Reducing flicker noise in free space optical communication

Abstract

In some embodiments, an optical communication system may include a light source, a modulator, and an optical receiver. The light source may be configured to generate a beam comprising a series of light pulses. The optical receiver may have a detection window duration of 1 nanosecond or less. As the first pulse travels through a variable refractive medium, photons in the first pulse may be refracted, thus traveling along different ray paths to reach the optical receiver according to a time distribution curve. The full width at half maximum (FWHM) value of the time distribution curve may be greater than the coherence time value of the first pulse, and the detection window of the optical receiver may be greater than the FWHM value of the time distribution curve.

Description

[0001] Cross-reference to related applications

[0002] This patent application is a PCT international application and claims the benefit of U.S. nonprovisional serial number 17 / 932,364, filed September 15, 2022. The above application is incorporated herein by reference. Technical Field

[0003] The topics described in this article relate to free-space optical (FSO) wireless transmission, including optical communication, remote sensing, laser ranging, and power beam transmission, and more specifically to enhanced optical transmission efficiency achieved by using ultrashort pulse laser (USPL) sources to propagate beams through variable refractive media (e.g., the Earth's atmosphere) for wavelength propagation. Background Technology

[0004] FSO (Fiber Optic Spinning) communication has the potential to significantly increase data throughput, reduce costs, and increase access to high-speed internet and other communication technologies. However, to date, FSO communication systems have had limited success rates due to atmospheric interference, which shortens the distance over which data can be optically transmitted and introduces errors. Meanwhile, alternative communication technologies such as radio frequency (RF) and microwave communication face severe spectrum limitations and cannot be used to transmit sufficient data to meet demand. Currently available optical systems cannot produce sufficiently accurate, reliable, and usable data transmission results to reliably alleviate the communication burden on these RF and microwave systems and improve data transmission and access; furthermore, current optical systems are also unsuitable for long-distance data transmission.

[0005] Therefore, there is a need for optical communication systems capable of providing highly reliable and available data transmission over long distances. Furthermore, there is a need for optical communication systems capable of reliably transmitting data over long distances (e.g., half a mile or more). Summary of the Invention

[0006] The following is a simplified overview to provide a basic understanding of some of the aspects described herein. This overview is not an exhaustive summary of the claimed subject matter. It is not intended to identify the key or defining elements of the claimed subject matter, nor to define its scope.

[0007] In some embodiments, an optical communication system for optically transmitting data through a variable refractive medium may include a light source, a modulator, and an optical receiver. The light source may be configured to generate a beam comprising a series of light pulses, each having a duration of less than 100 picoseconds. The modulator may be configured to modulate the series of light pulses in response to a data transmission signal, thereby encoding transmitted data into the series of light pulses. The optical receiver may have a detection window duration of less than 1 nanosecond and a detection threshold. The optical receiver may be configured to indicate whether the optical energy received during a given detection window is greater than the detection threshold. The series of light pulses may include a first light pulse having a coherence length of less than 400 micrometers. As the first pulse travels through the variable refractive medium, photons in the first pulse may be refracted, thereby traveling towards the optical receiver along different ray paths of different lengths, and the photons of the first pulse may arrive at the optical receiver according to a time distribution curve that depends at least in part on the duration of the first pulse and the lengths of the different ray paths taken by the photons in the first pulse to reach the optical receiver. The full width at half maximum (FWHM) value of the time distribution curve can be at least three times the coherence time value equal to the coherence length of the first pulse divided by the speed of light passing through the variable refractive medium, and the detection window of the optical receiver can be at least six times the FWHM value of the time distribution curve.

[0008] In some embodiments, a laser ranging system may include a light source and a light receiver. The light source may be configured to generate a beam comprising a series of light pulses, each having a duration of less than 100 picoseconds. The light receiver may have a detection window duration of less than 1 nanosecond and a detection threshold. The light receiver may be configured to indicate whether the optical energy received during a given detection window is greater than the detection threshold. The series of light pulses may include a first light pulse having a coherence length of less than 400 micrometers. As the first pulse travels through a variable refractive medium, photons in the first pulse may be refracted, thus traveling towards the light receiver along different ray paths of different lengths. The photons of the first pulse may reach the light receiver according to a time distribution curve, which depends at least in part on the duration of the first pulse and the lengths of the different ray paths taken by the photons in the first pulse to reach the light receiver. The full width at half maximum (FWHM) value of the time distribution curve may be at least three times the coherence length of the first pulse divided by the coherence time value of the light speed through the variable refractive medium, and the detection window of the light receiver may be at least six times the FWHM value of the time distribution curve. The laser ranging system can be configured to send a series of light pulses toward a surface, receive at least a portion of the series of light pulses that has been reflected by the surface, and determine the distance of at least a portion of the surface relative to the laser ranging system based on the time of flight of the received portion of the series of light pulses.

[0009] Other variations covered within these systems and methods are described in the following detailed description of the invention. Attached Figure Description

[0010] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate certain aspects of the subject matter disclosed herein, and together with the textual description, help to explain certain principles associated with the disclosed embodiments.

[0011] Figure 1 An example of an optical communication platform is described, which includes a USPL source as a light source and free-space coupling for transmission to a remote optical receiving terminal.

[0012] Figure 2 An example of an optical communication platform is described, which includes an optical fiber coupling of a USPL source as a light source for transmission to a remote optical receiving terminal.

[0013] Figure 3 An example of an optical communication platform is described, which includes a USPL source coupled to an external modulator via optical fiber for transmission to a remote optical receiving terminal.

[0014] Figure 4 An example of an optical communication platform, including a USPL source, is described, which transmits to a remote optical receiving terminal via optical fiber coupling with an external modulator through an optical fiber medium.

[0015] Figure 5 Examples of transmitting and receiving elements are depicted, which may be of the type derived from hyperbolic mirror manufacturing techniques or conventional Newtonian designs.

[0016] Figure 6 An example of an optical fiber amplifier element is depicted, which is identified and used to enhance the transmission power of an optical transmitter for transmission to a remote optical receiving terminal.

[0017] Figure 7 An example of a USPL laser device is depicted in a point-to-point configuration, where an optical fiber is coupled to an external modulator for transmission to a remote optical receiving terminal.

[0018] Figure 8 An example of a USPL laser device coupled to an external modulator for transmission in a point-to-multipoint configuration is depicted.

[0019] Figure 9 An example of the use of a USPL source as a tracking and alignment (pointing) beacon source is depicted.

[0020] Figure 10An example of USPL laser source polarization is depicted, which is multiplexed onto the transmitted optical signal to provide polarization multiplexing USP-FSO (PM-USP-FSO) functionality.

[0021] Figure 11A and Figure 11B Examples of USPL-FSO transceivers used in line-of-sight laser communication applications and non-line-of-sight laser communication applications are described respectively.

[0022] Figure 12 This describes an example of light from a data signal propagating forward being backscattered due to its interaction with airborne particles that are the subjects of the investigation.

[0023] Figure 13 A USPL laser source is described as an optical receiving technique for improving detection sensitivity; examples of the USPL laser source and the optical receiving technique for improving detection sensitivity are also described.

[0024] Figure 14 An example of a USPL-FSO transceiver is depicted as a rangefinder and position determination device used and operated across an infrared wavelength range, optionally including light from data signals, for target identification purposes.

[0025] Figure 15 An example of a USPL pulse multiplier device consistent with the implementation of the present topic is depicted.

[0026] Figure 16 Another example of a device for generating high pulse rate USPL optical flow is depicted, consistent with the implementation of the present topic.

[0027] Figure 17 Another example of an optical device is depicted for generating USPL RZ data streams from conventional transmission networking elements.

[0028] Figure 18 An example of implementing a USPL pulse multiplier device for generating a 10×TDM type signal system to give a 100Gbps output is described.

[0029] Figure 19 An example of implementing another type of USPL pulse multiplier device to extend the pulse repetition rate for high-capacity networks is described.

[0030] Figure 20 An example of implementing another type of USPL pulse multiplier device to extend the pulse repetition rate for high-capacity networks is described.

[0031] Figure 21Examples of actively mode-locked linear fiber lasers with feedback regeneration systems are described: fiber reflectors (FR), wavelength division multiplexers (WDM), erbium-doped fiber (EDF), optical couplers (OC), photodetectors (PD), phase-locked loops (PLL), and Mach-Zehnder modulators (MZM).

[0032] Figure 22 and Figure 23 Examples of passively mode-locked linear fiber lasers using carbon nanotube saturable absorbers are described: fiber reflector (FR), wavelength division multiplexer (WDM), erbium-doped fiber (EDF), optical coupler (OC), and saturable absorber (SA).

[0033] Figure 24 Examples of time delay stabilization mechanisms are described: optical couplers (OCin, OCout), photodetectors (PDin, PDout), high-pass filters (HPF), low-pass filters (LPF), phase-locked loops (PLL), phase comparators (PC), frequency dividers (1 / N), clock data recovery systems (CDR), piezoelectric actuators (PZ1...PZN), and summing operational amplifiers, used to stabilize the pulse-to-pulse relationship of optical pulses generated from the USPL source.

[0034] Figure 25A and Figure 25B The diagrams and graphs include examples of control mechanisms that use idealized PZ actuators to stabilize the output frequency of a TDM source.

[0035] Figure 26 An example of time-domain multiplexing (TDM) is depicted, in which TDM uses parallel time-delayed channels to multiplex the pulse train, thereby making the delay channels “consistent” with each other (because the frequency of the output multiplexed pulse train is ideally as insensitive as possible to environmental changes, the feedback loop control system can correct the delay units for any fluctuations that impair the stability of the output repetition rate, and can provide feedback through interconnection with a neural network).

[0036] Figure 27 An example of using fiber-optic collimators along with piezoelectric transducers to control individual MFC circuits is depicted.

[0037] Figure 28 An example of timing from a USPL modulation source for a TDM chip is depicted, used to provide terabits per second (or faster) with a multiplier photonic chip.

[0038] Figure 29 An example of timing from a USPL modulation source for a TDM chip is depicted, used to employ a multiplier photonic chip operating in a WDM configuration to provide terabits per second (or faster).

[0039] Figure 30 An example of the construction of a computer-aided system is described, which can use recursive linear polarization adjustment to control the pulse width of an all-fiber mode-locked laser, while using a synchronous self-regeneration mechanism to stabilize the cavity repetition rate, and can also provide tunability of repetition rate and pulse width.

[0040] Figure 31 An example of a modified pulse interleaving scheme using pulse multiplication technology is described, in which a low repetition rate pulse train of a well-characterized, well-mode-locked laser can be coupled to an integrated optical directional coupler, wherein a well-defined portion of the pulse is tapped out and “re-looped” in the optical loop with an optical delay equal to the expected inter-pulse interval in the output pulse train, and is recoupled to the output of the directional coupler.

[0041] Figure 32 This is a process flowchart illustrating the features of a method consistent with the implementation of the present topic.

[0042] Figure 33 This is another process flowchart illustrating the features of a method consistent with the implementation of the present topic.

[0043] Figure 34 This is another process flowchart illustrating the features of a method consistent with the implementation of the present topic.

[0044] Figure 35A and Figure 35B An exemplary node that can be used to send and / or receive information is shown.

[0045] Figure 36 An exemplary arrangement is shown in which data is transmitted from a first communication network 3542 to a second communication network 3544 across an optical communication distance D using a transmitting node 3510 and a receiving node 3530.

[0046] Figure 37 An exemplary beam is shown traveling across an optical communication distance D (such as 1 mile) through a constant refractive medium.

[0047] Figure 38 A schematic representation of photons in a beam traveling through a variable refractive medium is provided.

[0048] Figure 39 This diagram illustrates the widening of a pulse as it travels across the distance of an optical communication.

[0049] Figure 40 An exemplary time distribution curve of a short-duration pulse 4010 is shown, which travels a considerable distance through a variable refractive medium and has been broadened in time.

[0050] Figure 41 A schematic representation of an optical pulse arriving within the detection window of an optical receiver is shown.

[0051] Figure 42 An example of test data received over a mile-long optical communication distance is shown.

[0052] Figure 43 An exemplary ranging node is shown, which can be used to detect objects or surfaces and determine the position of these objects relative to the node. Detailed Implementation

[0053] While aspects of the subject matter of this disclosure may be embodied in various forms, the following description and accompanying drawings are intended only to disclose some of these forms as specific examples of the subject matter. Therefore, the subject matter of this disclosure is not intended to be limited to the forms or embodiments described and illustrated herein.

[0054] Figure 1 An example of an optical communication platform 100 configured to use a USPL source as a light source for transmission is shown. Figure 1 As shown, the USPL source 102 can be directly modulated by an external source element 104. Optical power from the USPL source 102 can optionally be coupled across free space 110 to the transmitting element 106 via an optical telescope. The transmitting element 106 may optionally include optical components formed using hyperbolic mirror fabrication techniques or conventional Newtonian designs. A reciprocal receiving telescope located at the receiver system can provide optical reception. Consistent with embodiments of the present subject, each optical transmission platform can be designed to operate as a bidirectional unit. In other words, the transmitting element 106 of the optical communication platform 100 can also function as a receiving element. Generally, unless explicitly stated otherwise, the described transmitting element 106 can also be considered as functioning as a receiving element, and vice versa. An optical element performing both transmitting and receiving functions may be referred to herein as an optical transceiver.

[0055] Figure 2 It shows including Figure 1 An example of an optical communication system 200 for an optical communication platform 100. Figure 2 The diagram also shows a second complementary receiving element 204, which may be a receiving telescope located at a distance relative to the transmitting element 106. As described above, both the transmitting element 106 and the receiving element 204 may be bidirectional, and each element may act as both the transmitting element 106 and the receiving element 204, depending on the instantaneous direction of data transmission in the optical communication system 200. Unless otherwise explicitly stated, this feature applies to both the transmitting and receiving elements throughout this disclosure. Either or both of the transmitting element 106 and the receiving element 204 may be an optical telescope or other device for transmitting and receiving optical information.

[0056] Figure 3 An example of an optical communication platform 300 is shown for using a USPL source 102 that is optically coupled to an external modulator 302 via an optical fiber medium 304 and connected to a transmitting element 106 via an additional transmission medium 306, which may optionally be an optical fiber medium, a free-space connection, etc. The USPL source 102 can be externally modulated by the external modulator 302, such that the optical power from the USPL source 102 is optically coupled to the transmitting element 106 or processed via an equivalent optical telescope.

[0057] Figure 4 It shows including Figure 3 An example of an optical communication system 400 from an optical communication platform 300. In Figure 4 The second complementary receiving telescope 204 is also shown, as mentioned above. Figure 2 It can be a receiving telescope located at a distance relative to the transmitting element 106.

[0058] Figure 5 An example of an optical communication architecture 500 is shown. Figure 5 The architecture 500 can include Figure 4 The components may further include a first communication network 502 connected to the first optical communication platform 300. The receiving element 204 is part of a second optical communication platform 504, which may optionally include components similar to those of the first optical communication platform 300. A second communication network 506 may be connected to the second optical communication platform 504, enabling optical transmission of data between the transmitting element 106 and the receiving element 204, or transmission between the first communication network 502 and the second communication network 506. Each of the first and second communication networks may include one or more optical networking features and electrical networking features.

[0059] Figure 6 An example of an optical communication system 600 is shown. As part of an optical communication platform 602, a USPL source 102 is coupled to an external modulator 302, for example, via optical fiber 202 or other transmission medium. Light from the USPL source 102 propagates via a transmitting element 106 in a manner similar to that described above. An optical amplifier element 604 (which may optionally be an optical fiber amplifier element) can be used to increase the optical transmission power and may optionally be disposed between the external modulator 302 and the transmitting element 106 and connected to one or both of the external modulator and the transmitting element via an additional transmission medium 306, which may optionally be an optical fiber medium, a free-space connection, etc. Figure 6A second complementary receiving element 204 located at a distance relative to the optical communication platform 602 is also shown. It is readily understood that the second optical communication platform 504, including the receiving element 204, may also include an optical amplifier element 604. The first communication network 502 and the second communication network 506 may be connected to the two optical communication platforms 602 and 504, respectively.

[0060] Figure 7 An example of an optical communication system 700 is shown. Figure 6 The optical communication platform 602 shown can communicate with the second optical communication platform 702, which in this embodiment may include a receiving element 204 and an optical preamplifier 704. Other components similar to those shown in the optical communication platform 602 may also be included in the second optical communication platform 702, although they are... Figure 7 Not shown in the diagram. It should be understood that a two-way optical communication platform may include both an optical preamplifier 704 for amplifying the received optical signal and an optical amplifier element 604 for enhancing the transmitted optical signal.

[0061] and Figure 7 The embodiments shown, as well as other embodiments of the present subject, may include optical amplification (e.g., for either or both of optical amplifier element 604 or optical preamplifier 704) to enhance the optical budget of the data link between transmitting element 106 and receiving element 204 (or vice versa), for example, using one or more of an erbium-doped fiber amplifier (EDFA), a high-power erbium-ytterbium-doped fiber amplifier (Er / Yb-DFA), or equivalent devices, which may include, but are not limited to, semiconductor optical amplifiers (SOA).

[0062] Figure 8 An example of an optical communication system 800 is shown. Figure 6 The optical communication platform 602 shown can communicate with the second optical communication platform 802. In this embodiment, the second optical communication platform may include... Figure 7 The similar receiving element 204 and optical preamplifier 704 shown are illustrated. Figure 8 As shown, the second optical communication platform 802 may further include an optical receiver circuit 804, which can receive amplified and electrically recovered data received at the receiving element 204 and amplified by an optical preamplifier. Multiple clock sources 806 can be docked as needed to multiple remote multipoint network connections with multiple communication networks 810. Similarly, a complementary set of clock sources and multiple communication networks can be combined with the optical communication platform 602 (e.g., instead of...). Figure 8 (A single communication network 502 shown in the figure).

[0063] Figure 9 An example of an optical communication system 900 is shown. An optical communication platform 902 (which can be used in conjunction with the system first referred to herein) Figure 6 The optical communication platform 602, characterized by elements similar to those described, may further include an additional USPL source 904 that acts as a tracking and alignment (pointing) beacon source. The second optical communication platform 906 may also include an additional USPL source 910 that acts as a tracking and alignment (pointing) beacon source. The tracking and alignment (pointing) beacon sources 904, 910 may optionally originate from available communication sources used in data transmission, or may be provided by separate dedicated USPL sources. Additionally, each USPL beacon source 904, 910 may include an in-band or out-of-band source (thereby realizing the advantage of available optical amplification sources) or originate from dedicated optical amplification resources.

[0064] Figure 10 An example of an FSO communication system 1000 including a dual-polarization USPL-FSO optical data link platform 1001 is shown, in which USPL sources are polarization-multiplexed onto the transmitted optical signal, thereby providing polarization-multiplexed USP-FSO (PM-USP-FSO) functionality. Two USPL sources 102 and 1002 are fiber-coupled to either a directly modulated modulation unit 1004 or an externally modulated modulation unit 1006, respectively. Each corresponding modulated signal is optically amplified by optical amplifier units 1010 and 1012, and then the optical polarization state is adjusted using polarization units 1014 and 1016. The polarization state signal is fiber-coupled to a polarization-dependent multiplexer (PDM) unit 1020, which is then connected to an optical transmission platform unit 1022, which can be similar to the transmitting element 106 discussed above. The PDM 1020 multiplexes light with different polarization states into a single pulse train for transmission via the optical transmission platform unit 1022. This could include USPL optical beacon 904, to provide the same information as mentioned above. Figure 9 The capabilities described above are similar, thus enabling operation, for example, with or in conjunction with a second USPL optical beacon 906 at a receiving platform 1024, which may include receiving elements 204 similar to those described above. As previously noted, receiving element 204, along with other features and components of receiving platform 1024, generally supports transmission functionality, thereby establishing a bidirectional link. The received signal recovered by receiving element 204 can provide an optical signal, which is interfaced with a suitable polarization-dependent demultiplexer 1026 capable of providing two signals for further optical amplification using amplifying elements 1030, 1032. Each optically amplified signal provided by amplifying elements 1030, 1032 can be interfaced to a suitable optical network 1034, 1036 for network use.

[0065] Figure 11AAn example of system 1100 is shown, in which the USPL-FSO transceiver can be used in line-of-sight optical communication (e.g., "laser communication") applications, and Figure 11B An example of system 1150 is shown, in which a USPL-FSO transceiver can be used in non-line-of-sight laser communication applications. As the transmitted light travels through the atmosphere, advantages for some implementations of the subject matter can be achieved due to the scattering of the light signal transmitted from the transmitting element. This scattering allows for non-line-of-sight communication. Furthermore, the radio components used in such communication systems can operate in the solar-blind portion of the UV-C band, where light is emitted at wavelengths of 200 nm to 280 nm. In this band, solar radiation is strongly attenuated by the Earth's atmosphere as it propagates through the environment. This means that as solar radiation gets closer to the ground, the amount of background noise radiation decreases dramatically, and low-power communication link operation becomes possible. On the other hand, environmental elements such as oxygen, ozone, and water can weaken or interrupt communication broadcasts, thus limiting applications to short-range uses.

[0066] When UV waves are dispersed throughout the atmosphere, they are typically strongly scattered into a wide variety of signal paths. Signal scattering is crucial for UV systems operating in non-line-of-sight conditions, and communication performance can be highly dependent on the direction of the transmitting beam and the receiver's field of view. Figure 11A The line-of-sight arrangement 1100 shown can be used with, for example... Figure 11B The non-line-of-sight arrangement 1150 shown differs in bandwidth dimensions. Ultraviolet communication may be more heavily dependent on the transmitter's beam position and the receiver's field of view. Therefore, improving the pointing apex angle, for example, by employing supplementary equipment to experiment with enhancing the UV-C signal, may be advantageous.

[0067] Figure 12 An example of a remote sensing system 1200 is shown, in which a USPL source 102 is optically coupled via an optical fiber component 202 to an optical transmitting element 1202 capable of transmitting and receiving optical signals. Some of the forward-propagating light (including light from data signals passing through the optical transmitting element 1202) is backscattered by interaction with airborne particles that are the objects of investigation. The optical backscattered signal is detected by the optical transmitting element 1202 or a similar receiving aperture and is transmitted for transmission. Figure 12The detection circuit 1204 and other components perform detection and spectral analysis. The identification characteristics of particles within the target atmospheric region 1206 under investigation can be calibrated using known methods, such as using predetermined spectral calibration measurements based on one or more of ultraviolet, infrared, and Raman spectroscopy. Consistent with this implementation, using a USPL laser source operating within the spectral range of interest, the optical system can be operated as a lidar instrument providing enhanced resolution and detection sensitivity. The adjustable spectral range facilitates the assessment and analysis of atmospheric chemical composition.

[0068] Utilizing techniques such as hyperbolic mirror fabrication by focusing the received signal onto an ideal point or optical transmission terminals manufactured using conventional Newtonian designs, USPL-FSO transceivers can be used for remote sensing and detection of identifying features of airborne elements using ionizing or non-ionizing detection techniques. Furthermore, certain adaptations can be related to ionization detection over long distances, including controlled ionization already shown to occur at these frequencies and ionization processes that can be focused at a distance to adjust atmospheric penetration depth (especially in weather and clouds).

[0069] Figure 13 An example of using a USPL source and optical receiving technology to improve detection sensitivity is shown. Researchers at the National Institute of Standards and Technology (NIST) have developed a laser ranging system that can precisely locate multiple objects with nanometer-level accuracy over distances up to 100 km. LiDAR (light detection and ranging) systems have applications ranging from precision manufacturing on Earth to maintaining perfectly aligned satellite networks (Nature Photonics DOI:10.1038 / NPHOTON.2009.94). The NIST device uses two coherent broadband fiber laser frequency combs. The frequency combs output a series of stable, short pulses that also contain highly coherent carrier waves spanning the pulse train extension. This means that interferometry and time-of-flight measurements can be performed simultaneously using the frequency combs, thereby enhancing analytical capabilities for application-specific situations.

[0070] exist Figure 13In the arrangement shown, two phase-locked frequency combs 1301 and 1302 are used in a coherent linear optical sampling configuration, also known as multiheterodyne, where one frequency comb measures two distance paths while the other provides distance information encoded in the light from the first comb. A pulse from one frequency comb 1301 can be emitted from an optical fiber and directed toward two glass plates, namely a reference 1303 and a target 1304. Plates 1303 and 1304 can reflect a portion of the pulse (e.g., approximately 4%) back along the fiber, effectively creating two new pulses. The time interval between these two pulses 1301 gives the distance between the movable target plate and the reference plate. The second frequency comb 1302 is tightly phase-locked with the first frequency comb but has a slightly different repetition rate. Due to the different delays between consecutive pulses during source interference, the second frequency comb can sample slightly different portions of the light from the electric field of the first comb.

[0071] Usage Reference Figure 13 The described technique allows for the replacement of the two coherent broadband fiber laser sources with two suitable USPL sources, used within the outlined configuration, which fiber-couples each USPL source to a dedicated free-space optical telescope design. By doing so, overall efficiency, optical ranging, and accuracy can be significantly improved.

[0072] In some embodiments, the native pulse repetition rate of the USPL laser source may be 50 MHz or lower, which may be an undesirable low frequency for optical data transmission, thus limiting the system to low data rate applications of 50 Mbps or lower. Therefore, systems with increased USPL operating speeds are needed to provide data transmission solutions exceeding 50 Mbps.

[0073] Figure 14 An example of a remote sensing system 1400 is shown, in which a USPL source 102 is optically coupled via fiber optic component 202 to an optical transmitting element 1202 capable of transmitting and receiving optical signals. Light propagating forward through the optical transmitting element 1202 (including light from data signals) is backscattered through interaction with known and unknown targets within the atmospheric region 1206, which are objects of investigation. The optical backscattered signal, including light from data signals, is detected by the optical transmitting element 1202 or a similar receiving aperture and is transmitted for transmission. Figure 14 The detection circuit and spectral analysis component 1402 in the middle perform detection and analysis. The identification characteristics of particles within the area 1206 under investigation can be calibrated, for example, in which ranging analysis can be performed. Figure 14System 1400 may include a USPL-FSO transceiver that is used and operated across the infrared wavelength range as a rangefinder and position determination device for target identification and interrogation applications. As used herein, the term "optical" includes at least visible wavelengths, infrared wavelengths, and near-infrared wavelengths.

[0074] Figure 15 An optical pulse multiplier module 1500 is shown that can increase the repetition rate of the output from a USPL source 102. An exemplary USPL may have a pulse width of 10-100 femtoseconds and a repetition rate of, for example, 50 MHz. The output from the USPL 102 can be fed as input 1502 into a USPL photonic chip pulse multiplier module 1504. In this example, the photonic chip may include a 20,000:1 beamsplitter element 1506 that splits the input into discrete optical units. Each optical unit on opposite sides of the beamsplitter element 1506 contains a 50 MHz pulse train. Each optical unit then passes through a delay controller (fiber loop or lens array) 1510, which time-delays the pulse train of that unit, for example, by several picoseconds. Thus, successive optical units are delayed by increasing picoseconds. All these pulse trains with their unique time delays are combined into a single pulse train using a 20,000:1 optical combiner element 1512 in a manner similar to time-division multiplexing. The desired ratios of the beam splitter and combiner can be controlled, thus providing the necessary optical design for the required application. The final output 1514 is a pulse train of 10-100 femtosecond pulses with a repetition rate of 1 THz. This THz pulse train can then be modulated by a 10 GigE signal or a 100 GigE signal, for example, as... Figure 28 As shown, this generates 100 femtosecond pulses per bit for a 10 GigE system and 10 femtosecond pulses per bit for a 100 GigE system. The applications cited are not limited to the specific data rates of 10 Gbps and 100 Gbps, but can be adapted to the requirements of the application under consideration. These numbers are for illustrative purposes only. Implementations of the present subject can use any multiplier factor to increase the repetition rate of the USPL to any arbitrary repetition rate via the photonic chip pulse multiplier module 1504. Other examples for generating enhanced USPL repetition rates are illustrated in this submission.

[0075] Figure 16 A system 1600 for generating, transmitting, and receiving high pulse rate USPL optical flow is depicted. An optical chip multiplexing module 1610 (e.g., which can be used with a reference) Figure 15 The similar approach discussed can be used in this application. In this scheme for implementing USPL pulse multiplication, signals 1601, 1602, 1603, and 1604 ( Figure 16Four signals are shown (but it should be understood that any number is within the scope of the present topic), and a series of 10GigE router connections (10GigE is not intended to be a limiting feature) are described and docked to the optical chip multiplexing module 1610. In operation, the optical chip multiplexing module 1610 can support full-duplex (Tx and Rx) connectivity with 10GigE routers 1601, 1602, 1603, and 1604. The optical chip multiplexing module 1610 can provide efficient modulation of the incoming optical signals 1601, 1602, 1603, and 1604 via the USPL signal 1685 output from the USPL source 1690. The optical chip multiplexing module 1610 can provide the ability to modulate and multiplex these incoming optical signals.

[0076] At the remote receiving site where the receiving device is located, appropriate receiver element 1665 can be used to recover all signals transmitted via transmitting element 1660 at the transmitting device. A complementary set of optical chip multiplexing modules 1675 can provide the necessary capability to demultiplex the received data stream shown in the unit for transmission to a series of routers 1601', 1602', 1603', 1604' (depicting four such routers is not intended to be a limitation). End-to-end network connectivity can be demonstrated via network endpoint elements.

[0077] Figure 17 An exemplary system 1700 is depicted, in which an optical chip is interconnected to a wavelength division multiplexing (WDM) system. WDM systems have the advantage of not requiring timing or synchronization (as is required with a 10GigE (or other speed) router 1701) because each 10GigE signal operates independently of other such signals at its own wavelength. Timing or synchronization between the TDM optical chip and the 10GigE router can be critical in the TDM optical chip. The GbE switch 1701 can provide the necessary electrical RF signal 1705, either directly or by using the USPL pulse multiplier module previously detailed herein, to modulate the USPL source 1702. A typical RZ output 1710 can be coupled to an external modulator 1720 (which can be modulated using an NRZ clock source for the switch 1701), thereby generating an RZ modulation spectrum 1730. The conversion process using readily available equipment can provide the ability to introduce the USPL source and its benefits into the terrestrial backhaul network spectrum.

[0078] To enable successful bridging of the optical chip system between two remote 10GigE switches, the chip can function like a simple optical fiber. Therefore, the timing of the TDM chip can be driven by the 10GigE switch 1701. Both active mode-locked USPL (40 GHz, 1 picosecond pulse width) and passive mode-locked USPL (50 MHz, 100 femtosecond pulse width) can be driven by RF timing signals.

[0079] Figure 18 A device 1800 is shown that can support an alternative approach for operations at high pulse repetition data rates, such as for extremely high data rate operations, where optical chip designs can be performed using fiber optics or free-space optics. A 50MHz USPL source 1801 can be coupled to a series of optical delay controller elements 1802 (which can be designed with fiber optic loops or offset lenses) to result in an exact 10.313Gbps RZ output stream, which is a 10GigE line rate (greater than 10Gbps due to 64B / 66B encoding). A beam splitter element 1803, together with a variable optical delay line 1804, provides the function of splitting the incoming optical signal string 1801 into (in this example) 206 paths. After introducing sufficient delay by design, all signals are multiplexed together by a combiner element 1805. In doing so, a series of identical optical signals with equal spacing between adjacent pulses form a pulse continuum for modulation. Before entering the EO modulator element 1806, all optically incoming signals can be pre-emphasized using techniques such as typical optical amplification to produce a uniform power spectrum for each outgoing signal from the combiner element 1805. The regulated outgoing signals can then be coupled into the EO modulator element 1806 and modulated with the available NRZ signal from the 10GigE signal source element 1807. The modulated 10GigE output 1809 can be connected to an EDFA and then to the TX of an FSO system (or fiber optic system). The Rx side (after the detector) can be directly fed into a 10GigE switch as a modulated and amplified output 1810.

[0080] Figure 19 Another example of a device 1900 for USPL pulse multiplication, consistent with the implementation of the present topic, is shown. Consistent with this scheme, the 10×TDM system is configured to deliver a 100Gbps output. The TDM demultiplexing chip can be located on the receiving side of the communication link to decompose the individual 10GigE signals, and can include features for… Figure 19 The design shown is a reversible scheme.

[0081] like Figure 18As shown, a 50MHz USPL source 1801 can be fed into a series of optical delay controller elements 1802 (which can be designed with fiber loops or offset lenses) to result in an exact 10.313Gbps RZ output stream, which is a 10GigE line rate (greater than 10Gbps due to 64B / 66B encoding). A beam splitter element 1803, along with a variable optical delay line 1804, provides the function of splitting the incoming optical signal string 1801 into (in this example) 206 paths. After introducing sufficient delay by design, all signals are multiplexed together by a combiner element 1805. However, as... Figure 18 As an alternative to the single modulator element 1806 shown, the 10.313 GHz RZ output 1901 from the combiner element 1805 can be fed into the second beamsplitter element 1910, in which case the second beamsplitter element can be a 10× beamsplitter that splits the optical signal into ten parallel paths. Other embodiments of this design can support various beam splitting ratios depending on design requirements. The optical paths exiting the second beamsplitter element 1910 are individually connected to designated optical delay lines 1920. Each individual delay path is connected to a dedicated optical modulator in a set of optical modulators 1930 modulated with an available NRZ signal from the 10×10 GigE signal source element 1931, thereby generating a series of modulated optical signals 1935. An optical combiner, identified as 1940, provides a single optical pulse train 1950. The series of optical pulses in the single optical pulse train 1950 can be coupled to an appropriate optical amplifier for desired optical conditioning for network use.

[0082] Figure 20 Another example of a device 2000 for USPL pulse multiplication, consistent with the implementation of the present subject, is shown. The depicted device 2000 can provide the ability to achieve high USPL pulse repetition data rates for network applications through modulation of pulses within low repetition rate channels. By applying direct modulation to each channel on the delay controller, it is advantageous to create modulation schemes that are not limited by current speed constraints from electronic technology. The implementation of the present subject can provide a mechanism to enhance the data transmission capacity of a system by using current standard electronic modulation speeds (at... Figure 20In the example, each channel is modulated separately with a 100×10 GigE signal input at a rate of 2001, and each channel is multiplexed into a single high-repetition-rate pulse stream. In this scheme, the current standard, limited by the speed of the electro-optic modulator (40 Gbps), can be enhanced by approximately N orders of magnitude, where N is the number of channels in the time multiplexer. For example, a 100-channel TDM (where each channel is amplitude modulated at the current standard data rate) could provide a data rate of up to 4 Tbps. N may be limited by the width of the optical pulse itself. Under the constraint of carrying information at 1 bit / pulse, the time slot occupied by 1 bit is the width of the pulse itself (in this sense, the RZ system will converge to NRZ). For example, in this scheme, a 40 fs pulse-width laser with a 40 GHz repetition rate can carry information at a maximum rate of 25 Tbps. This scheme can be used for 40Gbps channel modulation schemes (i.e., 1 bit per 25ps) and can correspond to the capacity of N to 625 channels in a single transmission, which can be the number of 40fs time intervals matched to the 25ps time interval. A significant advantage of this scheme is its ability to "optically enhance" otherwise data-capacity modulation schemes while still interfacing with existing data-rate-limited modulators. For example, amplitude modulators based on Mach-Zehnder interferometers can be easily integrated into TDM IC packages because of the need to branch the channel into two separate paths, add tiny phase modulators (nonlinear crystals) to one of these paths, and combine these paths for interference.

[0083] Figure 20Includes a USPL source 2010 coupled to a multiport optical beamsplitter element 2020. The number of identified optical ports is not limited to those described or shown herein. A series of optical delay lines 2030 provide the desired optical delay between each parallel path from the multiport optical beamsplitter element 2020 and can be customized for a specific application. The optical delay paths from the optical delay lines 2030 are combined using an optical combiner element 2035. The resulting merged optical data stream, appearing through element 2040, represents a multiplication enhancement of the pulse repetition rate of the original USPL source identified by element 2010. Further enhancement of the pulse repetition rate is achieved by using element 2041 (described via an optical beamsplitter, where the incoming signal 2040 is split into a series of paths, not limited to those identified via element 2041). Optical delay can be introduced into each path within the device via a second delay controller 2045, as identified via a second set of optical delay paths 2042. Next, using an available RF signal source identified by signal input 2001, each parallel path 2042 is modulated by modulation element 2044. Optical combiner element 2050 integrates all incoming signals into a single data stream 2060.

[0084] Optical pre-emphasis and deemphasis techniques can be introduced within each of the described components to customize the spectrum, thereby achieving a uniform or asymmetric optical power distribution. Pre-emphasis and deemphasis can be accomplished using commonly used optical amplifiers, such as erbium-doped optical amplifiers (EDFAs).

[0085] Figure 21 An example of a system 2100 is depicted, including a mode-locked USPL source 2101 that can be used to appropriately generate the required clock and data streams for an application. Mode-locked lasers can represent a high-performance, high-precision clock source option in digital communication systems. In this regard, mode-locked fiber lasers (in linear or ring configurations) can be an attractive preferred option because they can achieve pulse widths and repetition rates up to GHz over the USPL source region. In addition, fiber offers compactness, low cost, low sensitivity to thermal noise, low jitter, and the absence of problems associated with diffraction or airborne dust contamination, to name just a few. In communication scenarios, pulse width determines the available bandwidth of the system, and repetition rate limits the data rate. Pulse width can be determined by the inherent characteristics of the laser cavity (i.e., a balance between total group velocity dispersion (GVD) and the choice of saturable absorber (for passive systems)) or the bandwidth of the active element (for active mode-locked systems). The repetition rate of the pulse train is limited by the fiber length. For example, in a linear laser, the fundamental mode vos of the laser can be expressed as:

[0086]

[0087] Where c is the speed of light in a vacuum, and n g is the average group refractive index, and L is the cavity length. Therefore, a 10 cm long fiber laser cavity element 2110 with an average group refractive index of 1.47 will have a repetition rate of 1 GHz. In strictly passive systems, mode-locking can be achieved by using a saturable absorber. In active lasers, an amplitude modulator element 2150 can be inserted into the cavity to increase the laser's repetition rate (harmonic mode-locking). To achieve a high repetition rate clock using a mode-locked USPL source, (i) such as Figure 21 The diagram shows one or more of the intracavity amplitude Mach-Zehnder modulator (MZM) 2150 and (ii) a low-threshold saturable absorber. These techniques, known as “harmonic mode-locking,” can be used in ground, seabed, or FSO systems for air, space, or seabed applications.

[0088] exist Figure 21 The 980nm pump element 2102 coupled to the optical WDM device 2105 is detailed. An erbium-doped optical amplifier 2110 or equivalent can be used to create a nonlinear environment, thereby obtaining mode-locked pulse train emission within a closed cavity established between two Faraday reflectors 2101 and 2160 located at both ends of the optical USPL cavity. The device is capable of establishing a self-contained series of optical pulses exceeding 100 Gbps and essentially highly synchronized at the module's output port 2170. The EDFA 2110 can be specifically designed to achieve a high-gain nonlinear medium. A phase-locked loop 2130 can maintain a synchronized clock source by modulating the signals of components 2120, 2130, and 2150 of a self-contained high-repetition-rate pulse generator, thereby providing favorable operational stability. To achieve high repetition rates in lasers limited by their size (length for linear lasers and circumference for ring lasers), intracavity generation of excitation mode multiples may be required. In active mode, the amplitude modulator in the inserted cavity modulates the loss of the system operating as a "threshold-gated" device. For this to succeed, the control signal for the modulator may need to reference the laser's own oscillation to avoid the drive signal "forcing" an external frequency oscillation on the laser. This can be achieved by introducing a phase-locked loop element 2130 or a synchronous oscillator circuit to track and lock onto the laser's repetition rate and regenerate the signal. In the case of the PLL, the RF output can be set to a multiple of the input signal (much like this device is used in cellular phone technology), and the laser's repetition rate is increased. This signal can then be used to trigger a pulse generator or in conjunction with a low-pass filter. An MZ amplitude modulator 2150 outside the laser cavity can be used to create on-off keying (OOK) modulation of the pulse train emanating from the mode-locked laser.

[0089] Figure 22 A graphical depiction of 2200 is shown, illustrating the effect of loss modulation introduced into the input pulse train 2201 due to the presence of amplitude modulator 2205 along with a control signal NRZ signal 2210 consisting of a bit sequence as illustrated. The signal obtained at the output of device 2220 represents an NRZ to RZ converter device for telecommunications and scientific applications, where such applications can benefit from RZ data streams. A clock signal 2201 (optical input) at a given pulse repetition rate passes through modulator 2205. Simultaneously, a control signal consisting of a sequence of 1s and 0s can be applied to the RF port of modulator element 2215. When modulator element 2215 is biased to minimum transmission, the loss experienced by the optical signal may be at its maximum in the absence of a control signal. With the presence of the RF signal (1), the loss is reduced to a minimum (OPEN GATE), thus functioning as an on / off keyed modulation device. The pulse width of the output optical signal is typically much smaller than the time slot occupied by a single bit of information (even less than half a clock cycle in the NRZ scheme), making the system truly RZ, as indicated by component 2220.

[0090] Figure 23 An exemplary system 2300 is shown for generating a high optical harmonic USPL pulse stream with a high pulse repetition rate using a saturable absorber (SA) device 2330. In some examples, the SA device 2330 may include carbon nanotubes. Passively mode-locked fiber lasers using carbon nanotube SA (CNT-SA) are another attractive option for high repetition rate sources due to their ability to generate high harmonics with a fundamental repetition rate. In the described scheme, a closed, self-contained optical cavity is constructed, in which two Faraday reflectors 2301 and 2350 form the optical cavity. Although Figure 23 The diagram shows a high-power erbium-doped fiber amplifier (EDFA) 2310, but any antiphase medium that generates a nonlinear optical cavity can also be used. Seed laser 2315, such as... Figure 23 The 980nm pump laser shown can be used to generate high repetition rate optical strings. Specifically, any suitable pump laser can be considered depending on the desired optical wavelength and pulse repetition rate. The SA element 2330 can be placed within the cavity to establish the required optical pulse characteristics 2350 as needed according to design requirements.

[0091] Figure 23 A schematic diagram illustrating an example of a laser that can be used in one or more embodiments of the present topic is shown. Figure 22Unlike the active lasers shown, the MZ modulator here can be replaced by the SA element 2330. For ground, seabed, or FSO systems in air, space, or seabed applications, technologies similar to those described herein can be used in fiber-optic power plant distribution systems or FSO systems.

[0092] Figure 24 A scheme for providing time-domain multiplexing (TDM) is illustrated, where TDM uses parallel time-delayed channels to multiplex the pulse train. In some cases, manipulating the delay channels to make them “consistent” with respect to each other may become important. Ideally, the frequency of the output multiplexed pulse train should be as insensitive as possible to environmental variations. To this end, a proposed feedback loop control system is designed to correct the delay units for any fluctuations that compromise the stability of the output repetition rate.

[0093] Figure 24 An illustration of an example of a delay control system 2400 is shown. The control loop can be implemented in one of several ways consistent with the current topic. Figure 24 One possibility is described for illustrative purposes. An input pulse train enters a TDM and is multiplexed into N paths, each with its own delay line. If the paths are made of low-bending-loss fiber waveguides, each path can be wound around a cylindrical piezoelectric actuator (PZ) with radius R. The actuator typically expands radially due to a control voltage (Vc). This expansion ΔR, linearly proportional to Vc, results in a fiber length change ΔL = 2πNΔR, where N is the number of fiber turns around the PZ. For terahertz multiplexing, the delay between pulses (and consequently, PZ1) must be 1 picosecond. This could require a length change of 200 micrometers, corresponding to ΔR = 32.5 micrometers for a one-turn PZ actuator. Most commercially available piezoelectric actuators are highly linear and operate well within this range. Therefore, the control mechanism can be based on several PZ actuators (each PZ actuator has a number of turns corresponding to a multiple of the first delay, i.e., (32 microns, 64 microns, 96 microns, etc.)) and controlled by a single voltage Vc. The control voltage is determined by a feedback system that uses a phase comparator (PC) to compare the frequency of the output signal, using a 1 / N divider, with the frequency of the input signal. The frequency of the "slow" input optical signal (determined by...) Figure 24The waveform (with τRT) is converted into an RF signal using a photodetector PDin. To reduce the effects of electronic jitter, a "differentiator" (or high-pass filter) is applied to this RF signal to steepen the leading edge of the pulse. A phase-locked loop (PLL) is used to track and lock the signal and regenerate it as a 50% duty cycle waveform. Similarly, on the output side, the optical signal is picked up by a photodetector PDout, high-pass filtered, and regenerated using the clock output port of the clock and data recovery system. The clock of the output signal, having a frequency N times that of the input signal, is sent to an N-fold divider before entering the phase comparator. From the phase comparator, the DC voltage level representing the mismatch between the input and output signals (very similar to that used in the architecture of a PLL circuit) indicates the correction direction of the actuator. A low-pass filter adds a time constant to the system to enhance its insensitivity to parasitic noise.

[0094] Unlike PLLs, CDRs can be advantageously used in the output, allowing the output signal to be modulated or unmodulated. This system can be designed to operate in both unmodulated and "TDM in-modulation" (i.e., one modulator at each delay path) schemes. However, this is a completely deterministic method of compensating for variations in delay line length. Ideally, from a practical standpoint, all delay paths should reference the same "thermal level," meaning they are simultaneously sensitive to the same thermal changes. If each line senses different changes, the system will be unable to correct for these in real time.

[0095] Alternatively, a fully statistical approach may include summing operational amplifier circuits (S1...SN) to deliver control voltages to the actuator. Using this method, the input voltages (V1 to VN) can be used to compensate for length differences between lines in a completely static sense, which they would otherwise be used for initial fine-tuning of the system. This approach must also typically compensate for, or at least account for, any bending loss requirements of the optical fiber used. Some newly marketed optical fibers can have a critical radius of only a few millimeters.

[0096] When each delay line senses different temperature variations or experiences unrelated length variations due to parasitic local noise, the previously described method may encounter difficulties in performing real-time correction as is. A more robust approach, operating in a fully statistical sense and consistent with some implementations of the present topic, can be used. In such an approach, summing over the operational amplifier circuitry (S1...SN) can be used to deliver control voltages to the actuator. In this case, the input voltages (V1 to VN) can be used to compensate for length differences between delay lines in a fully statistical sense, which might otherwise only be available for initial fine-tuning (calibration) of the system.

[0097] Refer again Figure 24The input USPL source, identified as element 2401, is coupled to optical coupler element 2403, such that one branch of the coupler is connected to an optical photodiode selected for operation at the running data rate of 2401. Using standard electronic filtering techniques described by elements 2404, 2405, and 2406, the electrical square wave representation of the incoming USPL signal is extracted and identified by element 2407. A second optical branch of coupler 2403 is connected to the appropriate optical beamsplitter element identified as 2410, where the incoming signal entering 2410 is split into 206 parallel optical paths. Variable-rate optical delay lines are also shown, established in parallel for each of the parallel branches of beamsplitter element 2410. The parallel piezoelectric element is identified by element 242N and is electronically controlled by the feedback circuit shown in the figure. A control voltage, identified by Vc, is generated by photodiode 2485 in conjunction with electronic circuit elements 2480 and 2475. Clock and data recovery (CDR) element 2475 generates a clock source for controlling each of the PZ elements. After an appropriate delay is introduced into each branch of element 2410, the optical path, identified as 244N, is merged. This generates a pulse-multiplied USPL signal 2490.

[0098] Figure 25A A schematic diagram of the fiber optic PZ actuator 2500 is shown, and Figure 25B A graph 2590 showing the radius versus voltage for this type of actuator is provided. These appendices... Figure 1 The operation of a PZ actuator is illustrated, which is used to increase the pulse repetition rate of an incoming USPL pulse train by inducing an optical delay. Although shown as an element for generating the pulse repetition rate to enhance the USPL signal, the same technique can be used in other optical devices that require or benefit from optical delay. The basic structure of the device is a fiber-based PZ actuator 2501. When a voltage 2550 is applied to electrode 2520, voltage-induced stress is generated within the fiber, resulting in a time delay of the optical signal traveling through the fiber. By varying the applied voltage, a performance curve of optical delay versus applied voltage is obtained, as shown in the figure. Figure 25B The curve is shown in graph 2590.

[0099] Figure 26 An illustration is shown illustrating the features of an exemplary statistical corrector 2600. Figure 26The coarse correction controller 2640 shown corresponds to the system described in the previous section, which can correct for length variations picked up simultaneously by all delay lines. As previously mentioned, these variations are expected to occur on a much slower timescale than parasitic variations “within the delay line.” This latter effect can manifest as period-to-period jitter introduced into the system. This type of jitter can be monitored using an RF spectrum analyzer (RFA), which causes the repetition rate lines of the system to display “sidelines” (or sidebands), a result of the analyzer mixing together noise frequencies originating from non-uniform time intervals between consecutive pulses. Such a pattern can be processed using an analog-to-digital converter (ADC) and stored as an array of values, which is then fed into a neural network (NN) machine. Neural network machines are known to have excellent adaptive properties, allowing them to essentially learn patterns from external events by adapting to a new set of inputs and outputs. In this scenario, a set of inputs can be generated from a set of "imperfect observations," i.e., the "noisy" outputs of the TDM system, detected by an RFA and converted into a digital array by an ADC ({f1,f2,...,fN}, where fi is the frequency component picked up by the RFA). A set of outputs can be generated by corrections ({V1,V2,...,VN}, where Vt is the compensated input voltage of the summing operational amplifier), which are needed to eliminate the output frequency set from unwanted excessive frequency noise attributed to external disturbances to the system. With a sufficiently large number of {f,V} pairs, where f and V are frequency and voltage arrays respectively, a statistical set can be constructed to train the neural network (NN) to learn fundamental patterns associated with the presence of noise within the channels. These machines can be commercially available as ICs from several manufacturers or implemented as software and used in conjunction with computer feedback control mechanisms. A single-layer perceptual neural network or ADALINE (adaptive linear neuron or later adaptive linear element) should be sufficient to accomplish this task.

[0100] Related to the above Figure 24 Similar to the description provided, the statistical corrector element 2670 may include, with Figure 24 Electronic circuit elements 2480 and 2475, and photodiode 2485, are similar to or provide similar functions to these electronic circuits. For Figure 26 The illustrated scheme uses an RF spectrum analyzer 2695, together with a neural network 2670 and a coarse correction controller element 2640, to perform the optical delay requirements introduced into a series of parallel PZ elements 262N.

[0101] Figure 27The concept and capabilities of a scheme consistent with the implementation of the present subject are illustrated, where performance, accuracy, and resolution can be improved by replacing the piezoelectric disk (PZ) modules identified by elements 2795 and 272N, where an optical delay line is obtained using a compact microfiber-based collimator (MFC) 2795 surrounded by a ceramic disk. While a technique for improving the native pulse repetition rate of a USPL pulse train is shown, the illustrated design is not limited to such applications but can be applied to or extended to other needs in the field of optics where optical delay is required. Doing so allows for the introduction of a more controllable amount of time delay within each MFC element of the circuit. Improvements utilizing MFC elements can enhance response, resolution, and the reproduction of voltage responses required in mass production setups. Figure 27 The concept of mid-signature can be incorporated into precision-manufactured components that can act as complementary pairing units to reduce USPL pulse-to-pulse jitter and achieve data encryption requirements.

[0102] Further reference Figure 27 A USPL source 2701 with a certain pulse repetition rate is split into a preselected number of optical paths 271N (which may be a number other than 206), as identified by beam splitter element 2705. Using elements described by 2795 and 272N, a properly controlled delay 273N is introduced into each parallel branch of the split optical paths 271N. The resulting delayed paths 274N are added together by optical combiner element 2760. A pulse-doubled USPL signal 2780 is generated.

[0103] A potential drawback of some previously available TDM designs (where fiber is "wound" around the piezoelectric actuator) is that the mechanism must meet the bending loss requirements of the fiber used. Some newly marketed fibers have a critical radius of only a few millimeters. To correct this problem, the implementation of the present subject uses a micromachined air-gap U-shaped support instead of a fiber-wound cylindrical piezoelectric element. Figure 27This principle is illustrated. In this scheme, the piezoelectric actuators (PZ1,...PZN) can be replaced by a microfiber collimator (MFC) and an air-gap U-shaped support structure constructed from microrings made of piezoelectric material. However, in this case, the piezoelectric actuators expand longitudinally in response to control voltages (V1,V2,...VN), thereby increasing (or decreasing) the air gap distance between the collimators. As with the cylindrical piezoelectric case, a single voltage Vc can be used to drive all the piezoelectric devices, provided that the gain (G1,G2,...GN) of each channel is adjusted accordingly to provide the correct expansion for each line. Ideally, the gain adjustment should be G1, 2G1, 3G1, etc., except for the inherent bias of the system (i.e., the intrinsic differences between operational amplifiers), thus providing an expansion in multiples of τRT / N. Another way to implement such a scheme is to use multiple piezoelectric rings at the channels. In this way, channels with 1, 2, 3, or N piezoelectric rings can be driven by the same voltage, with all amplifiers at the same gain.

[0104] Figure 28 A conceptual representation of an optical chip system 2800 is provided, which is used to successfully bridge two remote 10GigE switches. Ideally, such a connection can function similarly to a simple fiber optic cable. The timing of the TDM chip can be driven by the 10GigE switch.

[0105] refer to Figure 28 A USPL source 2805, identified by 2806, with a predetermined native pulse repetition rate, is connected to an optical pulse multiplier chip 2807. Component 2807 is designed to convert the incoming pulse repetition rate signal 2806 to an appropriate level for operation in conjunction with a high-speed network Ethernet switch identified by 2801. Switch 2801 provides a reference signal 2802 for modulating signal 2809 via a standard electro-optic modulator 2820 at the data rate of interest. The resulting RZ optical signal is generated as shown in component 2840.

[0106] An alternative to running timing from a 10 GigE switch is to build the USPL to terabits per second (or faster) using a multiplier photonic chip, and then modulate this terabits per second signal directly from the 10 GigE switch. Each bit will have around 100 pulses. One advantage of this approach is that it eliminates the need for a separate timing signal to run from the switch to the USPL. The USPL only needs to pump out terabits per second pulses via the multiplier chip. Another advantage is that the output of the multiplier chip does not have to be exactly 10.313 Gbps or 103.12 Gbps. It only needs to be at a rate of approximately 1 terabits per second. This limitation is not a problem when each 10 GigE bit has 100, 101, or 99 pulses. Another advantage is that each bit will have many 10 USPLs, so the 10 GigE signal will have atmospheric propagation (fog and flicker) advantages. Another advantage can be achieved at the receiver end. If a bit has around 100 USPL pulses within that single bit, the detector will be more likely to detect that bit. This results in improved receiver sensitivity and thus an improved range for the FSO system. Another advantage is that upgrading to 100GigE is as simple as replacing a 10GigE switch with a 100GigE switch. In this case, there will be approximately 10 pulses per bit.

[0107] From a purely signal processing perspective, this scheme demonstrates an efficient way to transmit data and clock data combined in a single transport stream. Much like "sampling" bits using a stream of optical pulses, this scheme has the advantage that the bit "size" is determined by the maximum number of pulses it carries, thus establishing a basis for counting bits as they arrive at the receiver. In other words, if a bit unit has time slots capable of matching N pulses, the system clock can be established as "a new information bit" after every 5th bit.

[0108] For ground, seabed, or FSO systems in air, space, or seabed applications, technologies similar to those described herein can be used within fiber-optic power plant distribution systems or FSO systems, and for the first time, an example is illustrated of how interconnection from USPL sources to optical network elements can be achieved for networking applications.

[0109] Figure 29 System 2900 is shown, which exemplifies Figure 28 This is a conceptual network extension of the design concept reflected in the diagram. Each of the multiple USPL sources 2901, 2902, and 2903 (it should be noted that although three are shown, any number is within the scope of this topic) is modulated via a dedicated optical switch and USPL laser multiplier chip circuitry, configured according to a WDM arrangement. See reference... Figure 28As described, electrical signals from each Ethernet switch can be used to modulate dedicated optical modulators 2911, 2922, and 2928 for each optical path. Optical power for each segment of the system can be provided by optical amplification elements 2931, 2932, and 2933 for amplification. Each amplified USPL path can then be coupled to a suitable optical combiner 2940 for transmission to network 2950, ​​and can be free-space or fiber-based as needed. The output from the WDM module can then be configured to transmit element 102 for FSO transmission or configured into fiber optic power plant equipment.

[0110] For ground, seabed, or FSO systems in air, space, or seabed applications, technologies similar to those described herein can be used within fiber-optic power plant distribution systems or FSO systems, and for the first time, an example is illustrated of how interconnection from USPL sources to optical network elements can be achieved for networking applications.

[0111] Figure 30 A schematic diagram of an experimental setup for an implementation of the present topic is shown, which includes constructing a computer-aided system to control the pulse width of an all-fiber mode-locked laser using recursive linear polarization adjustment, while stabilizing the cavity repetition rate using a synchronous self-regeneration mechanism. This design also provides tuning capability for both the repetition rate and pulse width.

[0112] A fiber ring laser is represented by an inner blue loop, in which all intracavity fiber branches are coded in blue, except for the positive high-dispersion fiber outside the loop, which is part of the fiber grating compressor (coded in dark brown). The outer loop represents the feedback active system.

[0113] Figure 30 A diagram of System 3000 is shown, illustrating the features of the USPL module that provides pulse width control and pulse repetition rate control through all the components that function to provide pulse repetition rate control and pulse width control: mirrors (M1, M2), gratings (G1, G2), lengths (L1, L2), second harmonic generator (SHG), photomultiplier tube (PMT), lock-in amplifier (LIA), data acquisition system (DAC), detector (DET), clock extraction mechanism (CLK), frequency-to-voltage controller (FVC), high voltage driver (HVD), reference signal (REF), pulse generator (PGEN), amplitude modulator (AM), isolator (ISO), piezoelectric actuator (PZT), optical coupler (OC), polarizer (POL), and polarization controller (PC).

[0114] Passive mode-locking mechanisms can be based on nonlinear polarization rotation (NPR), which can be used in mode-locked fiber lasers. In this mechanism, weakly birefringent single-mode fiber (SMF) can be used to create elliptically polarized light in a forward-propagating pulse. As the pulse travels along the fiber, it undergoes a nonlinear effect in which intensity-dependent polarization rotation occurs. By the time the pulse reaches the polarization controller (PC) 3001, the polarization state of the high-intensity portion of the pulse has undergone more rotation than the low-intensity portion. The controller can perform a function that rotates the high-intensity polarization component of the pulse, bringing its orientation as close as possible to the axis of the alignment polarizer (POL). Therefore, as the pulse passes through the polarizer, its lower-intensity component experiences more attenuation than the high-intensity component. Consequently, the pulse exiting the polarizer becomes narrower, and the entire process acts as a fast saturable absorber (FSA). This nonlinear effect, combined with the group velocity dispersion (GVD) of the loop, stabilizes after several round trips, achieving passive mode-locking. By using different types of optical fibers (such as single-mode, dispersion-shifted, polarization-maintaining, etc.) and summing their contributions to the average GVD of the laser, the total GVD of the optical loop can be customized to produce a specific desired pulse width within an error margin.

[0115] Actively controlling linear polarization rotation from a PC can significantly improve laser performance. This can be achieved using a feedback system that tracks the evolution of the pulse width. Figure 1The outer ring in the diagram represents a system that can be used to maximize compression and thus the average power of the pulse. The pulse exiting the fiber ring laser via the OC is expected to have a width on the order of several picoseconds. An external pulse compression scheme using a fiber grating compressor is used to narrow the pulse to below 100 fsec. This technique has been widely used in many reported experiments, producing high-energy, high-power USPL pulses. Here, the narrowed pulse is focused onto a second harmonic generator (SHG) crystal and detected using a photomultiplier tube (PMT). A lock-in amplifier (LIA) provides an output DC signal to a data acquisition card (DAC). This signal follows changes in pulse width by tracking increases or decreases in peak pulse power. Similar techniques have been successfully used in the past, except in this case, a spatial light modulator (SLM) is used as an alternative. Here, a programmable servo mechanism directly controls the linear polarization rotation using actuators on a PC. Using the DC signal data provided by the DAC, decision-making software (such as, but not limited to, LabVIEW or MATLAB / SIMULINK) can be developed to control the servo mechanism, which in turn adjusts the rotation angle of the input pulse relative to the polarizer axis. These adjustments performed by the actuator are achieved using stress-induced birefringence. For example, if the pulse width decreases, the mechanism will prompt the actuator to compensate by rotating linearly in a certain direction, and if the pulse width increases, it will do the opposite, both with the goal of maximizing the average output power.

[0116] A self-regenerative feedback system, synchronized with the repetition rate of the optical oscillation and used as the drive signal for the amplitude modulator (AM), can regulate the laser's round-trip time. In active systems, the amplitude modulator acts as a threshold gating device by modulating the loss in sync with the round-trip time. In recent reports, this technique has successfully stabilized mode-locked lasers. The signal picked up from the optical coupler (OC) by the photodetector (DET) can be electronically locked and regenerated using a clock extraction mechanism (CLK) such as a phase-locked loop or a synchronous oscillator. The regenerated signal triggers a pulse generator (PGen), which then drives the modulator. In a fully synchronized scenario, the AM will "turn on" at each round-trip time (TRT) with each pulse passing through it. As the CLK follows the changes on the TRT, the drive signal for the AM will also change accordingly.

[0117] An external reference signal (REF) can be used to tune the repetition rate of the cavity. This can be compared to a signal recovered from the CLK using a mixer, and the output is used to drive a piezoelectric (PZT) system whose cavity length can be adjusted. Using a PZT system to adjust the cavity length is a well-known concept, and similar designs have been successfully demonstrated experimentally. Here, a linear frequency-to-voltage converter (FVC) can be calibrated to provide an input signal to the high-voltage driver (HVD) of the PZT. The PZT will adjust the cavity length to match the repetition rate of the REF signal. For example, if the REF signal increases its frequency, the output of the FVC will decrease, and the HV drive level to the piezoelectric column will also decrease, forcing it to contract, thus increasing the laser's repetition rate. The opposite occurs when the reference repetition rate decreases.

[0118] A pair of negative dispersion gratings can be used to tune the pulse width to a "transform limit" value. This chirped pulse compression technique is well-established, and pulse compression as narrow as 6 fs has been reported. The idea is to mount the grating-to-pulse compressor on a moving stage that translates along a line that sets the spacing between the gratings. The compression factor changes with the distance.

[0119] In an example of a data modulation scheme consistent with the implementation of the present topic, a passively mode-locked laser can be used as an ultrafast pulse source, which limits our flexibility in changing the data modulation rate. To scale up the data rate of our system, we need to increase the fundamental repetition rate of our pulse source. Traditionally, the repetition rate of a passively mode-locked laser is increased by shortening the laser cavity length or by harmonic mode-locking the laser. Both techniques result in a reduction in the peak power of the pulse within the cavity, leading to longer pulse widths and less stable mode-locking.

[0120] One solution to this problem involves using an improved pulse interleaving scheme through a technique we call pulse multiplication. Figure 31This concept is illustrated. A low-repetition-rate pulse train from a well-characterized, well-mode-locked laser 3101 is coupled to an integrated optical directional coupler 3180, where a defined portion of the pulse is detached and “re-looped” in the optical loop with an optical delay 3150 equal to the expected inter-pulse interval in the output pulse train, and recoupled to the output of the directional coupler. For example, to generate a 1 GHz pulse train from a 10 MHz pulse train, an optical delay of 1 ns is required, and the optical delay may need to be precisely controlled so that the 100th pulse in the train can coincide with the input pulse from the 10 MHz source. The optical delay loop includes an optical gain 3120 to compensate for signal attenuation, a dispersion compensation 3160 to recover the pulse width, and active optical delay control 3150. Once pulse multiplication occurs, the output pulse train is OOK modulated by data stream 3182 3175 to generate RZ signal 3190, and amplified in erbium-doped fiber amplifier 3185 to bring the pulse energy to the same level as the pulse train (or to the expected output pulse energy level).

[0121] One or more features described herein, whether considered individually or in combination, can be included in various aspects or embodiments of the present subject matter. For example, in some aspects, an optical wireless communication system may include at least one USPL laser source, which may optionally include one or more of picosecond, nanosecond, femtosecond, and attosecond type laser sources. An optical wireless communication system may include a USPL source that may be fiber-coupled or free-space coupled to an optical transmission system, may be modulated using one or more modulation techniques for point-to-multipoint communication system architectures, and / or may utilize an optical transmission terminal or telescope manufactured using hyperbolic mirror fabrication techniques, conventional Newtonian mirror fabrication techniques, or other functionally equivalent or similar techniques. Moreover, or alternatively, aspherical optical designs may be used to minimize, reduce, etc., the obstruction of the received optical signal.

[0122] A free-space optical transmission system consistent with the embodiments of the present topic can be designed using a USPL laser that focuses the received signal to an ideal point. In some embodiments, a telescope or other optical element for focusing and transmitting light can be considered the transmitting element, and a second telescope or other optical element located at a remote position relative to the first telescope or other optical element for focusing and receiving light can act as the receiving element to create an optical data link. Both optical communication platforms can optionally include the components required to provide both transmitting and receiving functions and can be referred to as USPL optical transceivers. Either or both of the telescopes or other optical elements for focusing and transmitting light can be coupled to the transmitting USPL source via optical fiber or via free-space coupling with the transmitting element. Either or both of the telescopes or other optical elements for focusing and receiving light can be coupled to the receiving endpoint via optical fiber or via free-space coupling with the optical receiver. Free-space optical (FSO) wireless communication systems, including one or more USPL sources, can be used in the following ways: within the framework of an optical communication network; in conjunction with an optical fiber backhaul network (and can be used transparently within the optical communication network); within the optical communication network (and can be modulated using on-off keying (OOK) non-return-to-zero (NRZ) and return-to-zero (RZ) modulation techniques within the 1550nm optical communication band); within the optical communication network (and can be modulated using differential phase shift keying (DPSK) modulation techniques); within the optical communication network (and can be modulated using common modulation techniques for point-to-point communication system architectures using common free-space optical transceiver terminals); within the optical communication network utilizing D-TEK detection technology; within the communication network used in conjunction with erbium-doped fiber amplifiers (EDFAs) and high-power erbium-doped ytterbium-doped fiber amplifiers (Er / Yb-DFAs); within the optical communication network (and can be modulated using common modulation techniques for point-to-multipoint communication system architectures), etc.

[0123] In some respects, USP technology can be used as a beacon source to provide optical tracking and beam steering for automatic tracking capabilities and to maintain terminal co-alignment during operation. The recovered clock and data extracted at the receiving terminal can be used for multi-hop spans to extend network reach. Similar benefits can be provided to this optical network in a WDM configuration, thereby increasing the effective optical bandwidth of the carrier data link. Moreover, or alternatively, the USP laser source can be polarization-multiplexed onto the transmitted optical signal to provide polarization-multiplexed USP-FSO (PM-USP-FSO) functionality. The recovered clock and data extracted at the receiving terminal can be used for multi-hop spans to extend network reach and can include a general large bandwidth operating range for providing data rate-constant operation. Optical preamplifiers or semiconductor optical amplifiers (SOAs) can be used before the optical receiver elements and, alternatively or in combination with the recovered clock and data extracted at the receiving terminal, can be used for multi-hop spans to extend network reach, thus providing a general large bandwidth operating range for providing data rate-constant operation. It is possible to maintain terminal co-alignment during operation, enabling significant improvements in performance and terminal co-alignment through the use of USPL technology, USPL data sources, and an improved scheme for maintaining transceiver alignment using USPL laser beacons.

[0124] In some respects, utilizing hyperbolic mirror fabrication techniques that focus the received signal to an ideal point or optical transmission terminals manufactured using conventional Newtonian design, USPL-FSO transceivers can be used for remote sensing and detection of airborne elements using ionizing or non-ionizing detection techniques. USPL-FSO transceivers consistent with embodiments of the present subject can be used in non-line-of-sight laser communication applications. USPL-FSO transceivers consistent with embodiments of the present subject allow for: adjustment of the distance at which scattering effects (enabling NLOS techniques) occur, receiving techniques for improving detection sensitivity using DTech detection schemes, and increased bandwidth via a broadband detector including a frequency comb. USPL-FSO transceivers consistent with embodiments of the present subject can be used in conjunction with adaptive optics (AO) techniques for performing incoming light wavefront correction (AO-USPL-FSO). USPL-FSO transceivers consistent with embodiments of the present subject can be used and operated across the infrared wavelength range. The USPL-FSO transceiver, consistent with the implementation of the present subject matter, can be used in both single-mode and multimode fiber configurations in conjunction with optical add-drop and optical multiplexing techniques. The USPL-FSO transceiver, consistent with the implementation of the present subject matter, can be used and operated across the infrared wavelength range as a rangefinder and position determination device for target identification and interrogation applications.

[0125] In other aspects of the current topic, a range of switched network connections, such as 10GigE or 100GigE connections, can be connected from one point to another, for example, via time division multiplexing (TDM) through fiber optics or free-space optics.

[0126] Mode-locked USPL sources, consistent with the implementation methods described in this paper, can be used to generate both clock and data streams. Mode-locked lasers can represent a high-performance, high-precision clock source option in digital communication systems. In this regard, mode-locked fiber lasers (in linear or ring configurations) can be an attractive preferred option because they can achieve pulse widths and repetition rates up to GHz in the USPL source region.

[0127] High-order harmonics can be generated using carbon nanotube saturable absorbers (CNT-SA). Passive mode-locked fiber lasers using CNT-SA have become a high repetition rate source option due to their ability to easily generate high-order harmonics with a fundamental repetition rate.

[0128] FSO can be used for terrestrial, space, and seabed applications.

[0129] Conditional path length control from the beam splitter to the stop can be an important parameter. TDM multiplexing, consistent with the implementation described in this paper, can be used to control the relative time-domain delay between the stop and the source path. Each pulse train can be controlled using a parallel time-delay channel. This technique can be used to control conventional multi-transmit FSO stop systems employing both WDM and TDM systems. For both TDM and WDM systems, the pulse-to-pulse interval of the USPL laser can be maintained and controlled to meet precise time-domain requirements. The described technique can be used in both TDM and WDM fiber-based systems. The use of TDM multiplexers as described herein can be used to implement unique encryption on the transmitted optical signal. Complementary TDM multiplexers can be used to reverse the incoming received signal and thereby recover the unique identifying characteristics of the pulse signal. The TDM multiplexers described herein can be used to control WDM pulse characters for WDM encryption. TDM multiplexers can be used in conventional FSO systems where multiple stops connected to a common source signal enable control over the time delay between pulses to maintain a constant path length. TDM multiplexers can be used in both TDM fiber-based and FSO-based systems. A TDM multiplexer can be an enabling technique for controlling the optical pulse train relationship of a USPL source. By measuring the neural correction factor to obtain the same pulse relationship, the TDM multiplexer can be used as an atmospheric link characterization function across optical links.

[0130] Any combination of PZ disks can be used in the transmitter, and an unlimited number of encryption combinations can be provided for USPL-based systems (both fiber-based and FSO-based). Timing can be run from a 10GigE switch or equivalent, and the USPL can be built to terabits per second (or faster) using a multiplier photonic chip, and this terabits per second signal can be modulated directly from a 10GigE switch. When running in a WDM configuration, it can include interfaces with fiber-based systems or with FSO network elements.

[0131] The system can accept ultrafast optical pulse trains and generate optical pulse trains with the same pulse width, spectral content, and chirp characteristics as the input optical pulses, and whose pulse repetition rate is an integer multiple of the input pulse's pulse repetition rate. This can be achieved by tapping a portion of the input pulse power in a 2×2 optical coupler with an actively controllable optical coupling coefficient, recirculating the tapped pulse in a round trip in an optical delay line with optical amplification, optical isolation, optical delay (path length) control, optical phase and amplitude modulation, and compensation for the time and spectral evolution of the optical pulse in the optical delay line to minimize the time pulse width at the device output, and then recombining this power using the 2×2 optical coupler.

[0132] Passive or active optical delay control can be used, as well as optical gain utilizing rare-earth-doped optical fibers and / or rare-earth-doped integrated optics and / or electrically pumped or optically pumped semiconductor optical amplification. Fiber Bragg gratings and / or bulk Bragg gratings can be used to provide dispersion compensation. Wavelength division multiplexing data modulation of pulses crossing delay lines can be used, as well as pulse-coded data modulation of pulses crossing delay lines.

[0133] For FSO applications, conventional USPL sources can be customized by synthesizing USPL square wave pulses using microlithography amplitude and phase masking techniques. The ability to adjust pulse width using control techniques and similar schemes, and the capacity for active pulse control, can improve propagation efficiency through FSO transmission links, thereby enhancing system availability and the level of received optical power.

[0134] Active programmable pulse shapers can be used to actively control the USPL pulse width, which can include matching real-time atmospheric conditions to maximize propagation through a constantly changing environment. In FSO applications, one or more of the following techniques can be used to technically adapt the optical time spectrum: Fourier transform pulse shaping, liquid crystal modular (LCM) arrays, liquid crystal on silicon (LCOS) technology, programmable pulse shaping using an acousto-optic modulator (AOM), acousto-optic programmable dispersion filter (AOPDF), and polarization pulse shaping.

[0135] Figure 32 A process flowchart 3200 illustrating the features of the exemplary method is shown; one or more of these features may appear in the embodiments of the present subject. At 3202, a beam is generated, each containing an optical pulse with a duration of approximately 1 nanosecond or less. At 3204, a modulation signal is applied to the beam to generate a modulated optical signal. This modulated signal carries data for transmission to a remote receiving device. At 3206, the modulated optical signal is received at an optical transceiver within the optical communication platform, and at 3210, the optical transceiver is used to transmit the modulated optical signal for reception by a second optical communication device.

[0136] Figure 33 Another process flowchart 3300 illustrates features of the exemplary method, one or more of which may appear in the embodiments of the present subject. At 3302, a beam of light pulses, each with a duration of approximately 1 nanosecond or less, is generated, for example using a USPL source. The beam of light pulses is transmitted towards a target atmospheric region via an optical transceiver at 3304. At 3306, the optical information received at the optical transceiver is analyzed as a result of optical scattering of the light pulse beam from one or more objects in the target atmospheric region.

[0137] Figure 34 Another process flowchart 3400 illustrating the features of the exemplary method is shown; one or more of these features may appear in embodiments of the present subject matter. At 3402, a first beam and a second beam comprising optical pulses are generated, for example, from a USPL source. At 3404, a first modulation signal is applied to the first beam to generate a first modulated optical signal, and a second modulation signal is applied to the second beam to generate a second modulated optical signal. At 3406, a first polarization state of the first modulated optical signal is adjusted. Optionally, a second polarization state of the second modulated optical signal may also be adjusted. At 3410, the first modulated optical signal having the adjusted first polarization state is multiplexed with the second modulated signal. At 3412, the first modulated optical signal having the adjusted first polarization state, multiplexed with the second modulated signal, is transmitted by an optical transceiver for reception by a second optical communication device.

[0138] Figure 35A and Figure 35B Exemplary nodes that can be used to send and / or receive information are shown. Sending node 3510 and receiving node 3530 can be the communication platform described above, including reference... Figures 1 to 9Additionally, although the transmitting node 3510 is shown having components for generating and transmitting data-bearing optical signals, and the receiving node 3530 is shown having components for receiving optical signals and extracting data from them, these components can be combined into a single node configured to both transmit and receive optical signals. In some embodiments, for example, a telescope 3522 can act as an aperture for both transmitting and receiving optical signals.

[0139] Figure 35A An exemplary transmitting node 3510 is illustrated. In some embodiments, transmitting node 3510 may include a source 3512. In some embodiments, source 3512 may be a USPL source, a superluminescent diode, or other source. In other embodiments, source 3512 may be a continuous wave source. Preferably, source 3512 may be configured to generate a beam of light pulses, wherein each pulse has a coherence length of less than 400 micrometers. The coherence length of the source is determined as: Where C is a shaping constant equal to 1 / 2, λ is the center wavelength of the pulse, and Δλ is the full width at half maximum (FWHM) spectral width of the pulse. In some embodiments, the coherence length may be less than 1 mm, less than 600 μm, less than 400 μm, less than 200 μm, less than 100 μm, less than 50 μm, or less than 1 μm. In embodiments using a continuous wave source, these values ​​may refer to the coherence length of the continuous wave beam, rather than the coherence length of the pulse.

[0140] In some embodiments, source 3512 may have a center wavelength in the infrared range. In other instances, the center wavelength of source 3512 may be between 1400 nm and 1700 nm. In some embodiments, source 3512 may be configured to output pulses at a repetition rate of at least 50 MHz, 100 MHz, 200 MHz, 500 MHz, 800 MHz, 1 GHz, 1.25 GHz, 1.5 GHz, 2 GHz, 5 GHz, or 10 GHz. Source 3512 may include (internal or external) a pulse multiplier, as generally described above, including a reference... Figure 15 as well as Figures 18 to 20 In some embodiments, the pulse width may be less than 10 ns, less than 1 ns, less than 500 ps, ​​less than 300 ps, ​​less than 100 ps, ​​less than 50 ps, ​​less than 10 ps, ​​less than 1 ps, less than 700 fs, less than 500 fs, less than 300 fs, less than 200 fs, or less than 100 fs.

[0141] Transmitting node 3510 may optionally include beam splitter 3514. Beam splitter 3514 can be configured to split a pulse from source 3512 into multiple separate pulses with different wavelength bands. For example, a pulse with an original spectral width of 1500 nm to 1600 nm can be split into twenty-five pulses, each pulse having a corresponding spectral width of 4 nm from 1500 nm to 1600 nm (e.g., 1500 nm to 1504 nm, 1504 nm to 1508 nm, 1508 nm to 1512 nm, etc.). Beam splitter 3514 can use any known beam splitting mechanism. Each of the multiple separate pulses may have a coherence length of less than 1 mm, less than 600 μm, less than 400 μm, less than 200 μm, less than 100 μm, less than 50 μm, or less than 1 μm.

[0142] Transmitting node 3510 may include one or more modulators 3516. In some embodiments, each of the modulators 3516 may be a Mach-Zehnder modulator (MZM). Modulator 3516 may receive a data signal indicating data to be transmitted in the beam, and based on this data signal, may encode data into pulses of the beam using on / off keying or other modulation techniques. In some embodiments, modulator 3516 may allow pulses to pass to indicate a "1" in the bit stream, and may block pulses or reduce the amplitude of pulses to indicate a "0" in the bit stream. In a split-beam embodiment, each of a plurality of separate pulses may be directed to a corresponding modulator 3516 among a plurality of modulators. In other embodiments, each of a plurality of separate pulses may be modulated by a single modulator 3516. For example, the separate pulses may be time-delayed and interleaved relative to each other, and modulator 3516 may encode data into each pulse at a repetition rate higher than the pulse generation repetition rate of the source pulses. When the source 3512 generates pulses at a rate of at least 1 GHz, for example, a beam splitter can divide each pulse into twenty-five or more separate pulses, which can be modulated by one or more modulators 3516 to encode data at a rate of at least 25 Gbps. In some embodiments, the source can generate pulses at a rate of at least 1 GHz, and the beam splitter can divide each pulse into at least ten, at least twenty, at least thirty, at least forty, or at least fifty separate pulses to generate data rates of at least 10 Gbps, at least 20 Gbps, at least 30 Gbps, at least 40 Gbps, or at least 50 Gbps. In some embodiments, the FWHM bandwidth of the source can be at least 100 nm, at least 150 nm, or at least 200 nm, which allows the pulses to be divided into more separate pulses without reducing the coherence length of those pulses to below the level described below. Figure 40 and Figure 41 The value described.

[0143] After modulation, the pulses (optionally, split pulses in the case of a beam splitter) can be passed to an optional threshold filter 3518. In some embodiments, the threshold filter can be a saturable absorber (or different nonlinear devices) that attenuates weak pulses and transmits strong pulses. The threshold filter 3518 can be configured to eliminate or sufficiently reduce pulses below a defined threshold while allowing pulses above that threshold to pass. In some embodiments, the modulator 3516 can significantly attenuate pulses intended to transmit "0", but the modulator may be imperfect and a certain amount of optical energy may pass through, which, when amplified by the amplifier 3520, may produce a signal strong enough to generate bit errors. By using the threshold filter 3518, the pulses intended to be eliminated can be eliminated more sufficiently, thereby improving the data transmission accuracy of the system.

[0144] The modulated pulse can be passed to amplifier 3520, which can amplify the amplitude of the pulse transmitted by telescope 3522 (which may be, for example, an aperture and / or a lens). In the case of using a beam splitter, the separated pulses can be recombined using a combiner (not shown) before or after being passed to amplifier 3520.

[0145] Figure 35B An exemplary embodiment of a receiving node 3530 is shown, which can be configured to receive a light beam transmitted by, for example, a transmitting node 3510 and extract data from the light beam. The receiving node 3530 may include an aperture 3532, an optional beam splitter 3534, and one or more optical receivers 3536, which may have source-specific characteristics, as described in detail below. The optical receiver 3536 may include a photodiode and processing circuitry. In some embodiments, the optical receiver 3536 may be, for example, an avalanche photodiode. In some embodiments, the processing circuitry of the optical receiver may determine whether the received light in a detection window exceeds a detection threshold and output bit data (e.g., "0" or "1") for that window based on the determination result. The receiving node 3530 may be an optical communication platform as described above. In some embodiments, components of the transmitting node 3510 and the receiving node 3530 may be included in a single transceiver node.

[0146] The aperture 3532 can be configured to receive optical signals, such as those from... Figure 35AThe transmitting node 3510 described herein transmits a light beam. In some embodiments, the light received at the aperture 3532 may pass through a filter that filters out light of wavelengths not close to the center wavelength of the source. For example, the source in the transmitting node may have a center wavelength between 1500 nm and 1700 nm, and the filter at the receiving node 3530 may block or reduce light outside the source band. For example, the filter may reduce the amplitude of light below 1500 nm. Optionally, the filter may additionally block longer wavelengths of light, or the threshold may be set at a lower wavelength, such as 1480 nm or 1460 nm. Optionally, the receiving node 3530 may include a beam splitter 3534 that can split pulses in the received beam into multiple separate pulses of different wavelength bands. When pulses are split and individually modulated at the transmitting node 3510, the pulses may be split into the same wavelength band by the beam splitter 3534 in the receiving node. The pulses (combined pulses or separate pulses in the case of using a beam splitter) may then be processed by one or more optical receivers 3536. In embodiments where the pulse is divided into multiple separate pulses, each pulse can be directed to a corresponding optical receiver, which can be configured to determine whether an "on" or "off" signal was transmitted within a given detection window. In some embodiments, encoding modes other than on / off keying, such as frequency modulation, can be used. Reference will be made below. Figure 41 Additional details are provided regarding the optical receiver 3536.

[0147] Figure 36 An exemplary arrangement is shown, in which a sending node 3510 and a receiving node 3530 (such as those mentioned above) are used. Figures 35A to 35B The described optical communication network 3542 transmits data across an optical communication distance D from a first communication network 3542 to a second communication network 3544. Data can be received from the optical communication network 3542, encoded into a light beam, and transmitted across the optical communication distance D using a transmitting node 3510. A receiving node 3530 can receive the light beam, extract the transmitted data, and pass the data to the communication network 3544. In some embodiments, data from the communication network 3544 can also be transmitted from node 3530 back to node 3510, which can then pass the data to the communication network 3542 to enable bidirectional communication. In some embodiments, the optical communication distance can be at least 0.5 miles, at least 1 mile, at least 2 miles, at least 3 miles, at least 5 miles, at least 7 miles, at least 10 miles, or at least 20 miles.

[0148] Figure 37An exemplary beam is shown traveling across an optical communication distance D (such as 1 mile) through a medium with a perfectly uniform refractive index. Even in a medium with a perfectly constant refractive index, the beam will naturally spread due to diffraction; however, the beam retains the same shape and only expands by an amount proportional to the propagation distance, and there is no beam flash effect in a medium with a uniform refractive index.

[0149] Figure 38 A schematic representation of photons in a beam traveling through a variable refractive medium is provided. The atmosphere experiences fluctuations in temperature, density, pressure, humidity, aerosols, wind, convection, and other parameters, causing variations in its refractive index. When a beam of light passes through the atmosphere or another variable refractive medium (such as water), the photons within that beam can be refracted in a slightly different way than other photons. Figure 38 As shown, due to the variation in refractive index in a variable refractive medium, different ray paths within a beam may be subjected to different refractions. Consequently, in systems that transmit over sufficiently large optical communication distances D and receive free-space beams at the receiving node (such as the system shown in Figure 35), different photons within a single pulse can travel paths of different lengths to reach the receiving node and may arrive at different times. If the time delay is less than the coherence length of the source, these differences in path lengths, along with the time required for photons to travel these distances, can generate coherent interference and degrade signal quality in free-space optical communication systems. This paper describes solutions to this problem, including references... Figure 40 and Figure 41 And as in such Figure 35A , Figure 35B and Figure 36 The systems shown are those that are used in the system.

[0150] In addition to variations in path length, photons within a pulse can travel at variable speeds due to changes in atmospheric conditions, including humidity, temperature, and density. Because different photons within a pulse travel through slightly different atmospheric conditions, they may travel at different speeds and arrive at different times. Furthermore, different wavelengths of light within a pulse can travel at different speeds, which can further broaden the pulse as it passes through a variable refractive medium.

[0151] Figure 39 A schematic representation of a pulse emitted by a transmitter and received by an optical receiver is shown. (As shown) Figure 39 As shown, when a pulse is transmitted by a transmitting node, the pulse can have a pulse width of 90 femtoseconds. The pulse can then travel an optional transmission distance, where it can be received by an optical receiver having a detection window 4020 with a predetermined duration, for example, 500 picoseconds. When the pulse is received by the optical receiver, its received pulse width may be widened due to the passage through a variable refractive medium, as described above. Figures 37 to 38 As described, due to variations in the beam's path length and the atmospheric conditions it traverses, different photons may arrive at the detector at different times according to a distribution curve that can have a duration longer than the pulse duration at the time of emission. The amount of broadening can vary depending on the length of the optical communication distance and atmospheric conditions, including humidity, temperature, density, and the presence of aerosols such as fog. Under some conditions, this broadening can be on the order of picoseconds or greater.

[0152] The pulse can have a time distribution curve as shown in the figure. Although a normal time distribution curve is shown, other pulse shapes are also possible. By making the width of curve 4010 longer than the coherence length of the emitted pulse (e.g., three times it), coherent beam interference and coherent beam scintillation can be reduced.

[0153] Figure 40 An exemplary time distribution curve is shown for a short-duration (e.g., approximately 100 femtoseconds) pulse 4010 that travels a considerable distance (e.g., one mile) through a variable refractive medium and is broadened in time. The pulse may have an FWHM duration 4030 and a coherence time 4040 when it reaches the optical receiver, the coherence time being equal to the pulse's coherence length divided by the speed of light through the variable refractive medium. In some embodiments, the FWHM duration 4030 may be greater than the pulse's coherence time 4040. Preferably, the FWHM duration 4030 may be at least 2, at least 3, at least 4, at least 5, at least 6, at least 8, at least 10, or at least 12 times the pulse's coherence time 4040. By ensuring that the FWHM duration 4030 of the pulse received at the optical receiver is relatively large compared to the coherence time 4040 of the pulse 4010, interference between different ray paths of the pulse when the pulse arrives at the optical receiver at different times can be reduced, and reduced noise and higher quality signals can reach the optical receiver.

[0154] The optical receiver can have a detection window 4020, which has a specified duration. Shorter detection windows generally allow for higher data throughput. For example, in a system using on / off keying for data modulation, an optical receiver with a 1 nanosecond detection window can extract up to 1 Gbps, while an optical receiver with a 100 picosecond detection window can extract up to 10 Gbps. The optical receiver can have repeating detection windows of less than 100 ns, less than 10 ns, less than 1 ns, less than 100 ps, ​​or less than 10 ps.

[0155] However, pulse length and time broadening can cause photons from pulses intended to be received in one detection window to fall into adjacent detection windows. This phenomenon can lead to bit errors if the transmitted photons should not be received in the adjacent detection window (e.g., because a "0" is transmitted at that bit position). Therefore, to maximize data transmission accuracy, it is important that the FWHM duration 4030 of the pulse received at the optical receiver is greater than the coherence length 4040 of the pulse (and preferably at least three times it), while the FWHM duration 4030 of the pulse received at the optical receiver should also be significantly shorter than the detection window 4020 of the optical receiver.

[0156] For example, the detection window 4020 may be at least 2, 5, 6, 7, 8, 10, or 20 times the FWHM duration 4030 of the pulse received at the optical receiver. Preferably, at least 95%, 99%, or 99.99% of the photons in the pulse arriving at the optical receiver may arrive at a corresponding arrival time separated from the center 4040 of the pulse's time distribution curve by a corresponding time difference, which is less than half the detection window duration of the optical receiver. Note that although the center 4040 of the pulse's time distribution curve is shown as being located at the center of the detection window 4020, this is not necessarily the case, and the pulse may arrive earlier or later than the midpoint of the detection window. The center 4040 of the time distribution curve may preferably be located at or near the center of the detection window 4020 to reduce the possibility of photons in the pulse spilling into adjacent detection windows. In some embodiments, the distance between the center of the time distribution curve 4040 and the center of the detection window 4020 can be less than 100 picoseconds, 50 picoseconds, 20 picoseconds, 10 picoseconds, 5 picoseconds, 1 picosecond, 800 femtoseconds, or 500 femtoseconds.

[0157] By specifying the relationship between the pulse coherence time 4040, the FWHM duration 4030 when the pulse arrives at the optical receiver, and the detection window 4020 of the optical receiver in the manner described herein, data transmission accuracy and effective transmission range can be greatly improved (see below for details). Figure 42(Discussion based on test results). The FWHM duration 4030 when the pulse arrives at the optical receiver can vary, depending on the pulse length transmitted from the source, the medium through which the pulse travels (e.g., atmospheric pressure, temperature, sunlight intensity, aerosol), and the distance the pulse travels to reach the optical receiver. Therefore, it may be necessary to reduce the pulse coherence time 4040 and / or increase the detection window 4020 of one or more optical receivers, depending on the conditions of the optical communication system. Thus, reducing the coherence time 4040 and increasing the detection window 4020 can improve data transmission quality while negatively impacting data throughput. In some embodiments, the system can be configured to determine the data transmission quality of the system (e.g., bit error rate or a signal value measurement that is above or below a detection threshold), and in response to the determined data transmission quality, modify either or both of the pulse coherence time 4040 and the optical receiver detection window duration 4020.

[0158] Similarly, when using sources capable of continuously emitting light, such as continuous-wave sources or superluminescent diodes, the emitted light can be gated into pulses (or otherwise converted into pulses using data modulation or other known techniques). These pulses occupy only a relatively small fraction of the detection window duration and can be timed to arrive at or near the center of the detection window of the optical receiver. Gating and timing the pulses in this way reduces the risk that photons in the "open" window (in which light is intended to propagate) might spill into the "closed" window (in which light is not intended to propagate) and cause errors. Therefore, the pulse duration and position relative to the detection window described above can also be applied to pulses generated using sources capable of continuously emitting light. In such cases, although these sources can emit light continuously, the effective output can be "off" for most of the time, even during the "open" transmission window intended for light propagation, thus leaving sufficient interval between the center of the pulse and the end of the detection window to avoid spillover. For example, during the “open” bit window of the intended transmission of light, the effective output from a continuous emission source may be “open” for less than 50%, less than 30%, less than 20%, or less than 10% of the corresponding transmission bit window.

[0159] Figure 41 A schematic representation of an optical pulse arriving within detection windows 4020a, 4020b, and 4020c of an optical receiver is shown. The optical pulse can have any shape and may generally be broadened to some extent due to its travel across the optical communication distance through a variable refractive medium. In the first detection window 4020a, the optical pulse may arrive at or near the center of the window and may cause the total received light in that window to exceed a detection threshold V. thThis can be processed by the optical receiver circuitry to indicate that a pulse has been received within the window. In some embodiments, this can cause the optical receiver to output a "1" for this detection window. At the end of detection window 4020a and before detection window 4020b, the optical receiver circuitry can be reset and return to zero. In detection window 4020b, no pulses are transmitted (e.g., because it is intended to transmit a "0" and the modulator at the transmitting node blocks the pulse), and the total light received in window 4020b may be below the detection threshold V. th This allows the optical receiver to output "0" for this detection window. The optical receiver circuit can be reset again and return to zero, and this cycle can be repeated with the third window 4020c, and so on.

[0160] Detection threshold V th It can be configured to be high enough that ambient light will not trigger false alarms, but low enough that real pulses will reliably exceed the detection threshold V. th Importantly, the pulse must sufficiently exceed the noise floor to ensure a adequate signal difference between the "open" and "closed" bit windows, making the detection threshold V... th It can be high enough to ignore ambient noise, yet low enough to capture every transmitted pulse. This is particularly challenging over longer distances (e.g., a mile or more) and under suboptimal environmental conditions (e.g., partially sunny, with high aerosol levels). (This article is related to...) Figures 39 to 41 The described relationship between pulse length, coherence time, and detection window at the optical receiver significantly improves signal quality transmission and allows for an effective detection threshold V even for free-space optical systems transmitting data over optical transmission distances exceeding 1 mile, 2 miles, 3 miles, 5 miles, or 7 miles. th .

[0161] In a configuration with a beam splitter and multiple optical receivers, each of the optical receivers can generate a bitstream based on separate pulses directed to that receiver, and the bitstreams from the various optical receivers can be interleaved to produce a combined bitstream with a higher data rate. This combined bitstream can be output to as described above (including contact...). Figure 36 ) communication network.

[0162] Figure 42 An example of test data received over a one-mile optical communication distance is shown. The test data will use the contact information above. Figure 35A The optical signal generated by the described transmitting node is compared with an optical signal generated using a continuous wave source with the same average power as the USPL source. Specifically, in order to generate Figure 42 The data shown in the top row of the chart is incorporated into the above connection. Figure 35AThe USPL source in the described transmitting node is used to transmit data over a one-mile optical communication distance. The received signal is directed to a sheet of white paper, and an infrared camera is placed behind the paper to record the light passing through it. To generate... Figure 42 The data shown in the bottom row of the charts were generated using the same experimental setup with a continuous wave source having the same average power and optical communication distance as the USPL source. Light from both the USPL and CW sources was directed onto the same white sheet of paper, and two signal spots were captured in the same frame using an infrared camera. The spot size was approximately 12 inches in diameter. Background ambient light was subtracted from each pixel, and each pixel was subjected to threshold logic such that pixels with received light signals above a threshold were set to "white," and pixels with received light signals below a threshold were set to "black." The four images shown for each source are taken from the same frames in the video feed, and these frames are equidistant at 10-second intervals. Frame A shows the signals received from the USPL and CW sources at 10 seconds, frame B shows the signals received from the USPL and CW sources at 20 seconds, frame C shows the signals received from the USPL and CW sources at 30 seconds, and frame D shows the signals received from the USPL and CW sources at 40 seconds.

[0163] This data indicates that the transmitting node described in this paper generates ultrashort pulses that are significantly more clustered and reliably exceed the detection threshold within the detection field. When applied to devices using the aforementioned (including references) Figures 35B to 41 When a communication system with a light receiver exhibits the characteristics of [the described system], this results in a significantly improved data transmission accuracy. Tests conducted by the applicant on the system according to this description have demonstrated free-space optical communication distances with zero bit error rate exceeding 1 mile, 2 miles, 3 miles, 5 miles, and up to 7.4 miles, measured over time intervals of at least 10 seconds, at least 30 seconds, at least 60 seconds, at least 10 minutes, at least 30 minutes, and at least 1 hour. In some embodiments, the system described herein can transmit data across an optical communication distance of at least one mile and has a measured bit error rate of less than one part per million, less than one part per billion, less than one part per trillion, or less than one part per quadrillion over a measurement period of at least sixty seconds. To the applicant's knowledge, no other free-space optical system has achieved similarly low bit error rates across even half a mile of optical communication distance.

[0164] Therefore, the systems described herein allow for significantly improved data transmission accuracy and communication link distance, and they also allow for the use of free-space optical communication under harsh environmental conditions (e.g., rain, fog, atmospheric scintillation) that render free-space optical communication ineffective in existing systems. In some embodiments, the improved data transmission quality and range may also allow for the application of free-space optical communication to systems that were previously impossible to use effectively. For example, transmitting and / or receiving nodes according to this disclosure can be provided in Earth-orbiting satellites to provide ground-to-air and / or air-to-ground free-space optical communication. Due to the amount of atmosphere traversed between Earth's surface and space, no one has yet demonstrated effective optical data transmission using techniques prior to this disclosure, but the techniques described herein can enable effective optical communication over this distance.

[0165] Figure 43 An exemplary ranging node 4400 is shown, which can be used to detect objects or surfaces and determine the positions of these objects relative to the node. The ranging node 4400 generally includes the contact information described above. Figure 35A and Figure 35B The components of the transmitting node 3510 and receiving node 3530 are described. For example, the ranging node 4400 may include a source 3512, a beam splitter, one or more modulators, an amplifier, and a telescope. These components can be collectively configured to emit light pulses that travel toward the surface S through a variable refractive medium. For the laser ranging node, data modulation is optional but may include encoding information associated with the pulses, nodes, or other information. Photons from the light pulses can be reflected by the surface S and return to node 4400. The total travel distance of the light pulse from the ranging node to the received reflected pulse can be twice the distance from the node to the surface S. Upon returning to the node, the pulse can be received by an aperture 3532, optionally split by a beam splitter 3534, and analyzed using one or more optical receivers 3536. Each of these components may have [related to the above description]. Figures 35A to 41 The corresponding components described have the same properties and parameters. The ranging node 4400 may additionally include a time-of-flight (TOF) circuit 4410, which can be configured to determine the time of flight of a pulse arriving at the surface S and returning to the node 4400, and thereby determine the distance of the surface S relative to the ranging node 4400.

[0166] One or more aspects or features of the subject matter described herein may be implemented in digital electronic circuits, integrated circuits, application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), computer hardware, firmware, software, and / or combinations thereof. These different aspects or features may be implemented in one or more computer programs that can be executed and / or interpreted on a programmable system comprising at least one programmable processor, which may be coupled for special or general purposes to receive data and instructions from a storage system, at least one input device, and at least one output device, and to transfer data and instructions to the storage system, at least one input device, and at least one output device.

[0167] These can also be referred to as programs, software, software applications, applications, components, or code. Computer programs include machine instructions for a programmable processor and can be implemented using high-level procedural and / or object-oriented programming languages ​​and / or assembly / machine languages. As used herein, the term "machine-readable medium" refers to any computer program product, device, and / or apparatus for providing machine instructions and / or data to a programmable processor, such as disks, optical disks, memories, and programmable logic devices (PLDs), containing a machine-readable medium that receives machine instructions as a machine-readable signal. The term "machine-readable signal" refers to any signal used to provide machine instructions and / or data to a programmable processor. Machine-readable media can store such machine instructions non-transitory, such as like non-transitory solid-state memory or magnetic hard disk drives or any equivalent storage medium. Machine-readable media can alternatively or additionally store such machine instructions in a temporary manner, such as like such machine instructions are stored in a processor cache or other random access memory associated with one or more physical processor cores.

[0168] To provide interaction with the user, one or more aspects or features of the subject matter described herein can be implemented on a computer having a display device for displaying information to the user (such as a cathode ray tube (CRT), liquid crystal display (LCD), or light-emitting diode (LED) monitor) and a keyboard and pointing device (such as a mouse or trackball) through which the user can provide input to the computer. Other types of devices may also be used to provide interaction with the user. For example, feedback provided to the user can be any form of sensory feedback, such as visual, auditory, or tactile feedback; and input from the user can be received in any form, including but not limited to acoustic, voice, or tactile input. Other possible input devices include, but are not limited to, touchscreens or other touch-sensitive devices, such as single-point or multi-point resistive or capacitive touchpads, voice recognition hardware and software, optical scanners, optical indicators, digital image capture devices, and associated interpretation software. A computer located remotely relative to the analyzer can be connected to the analyzer via a wired or wireless network to enable data exchange between the analyzer and the remote computer (e.g., receiving data from the analyzer at the remote computer and transmitting information such as calibration data, operating parameters, and software upgrades or updates) as well as remote control and diagnostics of the analyzer.

[0169] Although the subject matter of this disclosure, including various combinations and sub-combinations of features, has been described and illustrated in considerable detail with reference to certain illustrative embodiments, those skilled in the art will readily recognize other embodiments, variations, and modifications covered within the scope of this disclosure. Furthermore, the description of such embodiments, combinations, and sub-combinations is not intended to convey that the claimed subject matter requires features or combinations of features other than those expressly recited in the claims. Therefore, the scope of this disclosure is intended to include all modifications and variations covered within the spirit and scope of the appended claims.

Claims

1. An optical communication system for transmitting data optically through a variable refractive medium, the system comprising: A light source configured to generate a beam comprising a series of light pulses, each light pulse having a duration of less than 100 picoseconds; A modulator configured to modulate the series of optical pulses in response to a data transmission signal, thereby encoding the transmitted data into the series of optical pulses; An optical receiver, the optical receiver having: The duration of the detection window is less than 1 nanosecond; as well as A detection threshold, wherein the optical receiver is configured to indicate whether the optical energy received during a given detection window is greater than the detection threshold; in: The series of optical pulses includes a first pulse having a coherence length of less than 400 micrometers; As the first pulse travels through the variable refractive medium, the photons in the first pulse are refracted, thereby traveling toward the light receiver along different ray paths of different lengths. The photons of the first pulse arrive at the optical receiver according to a time distribution curve, which depends at least in part on the duration of the first pulse and the different lengths of the different ray paths taken by the photons in the first pulse to reach the optical receiver; The full width at half maximum (FWHM) of the time distribution curve is at least three times the coherence time value, which is equal to the coherence length of the first pulse divided by the speed of light passing through the variable refractive medium; and The duration of the detection window of the optical receiver is at least six times the FWHM value of the time distribution curve.

2. The optical communication system of claim 1, wherein the light source and the optical receiver are spaced at least one mile apart in free space, and the optical communication system has a measured bit error rate of less than one part per billion over a free space distance of at least one mile within a measurement period of at least sixty seconds.

3. The optical communication system according to claim 1, wherein the FWHM value of the time distribution curve is equal to at least six times the coherence time value of the first pulse divided by the speed of light through the variable refractive medium.

4. The optical communication system according to claim 1, wherein the FWHM value of the time distribution curve is at least ten times the coherence time value of the first pulse divided by the speed of light passing through the variable refractive medium.

5. The optical communication system of claim 1, wherein at least 95% of the photons of the first pulse arriving at the optical receiver arrive at a corresponding arrival time, the corresponding arrival time being a time difference from the center of the time distribution curve, the corresponding time difference being less than half the duration of the detection window of the optical receiver.

6. The optical communication system according to claim 1, wherein the light source is located at a ground station and the optical receiver is located on an Earth orbit satellite, and the optical communication system has a measured bit error rate of less than one part per billion over a free-space optical communication distance between the ground station and the Earth orbit satellite within a measurement period of at least sixty seconds.

7. The optical communication system of claim 1, wherein the series of optical pulses generated by the light source has a center wavelength between 1500 nm and 1700 nm, and the optical receiver is disposed on a detection node, the detection node comprising a filter configured to reduce the amount of light with wavelengths below 1500 nm reaching the optical receiver.

8. The optical communication system according to claim 1, wherein: The light source is located in the transmitting node; The transmitting node includes a beam splitter configured to divide the series of optical pulses into multiple separate pulses with different wavelength bands, wherein the first pulse is located among the multiple separate pulses. The transmitting node is configured to individually modulate each of the plurality of separate pulses in response to the data transmission signal, thereby encoding the transmitted data into the plurality of separate pulses; Each of the plurality of separate pulses has a corresponding coherence length of less than 400 micrometers; The optical receiver is located in the receiving node; The receiving node includes a beam splitter configured to direct the plurality of separate pulses to a corresponding optical receiver among a plurality of optical receivers; Each of the plurality of separate pulses includes a corresponding ray path arriving at the corresponding optical receiver among the plurality of optical receivers according to a corresponding time distribution curve; and Each of the plurality of separate pulses has a corresponding FWHM value for its time distribution curve, the corresponding FWHM value being at least three times the corresponding coherence length of the corresponding separate pulse divided by the corresponding coherence time value of the speed of light through the variable refractive medium.

9. The optical communication system according to claim 1, wherein the light source is an ultrashort pulse laser (USPL) source, and the duration of each pulse in the series of optical pulses is less than 500 femtoseconds.

10. The optical communication system according to claim 1, wherein the optical communication system further comprises: An amplifier, optically connected to the modulator and configured to amplify the amplitude of the series of optical pulses; as well as A threshold filter is configured to receive the series of optical pulses after the transmitted data has been encoded by the modulator and before the series of optical pulses arrive at the amplifier, wherein the threshold filter is configured to selectively attenuate pulses having an amplitude less than a threshold of the threshold filter.

11. A laser ranging system, the system comprising: A light source configured to generate a beam comprising a series of light pulses, each light pulse having a duration of less than 100 picoseconds; An optical receiver, the optical receiver having: The duration of the detection window is less than 1 nanosecond; as well as A detection threshold, wherein the optical receiver is configured to indicate whether the optical energy received during a given detection window is greater than the detection threshold; in: The series of optical pulses includes a first pulse having a coherence length of less than 400 micrometers; As the first pulse travels through a variable refractive medium, the photons in the first pulse are refracted, thus traveling toward the light receiver along different ray paths of different lengths. The photons of the first pulse arrive at the optical receiver according to a time distribution curve, which depends at least in part on the duration of the first pulse and the different lengths of the different ray paths taken by the photons in the first pulse to reach the optical receiver; The full width at half maximum (FWHM) of the time distribution curve is at least three times the coherence time value, which is equal to the coherence length of the first pulse divided by the speed of light passing through the variable refractive medium. The duration of the detection window of the optical receiver is at least six times the FWHM value of the time distribution curve; and The laser ranging system is configured to send the series of light pulses toward a surface, receive at least a portion of the series of light pulses that has been reflected by the surface, and determine the distance of at least a portion of the surface relative to the laser ranging system based on the time of flight of the received portion of the series of light pulses.

12. The laser ranging system of claim 11, wherein the pulse travels a total distance of at least one mile, the total distance being measured by means of a distance from the laser ranging system to the surface and back to the laser ranging system, the laser ranging system having a bit error rate of less than one part per billion over a free-space optical communication distance of at least one mile within a measurement period of at least sixty seconds.

13. The laser ranging system of claim 11, wherein the FWHM value of the time distribution curve is equal to at least six times the coherence time value of the first pulse divided by the speed of light through the variable refractive medium.

14. The laser ranging system of claim 11, wherein the FWHM value of the time distribution curve is at least ten times the coherence time value of the first pulse divided by the speed of light through the variable refractive medium.

15. The laser ranging system of claim 11, wherein at least 95% of the photons of the first pulse arriving at the optical receiver arrive at a corresponding arrival time, the corresponding arrival time being a time difference from the center of the time distribution curve, the corresponding time difference being less than half the duration of the detection window of the optical receiver.

16. The laser ranging system of claim 11, wherein the light source and the light receiver are located on a ground station and the surface is disposed on an Earth orbit satellite.

17. The laser ranging system of claim 11, wherein the series of light pulses generated by the light source has a center wavelength between 1500 nm and 1700 nm, and the light receiver is disposed after a filter configured to reduce the amount of light with wavelengths below 1500 nm reaching the light receiver.

18. The laser ranging system according to claim 11, wherein: The laser ranging system includes a first beam splitter configured to divide the series of optical pulses into multiple separate pulses with different wavelength bands, wherein the first pulse is located among the multiple separate pulses. The laser ranging system is configured to individually modulate each of the plurality of separate pulses in response to a data transmission signal, thereby encoding the transmission signal data into the plurality of separate pulses; Each of the plurality of separate pulses has a corresponding coherence length of less than 400 micrometers; The laser ranging system includes a second beam splitter configured to direct the plurality of separate pulses to a corresponding optical receiver among a plurality of optical receivers. Each of the plurality of separate pulses includes a corresponding ray path arriving at the corresponding optical receiver among the plurality of optical receivers according to a corresponding time distribution curve; and Each of the plurality of separate pulses has a corresponding FWHM value for its time distribution curve, the corresponding FWHM value being at least three times the corresponding coherence length of the corresponding separate pulse divided by the corresponding coherence time value of the speed of light through the variable refractive medium.

19. The laser ranging system according to claim 11, wherein the light source is an ultrashort pulse laser (USPL) source, and the duration of each pulse in the series of optical pulses is less than 500 femtoseconds.

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