WO2001005072A1 - Signalling system - Google Patents
Signalling system Download PDFInfo
- Publication number
- WO2001005072A1 WO2001005072A1 PCT/GB2000/002633 GB0002633W WO0105072A1 WO 2001005072 A1 WO2001005072 A1 WO 2001005072A1 GB 0002633 W GB0002633 W GB 0002633W WO 0105072 A1 WO0105072 A1 WO 0105072A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- signal
- signalling device
- optical signal
- signalling
- operable
- Prior art date
Links
Classifications
-
- 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
- H04B10/1125—Bidirectional transmission using a single common optical path
-
- 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
- H04B10/114—Indoor or close-range type systems
- H04B10/1149—Arrangements for indoor wireless networking of information
-
- 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
- H04B10/25—Arrangements specific to fibre transmission
- H04B10/2587—Arrangements specific to fibre transmission using a single light source for multiple stations
Definitions
- the present invention relates to a signalling system.
- the invention has particular, although not exclusive, relevance to the alignment of an optical beam used in an optical communication system.
- WO 98/35328 a point to multipoint data transmission system which uses a retro-reflector to receive collimated laser beams from a plurality of user terminals, to modulate the received laser beams and to reflect them back to the respective user terminals.
- This point to multipoint data transmission system employs pixelated reflector/modulator arrays and a telecentric optical lens system. Each pixel in the array maps to a unique angular position in the field of view of the telecentric optical lens system. Communications with each of the user terminals is then achieved using the appropriate pixel in the array which maps to the direction in which the user terminal is located within the field of view.
- the present invention aims to provide an alternative technique for maintaining alignment between the laser beam transmitted by the receiving end of the system towards the retro-reflector.
- Figure 1 is a schematic diagram of a video broadcast system for supplying video signals for a plurality of television channels, to a plurality of remote users;
- Figure 2 is a schematic block diagram of a local distribution node and a user terminal which forms part of the video broadcast system shown in Figure 1;
- Figure 3 is a schematic diagram of a retro-reflector array and lens system employed in the local distribution node shown in Figure 2 ;
- Figure 4 is a schematic diagram of a pixelated modulator array forming part of the retro-reflecting modulator unit shown in Figure 3 ;
- Figure 5 is a perspective schematic view of the components in the user terminal which forms part of the system shown in Figure 3;
- Figure 6 is a plot illustrating the intensity profile of the laser beam generated by the user terminal shown in Figure 5 ;
- Figure 7 is a block diagram illustrating a control circuit which forms part of the user terminal shown in Figure 5 ;
- Figure 8 is a perspective schematic view of an alternative user terminal which may be used in the system shown in Figure 3.
- Figure 1 schematically illustrates a video broadcast system for supplying video signals, for a plurality of television channels, to a plurality of remote users.
- the system comprises a central distribution system 1 which transmits optical video signals to a plurality of local distribution nodes 3 via a bundle of optical fibres 5.
- the local distribution nodes 3 are arranged to receive the optical video signals transmitted from the central distribution system 1 and to transmit relevant parts of the video signals to respective user terminals 7 (which are spatially fixed relative to the local distribution node 3 ) as optical signals through free space, i.e. not as optical signals along an optical fibre path.
- each user terminal 7 informs the appropriate local distribution node 3 which channel or channels it wishes to receive (by transmitting an appropriate request) and, in response, the local distribution node 3 transmits the appropriate video data, to the respective user terminals 7.
- Each local distribution node 3 does not, however, broadcast the video data to the respective user terminals 7. Instead, each local distribution node 3 is arranged (i) to receive an optical beam transmitted from each of the user terminals 7 which are in its locality, (ii) to modulate the received beams with the appropriate video data for the desired channel or channels, and (iii) to reflect the modulated beams back to the respective user terminals 7.
- each of the local distribution nodes 3 can also transmit optical data, such as status reports, back to the central distribution system 1 via the respective optical fibre bundle 5, so that the central distribution system 1 can monitor the status of the distribution network.
- FIG. 2 schematically illustrates in more detail the main components of one of the local distribution nodes 3 and one of the user terminals 7 of the system shown in Figure 1.
- the local distribution node 3 comprises a communications control unit 11 which (i) receives the optical signals transmitted along the optical fibre bundle 5 from the central distribution system 1; (ii) regenerates the video data from the received optical signals; (iii) receives messages 12 transmitted from the user terminals 7 and takes appropriate action in response thereto; and (iv) converts the appropriate video data into data 14 for modulating the respective light beams 15 received from the user terminals 7.
- the communications control unit 11 will encode the video data with error correction coding and coding to reduce the effects of inter-symbol- interference and other kinds of well known sources of interference such as from the sun and other light sources .
- the local distribution node 3 also comprises a retro- reflector and modem unit 13, which is arranged to receive the optical beams 15 from the user terminals 7 which are within its field of view, to modulate the respective light beams with the appropriate modulation data 14 and to reflect the modulated beams back to the respective user terminals 7.
- the retro-reflector and modem unit 13 retrieves the message 12 and sends it to the communications control unit 11 where it is processed and the appropriate action is taken.
- the retro-reflector and modem unit 13 has a horizontal field of view which is greater than +/- 50° and a vertical field of view of approximately +/- 5°.
- Figure 2 also shows the main components of one of the user terminals 7.
- the user terminal 7 comprises a laser diode 17 for outputting a laser beam 19 of coherent light.
- the user terminals 7 are designed so that they can communicate with the local distribution node 3 within a range of approximately 200 metres with a link availability of 99.9 per cent.
- the laser diode 17 is a 150 mW laser diode which outputs a laser beam having a wavelength of 850 ran.
- this embodiment makes use of the fact that if the laser beam is interrupted by a person, then this will be detectable at the receiver (since such an interruption of the beam causes an almost instantaneous drop in received signal level) and hence in this situation, the power output of the laser can be reduced to safe levels.
- the output laser beam 19 is passed through a collimator 21 which reduces the angle of divergence of the laser beam 19.
- the resulting laser beam 23 is passed through a beamsplitter 25 to a pair of steerable mirrors 26 which are used to steer the laser beam.
- the laser beam then passes through an optical beam expander 27, which increases the diameter of the laser beam to approximately 50 mm for transmittal to the retro- reflector and modem unit 13 located in the local distribution node 3.
- the optical beam expander 27 is used because a large diameter laser beam has a smaller divergence than a small diameter laser beam.
- the optical beam expander 27 has the further advantage that it provides a fairly large collecting aperture for the reflected laser beam and it concentrates the reflected laser beam into a smaller diameter beam.
- the smaller diameter reflected beam is then split from the path of the originally transmitted laser beam by the beamsplitter 25 and focussed onto a photo-diode 29 by a lens 31. Since the operating wavelength of the laser diode 17 is 850nm, a silicon avalanche photo-diode (APD) can be used, which is generally more sensitive than other commercially available photo detectors, because of the low noise multiplication which can be achieved with these devices.
- APD silicon avalanche photo-diode
- the electrical signals output by the photo- diode 29, which will vary in dependence upon the modulation data 14, are then amplified by the amplifier 33 and filtered by the filter 35.
- the filtered signals are then supplied to a control unit 37 which regenerates the clock and the video data using standard data processing techniques.
- the retrieved video data 38 is then passed to the user unit 39, which, in this embodiment, comprises a television receiver in which the video data is displayed to the user on a CRT (not shown).
- the control unit 37 is also used to control the steering of the steerable mirrors 26 so that the laser beam is optimally aligned with the local distribution node 3.
- the control unit 37 also monitors and keeps a history of the recent signal strength so that, if the beam is interrupted, it can pass a control signal to the laser control unit 41 so that the power of the laser diode 17 is reduced to a class 1 level (0.25mW). Provided this power reduction can be achieved within one millisecond of the beam being interrupted, this would provide a system which could be considered as class 1 eye safe.
- the control unit 37 can distinguish between slowly varying signal levels (caused for example by deteriorating atmospheric conditions) and sudden interruptions caused by, for example, a person interrupting the beam.
- the user unit 39 can receive an input from the user, for example indicating the selection of a desired television channel, via a remote control unit (not shown).
- the user unit 39 generates an appropriate message 12 for transmittal to the local distribution node 3.
- This message 12 is output to the laser control unit 41 which controls the laser diode 17 so as to cause the laser beam 19 output from the laser diode 17 to be modulated with the message 12.
- the laser control unit 41 should modulate, for example, the phase of the transmitted laser beam.
- the laser control unit 41 could apply a small signal modulation to the laser beam 19 to create a low-bandwidth control channel between the user terminal 7 and the local distribution node 3. This is possible provided the detector in the local distribution node 3 can detect the small variation in the amplitude of the received laser beam. Furthermore, such a small signal amplitude modulation of the laser beam would not affect a binary "on” and "off” type modulation which could be employed by the retro-reflector and modem unit 13.
- FIG 3 schematically illustrates the retro-reflector and modem unit 13 which forms part of the local distribution node 3 shown in Figure 2.
- the retro-reflector and modem unit 13 comprises a wide angle telecentric lens system 51 and an array of modulators and detectors 53.
- the design of such a wide angle telecentric lens using fisheye lens techniques is well known to those skilled in the art.
- the telecentric lens 51 comprises lens elements 61 and 55 and a stop member 57, having a central aperture 59.
- the size of the aperture 59 is a design choice and depends upon the particular requirements of the installation.
- the structure and function of the telecentric lens system is described in the applicants earlier International application WO 98/35328, the contents of which are incorporated herein by reference.
- FIG 4 is a schematic representation of the front surface (i.e. the surface facing the lens system 51) of the modulator and detector array 53 which, in this embodiment, comprises 100 columns of modulator/detector cells and 10 rows of modulator/detector cells (not all of which are shown in the figure) .
- Each modulator/detector cell c 13 comprises a modulator i ⁇ and a detector d x - located adjacent the corresponding modulator.
- the size 71 of the cells ⁇ is between 50 and 200 ⁇ m, with the spacing (centre to centre) 72 between the cells being slightly greater than the cell size 71.
- the telecentric lens 51 is designed so that the spot size of a focussed laser beam from one of the user terminals 7 corresponds with the size 71 of one of the modulator/detector cells c ii r as illustrated by the shaded circle 73 shown in Figure 4, which covers the modulator/detector cell c 22 •
- each of the detectors d 1:] comprises a photo-diode which is connected to an associated amplifier, filter and clock recovery and data retrieval unit, which operate to detect any modulation of the corresponding laser beam and to regenerate any messages 12 which are transmitted from the corresponding user terminal 7. All the recovered messages 12 are then transmitted back to the communications control unit 11 where they are processed and appropriate actions are taken.
- FIG. 5 is a perspective schematic view of the user terminal shown in Figure 2.
- light from the laser diode 17 passes through a collimator lens 21 and through a beamsplitter 25 to the steerable mirrors 26-1 and 26-2.
- steerable mirror 26-1 is mounted for rotation on the drive shaft 81-1 of motor 83-1 and can therefore be rotated about the vertical axis 85 of the shaft 81-1.
- the mirror 26-1 can therefore be used to steer the laser beam horizontally.
- the laser beam reflected from the mirror 26-1 hits the mirror 26-2 which is mounted for rotation with the drive shaft 81-2 of the second motor 83-2.
- the drive shaft 81-2 is operable to rotate the mirror 26-2 about the horizontal axis 87.
- the mirror 26-2 can steer the laser beam in the vertical direction. Consequently, the combination of the two mirrors 26-1 and 26-2 can steer the laser beam in any desired direction towards the appropriate local distribution load 3.
- the control unit 37 controls the positions of the mirrors 26-1 and 26-2 by outputting appropriate control signals to the motors 33-1 and 33-2.
- the control unit 37 controls the motors 83 in order to maximise the level of the signal reflected from the local distribution node 3.
- typically the laser beam generated by the laser diode 17 will be non-uniform, and in many instances will approximately have a Gaussian profile. This is illustrated in Figure 6.
- control unit 37 uses a phase sensitive detection technique. This is achieved by applying a small amplitude oscillation to each of the two mirrors 26-1 and 26-2. The resulting small modulation in the received signal strength (due to the oscillation of the mirrors) is detected by mixing the received signal with the modulating signal applied to the motors 83-1 and 83-2 used to cause the mirrors to oscillate. This is illustrated in Figure 7.
- Figure 7 shows a dither signal generator 91 which generates the modulating signals used to cause the two mirrors 26 to oscillate.
- dither signal generator 91 generates two dither signals 93-1 and 93-2 which are passed to a motor controller 95.
- the motor controller 95 uses the dither signal 93-1 to control the motor 83-1 and it uses the dither signal 93-2 to control the motor 83-2.
- the signal 97 output from the filter 35 (shown in Figure 2) is input to two mixers 99-1 and 99-2 where the signal is mixed with a respective one of the two dither signals 93-1 and 93-2.
- the two dither signals 93-1 and 93-2 are preferably at different frequencies which are not harmonically related, in order that there is no cross talk between the signals derived from the respective mixers 99-1 and 99-2.
- the outputs from the mixers 99 are then filtered by a respective low pass filter 101-1 and 101-2 to remove the high frequency components.
- the filtered signals are then converted into digital signals by the analogue to digital converter 103 and then passed to the microprocessor 105 for processing.
- the microprocessor 105 can process the signals output by the analogue to digital converter 103 and output an appropriate control signal to the motor controller 95 to cause the mirrors 26 to be adjusted so that the beam is optimally aligned with the retro-reflector .
- Figure 7 also shows that the control unit 37 includes a clock recovery and data regeneration unit 107 which is used to regenerate the modulation data 14 sent from the local distribution node 3. As shown, this data is output to the user unit 39.
- Figure 7 also shows that the signal 97 is input directly to the microprocessor 105, via the analogue to digital converter 103, so that the microprocessor 105 can (i) continuously monitor the signal strength of the received beam; (ii) store, in the memory 109, the recent history of the received signal strength; and (iii) if appropriate, output a control signal to the laser control unit 41 in order to reduce the power of the transmitted laser beam.
- two mirrors were mounted for rotation about orthogonal axes so that the user terminals can steer their laser beams towards the retro- reflector within the local distribution node.
- a single mirror may be used if two-axis movement is provided.
- a similar steering operation can be achieved using refraction or diffraction techniques.
- An example of a diffractive technique would be to use an acousto-optic scanner in which a surface acoustic wave is launched into a piezoelectric material, the propagation wave forming a moving diffraction grating.
- a laser beam incident on the piezoelectric material is then diffracted by the grating, with the angle of diffraction being related to the grating pitch, and hence to the drive frequency.
- the laser beam is therefore steered by variation of the drive frequency.
- this type of system is not preferred due to high cost, low efficiency and the need to provide relatively high drive frequencies (several MHz).
- a second type of diffractive system is the hologon, named by analogy with the polygon reflective scanner found in laser printers.
- Such a system comprises a disk of transparent material (typically glass or plastic) whose surface is embossed with a computer generated hologram.
- the hologram is designed to deflect an incoming laser beam through an angle which depends on the position of the beam on the surface of disk. Steering of the beam is achieved by rotating the disk with respect to the incident beam.
- two such hologons would be required to steer the beam in two directions.
- Such a diffractive system has the advantages that the hologons may be mounted on stepper motors and hence only consume power during a change in beam steering; the beam deflection achieved is set in advance by design and can be chosen arbitrarily; and the hologons are cheap since they can be embossed like a CD.
- the hologon system suffers from the disadvantage of high design and tooling costs for the hologon and low optical efficiency since some of the optical power is lost through the diffraction process.
- Refractive steering of the laser beam may be achieved using two wedge prisms.
- Figure 8 shows the main components of a user terminal which employs two wedge shape prisms 109- 1 and 109-2 located between the optical beam expander 27 and the beamsplitter 25. If the two prisms 109 are rotated by an equal amount but in opposite directions, the laser beam is steered in the horizontal plane. The amount of the deviation is set by the angle of rotation, the prism wedge angle and the prism refractive index. To achieve vertical deviation of the laser beam, the two prisms are rotated in the same direction, to effectively rotate the plane of deviation. Therefore, any arbitrary ⁇ , ⁇ deviation can be achieved.
- the refractive solution illustrated in Figure 8 has a number of advantages.
- the prism parameters can be chosen so that a full rotation of the prisms gives the full range of deviation required, thereby minimising the precision required of the rotation mechanism (not shown) used to rotate the prisms.
- the prisms can be readily rotated using stepper motors which only require power during a change in the beam steering. Further, since a similar optical system has been used since approximately 1930, to implement range finders in a number of cameras, the prisms and rotation mechanisms required are readily available and low cost items .
- a high powered laser was used and the power output of the laser was reduced in the event of the beam being interrupted.
- the ability to be able to control the power of the laser beam in this way is applicable to any retro-reflecting communication technique, since the received signal level gives a reliable indication of the link integrity and since the laser is physically located at the receiver end, its output power can be controlled by electronics at the receiver.
- an array of QCSE modulators were used in the retro-reflecting end of the communications link. These QCSE modulators either absorb or reflect incident light.
- QCSE modulators either absorb or reflect incident light.
- other types of reflectors and modulators can be used.
- a plane mirror may be used as the reflector and a transmissive modulator (such as a liquid crystal) may be provided between the lens and the mirror.
- beamsplitters may be used to temporarily separate the path of the incoming beam from the path of the reflected beam and, in this case, the modulator may be provided in the path of the reflected beam so that only the reflected light is modulated.
- such an embodiment is not preferred since it requires additional optical components to split the forward and return paths and then to recombine the paths after modulation has been effected.
- a telecentric lens was used In front of the array of retro-reflectors. Whilst the use of a telecentric lens is preferred, it is not essential. Further, if a telecentric lens is used, the back focal plane of the lens may be curved or partially curved, in which case the array of modulators should also be curved or partially curved to match the back focal plane of the telecentric lens.
- the amplitude modulation of the signal strength caused by the oscillation of the mirrors was detected by mixing the signal with the dither signals.
- the microprocessor 105 may detect the variation in the signal strength from the digital samples generated from the received signal itself. The microprocessor 105 could then cause the beam to be steered in a direction and if the variation increases then it can steer the laser beam in the opposite direction.
Abstract
Description
Claims
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU59955/00A AU763790B2 (en) | 1999-07-08 | 2000-07-10 | Signalling system |
EP00946067A EP1197018A1 (en) | 1999-07-08 | 2000-07-10 | Signalling system |
JP2001509187A JP2003528478A (en) | 1999-07-08 | 2000-07-10 | Signaling system |
CA002383142A CA2383142A1 (en) | 1999-07-08 | 2000-07-10 | Signalling system |
Applications Claiming Priority (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
GB9916081.4 | 1999-07-08 | ||
GBGB9916082.2A GB9916082D0 (en) | 1999-07-08 | 1999-07-08 | Eye safe laser communication system |
GBGB9916081.4A GB9916081D0 (en) | 1999-07-08 | 1999-07-08 | Beam alignment system |
GB9916082.2 | 1999-07-08 |
Publications (1)
Publication Number | Publication Date |
---|---|
WO2001005072A1 true WO2001005072A1 (en) | 2001-01-18 |
Family
ID=26315748
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/GB2000/002633 WO2001005072A1 (en) | 1999-07-08 | 2000-07-10 | Signalling system |
Country Status (5)
Country | Link |
---|---|
EP (1) | EP1197018A1 (en) |
JP (1) | JP2003528478A (en) |
AU (1) | AU763790B2 (en) |
CA (1) | CA2383142A1 (en) |
WO (1) | WO2001005072A1 (en) |
Cited By (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2001045981A2 (en) | 1999-12-22 | 2001-06-28 | Quantumbeam Limited | Optical free space signalling system |
GB2360656A (en) * | 1999-11-30 | 2001-09-26 | Agilent Technologies Inc | Transceiver using diffractive optical element to direct beams |
GB2383910A (en) * | 2002-01-07 | 2003-07-09 | Quantumbeam Ltd | Optical free space signalling system |
EP1379016A1 (en) * | 2001-03-15 | 2004-01-07 | Vladimir Isfandeyarovich Adzhalov | Access method for data packet networks |
US7832612B2 (en) | 2008-09-19 | 2010-11-16 | Ethicon Endo-Surgery, Inc. | Lockout arrangement for a surgical stapler |
RU2752790C1 (en) * | 2020-09-29 | 2021-08-05 | Федеральное государственное автономное образовательное учреждение высшего образования "Белгородский государственный национальный исследовательский университет" (НИУ "БелГУ") | Method and apparatus for multi-channel reception and transmission of optical signals based on forming sector directivity patterns and azimuth tracking system |
Families Citing this family (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JP4068365B2 (en) * | 2002-02-26 | 2008-03-26 | 株式会社リコー | Coordinate input device |
JP4585378B2 (en) * | 2005-06-02 | 2010-11-24 | 日本電信電話株式会社 | Hybrid optical axis correction device for optical space communication system |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4777660A (en) * | 1984-11-06 | 1988-10-11 | Optelecom Incorporated | Retroreflective optical communication system |
EP0580905A1 (en) * | 1992-07-28 | 1994-02-02 | BRITISH TELECOMMUNICATIONS public limited company | Optical radiation devices |
US5347387A (en) * | 1992-03-24 | 1994-09-13 | Rice Robert C | Self-aligning optical transceiver |
US5689354A (en) * | 1994-02-04 | 1997-11-18 | Canon Kabushiki Kaisha | Optical space communication apparatus |
WO1998035328A2 (en) * | 1997-02-11 | 1998-08-13 | Scientific Generics Limited | Signalling system |
US5822099A (en) * | 1995-08-31 | 1998-10-13 | Sony Corporation | Light communication system |
-
2000
- 2000-07-10 AU AU59955/00A patent/AU763790B2/en not_active Ceased
- 2000-07-10 EP EP00946067A patent/EP1197018A1/en not_active Withdrawn
- 2000-07-10 JP JP2001509187A patent/JP2003528478A/en active Pending
- 2000-07-10 WO PCT/GB2000/002633 patent/WO2001005072A1/en not_active Application Discontinuation
- 2000-07-10 CA CA002383142A patent/CA2383142A1/en not_active Abandoned
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US4777660A (en) * | 1984-11-06 | 1988-10-11 | Optelecom Incorporated | Retroreflective optical communication system |
US5347387A (en) * | 1992-03-24 | 1994-09-13 | Rice Robert C | Self-aligning optical transceiver |
EP0580905A1 (en) * | 1992-07-28 | 1994-02-02 | BRITISH TELECOMMUNICATIONS public limited company | Optical radiation devices |
US5689354A (en) * | 1994-02-04 | 1997-11-18 | Canon Kabushiki Kaisha | Optical space communication apparatus |
US5822099A (en) * | 1995-08-31 | 1998-10-13 | Sony Corporation | Light communication system |
WO1998035328A2 (en) * | 1997-02-11 | 1998-08-13 | Scientific Generics Limited | Signalling system |
Cited By (11)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
GB2360656A (en) * | 1999-11-30 | 2001-09-26 | Agilent Technologies Inc | Transceiver using diffractive optical element to direct beams |
GB2360656B (en) * | 1999-11-30 | 2004-01-14 | Agilent Technologies Inc | Transceiver |
US7265439B1 (en) | 1999-11-30 | 2007-09-04 | Avago Technologies Fiber Ip (Singapore) Pte. Ltd. | Low cost, high speed, high efficiency infrared transceiver |
WO2001045981A2 (en) | 1999-12-22 | 2001-06-28 | Quantumbeam Limited | Optical free space signalling system |
EP1379016A1 (en) * | 2001-03-15 | 2004-01-07 | Vladimir Isfandeyarovich Adzhalov | Access method for data packet networks |
EP1379016A4 (en) * | 2001-03-15 | 2006-08-16 | Vladimir Isfandeyarov Adzhalov | Access method for data packet networks |
US7590352B2 (en) | 2001-03-15 | 2009-09-15 | Vladimir Isfandeyarovich Adzhalov | Access method for data packet networks |
GB2383910A (en) * | 2002-01-07 | 2003-07-09 | Quantumbeam Ltd | Optical free space signalling system |
WO2003057221A1 (en) * | 2002-01-07 | 2003-07-17 | Quantumbeam Limited | Optical free space signalling system |
US7832612B2 (en) | 2008-09-19 | 2010-11-16 | Ethicon Endo-Surgery, Inc. | Lockout arrangement for a surgical stapler |
RU2752790C1 (en) * | 2020-09-29 | 2021-08-05 | Федеральное государственное автономное образовательное учреждение высшего образования "Белгородский государственный национальный исследовательский университет" (НИУ "БелГУ") | Method and apparatus for multi-channel reception and transmission of optical signals based on forming sector directivity patterns and azimuth tracking system |
Also Published As
Publication number | Publication date |
---|---|
EP1197018A1 (en) | 2002-04-17 |
JP2003528478A (en) | 2003-09-24 |
AU5995500A (en) | 2001-01-30 |
AU763790B2 (en) | 2003-07-31 |
CA2383142A1 (en) | 2001-01-18 |
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