocity requires full feedforward compensation. The output of the feedforward module is then added to the output of the feedback module, directly affecting the drive signal of the mirror actuator. This can improve tracking performance by up to 10 dB or more when compensating for the rotational motion of the platform, as measured by the RMS tracking error around the optical boresight.
[0053]
[0058] Figure 7 shows an example of a method 700 for adjusting the optical link alignment of a first communication device to a telecommunications device. As shown in block 702, the method includes receiving information indicating at least one external disturbance in the first communication device. In block 704, the method includes having one or more processors in the first communication device determine from that information an expiry estimate indicating a first error related to the effect of at least one external disturbance in the current time step. In block 706, the method includes having one or more processors in the first communication device determine from that information an expiry estimate indicating a second error related to the effect of at least one external disturbance in a previous time step. In block 708, the method includes having one or more processors determine a final control signal based on the expiry and expiry estimates. In block 710, the method includes having a controller actuate the optical assembly of the first communication device based on the determined final control signal.
[0054]
[0059] The features and methods described herein can provide optical communication systems with the ability to maintain communication links using less power output than typical systems, and improved tracking capabilities that result in higher communication performance, such as lower bit error rates and higher signal-to-noise ratios. The system can achieve increased availability, for example, 20% to 100% compared to 0% or near 0% without the features and methods described herein. The system enables more accurate beam targeting without the use of high-power beacon transmission to track remote terminals. Tracking without beacon transmission improves link throughput, enhances link tracking stability, and allows operation over a wider range of link distances with less power. Because the components within the communication system are fewer and / or smaller, and adjustments can be made at a smaller scale, the features described herein also allow for the use of narrower beamwidths, making the system more compact and efficient.
[0055]
[0060] Those skilled in the art will understand, by referring to the above and the various drawings, that it is possible to make certain modifications to this disclosure without departing from the scope of this disclosure. Although several implementations of this disclosure have been shown in the drawings, this disclosure is broad in scope as the art permits and this specification is intended to be read similarly, so this disclosure is not intended to be limited to such implementations. Accordingly, the above description should not be interpreted as limiting, but merely as an example of a particular implementation.
Claims
1. A method for adjusting the optical link alignment of a first communication device with respect to a telecommunications device, The first communication device receives information indicating at least one external disturbance, The first communication device comprises determining, from the information, a prior estimate of a first error relating to the influence of at least one external disturbance in the current time step, wherein determining the prior estimate includes mapping the information from the current time step to a first output by a feedforward gain scheduling method, The one or more processors of the first communication device determine from the information a retrospective estimate of a second error relating to the effect of the at least one external disturbance in the previous time step, The one or more processors determine the final control signal based on the prior estimation and the subsequent estimation, The controller operates the optical assembly of the first communication device based on the final control signal determined above. Methods that include...
2. The method according to claim 1, wherein the information indicating at least one external disturbance includes behavioral information of the telecommunications device from the previous time step.
3. The method according to claim 2, wherein the behavior information includes a set of elements related to the remote communication device.
4. The method according to claim 3, wherein the set of elements includes at least one of the following: the position of the telecommunications device, the orientation of the telecommunications device, the angular velocity of the telecommunications device, the acceleration of the telecommunications device, or the target position of the telecommunications device.
5. The method according to claim 2, wherein the behavior information is based on information regarding the at least one external disturbance in the previous time step, received from one or more sensors that the remote communication device communicates with or from one or more sensors that the first communication device communicates with.
6. Determining the prior estimate includes determining the first error, Determining the aforementioned ex post facto estimate includes determining the second error, The method according to claim 1.
7. The method according to claim 6, wherein the final control signal is determined by summing the first error and the second error.
8. Determining the aforementioned post-hoc estimation includes mapping the behavioral information from the previous time step to a second output using a feedback gain scheduling method, The first output is the prior estimate, The second output is the ex post estimate. The method according to claim 2.
9. The aforementioned feedforward gain scheduling method u_FF(t)=G_FF(m) Defined by, where u_FF(t) is the first output, t is time, G_FF is a feedforward function, and m is the information from the current time step. The method according to claim 8.
10. The aforementioned feedback gain scheduling method u_FB(t)=G_FB(m) Defined by, where u_FB(t) is the second output, t is time, G_FB is the feedback function, and m is the behavior information from the previous time step. The method according to claim 8.
11. The method according to claim 1, further comprising receiving the information, determining the prior estimate, determining the subsequent estimate, and determining the final control signal, repeated in a plurality of forward time steps.
12. The process further includes repeating the steps of receiving the aforementioned information, determining the subsequent estimation, and determining the final control signal over a plurality of forward time steps. The prior estimation is not determined in at least one forward time step, and the final control signal in the at least one forward time step is based solely on the subsequent estimation. The method according to claim 11.
13. The process further includes repeating the steps of receiving the aforementioned information, determining the prior estimation, and determining the final control signal over a plurality of forward time steps. The aforementioned post-hoc estimation is not determined in at least one forward time step, and the final control signal in the at least one forward time step is based solely on the aforementioned prior estimation. The method according to claim 11.
14. The method according to claim 1, wherein the controller operates the optical assembly of the first communication device based on the determined final control signal, which includes adjusting one or more actuators of the steering mechanism of the first communication device.
15. The method according to claim 1, further comprising instructing the remote communication device to adjust one or more actuators of the steering mechanism of the remote communication device based on the final control signal determined.
16. A communication device, A transmitter configured to transmit outbound optical signals to a remote communication device, A receiver configured to receive an inbound optical signal from the aforementioned remote communication device, By mapping information from the current time step to a first output using a feedforward gain scheduling method, a prior estimate is determined that shows a first error related to the influence of at least one external disturbance in the current time step. To determine a post-hoc estimate showing a second error relating to the effect of the at least one external disturbance in the previous time step, The final control signal is determined based on the aforementioned prior estimation and the aforementioned subsequent estimation. One or more processors configured to perform the following: A steering mechanism configured to adjust the communication device based on the final control signal when instructed by one or more of the aforementioned processors, Communication devices, including
17. The communication device according to claim 16, wherein the prior estimation and the subsequent estimation are determined based on information indicating the at least one external disturbance, and the information indicating the at least one external disturbance includes information on the behavior of the telecommunications device from the previous time step.
18. The aforementioned one or more processors The behavior information from the previous time step is mapped to the second output using a feedback gain scheduling method. It is further configured in this way, The first output is the prior estimate, and the second output is the post-estimation. The communication device according to claim 17.
19. The aforementioned feedforward gain scheduling method u_FF(t)=G_FF(m) Defined by, where u_FF(t) is the first output, t is time, G_FF is a feedforward function, and m is the information from the current time step. The communication device according to claim 18.
20. The aforementioned feedback gain scheduling method u_FB(t)=G_FB(m) Defined by, where u_FB(t) is the second output, t is time, G_FB is the feedback function, and m is the behavior information from the previous time step. The communication device according to claim 18.
21. The communication device according to claim 16, wherein the communication device is of a stationary type.
22. The communication device according to claim 16, wherein the communication device is mobile.