CA2677585C - Optical communication device, system and method - Google Patents
Optical communication device, system and method Download PDFInfo
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- CA2677585C CA2677585C CA2677585A CA2677585A CA2677585C CA 2677585 C CA2677585 C CA 2677585C CA 2677585 A CA2677585 A CA 2677585A CA 2677585 A CA2677585 A CA 2677585A CA 2677585 C CA2677585 C CA 2677585C
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/40—Transceivers
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B10/00—Transmission systems employing electromagnetic waves other than radio-waves, e.g. infrared, visible or ultraviolet light, or employing corpuscular radiation, e.g. quantum communication
- H04B10/11—Arrangements specific to free-space transmission, i.e. transmission through air or vacuum
- H04B10/112—Line-of-sight transmission over an extended range
- H04B10/1123—Bidirectional transmission
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B13/00—Transmission systems characterised by the medium used for transmission, not provided for in groups H04B3/00 - H04B11/00
- H04B13/02—Transmission systems in which the medium consists of the earth or a large mass of water thereon, e.g. earth telegraphy
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Abstract
An optical receiver or transceiver comprises a plurality of light receiving elements positioned to receive light from a plurality of directions. In some embodiments the optical receiver or transceiver comprises multiple light receiving elements, different light receiving elements being adapted to output an electric signal only in response to light of different wavelengths or range of wavelengths. In some embodiments the optical transceiver comprises a plurality of light receiving elements positioned to receive light from a plurality of directions, interspersed with light transmitting elements positioned to transmit light in a plurality of directions.
Description
OPTICAL COMMUNICATION DEVICE, SYSTEM AND METHOD
Field of the Invention This invention relates to communications devices. In particular, this invention relates to an optical communications device particularly suitable for adverse environments.
E3ackyound of the Invention Many industrial activities are carried on in environments unfavourable for human workers. For example, in underwater environments, these activities include mining, oil exploration and extraction, installation of telecommunications cables etc.
Mining in particular is a highly labour intensive activity, especially in an underwater environment because of the increased resistance to movement in water, potential health problems associated with persistent or prolonged deep-sea diving, and the cumbersome equipment required to enable workers to remain submerged for long periods of time.
Such industrial activities invariably benefit from automation, in both reduced labour costs and increased productivity. In land-based mining it is known to provide robotic mining equipment controlled by radio frequency (rf) communications.
This enables a relatively small number of workers to remotely control heavy machinery and equipment located in or on a surface mine (for example in open pit mining). There are benefits to avoiding reliance on rf communications for land-based mining, such as to avoid interference from other signals, or to alleviate the need for approval for use of regulated bandwidths. The benefits of automation in underwater activities could potentially be significantly greater, because of the reduced mobility of workers operating when submersed.
However, conventional communications methods are often unsuitable for supporting high bandwidth communications in certain environments, such as an underwater environment. especially for the control of robotic equipment which requires the exchange of relatively high data rates with a low error rate for the wireless transmission of multiple video signals. Electromagnetic radiation at radio frequencies travels poorly through water due to rapid absorption and attenuation. which severely - I -limits the ability to provide ongoing communications between a land- or surface-based control centre and submersed robotic equipment used in activities such as underwater mining.
Moreover, submersed robotic equipment can be very complex and difficult to operate. requiring a number of fine movements to guide and operate the equipment with the precision necessary for mining and other underwater applications. The observational skills and dexterity required to effectively operate such equipment is substantial and using conventional control systems requires sipificant training and experience, particularly when the operator is remote from the equipment.
It would accordingly be advantageous to provide a communications system for guiding and operating equipment and machinery in unfavourable environments, such as underwater environments, which is reliable, fast, and capable of high data rates for use in activities such as underwater mining.
=Brief Description of the Drawings is In drawings which illustrate by way of example only an embodiment of the invention, Figure I is a plan view of a first embodiment of an optical communication device according to the invention.
Figure 2 is a perspective view of the optical communication device according of Figure I.
Figure 3 is a side view of the optical communication device of Figure 1.
Figure 4 is a perspective view of another embodiment of an optical communication device according of the invention.
Figure 5 is a plan view of another embodiment of an optical communication device according to the invention.
Figure 6 is a side view of two optical communication devices according to the invention positioned back-to-back.
_ _ Figure 7 is a schematic diagram of the LED trigger circuit of the optical communication device of the embodiment of Figure 1.
Figure 8 is a block diagram of an LED trigger circuit for the optical communication device of the invention.
Figure 9 is a schematic perspective view of an underwater communications zone utilizing optical communication devices according to the invention suspended from buoys.
Figure 10 is a schematic perspective view of a terrestrial communications zone utilizing typical optical communication devices according to the invention on supports.
Figure 11 is a schematic perspective view of an underwater communications zone utilizing typical optical communication devices according to the invention suspended from a buoy in a chain.
Detailed Description of the Invention The present invention provides an underwater optical communications system and method, which is particularly suitable for use in communications with mobile robotics and automated equipment and machinery. The present invention is particularly suitable for any underwater, terrestrial or space environment where localized communication for (dc-operated robotics is required.
The present invention provides an optical receiver or transceiver comprising, a plurality of light receiving elements positioned to receive light from a plurality of directions, comprising a first light receiving element adapted to output an electric signal only in response to light of a selected first wavelength or range of wavelengths, and at least a second light receiving element adapted to output an electric signal only in response to light of a selected second wavelength or range of wavelengths different from the first wavelength or range of wavelengths, whereby the optical receiver or transceiver can simultaneously receive data independently in at least first and second optical signals respectively having the tirst and second wavelength or range of wavelengths.
The present invention provides an optical transceiver comprising a plurality of light emitting elements positioned so the optical transceiver emits light in a plurality of directions, and a plurality of light receiving elements positioned so the optical transceiver receives light from a plurality of directions, the light receiving elements being interspersed with light transmitting elements.
Figures 1-3 illustrate a first embodiment of the optical communication device, or optical transceiver 10, of the present invention. It will be appreciated that to while the light-emitting face 12 of the optical transceiver 10 of the first embodiment has multiple facets 14 for emitting light in a variety of directions, the number, orientation and size of facets 14 may vary to optimize the distribution of light emitted.
For example, the face 12 of the optical transceiver 10 may alternatively be flat or dome shaped.
Each facet 14 of the optical transceiver 10 may comprise a facet board 20 with a series of light emitting elements 22, for example light emitting diodes (LEDs) 22. These facet boards 20, which may for example be formed from heat resistant circuit board wafers, are attached to a support structure (not shown), such as a plastic frame. It will be appreciated that the number and configuration of the light emitting elements 22 on each board 20 may vary to optimize the distribution of light emitted by the optical transceiver 10. As illustrated in Figures 1 to 3, the optical transceiver of this embodiment has eight trapezoidal facet boards 20 and one octagonal top plate 15.
The top plate 15 has four holes (not shown) to which are affixed optical receivers.
The optical transceiver 10 of the present invention preferably emits light in the visible spectrum, via LEDs or any other suitable light emitting element 22. The precise wavelengths may be selected based on the attenuation characteristics of the environment, and may be achieved by selection of the light-emitting elements and/or by optical filtering. By way of example only, certain wavelengths of green light in the range around 5,100 to 5,200 Angstroms have been found to travel well through seawater. Wavelengths of red light in the range of 6,200 to 7,500 Angstroms have been found to travel well in terrestrial environments, notwithstanding the ambient light present. The particular wavelength and intensity of light most suitable for terrestrial optical communication may depend upon the transmissivity of the water or air, the type of suspension (e.g. organic, sedimentary, dust etc.) causing any cloudiness or murkiness or haze, and the spectral characteristics of ambient light within the communications zone. However, the particular wavelengths (use of more than one wavelength of light can be advantageous, as described below) and intensity of the light-emitting elements 22, can be optimized through experimentation, In a preferred configuration of the optical transceiver 10 of the invention, in each of the facet hoards 20 the number of light emitting elements 22 increases towards the base 18 of the optical transceiver 10, corresponding to the dimensions of the particular facet board 20. In the embodiment shown, each trapezoidal board may have 144 LEDs 22 which draws approximately 1 amp at 50% duty cycle of 10 MHz. Preferably, the face plate 26 also has 144 LEDs 22. The number of LEDs 22 may vary, depending upon the desired optical output of the device 10.
In the embodiment shown in Figure 1, the optical transceiver 10 emits light over a range of 180'. A total of 360 of light distribution can be achieved by coupling two optical transceivers 10 back-to-back in the manner illustrated in Figure 6. It will be appreciated that each optical transceiver 10 could alternatively be configured to have many more facets 14 with boards 20 affixed thereto and if desired opposed light emitting faces (equivalent to the two devices 10 shown in Figure 6) so as to emit light in all directions (i.e. 360').
Mirrors 40 may be attached to the base 18 to reflect and direct light emitted from the LEDs 22 out of the light emitting face of the optical transceiver 10, to enhance the light emitted. This further helps to distribute the light emitted out of the light emitting face and can compensate for any decrease in light emitting elements 22 due to occlusion caused by detector modules 32 fixed to the face plate 26.
The mirrors 40 help to reduce the effect of gaps between the facet boards 20. The mirrors 41 may be configured to have a shape complementary to the shape of the adjacent facet board 20, to optimize the amount reflected while still maintaining sufficient light -s-emission over the desired 180c range of the device 10 shown. Mirrors 40 and 41 may be angled to reflect light out of the light emitting face with a desired pattern or dispersion. In the embodiment shown, the mirrors 40 and 41 can increase the light transmission efficiency out of the light-emitting face (i.e. in the forward direction) by about 20%.
The optical tranceiver 10 also functions to detect light transmitted from a complementary optical communication device. Detector modules 32 comprise optical receiving elements 30. each for example comprising an avalanche photodiode (APD), that may be coupled to the optical transceiver 10 to receive light emitted from other optical transceivers 10 or from other types of optical beacons (not shown). In the first embodiment. four detector modules 32 are used, however it will be appreciated that this number may vary.
The optical receiving elements 30 contained within the detector modules 32 may comprise any detector sensitive to the particular wavelength(s) of light selected for the light emitting elements 22.
In the embodiment shown in Figures 1, 2 and 3, each detector module 32 comprises a casing 34 connected by screws (not shown) to the comers of the face plate 26 of the optical transceiver 10. The casing 34 includes the optical receiving element 30 recessed in an opening 38 at the apex of a concave reflective channeling dish 39 to focus the incoming light directly at the optical receiving element 30 to maximize the light received. By recessing the optical receiving element 30 in this manner, the light emitted from the optical transceiver 10 does not add to the ambient light or optical 'noise' affecting the sensitivity of the optical receiving element 30.
In another embodiment, shown in Figure 4, detector modules 32 are coupled to the face plate 26 and also to the interstitual spacing between the facet boards 20 bearing the light emitting elements 22. In this configuration, the detector modules 32 receive light signals over a range of 180'. .A total of 360' of light reception can be achieved by coupling two optical transceivers 10 back-to-back in the manner illustrated in Figure 6. In another embodiment, shown in Figure 5, a number of optical receiving elements 30 are included in one larger detector module 32 mounted in a hole (not shown) in the center of the face plate 26.
Each detector module 32 is also positioned with its optical axis face away from the light emitting elements 22 to reduce opportunities fifr light from the light emitting elements 22 striking the optical receiving elements 30. Additional light emitting elements 22 may be disposed on the plate 15, tbr example between the detector modules 32 in the embodiment of Figures I to 4 or distributed about the detector module 32 in the embodiment of Figure 5.
Reducing ambient light or optical 'noise' from the device 10 itself may to also be achieved by interspersing the optical receiving elements 30 amongst the light emitting elements 22 (not shown), wherein the optical receiving elements 30 are set back or recessed into the interstitial spacing between the light emitting elements 22, or otherwise shielded so that light emitted by the optical transceiver 10 does not add to the ambient light or optical 'noise' affecting the sensitivity of the optical receiving elements 30.
The detector modules 32, or light receiving elements 30, may bear filters 37 or a similar means of selective filtering to restrict the light received by each light receiving element 30 to a particular wavelength or range of wavelengths within the visible spectrum. In this manner, different light receiving elements 30 on the same optical transceiver 10 may receive light signals of different predetermined frequencies or wavelengths emitted from other optical communication devices. By configuring the light receiving elements 30 to receive multiplexed optical signals, the data reception capability of the optical transceiver 10 increases as a factor of the multiplexing capacity of the light receiving elements 30 coupled to the optical transceiver 10. By using filters 37 or a similar means of selective filtering to restrict the light received by each light receiving element 30 to a discrete wavelength or wavelengths within the visible spectrum, the required guard bands may be minimized. For example, with accurate filtering, the guard bands may be reduced to one angstrom in width.
The wavelengths of light available for data transfer for a given environment may be maximized in this manner, and the data transfer capacity may be expressed as a function of the effective wavelengths available through filtering in a given medium, minus the guard bands required, multiplied by the effective bit rate.
The light receiving elements 30 may be coupled to light sensing circuitry 50, which may have a sensitivity threshold, for example using a Schmidt trigger comparator or other comparator to establish a base light level below which the light receiving elements 30 do not register a light pulse, which can be set according to the average and/or peak ambient light levels within the communications zone 100.
This maximizes reliability of the communications system, ensuring that the light receiving elements 30 are not saturated by ambient light so that all received light pulses generated from other optical transceivers 10 will be processed as communications signals.
A transparent transceiver dome 16 may be used to enclose the optical transceiver 10, including all electronics. The dome 16 may be made of glass or plexiglass, or a similar material, that minimizes diffusion and reflection of emitted and incoming light. The dome 16 protects the instrumentation from the external environment, such as the water when used for underwater environments, and also from the accumulation of dust or dirt for terrestrial applications or in other environments. The dome 16 may have a waterproof seal 17, for example a rubber gasket, around its base 18 coupled to the casing of the optical transceiver 10 and may be bolted to a base plate 19.
Power may be provided through a battery pack (not shown) either located in the optical transceiver 10 or external to the dome 16 and connected via cables 62 through a hole 64 in the base plate 19 of the optical transceiver 10. Cables 62 can also he used Ibr data transmission through such a hole 64.
The facet board 20 of the optical transceiver 10 of the embodiments illustrated is based on a Complex Programmable Logic Device (CPLD) 72 with sufficient power to be capable of driving several loads synchronously. The input signal from the Ethernet media converter 74 is fanned out to various LED
trigger circuits 70 on each LED board 20, preferably through one CPLD 72. The optical transceiver 10 may include any number of LED boards 20, each comprising a plurality of LED trigger circuits 70.
Suitable LED trigger circuits 70, as illustrated in Figure 7, activate a plurality of LEDs 22 connected in parallel on one facet board 20. Preferably, each LED trigger circuit 70 activates two LEDs 22 connected in parallel as shown.
In its quiescent state there is no signal at the input of the Schmitt trigger inverter 76, so the inverter output is high and there is no voltage drop across the LEDs 22. The LEDs 22 are illuminated when a trigger signal, which may be in the range of 3.3 to 5.2 volts, transmitted from the CPLD 72 to the input of the Schmitt trigger inverter 76 in the LED trigger circuit 70. The output of the Schmitt trigger inverter 76 goes low for the duration of the trigger signal, creating a voltage drop across the LEDs 22 resulting in a current passing from the power source (not shown) through resistors 78 connected in series with the LEDs 22 and illuminating the LEDs 22. A connection to ground prevents current from -flowing into the Schmitt trigger inverter 76, which could damage the component.
This design is preferable over designs which trigger several LEDs 22 connected in series through the base of an RF transistor. With LEDs 22 connected in series, approximately 45 V power supply was needed to reliably switch 7 LEDs 22, and due to the competing speed-power output of transistors, such a circuit could not be operated at the desired 10 MHz frequency frequency. The LED trigger circuit shown in Figure 7 is capable of switching at 10 MHz and operates at +5V. The higher LED trigger speed allows for faster data transfer.
The trigger signal is generated by Ethernet media converter 74, which may tor example be a commercially available Ethernet media converter designed for inter-conversion of I OBaseT and fiber optic signals, modified to exploit its electrical inputs and outputs of the fiber optic channel. The Ethernet media converter 74 comprises an analog-to-digital converter (ADC) and an IP protocal converter for generating an IP-based signal from the digital output of the ADC. It will be appreciated that the Ethernet media converter 74, which is based on statistical network protocols, may be substituted by a media converter based on deterministic network protocols.
Ethernet hub 82 preferably communicates with an on-board IP-based camera 83. or any internal or external IP-based device, and a remote controller comprising a processing device, for example personal computer (PC) 85 and associated controls 87.
The electronics internal and external to the optical transceiver 10 are shown in Figure 8 for one channel of incoming light signals. When the optical transceiver 10 is configured to receive multiplexed optical signals through the use of optical filters 37 over the detector modules 32, or a similar means of selective filtering to render each light receiving element 30 reactive to a particular wavelength or range of wavelengths within the visible spectrum, similar electronics to those shown in Figure 8 may be used for each channel of light.
Preferably. the APD readout electronics 80 comprises the following components: (a) an APD module 32 comprising a bias power supply with temperature compensation, a transimpedance amplifier and a capacitor to filter the output signal; a summing amplifier 84; and a wide dynamic range automatic gain amplifier 86.
One embodiment of the invention utilizes a transimpedance amplifier chip (not shown) from Analog Devices, an APD bias supply (not shown) from Matsusada Precision, and APD sensors 30 from Hamamatsu Corporation. An APD module 32 with only a APD bias supply and transimpedance amplifier may also be used, such as is commercially available from Hamamatsu Corporation. It will be appreciated that similar devices may be obtained from other sources to accomplish the similar result.
The summing amplifier 84 sums the output voltages from all the transimpedance amplifiers connected to individual sensors 30 or optical receiving elements 30 where multiple API) modules 32 are used. The output of the summing amplifier is transmitted to the automatic gain amplifier 86, which includes a filter module or notch filter to minimize mismatching and filter unwanted low and high frequencies. The output of the automatic gain amplifier 86 is at a predetermined fixed voltage, preferably around 2.5 to 5 volts, and is thus independent of the intensity of light received by the light receiving elements 30.
based distribution board 72 for activating the plurality of LEDs 22 via trigger circuits 70 in each LED board 20.In the embodiment shown the digital output of the Ethernet media converter 74 is also sent to an Ethernet hub or switch 82 and on to PC
85 which contains software for managing and controlling the electronic circuitry and monitoring the data flow.
This design has enabled operation of the optical transceiver 10 in a wide dynamic range without using logarithmic amplifiers, which are prone to large drifts with small changes in operating parameters. There are many devices and systems for converting electrical pulses to discrete optical pulses, and for converting optical pulses to discrete electrical pulses, in the analogue and digital domains, which are well known to those skilled in the art. There are also optical communications systems described in the art, some of which are free space communications systems and some of which include multiplexing systems for achieving higher data rates, by way of non-limiting example only, the System and Method for Free Space Optical Communications Using Time Division Multiplexing of Digital Communication Signals described in U.S. Patent No. 6,246,498 issued to Dishman et al. on June 12, 2001; the Optical Space Communication Apparatus Sending Main Signals and an Auxiliary Signal for Controlling the Intensity at the Receiver described in U.S. Patent No. 5,610,748 issued to Sakanaka et al. on March 11, 1997; and the Optical Communications System described in U.S. Patent No. 5,896,211 issued to Watanabe on April 20, 1999. The invention is not intended to be limited to any particular opto-electric conversion methodology, multiplexing scheme or communications system.
Using for example wavelength division multiplexing (WDM), data rates of 10Mb/s or even higher can be achieved by present techniques for a single wavelength of light. In the first embodiment of the invention described above, each transceiving element 22 transmits light at a discrete wavelength, for example in the green portion of the visible light spectrum. By using various frequencies of light in this fashion, as long as the band separation is sufficient multi-directional communications can occur simultaneously without interference, thus enhancing the communications speed.
Moreover, as the frequency increases, both the data rate and the directional sensitivity of the optical receivers 30 increases.
Figure 9 illustrates a communications zone 100 in an underwater optical communications system in which the optical transceivers 10 of the present invention may be used both as fixed beacon transceivers and as mobile transceivers.
Figure 10 illustrates a communications zone 100 in terrestrial optical communications system in which the optical transceivers 10 of the present invention may be used and affixed to a surface vehicle 124. It will be appreciated that the principles of the invention can also be applied to other water, surface and space-based communications systems.
Further, although the communications system described herein is advantageously used in underwater or terrestrial mining applications, it can also be used for such tasks as border security (marine patrol), underwater inspection of boat hulls, inspection of water intake pipes, and many other applications.
The communications zone 100 is defined by optical transceivers 10 which are preferably dispersed generally uniformly throughout the communications zone 100. For underwater optical communications systems, the optical transceivers 10 may for example be buoyant and affixed to anchors (not shown) set on the floor of a body of water, or may be suspended from a boat or other buoyant object 102 floating on the water's surface, as illustrated in Figures 9 and 11.
Figure 9 illustrates a 'single cell' communications zone, in which the communications zone is defined between 'directional corner beacons each comprising a single optical communications device 10. The invention also provides a 'multiple-cell' embodiment in which the communications zone 100 comprises a matrix of interior optical transceivers 10 and peripheral optical transceivers 10 creating a network of optical transceivers 10. The optical transceivers 10 in the interior of the communications zone 100 are fully multi-directional, and may for example be spherical embodiments of the optical communications device, or may be the optical communications device 10 as shown adjoined as illustrated in Figure 6, by way of example only. A description of an optical communications zone may be found in international application no. PCT/CA2005/000027 published July 28, 2005.
Even in the 'single cell' communications zone embodiment illustrated in Figure 9, the optical transceivers 10 operating at the periphery of the communications zone 100 may instead be fully multi-directional, so that the communications zone 100 extends for some distance beyond the optical transceivers 10. It will be appreciated that it is possible to utilize peripheral optical transceivers 10 that are directional and emit light only toward the communications zone 100 as shown in Figures 9 and 10, in which case the communications zone 100 will not extend substantially beyond the peripheral optical transceivers 10. The optical transceivers 10 may be interconnected through a network, or may all be connected directly to a control station at which PC
85 is located.
The submersible craft 120 and the control station each comprise suitable electro-optical circuitry for converting optical data signals received by the optical transceivers 10 from the submersible craft 120 to electrical signals for controlling the craft 120, and for converting electrical control signals generated by the control station to optical signals transmitted by the optical transceivers 10 to the submersible craft 120. The light signals emitted by the light emitting elements 22 or may be modulated in any suitable fashion.
Figure 9 illustrates a submersible craft 120 which, like the optical transceivers 10, is provided with at least one optical transceiver 10. The craft 120 illustrated has one optical transceiver 10 such as the optical transceiver 10 of Figures 1 to 5. The optical transceivers 10 are dispersed about the communications zone 100 such that the submersible craft 120 is able to receive optical signals containing communication data from one or more optical transceivers 10 at all times, and to send optical communication data to one or more optical transceivers 10 at all times, regardless of the orientation of the craft 120 and regardless of the position of the craft 120 within the communications zone 100. The optical transceivers 10 are spaced closely enough to ensure that, within the communications zone 100, the submersible craft 120 is always in optical communication with at least one optical transceivers 10, and operate in a "hand-off" tashion similar to that used in cellular telephone systems, in which as the telephone transceiver moves from one cell to the next the cellular tower which the telephone transceiver is approaching establishes a communications link with the transceiver and the cellular tower from which the transceiver is receding cuts off its communications link.
At the same time, the optical transceivers 10 are preferably spaced far enough apart that they do not significantly interfere with the ability of the submersible craft 120 to manoeuvre through the communications zone 100. The ideal spacing may depend upon many factors, including the intensity of the light emitting elements 22, the sensitivity of the light receiving elements 30, the transmissivity of the water (including the particular cause of any cloudiness or murkiness), and ambient light levels within the communications zone 100.
It is also advantageous to space the optical transceivers 10 so that the is submersible craft 120 is always in optical communication with at least three optical transceivers to. This will allow for positioning and locating the submersible craft 120 by triangulation.
The optical transceivers 10 may also be located at varying elevations, to support triangulation for positioning/locating the submersible craft 120 vertically. For example, Figure 11 illustrates a communications zone 100 defined by a series of optical transceivers 10 suspended from a floating buoy 102. The suspended optical transceivers 10, which may be powered by a generator (not shown) or battery (not shown) on board the buoy 102, may be directional, or may comprise optical transceivers 10 configured in pairs as in Figure 6 so as to emit light in all directions.
The optical transceivers 10 are spaced closely enough to ensure that, within the communications zone 100, the submersible craft 120 is always in optical communication with at least one optical transceiver 10.
The optical transceivers 10 may be powered by battery 71 as described above, or by an electrical generator (not shown) contained in a land-based control centre or a or surface-based control centre such as a floating watercraft or communications relay buoy, and connected to the optical transceivers 10 by optical fibres or electrical cables (not shown). The submersible craft 120 may be powered by any suitable means. The control centre and the submersible craft 120 would in the first embodiment of the invention each comprise computers, an optical switching system, and an on-board Transmit/Receive link, each of which may be of conventional or any suitable design which is well known to those skilled in the art. By way of example only such a system is described in U.S. Patent No. 4,905,309 issued February 27, 1990 to Maisonneuve et at.
The communications methodology may comprise any conventional optical communications system, but preferably utilizes a packet-based system utilizing optical pulses to transmit the data packets. The first embodiment of the invention described above operates under a token passing system, in which each token is managed by a header and footer. Data, preferably including video from on-board cameras 83 located about the submersible craft 120, is transmitted optically from the on-board optical transceiver(s) 10 to the optical transceivers 10 about the communications zone 100. Data 132 and video information 134 are displayed at the control station for monitoring each submersible craft 120, and the return data stream 132 controls the submersible craft 120, steering it to a new position or orientation and/or initiating a task.
Figure 11 illustrates a vertical communications zone 100 for the invention, in which a number of optical transceivers 10 may be suspended in sequence. The vertical communications zone 100 may be suspended from buoy 102 with a water-tight, buoyant casing that also supports a Global Positioning System (GPS) antenna (not shown) and circuitry for precise positioning information and triangulation of the positions of the submersible craft 120, and optionally a solar cell (not shown) for primary or auxiliary power and battery recharging. The casing contains the power supply 71 for powering suspended optical transceivers 10; the electro-optical circuitry for converting optical signals to electrical control signals and vice versa for communications between the suspended optical transceivers 10 and the submersible crafts 120; and control circuitry for operating a second communications link, for example a radio frequency (RF) transceiver (not shown) coupled between the electro-and transmitting signals to a remote control station (provided for example on a as a ship or land-based structure) and thus allowing the submersible crafts 120 to be controlled from any desired distance from the communications zone 100.
It will be appreciated that the communications system and method of the invention can be used solely to control the submersible craft 120 within the communications zone 100. in which case the craft 120 does not need to be equipped with light emitting elements 22 and the optical transceivers 10 about the communications zone 100 do not need to be equipped with light receiving elements 30. However, preferably the system and method of the invention provides for bi-directional including communications from the craft 120 to the optical transceivers 10 about the communications zone 100, I'm example video transmissions, radar and/or sonar telemetry transmissions and the like, in which case both the optical transceivers 10 about the communications zone 100 and the craft 120 will be equipped with light emitting elements 22 and light receiving elements 30, respectively.
IS The control station may comprise a conventional display (not shown) for displaying a signal sent by cameras 122 on-board the submersible craft I 20, and any suitable control interface, for example a computer 85, allowing the operator to control the submersible craft 120 and its equipment through command signals transmitted to the optical transceivers 10 about the communications zone 100, and thus to the submersible craft 120. Where multiple submersible crafts 120 are used, each submersible craft 120 has a unique address and the packets in the digital data signals 132 (for example in IP protocol) comprise the address of the particular submersible craft 120 for which the command is intended, for example in the packet header, so that only the intended submersible craft 120 reacts to the command. Similarly, data signals 132 transmitted by each submersible craft 120 comprise the address of the particular submersible craft 120 transmitting the data 132, so that the control centre recognizes the source of the transmission.
Preferably the invention incorporates bit error rate testing and other techniques to ensure the integrity of the optical communications. Also, to reduce the lu likelihood of the loss of a craft 120 or land vehicle 124 in the event of a communications interruption, preferably the submersible craft 120 is designed to automatically stop and sink to the bottom of the body of water and the land vehicle 124 is designed to brake to a stop.
Various embodiments of the present invention having been thus described in detail by way of example, it will be apparent to those skilled in the art that variations and modifications may be made without departing from the invention.
The invention includes all such variations and modifications as fall within the scope of the appended claims.
Field of the Invention This invention relates to communications devices. In particular, this invention relates to an optical communications device particularly suitable for adverse environments.
E3ackyound of the Invention Many industrial activities are carried on in environments unfavourable for human workers. For example, in underwater environments, these activities include mining, oil exploration and extraction, installation of telecommunications cables etc.
Mining in particular is a highly labour intensive activity, especially in an underwater environment because of the increased resistance to movement in water, potential health problems associated with persistent or prolonged deep-sea diving, and the cumbersome equipment required to enable workers to remain submerged for long periods of time.
Such industrial activities invariably benefit from automation, in both reduced labour costs and increased productivity. In land-based mining it is known to provide robotic mining equipment controlled by radio frequency (rf) communications.
This enables a relatively small number of workers to remotely control heavy machinery and equipment located in or on a surface mine (for example in open pit mining). There are benefits to avoiding reliance on rf communications for land-based mining, such as to avoid interference from other signals, or to alleviate the need for approval for use of regulated bandwidths. The benefits of automation in underwater activities could potentially be significantly greater, because of the reduced mobility of workers operating when submersed.
However, conventional communications methods are often unsuitable for supporting high bandwidth communications in certain environments, such as an underwater environment. especially for the control of robotic equipment which requires the exchange of relatively high data rates with a low error rate for the wireless transmission of multiple video signals. Electromagnetic radiation at radio frequencies travels poorly through water due to rapid absorption and attenuation. which severely - I -limits the ability to provide ongoing communications between a land- or surface-based control centre and submersed robotic equipment used in activities such as underwater mining.
Moreover, submersed robotic equipment can be very complex and difficult to operate. requiring a number of fine movements to guide and operate the equipment with the precision necessary for mining and other underwater applications. The observational skills and dexterity required to effectively operate such equipment is substantial and using conventional control systems requires sipificant training and experience, particularly when the operator is remote from the equipment.
It would accordingly be advantageous to provide a communications system for guiding and operating equipment and machinery in unfavourable environments, such as underwater environments, which is reliable, fast, and capable of high data rates for use in activities such as underwater mining.
=Brief Description of the Drawings is In drawings which illustrate by way of example only an embodiment of the invention, Figure I is a plan view of a first embodiment of an optical communication device according to the invention.
Figure 2 is a perspective view of the optical communication device according of Figure I.
Figure 3 is a side view of the optical communication device of Figure 1.
Figure 4 is a perspective view of another embodiment of an optical communication device according of the invention.
Figure 5 is a plan view of another embodiment of an optical communication device according to the invention.
Figure 6 is a side view of two optical communication devices according to the invention positioned back-to-back.
_ _ Figure 7 is a schematic diagram of the LED trigger circuit of the optical communication device of the embodiment of Figure 1.
Figure 8 is a block diagram of an LED trigger circuit for the optical communication device of the invention.
Figure 9 is a schematic perspective view of an underwater communications zone utilizing optical communication devices according to the invention suspended from buoys.
Figure 10 is a schematic perspective view of a terrestrial communications zone utilizing typical optical communication devices according to the invention on supports.
Figure 11 is a schematic perspective view of an underwater communications zone utilizing typical optical communication devices according to the invention suspended from a buoy in a chain.
Detailed Description of the Invention The present invention provides an underwater optical communications system and method, which is particularly suitable for use in communications with mobile robotics and automated equipment and machinery. The present invention is particularly suitable for any underwater, terrestrial or space environment where localized communication for (dc-operated robotics is required.
The present invention provides an optical receiver or transceiver comprising, a plurality of light receiving elements positioned to receive light from a plurality of directions, comprising a first light receiving element adapted to output an electric signal only in response to light of a selected first wavelength or range of wavelengths, and at least a second light receiving element adapted to output an electric signal only in response to light of a selected second wavelength or range of wavelengths different from the first wavelength or range of wavelengths, whereby the optical receiver or transceiver can simultaneously receive data independently in at least first and second optical signals respectively having the tirst and second wavelength or range of wavelengths.
The present invention provides an optical transceiver comprising a plurality of light emitting elements positioned so the optical transceiver emits light in a plurality of directions, and a plurality of light receiving elements positioned so the optical transceiver receives light from a plurality of directions, the light receiving elements being interspersed with light transmitting elements.
Figures 1-3 illustrate a first embodiment of the optical communication device, or optical transceiver 10, of the present invention. It will be appreciated that to while the light-emitting face 12 of the optical transceiver 10 of the first embodiment has multiple facets 14 for emitting light in a variety of directions, the number, orientation and size of facets 14 may vary to optimize the distribution of light emitted.
For example, the face 12 of the optical transceiver 10 may alternatively be flat or dome shaped.
Each facet 14 of the optical transceiver 10 may comprise a facet board 20 with a series of light emitting elements 22, for example light emitting diodes (LEDs) 22. These facet boards 20, which may for example be formed from heat resistant circuit board wafers, are attached to a support structure (not shown), such as a plastic frame. It will be appreciated that the number and configuration of the light emitting elements 22 on each board 20 may vary to optimize the distribution of light emitted by the optical transceiver 10. As illustrated in Figures 1 to 3, the optical transceiver of this embodiment has eight trapezoidal facet boards 20 and one octagonal top plate 15.
The top plate 15 has four holes (not shown) to which are affixed optical receivers.
The optical transceiver 10 of the present invention preferably emits light in the visible spectrum, via LEDs or any other suitable light emitting element 22. The precise wavelengths may be selected based on the attenuation characteristics of the environment, and may be achieved by selection of the light-emitting elements and/or by optical filtering. By way of example only, certain wavelengths of green light in the range around 5,100 to 5,200 Angstroms have been found to travel well through seawater. Wavelengths of red light in the range of 6,200 to 7,500 Angstroms have been found to travel well in terrestrial environments, notwithstanding the ambient light present. The particular wavelength and intensity of light most suitable for terrestrial optical communication may depend upon the transmissivity of the water or air, the type of suspension (e.g. organic, sedimentary, dust etc.) causing any cloudiness or murkiness or haze, and the spectral characteristics of ambient light within the communications zone. However, the particular wavelengths (use of more than one wavelength of light can be advantageous, as described below) and intensity of the light-emitting elements 22, can be optimized through experimentation, In a preferred configuration of the optical transceiver 10 of the invention, in each of the facet hoards 20 the number of light emitting elements 22 increases towards the base 18 of the optical transceiver 10, corresponding to the dimensions of the particular facet board 20. In the embodiment shown, each trapezoidal board may have 144 LEDs 22 which draws approximately 1 amp at 50% duty cycle of 10 MHz. Preferably, the face plate 26 also has 144 LEDs 22. The number of LEDs 22 may vary, depending upon the desired optical output of the device 10.
In the embodiment shown in Figure 1, the optical transceiver 10 emits light over a range of 180'. A total of 360 of light distribution can be achieved by coupling two optical transceivers 10 back-to-back in the manner illustrated in Figure 6. It will be appreciated that each optical transceiver 10 could alternatively be configured to have many more facets 14 with boards 20 affixed thereto and if desired opposed light emitting faces (equivalent to the two devices 10 shown in Figure 6) so as to emit light in all directions (i.e. 360').
Mirrors 40 may be attached to the base 18 to reflect and direct light emitted from the LEDs 22 out of the light emitting face of the optical transceiver 10, to enhance the light emitted. This further helps to distribute the light emitted out of the light emitting face and can compensate for any decrease in light emitting elements 22 due to occlusion caused by detector modules 32 fixed to the face plate 26.
The mirrors 40 help to reduce the effect of gaps between the facet boards 20. The mirrors 41 may be configured to have a shape complementary to the shape of the adjacent facet board 20, to optimize the amount reflected while still maintaining sufficient light -s-emission over the desired 180c range of the device 10 shown. Mirrors 40 and 41 may be angled to reflect light out of the light emitting face with a desired pattern or dispersion. In the embodiment shown, the mirrors 40 and 41 can increase the light transmission efficiency out of the light-emitting face (i.e. in the forward direction) by about 20%.
The optical tranceiver 10 also functions to detect light transmitted from a complementary optical communication device. Detector modules 32 comprise optical receiving elements 30. each for example comprising an avalanche photodiode (APD), that may be coupled to the optical transceiver 10 to receive light emitted from other optical transceivers 10 or from other types of optical beacons (not shown). In the first embodiment. four detector modules 32 are used, however it will be appreciated that this number may vary.
The optical receiving elements 30 contained within the detector modules 32 may comprise any detector sensitive to the particular wavelength(s) of light selected for the light emitting elements 22.
In the embodiment shown in Figures 1, 2 and 3, each detector module 32 comprises a casing 34 connected by screws (not shown) to the comers of the face plate 26 of the optical transceiver 10. The casing 34 includes the optical receiving element 30 recessed in an opening 38 at the apex of a concave reflective channeling dish 39 to focus the incoming light directly at the optical receiving element 30 to maximize the light received. By recessing the optical receiving element 30 in this manner, the light emitted from the optical transceiver 10 does not add to the ambient light or optical 'noise' affecting the sensitivity of the optical receiving element 30.
In another embodiment, shown in Figure 4, detector modules 32 are coupled to the face plate 26 and also to the interstitual spacing between the facet boards 20 bearing the light emitting elements 22. In this configuration, the detector modules 32 receive light signals over a range of 180'. .A total of 360' of light reception can be achieved by coupling two optical transceivers 10 back-to-back in the manner illustrated in Figure 6. In another embodiment, shown in Figure 5, a number of optical receiving elements 30 are included in one larger detector module 32 mounted in a hole (not shown) in the center of the face plate 26.
Each detector module 32 is also positioned with its optical axis face away from the light emitting elements 22 to reduce opportunities fifr light from the light emitting elements 22 striking the optical receiving elements 30. Additional light emitting elements 22 may be disposed on the plate 15, tbr example between the detector modules 32 in the embodiment of Figures I to 4 or distributed about the detector module 32 in the embodiment of Figure 5.
Reducing ambient light or optical 'noise' from the device 10 itself may to also be achieved by interspersing the optical receiving elements 30 amongst the light emitting elements 22 (not shown), wherein the optical receiving elements 30 are set back or recessed into the interstitial spacing between the light emitting elements 22, or otherwise shielded so that light emitted by the optical transceiver 10 does not add to the ambient light or optical 'noise' affecting the sensitivity of the optical receiving elements 30.
The detector modules 32, or light receiving elements 30, may bear filters 37 or a similar means of selective filtering to restrict the light received by each light receiving element 30 to a particular wavelength or range of wavelengths within the visible spectrum. In this manner, different light receiving elements 30 on the same optical transceiver 10 may receive light signals of different predetermined frequencies or wavelengths emitted from other optical communication devices. By configuring the light receiving elements 30 to receive multiplexed optical signals, the data reception capability of the optical transceiver 10 increases as a factor of the multiplexing capacity of the light receiving elements 30 coupled to the optical transceiver 10. By using filters 37 or a similar means of selective filtering to restrict the light received by each light receiving element 30 to a discrete wavelength or wavelengths within the visible spectrum, the required guard bands may be minimized. For example, with accurate filtering, the guard bands may be reduced to one angstrom in width.
The wavelengths of light available for data transfer for a given environment may be maximized in this manner, and the data transfer capacity may be expressed as a function of the effective wavelengths available through filtering in a given medium, minus the guard bands required, multiplied by the effective bit rate.
The light receiving elements 30 may be coupled to light sensing circuitry 50, which may have a sensitivity threshold, for example using a Schmidt trigger comparator or other comparator to establish a base light level below which the light receiving elements 30 do not register a light pulse, which can be set according to the average and/or peak ambient light levels within the communications zone 100.
This maximizes reliability of the communications system, ensuring that the light receiving elements 30 are not saturated by ambient light so that all received light pulses generated from other optical transceivers 10 will be processed as communications signals.
A transparent transceiver dome 16 may be used to enclose the optical transceiver 10, including all electronics. The dome 16 may be made of glass or plexiglass, or a similar material, that minimizes diffusion and reflection of emitted and incoming light. The dome 16 protects the instrumentation from the external environment, such as the water when used for underwater environments, and also from the accumulation of dust or dirt for terrestrial applications or in other environments. The dome 16 may have a waterproof seal 17, for example a rubber gasket, around its base 18 coupled to the casing of the optical transceiver 10 and may be bolted to a base plate 19.
Power may be provided through a battery pack (not shown) either located in the optical transceiver 10 or external to the dome 16 and connected via cables 62 through a hole 64 in the base plate 19 of the optical transceiver 10. Cables 62 can also he used Ibr data transmission through such a hole 64.
The facet board 20 of the optical transceiver 10 of the embodiments illustrated is based on a Complex Programmable Logic Device (CPLD) 72 with sufficient power to be capable of driving several loads synchronously. The input signal from the Ethernet media converter 74 is fanned out to various LED
trigger circuits 70 on each LED board 20, preferably through one CPLD 72. The optical transceiver 10 may include any number of LED boards 20, each comprising a plurality of LED trigger circuits 70.
Suitable LED trigger circuits 70, as illustrated in Figure 7, activate a plurality of LEDs 22 connected in parallel on one facet board 20. Preferably, each LED trigger circuit 70 activates two LEDs 22 connected in parallel as shown.
In its quiescent state there is no signal at the input of the Schmitt trigger inverter 76, so the inverter output is high and there is no voltage drop across the LEDs 22. The LEDs 22 are illuminated when a trigger signal, which may be in the range of 3.3 to 5.2 volts, transmitted from the CPLD 72 to the input of the Schmitt trigger inverter 76 in the LED trigger circuit 70. The output of the Schmitt trigger inverter 76 goes low for the duration of the trigger signal, creating a voltage drop across the LEDs 22 resulting in a current passing from the power source (not shown) through resistors 78 connected in series with the LEDs 22 and illuminating the LEDs 22. A connection to ground prevents current from -flowing into the Schmitt trigger inverter 76, which could damage the component.
This design is preferable over designs which trigger several LEDs 22 connected in series through the base of an RF transistor. With LEDs 22 connected in series, approximately 45 V power supply was needed to reliably switch 7 LEDs 22, and due to the competing speed-power output of transistors, such a circuit could not be operated at the desired 10 MHz frequency frequency. The LED trigger circuit shown in Figure 7 is capable of switching at 10 MHz and operates at +5V. The higher LED trigger speed allows for faster data transfer.
The trigger signal is generated by Ethernet media converter 74, which may tor example be a commercially available Ethernet media converter designed for inter-conversion of I OBaseT and fiber optic signals, modified to exploit its electrical inputs and outputs of the fiber optic channel. The Ethernet media converter 74 comprises an analog-to-digital converter (ADC) and an IP protocal converter for generating an IP-based signal from the digital output of the ADC. It will be appreciated that the Ethernet media converter 74, which is based on statistical network protocols, may be substituted by a media converter based on deterministic network protocols.
Ethernet hub 82 preferably communicates with an on-board IP-based camera 83. or any internal or external IP-based device, and a remote controller comprising a processing device, for example personal computer (PC) 85 and associated controls 87.
The electronics internal and external to the optical transceiver 10 are shown in Figure 8 for one channel of incoming light signals. When the optical transceiver 10 is configured to receive multiplexed optical signals through the use of optical filters 37 over the detector modules 32, or a similar means of selective filtering to render each light receiving element 30 reactive to a particular wavelength or range of wavelengths within the visible spectrum, similar electronics to those shown in Figure 8 may be used for each channel of light.
Preferably. the APD readout electronics 80 comprises the following components: (a) an APD module 32 comprising a bias power supply with temperature compensation, a transimpedance amplifier and a capacitor to filter the output signal; a summing amplifier 84; and a wide dynamic range automatic gain amplifier 86.
One embodiment of the invention utilizes a transimpedance amplifier chip (not shown) from Analog Devices, an APD bias supply (not shown) from Matsusada Precision, and APD sensors 30 from Hamamatsu Corporation. An APD module 32 with only a APD bias supply and transimpedance amplifier may also be used, such as is commercially available from Hamamatsu Corporation. It will be appreciated that similar devices may be obtained from other sources to accomplish the similar result.
The summing amplifier 84 sums the output voltages from all the transimpedance amplifiers connected to individual sensors 30 or optical receiving elements 30 where multiple API) modules 32 are used. The output of the summing amplifier is transmitted to the automatic gain amplifier 86, which includes a filter module or notch filter to minimize mismatching and filter unwanted low and high frequencies. The output of the automatic gain amplifier 86 is at a predetermined fixed voltage, preferably around 2.5 to 5 volts, and is thus independent of the intensity of light received by the light receiving elements 30.
based distribution board 72 for activating the plurality of LEDs 22 via trigger circuits 70 in each LED board 20.In the embodiment shown the digital output of the Ethernet media converter 74 is also sent to an Ethernet hub or switch 82 and on to PC
85 which contains software for managing and controlling the electronic circuitry and monitoring the data flow.
This design has enabled operation of the optical transceiver 10 in a wide dynamic range without using logarithmic amplifiers, which are prone to large drifts with small changes in operating parameters. There are many devices and systems for converting electrical pulses to discrete optical pulses, and for converting optical pulses to discrete electrical pulses, in the analogue and digital domains, which are well known to those skilled in the art. There are also optical communications systems described in the art, some of which are free space communications systems and some of which include multiplexing systems for achieving higher data rates, by way of non-limiting example only, the System and Method for Free Space Optical Communications Using Time Division Multiplexing of Digital Communication Signals described in U.S. Patent No. 6,246,498 issued to Dishman et al. on June 12, 2001; the Optical Space Communication Apparatus Sending Main Signals and an Auxiliary Signal for Controlling the Intensity at the Receiver described in U.S. Patent No. 5,610,748 issued to Sakanaka et al. on March 11, 1997; and the Optical Communications System described in U.S. Patent No. 5,896,211 issued to Watanabe on April 20, 1999. The invention is not intended to be limited to any particular opto-electric conversion methodology, multiplexing scheme or communications system.
Using for example wavelength division multiplexing (WDM), data rates of 10Mb/s or even higher can be achieved by present techniques for a single wavelength of light. In the first embodiment of the invention described above, each transceiving element 22 transmits light at a discrete wavelength, for example in the green portion of the visible light spectrum. By using various frequencies of light in this fashion, as long as the band separation is sufficient multi-directional communications can occur simultaneously without interference, thus enhancing the communications speed.
Moreover, as the frequency increases, both the data rate and the directional sensitivity of the optical receivers 30 increases.
Figure 9 illustrates a communications zone 100 in an underwater optical communications system in which the optical transceivers 10 of the present invention may be used both as fixed beacon transceivers and as mobile transceivers.
Figure 10 illustrates a communications zone 100 in terrestrial optical communications system in which the optical transceivers 10 of the present invention may be used and affixed to a surface vehicle 124. It will be appreciated that the principles of the invention can also be applied to other water, surface and space-based communications systems.
Further, although the communications system described herein is advantageously used in underwater or terrestrial mining applications, it can also be used for such tasks as border security (marine patrol), underwater inspection of boat hulls, inspection of water intake pipes, and many other applications.
The communications zone 100 is defined by optical transceivers 10 which are preferably dispersed generally uniformly throughout the communications zone 100. For underwater optical communications systems, the optical transceivers 10 may for example be buoyant and affixed to anchors (not shown) set on the floor of a body of water, or may be suspended from a boat or other buoyant object 102 floating on the water's surface, as illustrated in Figures 9 and 11.
Figure 9 illustrates a 'single cell' communications zone, in which the communications zone is defined between 'directional corner beacons each comprising a single optical communications device 10. The invention also provides a 'multiple-cell' embodiment in which the communications zone 100 comprises a matrix of interior optical transceivers 10 and peripheral optical transceivers 10 creating a network of optical transceivers 10. The optical transceivers 10 in the interior of the communications zone 100 are fully multi-directional, and may for example be spherical embodiments of the optical communications device, or may be the optical communications device 10 as shown adjoined as illustrated in Figure 6, by way of example only. A description of an optical communications zone may be found in international application no. PCT/CA2005/000027 published July 28, 2005.
Even in the 'single cell' communications zone embodiment illustrated in Figure 9, the optical transceivers 10 operating at the periphery of the communications zone 100 may instead be fully multi-directional, so that the communications zone 100 extends for some distance beyond the optical transceivers 10. It will be appreciated that it is possible to utilize peripheral optical transceivers 10 that are directional and emit light only toward the communications zone 100 as shown in Figures 9 and 10, in which case the communications zone 100 will not extend substantially beyond the peripheral optical transceivers 10. The optical transceivers 10 may be interconnected through a network, or may all be connected directly to a control station at which PC
85 is located.
The submersible craft 120 and the control station each comprise suitable electro-optical circuitry for converting optical data signals received by the optical transceivers 10 from the submersible craft 120 to electrical signals for controlling the craft 120, and for converting electrical control signals generated by the control station to optical signals transmitted by the optical transceivers 10 to the submersible craft 120. The light signals emitted by the light emitting elements 22 or may be modulated in any suitable fashion.
Figure 9 illustrates a submersible craft 120 which, like the optical transceivers 10, is provided with at least one optical transceiver 10. The craft 120 illustrated has one optical transceiver 10 such as the optical transceiver 10 of Figures 1 to 5. The optical transceivers 10 are dispersed about the communications zone 100 such that the submersible craft 120 is able to receive optical signals containing communication data from one or more optical transceivers 10 at all times, and to send optical communication data to one or more optical transceivers 10 at all times, regardless of the orientation of the craft 120 and regardless of the position of the craft 120 within the communications zone 100. The optical transceivers 10 are spaced closely enough to ensure that, within the communications zone 100, the submersible craft 120 is always in optical communication with at least one optical transceivers 10, and operate in a "hand-off" tashion similar to that used in cellular telephone systems, in which as the telephone transceiver moves from one cell to the next the cellular tower which the telephone transceiver is approaching establishes a communications link with the transceiver and the cellular tower from which the transceiver is receding cuts off its communications link.
At the same time, the optical transceivers 10 are preferably spaced far enough apart that they do not significantly interfere with the ability of the submersible craft 120 to manoeuvre through the communications zone 100. The ideal spacing may depend upon many factors, including the intensity of the light emitting elements 22, the sensitivity of the light receiving elements 30, the transmissivity of the water (including the particular cause of any cloudiness or murkiness), and ambient light levels within the communications zone 100.
It is also advantageous to space the optical transceivers 10 so that the is submersible craft 120 is always in optical communication with at least three optical transceivers to. This will allow for positioning and locating the submersible craft 120 by triangulation.
The optical transceivers 10 may also be located at varying elevations, to support triangulation for positioning/locating the submersible craft 120 vertically. For example, Figure 11 illustrates a communications zone 100 defined by a series of optical transceivers 10 suspended from a floating buoy 102. The suspended optical transceivers 10, which may be powered by a generator (not shown) or battery (not shown) on board the buoy 102, may be directional, or may comprise optical transceivers 10 configured in pairs as in Figure 6 so as to emit light in all directions.
The optical transceivers 10 are spaced closely enough to ensure that, within the communications zone 100, the submersible craft 120 is always in optical communication with at least one optical transceiver 10.
The optical transceivers 10 may be powered by battery 71 as described above, or by an electrical generator (not shown) contained in a land-based control centre or a or surface-based control centre such as a floating watercraft or communications relay buoy, and connected to the optical transceivers 10 by optical fibres or electrical cables (not shown). The submersible craft 120 may be powered by any suitable means. The control centre and the submersible craft 120 would in the first embodiment of the invention each comprise computers, an optical switching system, and an on-board Transmit/Receive link, each of which may be of conventional or any suitable design which is well known to those skilled in the art. By way of example only such a system is described in U.S. Patent No. 4,905,309 issued February 27, 1990 to Maisonneuve et at.
The communications methodology may comprise any conventional optical communications system, but preferably utilizes a packet-based system utilizing optical pulses to transmit the data packets. The first embodiment of the invention described above operates under a token passing system, in which each token is managed by a header and footer. Data, preferably including video from on-board cameras 83 located about the submersible craft 120, is transmitted optically from the on-board optical transceiver(s) 10 to the optical transceivers 10 about the communications zone 100. Data 132 and video information 134 are displayed at the control station for monitoring each submersible craft 120, and the return data stream 132 controls the submersible craft 120, steering it to a new position or orientation and/or initiating a task.
Figure 11 illustrates a vertical communications zone 100 for the invention, in which a number of optical transceivers 10 may be suspended in sequence. The vertical communications zone 100 may be suspended from buoy 102 with a water-tight, buoyant casing that also supports a Global Positioning System (GPS) antenna (not shown) and circuitry for precise positioning information and triangulation of the positions of the submersible craft 120, and optionally a solar cell (not shown) for primary or auxiliary power and battery recharging. The casing contains the power supply 71 for powering suspended optical transceivers 10; the electro-optical circuitry for converting optical signals to electrical control signals and vice versa for communications between the suspended optical transceivers 10 and the submersible crafts 120; and control circuitry for operating a second communications link, for example a radio frequency (RF) transceiver (not shown) coupled between the electro-and transmitting signals to a remote control station (provided for example on a as a ship or land-based structure) and thus allowing the submersible crafts 120 to be controlled from any desired distance from the communications zone 100.
It will be appreciated that the communications system and method of the invention can be used solely to control the submersible craft 120 within the communications zone 100. in which case the craft 120 does not need to be equipped with light emitting elements 22 and the optical transceivers 10 about the communications zone 100 do not need to be equipped with light receiving elements 30. However, preferably the system and method of the invention provides for bi-directional including communications from the craft 120 to the optical transceivers 10 about the communications zone 100, I'm example video transmissions, radar and/or sonar telemetry transmissions and the like, in which case both the optical transceivers 10 about the communications zone 100 and the craft 120 will be equipped with light emitting elements 22 and light receiving elements 30, respectively.
IS The control station may comprise a conventional display (not shown) for displaying a signal sent by cameras 122 on-board the submersible craft I 20, and any suitable control interface, for example a computer 85, allowing the operator to control the submersible craft 120 and its equipment through command signals transmitted to the optical transceivers 10 about the communications zone 100, and thus to the submersible craft 120. Where multiple submersible crafts 120 are used, each submersible craft 120 has a unique address and the packets in the digital data signals 132 (for example in IP protocol) comprise the address of the particular submersible craft 120 for which the command is intended, for example in the packet header, so that only the intended submersible craft 120 reacts to the command. Similarly, data signals 132 transmitted by each submersible craft 120 comprise the address of the particular submersible craft 120 transmitting the data 132, so that the control centre recognizes the source of the transmission.
Preferably the invention incorporates bit error rate testing and other techniques to ensure the integrity of the optical communications. Also, to reduce the lu likelihood of the loss of a craft 120 or land vehicle 124 in the event of a communications interruption, preferably the submersible craft 120 is designed to automatically stop and sink to the bottom of the body of water and the land vehicle 124 is designed to brake to a stop.
Various embodiments of the present invention having been thus described in detail by way of example, it will be apparent to those skilled in the art that variations and modifications may be made without departing from the invention.
The invention includes all such variations and modifications as fall within the scope of the appended claims.
Claims (7)
1. An optical transceiver comprising, a plurality of light emitting elements positioned to emit light in a plurality of directions, a plurality of light receiving elements positioned to receive light from a plurality of directions and interspersed with the plurality of light emitting elements, the plurality of light receiving elements comprising, a first light receiving element adapted to output an electric signal only in response to light of a selected first wavelength or range of wavelengths, and at least a second light receiving element adapted to output an electric signal only in response to light of a selected second wavelength or range of wavelengths different from the first wavelength or range of wavelengths, a mirror coupled to the optical transceiver and configured to reflect light emitted from at least one light emitting element, whereby the optical transceiver can simultaneously receive data independently in at least first and second optical signals respectively having the first and second wavelength or range of wavelengths.
2. The optical transceiver of claim 1, wherein a plurality of mirrors are coupled to the optical transceiver and configured to reflect light emitted from at least one light emitting element.
3. The optical transceiver of claims 1 or 2, wherein at least one mirror is configured to compensate for occlusion caused by the placement of at least one light receiving element.
4. The optical transceiver of any one of claims 1 to 3, wherein the plurality of light emitting elements are included on a plurality of facet boards fixed to the transceiver and at least one mirror is configured to compensate for a gap between adjacent facet boards.
S. The optical transceiver of any one of claims 1 to 4, wherein the shape of at least one mirror is complementary to the shape of the adjacent facet board to optimize the amount of light reflected.
6. The optical transceiver of any one of claims 2 to 5, wherein the plurality of mirrors are included to improve the light emission from the transceiver to 180 degrees.
7. The optical transceiver of any one of claims 2 to 6, wherein the plurality of mirrors are configured to reflect light in a predetermined pattern.
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| CA2677585A1 (en) | 2011-03-03 |
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