WO1986007221A1 - Fiber optic repeater - Google Patents
Fiber optic repeater Download PDFInfo
- Publication number
- WO1986007221A1 WO1986007221A1 PCT/GB1986/000279 GB8600279W WO8607221A1 WO 1986007221 A1 WO1986007221 A1 WO 1986007221A1 GB 8600279 W GB8600279 W GB 8600279W WO 8607221 A1 WO8607221 A1 WO 8607221A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- fibre
- link
- transmission line
- fibre optic
- optical
- Prior art date
Links
- 239000000835 fiber Substances 0.000 title claims abstract description 31
- 230000005540 biological transmission Effects 0.000 claims abstract description 23
- 229910052779 Neodymium Inorganic materials 0.000 claims abstract description 14
- QEFYFXOXNSNQGX-UHFFFAOYSA-N neodymium atom Chemical compound [Nd] QEFYFXOXNSNQGX-UHFFFAOYSA-N 0.000 claims abstract description 14
- 229910052691 Erbium Inorganic materials 0.000 claims abstract description 13
- UYAHIZSMUZPPFV-UHFFFAOYSA-N erbium Chemical compound [Er] UYAHIZSMUZPPFV-UHFFFAOYSA-N 0.000 claims abstract description 13
- 230000003287 optical effect Effects 0.000 claims abstract description 7
- 239000013307 optical fiber Substances 0.000 claims description 18
- 230000008878 coupling Effects 0.000 claims description 14
- 238000010168 coupling process Methods 0.000 claims description 14
- 238000005859 coupling reaction Methods 0.000 claims description 14
- 238000004891 communication Methods 0.000 claims description 9
- 229910052761 rare earth metal Inorganic materials 0.000 claims description 7
- 150000002910 rare earth metals Chemical class 0.000 claims description 7
- 239000004065 semiconductor Substances 0.000 description 5
- 239000011521 glass Substances 0.000 description 3
- 238000000034 method Methods 0.000 description 2
- -1 Neodymium or Erbium Chemical class 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 239000004411 aluminium Substances 0.000 description 1
- 239000006185 dispersion Substances 0.000 description 1
- 239000002019 doping agent Substances 0.000 description 1
- 239000002223 garnet Substances 0.000 description 1
- 238000010348 incorporation Methods 0.000 description 1
- 229910052727 yttrium Inorganic materials 0.000 description 1
- VWQVUPCCIRVNHF-UHFFFAOYSA-N yttrium atom Chemical compound [Y] VWQVUPCCIRVNHF-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/09—Processes or apparatus for excitation, e.g. pumping
- H01S3/091—Processes or apparatus for excitation, e.g. pumping using optical pumping
- H01S3/0915—Processes or apparatus for excitation, e.g. pumping using optical pumping by incoherent light
- H01S3/0933—Processes or apparatus for excitation, e.g. pumping using optical pumping by incoherent light of a semiconductor, e.g. light emitting diode
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
- H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
- H01S3/05—Construction or shape of optical resonators; Accommodation of active medium therein; Shape of active medium
- H01S3/06—Construction or shape of active medium
- H01S3/063—Waveguide lasers, i.e. whereby the dimensions of the waveguide are of the order of the light wavelength
- H01S3/067—Fibre lasers
- H01S3/06754—Fibre amplifiers
Definitions
- This invention concerns fibre optic communication systems and in particular to methods and apparatus for reducing transmission losses in such systems.
- Optical fibre communications systems normally operate at 1.3um (minimum dispersion) and 1.55um (minimum attenuation) wavelengths using semiconductor laser sources. Fibre losses are overcome by using electronic amplifier/repeater units at intervals along the transmission lines, typically at distances of 10 to 100 Kms.
- a repeater amplifier for a fibre optic transmission system comprises:
- a first fibre optic coupling means for receiving light from an optical fibre transmission line
- a length of fibre optic transmission line comprising an optical link for transmitting light from the first coupling means to the second coupling means, the optical fibre forming the said link being doped with a rare-earth such as Neodymium or Erbium, and or LED (4) a diode laser ⁇ coupled to the fibre link to activate same and provide a positive gain in light level between the input coupling means and the output coupling means.
- a rare-earth such as Neodymium or Erbium
- the invention thus lies in the use of a rare-earth doped 5 glass or crystalline fibre where the rare-earth is selected to provide gain at either 1.3 - 1.4um (achieved using Neodynium) or 1.5 - 1.6um (achieved using Erbium). or LED
- the diode laserk operates at a wavelength in the range 700 to 900 nm if Neodymium is the dopant and 800 to 1000 nm if Erbium is used with Neodymium and Ytterbi sensitizers.
- the diode laser is coupled to the link by means of a dichroic beam splitter.
- the diode laser may be coupled by means of a grating or wavelength multiplexer.
- the invention also lies in an improved optical fibre 15 communication system which incorporates repeater amplifiers constructed in accordance with the invention at intervals along the length of the optical fibre transmission line.
- an improved 20 fibre optic transmission line comprises a length of optical fibre doped throughout its length with Neodymium or Erbium to an amount just sufficient to cancel out the line losses so that a light signal provided at one end of the line will travel the length of the line without 25 noticeable attenuation.
- the advantage of the invention is optimised by employing a carrier for the light signals of 1.318 microns wavelength in the case of Neodymium doping and 1.54 microns wavelength in the case of Erbium doping.
- Fig 1 illustrates one embodiment of the present invention
- Fig 2 illustrates a second embodiment of the invention
- Fig 3 illustrates an improved optical fibre communication system employing repeater amplifiers of the invention.
- Fig 1 an input fibre is shown at 10 coupling to a Neodynium doped length of fibre 12 via an optical coupler 14.
- a lens 16 couples the output of the doped fibre to a dichroic beamsplitter 18 which is supplied with light at a wavelength in the range 0.7 to 0.9um (700 to 900nm) from a diode laser source 20, light from which is coupled to the beamsplitter via a lens 22.
- the output from the diochroic beamsplitter is coupled via a third lens 24 to a second fibre cable 26.
- Fig 2 an alternative arrangement is shown in which the dichroic beamsplitter is replaced by a grating 28.
- the light from the diode laser source 20 is coupled as before through a lens 22, positioned now at an angle to the axis of the lens 16 which is much less than the 90° angle of the Fig 1 embodiment, and the output fibre 26 axis and its associated coupling lens 24 are likewise positioned off- axis by an angle sufficient to capture the diffracted light from the grating.
- a fibre optic communication system comprising a modulated light source and light sensitive receptor 30 serving as a transmitter/receiver and a second similar unit 32 distant therefrom and joined thereto through the intermediary of a number of lengths of optical fibre 34,36,38 etc.connected in series and at each junction coupled the one to the other through a repeater amplifier 40,42 etc., each of which is constructed in the manner shown in Fig 1.
- some or all of the repeater amplifiers may be dispensed with by using rare-earth doped optical fibres for the transmission line, typically Neodym ium or Erbium doped glass fires.
Landscapes
- Physics & Mathematics (AREA)
- Electromagnetism (AREA)
- Engineering & Computer Science (AREA)
- Plasma & Fusion (AREA)
- Optics & Photonics (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Lasers (AREA)
- Optical Communication System (AREA)
Abstract
Repeater amplifier in which a diode laser (20) or LED is coupled to a fibre link to activate the latter and provide positive gain, the link comprising a length (12) of the fibre optic transmission line doped with Neodymium or Erbium. An improved transmission line is described in which the line is effectively formed as a continuous repeater amplifier by doping the fibre optic line with Neodymium or Erbium to an amount just sufficient to cancel out line losses for optical signals transmitted therealong. Typical operaing wavelengths for the diode laser are 700 - 900nm. An advantage has been found by employing a carrier for the light signals of 1.318 microns for Neodymium doping and 1.54 microns for Erbium doping.
Description
FIBER OPTIC REPEATER
Field of invention.
This invention concerns fibre optic communication systems and in particular to methods and apparatus for reducing transmission losses in such systems.
Background to the invention.
Optical fibre communications systems normally operate at 1.3um (minimum dispersion) and 1.55um (minimum attenuation) wavelengths using semiconductor laser sources. Fibre losses are overcome by using electronic amplifier/repeater units at intervals along the transmission lines, typically at distances of 10 to 100 Kms.
Recently semiconductor laser amplifiers have been developed for incorporation into fibre transmission systems to optically amplify the signals. However such devices are not very reliable and in particular shift wavelength with age. Coupling between line and amplifier is difficult in view of the need to match the narrow stripe of a semiconductor laser amplifier, and additionlly semiconductor devices are polarisation sensitive and must either use polarisation preserving fibres (expensive) or a loss of efficiency has to be accepted due to incorrect polarisation, often amounting to 50% of the input.
US Patent 4040890 describes methods of making Neodymium doped Yttrium Aluminium Garnet (YAG) and glass lasers designed to operate.at wavelengths in the range 1.0 to 1.2um, typically at 1.06um.
It is an object of the present invention to provide an alternative line amplifier or repeater which can be inserted directly into an optical fibre transmission line and which does not suffer from the above disadvantages and is easily manufactured without the the low yield rates associated with semiconductor laser amplifiers.
It is another object of the present invention to provide an improved transmission line for use in fibre optic transmission systems.
Summary of the invention.
According to one aspect of the present invention a repeater amplifier for a fibre optic transmission system comprises:
(1) a first fibre optic coupling means for receiving light from an optical fibre transmission line;
(2) a second fibre optic coupling means for transmitting light to an optical fibre transmission line;
(3) a length of fibre optic transmission line comprising an optical link for transmitting light from the first coupling means to the second coupling means, the optical fibre forming the said link being doped with a rare-earth such as Neodymium or Erbium, and
or LED (4) a diode laser^coupled to the fibre link to activate same and provide a positive gain in light level between the input coupling means and the output coupling means.
The invention thus lies in the use of a rare-earth doped 5 glass or crystalline fibre where the rare-earth is selected to provide gain at either 1.3 - 1.4um (achieved using Neodynium) or 1.5 - 1.6um (achieved using Erbium). or LED Conveniently the diode laserkoperates at a wavelength in the range 700 to 900 nm if Neodymium is the dopant and 800 to 1000 nm if Erbium is used with Neodymium and Ytterbi sensitizers. 10 Typically the diode laser is coupled to the link by means of a dichroic beam splitter.
Alternatively the diode laser may be coupled by means of a grating or wavelength multiplexer.
The invention also lies in an improved optical fibre 15 communication system which incorporates repeater amplifiers constructed in accordance with the invention at intervals along the length of the optical fibre transmission line.
According to another aspect of the invention an improved 20 fibre optic transmission line comprises a length of optical fibre doped throughout its length with Neodymium or Erbium to an amount just sufficient to cancel out the line losses so that a light signal provided at one end of the line will travel the length of the line without 25 noticeable attenuation.
It has been found that the advantage of the invention is optimised by employing a carrier for the light signals of
1.318 microns wavelength in the case of Neodymium doping and 1.54 microns wavelength in the case of Erbium doping.
The invention will now be described by way of example with reference to the accompanying drawing in which:
Fig 1 illustrates one embodiment of the present invention,
Fig 2 illustrates a second embodiment of the invention, and
Fig 3 illustrates an improved optical fibre communication system employing repeater amplifiers of the invention.
In Fig 1 an input fibre is shown at 10 coupling to a Neodynium doped length of fibre 12 via an optical coupler 14. A lens 16 couples the output of the doped fibre to a dichroic beamsplitter 18 which is supplied with light at a wavelength in the range 0.7 to 0.9um (700 to 900nm) from a diode laser source 20, light from which is coupled to the beamsplitter via a lens 22.
The output from the diochroic beamsplitter is coupled via a third lens 24 to a second fibre cable 26.
In Fig 2 an alternative arrangement is shown in which the dichroic beamsplitter is replaced by a grating 28. The light from the diode laser source 20 is coupled as before through a lens 22, positioned now at an angle to the axis of the lens 16 which is much less than the 90° angle of the Fig 1 embodiment, and the output fibre 26 axis and its associated coupling lens 24 are likewise positioned off- axis by an angle sufficient to capture the diffracted
light from the grating.
In Fig 3 there is shown a fibre optic communication system comprising a modulated light source and light sensitive receptor 30 serving as a transmitter/receiver and a second similar unit 32 distant therefrom and joined thereto through the intermediary of a number of lengths of optical fibre 34,36,38 etc.connected in series and at each junction coupled the one to the other through a repeater amplifier 40,42 etc., each of which is constructed in the manner shown in Fig 1.
In accordance with one of the aspects of the invention some or all of the repeater amplifiers may be dispensed with by using rare-earth doped optical fibres for the transmission line, typically Neodym ium or Erbium doped glass fires.
Claims
1. A repeater amplifier for a fibre optic communication system comprising:
(1) a first fibre optic coupling means for receiving light from an optical fibre transmission line;
(2) a second fibre optic coupling means for transmitting light to a continuation of the optical fibre transmission line;
(3) a length of fibre optic transmission line comprising an optical link for transmitting light from the first coupling means to the second coupling means, the optical fibre forming the said link being doped with a rare-earth selected to provide gain at a transmission wavelength employed in the system, and or LED (4) a diode laserAcoupled to the fibre link to activate same and provide the said positive gain between the input and output coupling means.
2. A repeater amplifier as claimed in claim 1 in which the rare-earth is Neodymium and the diode laser is caused to operate at a wavelength such that the fibre optic link gain occurs at wavelengths in the range 1.3 to 1.4um.
3. A repeater amplifier as claimed in claim 1 in which the rare-earth is Erbium and the diode laser is caused to operate at a wavelength such that the fibre optic link gain occurs at wavelengths in the range 1.5 to 1.6um.
4. A repeater a plifier as claimed in claim 2 in which the diode laserAopefates at a wavelength' in the range of 700 - 900nm.
5. A repeater amplifier as claimed in claim 1 in which the diode laser-* is coupled to the link by means of a Dichroic beam splitter.
6. A repeater amplifier as claimed in claim 1 wherein the diode laser^is coupled to the link by means of a grating or wavelength multiplexer.
7. An improved optical fibre transmission line comprising a length of optical fibre doped throughout its length with Neodymium or Erbium to an amount just sufficient to cancel out the line losses to enable light signals to be transmitted therethrough without noticeable attenuation.
8. An optical fibre communication system comprising a fibre optic transmission line and at intervals therealong a repeater amplifier as claimed in claim 1.
. An optical fibre communication system comprising a length of fibre optic transmission line doped throughout its length with Neodymium or Erbium to an amount just sufficient to cancel out line losses to enable light signals to be transmitted therealong without noticeable attenuation and light transmitting and receiving means coupled thereto for transmitting and receiveng light signals.
10. An optical fibre communication system as claimed in - 8 - claim 8 or claim 9 further comprising an optical source for generating a carrier signal of specific wavelength.
11. An optical transmission system as claimed in claim 10 in which the specific wavelength is 1.318um in the case of Neodymium doping and 1.54um in the case of Erbium doping.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB858512980A GB8512980D0 (en) | 1985-05-22 | 1985-05-22 | Fibre optic transmissions systems |
| GB8512980 | 1985-05-22 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO1986007221A1 true WO1986007221A1 (en) | 1986-12-04 |
Family
ID=10579535
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/GB1986/000279 WO1986007221A1 (en) | 1985-05-22 | 1986-05-22 | Fiber optic repeater |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0222866A1 (en) |
| GB (3) | GB8512980D0 (en) |
| WO (1) | WO1986007221A1 (en) |
Cited By (13)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO1990000320A1 (en) * | 1988-07-04 | 1990-01-11 | Phased Array Lasers Pty Ltd | Face pumped, looped fibre bundle, phased-array laser oscillator |
| EP0409012A1 (en) * | 1989-07-17 | 1991-01-23 | PIRELLI CAVI S.p.A. | Unit for amplifying light signals in optical fiber transmission lines |
| WO1991005380A1 (en) * | 1989-09-26 | 1991-04-18 | Australian Electro Optics Pty. Ltd. | Folded bundle, laser fibre, phase-locked laser oscillator |
| WO1991009475A1 (en) * | 1989-12-14 | 1991-06-27 | British Telecommunications Public Limited Company | Lossless optical component |
| EP0485101A2 (en) * | 1990-11-09 | 1992-05-13 | Nortel Networks Corporation | Amplified optical fibre systems |
| DE4038503A1 (en) * | 1990-12-03 | 1992-06-04 | Kommunikations Elektronik | Optical fibre coupler for connection of glass fibre to plastics fibre - has converter for receiving infrared radiation at one end and transmitting visible light from other end |
| EP0492850A2 (en) * | 1990-12-20 | 1992-07-01 | AT&T Corp. | Isolated optical coupler |
| AU629844B2 (en) * | 1988-07-04 | 1992-10-15 | Phased Array Lasers Pty. Ltd. | End pumped, looped fibre bundle, phased array laser oscillator/amplifier |
| US5204923A (en) * | 1989-07-17 | 1993-04-20 | Pirelli Cavi S.P.A. | Unit for amplifying light signals in optical fiber transmission lines |
| US5282079A (en) * | 1988-06-10 | 1994-01-25 | Pirelli General Plc | Optical fibre amplifier |
| US5448663A (en) * | 1989-09-01 | 1995-09-05 | British Telecommunications Public Limited Company | Optical coupler |
| USRE35697E (en) * | 1990-07-16 | 1997-12-23 | Pirelli Cavi S.P.A. | Unit for amplifying light signals in optical fiber transmission lines |
| US8923511B2 (en) | 1997-04-23 | 2014-12-30 | Sony Corporation | Enciphering apparatus and method, deciphering apparatus and method as well as information processing apparatus and method |
Families Citing this family (14)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2231169A (en) * | 1989-04-27 | 1990-11-07 | Stc Plc | Optical fibres |
| GB2231168A (en) * | 1989-04-27 | 1990-11-07 | Stc Plc | Optical fibres |
| DE69004571T2 (en) * | 1989-06-22 | 1994-03-10 | British Telecomm | OPTICAL REFLECTION MEASUREMENT IN THE TIME AREA. |
| CA2019253C (en) * | 1989-06-23 | 1994-01-11 | Shinya Inagaki | Optical fiber amplifier |
| WO1991001066A1 (en) * | 1989-07-13 | 1991-01-24 | British Telecommunications Public Limited Company | Optical communications network |
| KR940001043B1 (en) * | 1989-07-20 | 1994-02-08 | 스미도모덴기고오교오 가부시기가이샤 | Fiber optic amplifier |
| US5058974A (en) * | 1989-10-06 | 1991-10-22 | At&T Bell Laboratories | Distributed amplification for lightwave transmission system |
| WO1991012509A1 (en) * | 1990-02-15 | 1991-08-22 | British Telecommunications Public Limited Company | Optical test apparatus |
| DE69222912T2 (en) * | 1991-08-29 | 1998-04-09 | Nippon Electric Co | Light receiving module |
| JP2808972B2 (en) * | 1992-02-27 | 1998-10-08 | 日本電気株式会社 | Optical amplifier |
| JP3284507B2 (en) * | 1993-06-28 | 2002-05-20 | 富士通株式会社 | Optical transmitting device and optical amplifying device for optical communication system |
| JPH08304664A (en) * | 1995-05-09 | 1996-11-22 | Furukawa Electric Co Ltd:The | Wavelength demultiplexing element |
| DE19517952A1 (en) * | 1995-05-16 | 1996-11-21 | Ams Optotech Vertrieb Gmbh | Optical amplifier with praseodymium-doped optical fiber |
| FR2769992B1 (en) * | 1997-10-21 | 2000-01-28 | Thomson Csf | POLARIZATION MODULATED OPTICAL DEVICE FOR MEASURING DISTANCE AND / OR OBJECT SPEED |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1344970A (en) * | 1961-10-27 | 1963-12-06 | American Optical Corp | Light energy generators and amplifiers |
| FR2012446A1 (en) * | 1968-07-06 | 1970-03-20 | Nippon Selfoc Co Ltd | |
| US3571737A (en) * | 1968-06-07 | 1971-03-23 | Bell Telephone Labor Inc | Transmission line |
| US3950707A (en) * | 1973-04-13 | 1976-04-13 | Canadian Patents And Development Limited | Quantum amplifier having passive core and active cladding providing signal gain by interaction of evanescent-wave components of signal and pump beams propagating along the core |
-
1985
- 1985-05-22 GB GB858512980A patent/GB8512980D0/en active Pending
-
1986
- 1986-05-19 GB GB868612164A patent/GB8612164D0/en active Pending
- 1986-05-22 WO PCT/GB1986/000279 patent/WO1986007221A1/en unknown
- 1986-05-22 GB GB08612422A patent/GB2175766A/en not_active Withdrawn
- 1986-05-22 EP EP19860903467 patent/EP0222866A1/en not_active Withdrawn
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FR1344970A (en) * | 1961-10-27 | 1963-12-06 | American Optical Corp | Light energy generators and amplifiers |
| US3571737A (en) * | 1968-06-07 | 1971-03-23 | Bell Telephone Labor Inc | Transmission line |
| FR2012446A1 (en) * | 1968-07-06 | 1970-03-20 | Nippon Selfoc Co Ltd | |
| US3950707A (en) * | 1973-04-13 | 1976-04-13 | Canadian Patents And Development Limited | Quantum amplifier having passive core and active cladding providing signal gain by interaction of evanescent-wave components of signal and pump beams propagating along the core |
Non-Patent Citations (1)
| Title |
|---|
| Proceedings of the IEEE, Volume 54, No. 10, October 1966, New York, (US) E. SNITZER "Glass Lasers", pages 1249-1261, see page 1250, Table 1 * |
Cited By (16)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US5282079A (en) * | 1988-06-10 | 1994-01-25 | Pirelli General Plc | Optical fibre amplifier |
| WO1990000320A1 (en) * | 1988-07-04 | 1990-01-11 | Phased Array Lasers Pty Ltd | Face pumped, looped fibre bundle, phased-array laser oscillator |
| AU629844B2 (en) * | 1988-07-04 | 1992-10-15 | Phased Array Lasers Pty. Ltd. | End pumped, looped fibre bundle, phased array laser oscillator/amplifier |
| US5204923A (en) * | 1989-07-17 | 1993-04-20 | Pirelli Cavi S.P.A. | Unit for amplifying light signals in optical fiber transmission lines |
| EP0409012A1 (en) * | 1989-07-17 | 1991-01-23 | PIRELLI CAVI S.p.A. | Unit for amplifying light signals in optical fiber transmission lines |
| US5448663A (en) * | 1989-09-01 | 1995-09-05 | British Telecommunications Public Limited Company | Optical coupler |
| WO1991005380A1 (en) * | 1989-09-26 | 1991-04-18 | Australian Electro Optics Pty. Ltd. | Folded bundle, laser fibre, phase-locked laser oscillator |
| WO1991009475A1 (en) * | 1989-12-14 | 1991-06-27 | British Telecommunications Public Limited Company | Lossless optical component |
| US5323474A (en) * | 1989-12-14 | 1994-06-21 | British Telecommunications Plc | Lossless optical signal splitter including remotely pumped amplifier |
| USRE35697E (en) * | 1990-07-16 | 1997-12-23 | Pirelli Cavi S.P.A. | Unit for amplifying light signals in optical fiber transmission lines |
| EP0485101A2 (en) * | 1990-11-09 | 1992-05-13 | Nortel Networks Corporation | Amplified optical fibre systems |
| EP0485101A3 (en) * | 1990-11-09 | 1993-03-31 | Northern Telecom Limited | Amplified optical fibre systems |
| DE4038503A1 (en) * | 1990-12-03 | 1992-06-04 | Kommunikations Elektronik | Optical fibre coupler for connection of glass fibre to plastics fibre - has converter for receiving infrared radiation at one end and transmitting visible light from other end |
| EP0492850A3 (en) * | 1990-12-20 | 1992-11-19 | American Telephone And Telegraph Company | Isolated optical coupler |
| EP0492850A2 (en) * | 1990-12-20 | 1992-07-01 | AT&T Corp. | Isolated optical coupler |
| US8923511B2 (en) | 1997-04-23 | 2014-12-30 | Sony Corporation | Enciphering apparatus and method, deciphering apparatus and method as well as information processing apparatus and method |
Also Published As
| Publication number | Publication date |
|---|---|
| GB8612422D0 (en) | 1986-07-02 |
| GB8612164D0 (en) | 1986-06-25 |
| GB2175766A (en) | 1986-12-03 |
| GB8512980D0 (en) | 1985-06-26 |
| EP0222866A1 (en) | 1987-05-27 |
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