EP0965228A2 - Recepteur optique grande puissance - Google Patents

Recepteur optique grande puissance

Info

Publication number
EP0965228A2
EP0965228A2 EP98955866A EP98955866A EP0965228A2 EP 0965228 A2 EP0965228 A2 EP 0965228A2 EP 98955866 A EP98955866 A EP 98955866A EP 98955866 A EP98955866 A EP 98955866A EP 0965228 A2 EP0965228 A2 EP 0965228A2
Authority
EP
European Patent Office
Prior art keywords
optical
sub
high frequency
γçó
signal
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP98955866A
Other languages
German (de)
English (en)
Inventor
Eric J. Schnettler
Kerry D. La Violette
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Koninklijke Philips NV
Original Assignee
Koninklijke Philips Electronics NV
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Koninklijke Philips Electronics NV filed Critical Koninklijke Philips Electronics NV
Publication of EP0965228A2 publication Critical patent/EP0965228A2/fr
Withdrawn legal-status Critical Current

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
    • H04B10/60—Receivers
    • H04B10/66—Non-coherent receivers, e.g. using direct detection
    • H04B10/69—Electrical arrangements in the receiver
    • 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
    • H04B10/60—Receivers
    • H04B10/66—Non-coherent receivers, e.g. using direct detection
    • H04B10/67—Optical arrangements in the receiver
    • H04B10/671—Optical arrangements in the receiver for controlling the input optical signal
    • H04B10/672—Optical arrangements in the receiver for controlling the input optical signal for controlling the power of the input optical signal
    • H04B10/674—Optical arrangements in the receiver for controlling the input optical signal for controlling the power of the input optical signal using a variable optical attenuator

Definitions

  • This invention is related to analog and digital signal conversion from an optical signal to an electronic or radio frequency signal.
  • the invention is most closely related to optical receivers for high speed information distribution.
  • an electrical signal regulates a source of light such as a laser or light emitting diode in order to convert an electrical signal into an optical signal.
  • a fiber optic cable is positioned to transmit the optical signal through the cable to a receiver.
  • a photodiode converts the optical signal back into an electrical signal.
  • Optical systems can be divided into long distance systems and short distance system.
  • long distance systems distortions and noise are primarily due to the length of the optical cable.
  • Such systems include computer networks and multiplexed digital telephone.
  • short distance optical systems distortion and noise are primarily due to the optical transmitter (which converts a high frequency electrical signal into an optical signal) and the optical receiver (which converts the optical signal back into an electrical signal), and the equipment connected to such systems.
  • Such systems include cable television distribution systems such as analog television systems which transmit NTSC or PAL television signals and digital television systems which transmit (MPEG-2) signals.
  • MPEG-2 digital television systems which transmit
  • the distortion and noise are produced in the optical cable over long distances, and to a lesser extent in the transmitter (that converts the electrical signals to optical signals), and in the receiver (that converts the optical signals back into electrical signals).
  • a digital repeater can be used to receive the signals from a first optical cable, remove the distortions and noise in the resulting electrical signal, and retransmit the digital signals through another optical cable.
  • Such repeaters are relatively costly and result in increased maintenance and increased energy use, so that energy and other resources could be conserved by increasing the distance that optical signals can be transmitted through fiber optic cables for a given frequency or bit rate without using a repeater or increasing the frequency or bit rate that can be transmitted through a fiber optic cable over a given distance without using a repeater.
  • analog signals can not generally be improved by using repeaters because noise and distortions can not easily be separated from the signal.
  • a head-end includes a laser transmitter which converts high frequency signals into optical signals to provide a multitude of television channels in an optical distribution network.
  • the signals travel to a multitude (e.g. 20-2000) of distribution nodes in which a receiver converts the optical signals back into high frequency electrical signals.
  • a receiver converts the optical signals back into high frequency electrical signals.
  • the electrical signal is amplified and transmitted through a coaxial cable distribution network to a large number of customers (e.g. 50-500) who are local to the distribution node.
  • customers e.g. 50-500
  • an optical splitter divides the optical signal into two approximately equal signals, each optical signal is separately converted into a respective high frequency electrical signal, the phase between the electrical signals is adjusted to match, and then the electrical signals are combined.
  • the signal to noise ratio is improved without increasing distortion.
  • the signal output to the customer is improved, and the coaxial distribution system can be extended to serve new customers.
  • a higher bit rate may be provided so that the throughput and reaction time of a computer network can be improved, the number of repeaters can be reduced, thus conserving energy and other resources.
  • Figure 1 is a block diagram illustrating a specific embodiment of the optical receiver of the invention in which the optical signal is split, received, and resulting electrical signals are phase adjusted and recombined.
  • Figure 2 is a block diagram depicting a specific embodiment of the analog cable television distribution system of the invention which uses the optical receivers of figure 1 to improve signal quality and otherwise improve performance of the network.
  • Figure 3 is a block diagram showing a specific embodiment of the digital computer network of the invention, in which computer nodes use the optical receivers of figure 1 to improve throughput and response time.
  • a high power optical receiver (HPOR) 100 receives an optical signal through input 101.
  • Attenuator 102 is selected or adjusted to provide the desired power level to minimize signal distortion and noise during conversion from optic to electrical signals.
  • An optical splitter 103 provides two independent optical signals.
  • the splitter may be, for example, a "Y" formed by melting an end of an optical fiber to another optical fiber as is well known in the art.
  • the splitter itself attenuates the signal so that at least in some systems the requirement for an input attenuator may be eliminated.
  • Each optical signal is independently received by respective optical to electrical converters 104 and 105.
  • the converters may each include, for example, a photodiode. Such converters are well known in the art.
  • the splitter and the two photo-diodes are both in a single package, even more preferably, the splitter and the two photodiodes are on a single integrated circuit.
  • a phase adjuster 106 matches the phase of the electrical signals.
  • Combiner 107 recombines the two electrical signals into a single signal, and the signal is output through conductor 108.
  • the phases of the electrical signals are adjusted so that the signal strength is increased but the distortions are not increased.
  • the signal to noise ratio of the combined signal is substantially greater (e.g. 1.3 db) than the signal to noise ratio of either of the separate signals.
  • the phase adjuster includes a circuit board 110 with a shielded conductor 111 on a surface with a gap 112 and a plug-in module 113 conductively interconnecting across the gap.
  • the module may have a section of shielded wire 114 of selected length to provide the desired phase adjustment.
  • the phase of the two electrical signals may be matched using a trial and error approach in which different plug-in modules having different conductor lengths (e.g. in gradients of 1/4 inch) are tried until the phases are matched.
  • an analog cable television distribution system 120 of the invention includes a head-end 121 and an analog distribution node 122 interconnected by optical cables 123-126.
  • each distribution node services a large number (e.g. 50-500) customers and such systems may have one head end and a multitude (e.g. 20-2000) of distribution nodes.
  • a multitude of programs are modulated by modulators 130, 132, and 133 to provide all the programs provided to a modulator, in its own high frequency channel. That is, each modulator provides a different modulation frequency for each program in the set of programs provided to such modulator through the respective input cable 127, 128, 129 for the modulator.
  • Each of the cables may include a large number of coaxial cables, for example, a separate cable for each program or small group of programs.
  • the modulated signals are output onto optical cables 123, 124 and 125 by transmitters 133, 134 and 135 respectively.
  • the transmitters simply convert the electrical signals into optical signals.
  • the transmitters typically include lasers which can be modulated at frequencies up to 750 MHz.
  • Inputs 140, 141, 142 of the analog distribution node are spliced to optic cables 123, 124 and 125 respectively within connector 143.
  • Inputs 140, 141 and 142 are connected to respective high power optical receivers (HPOR) 150, 151 and 152 which are receivers of the invention as described above with relation to figure 1.
  • HPOR high power optical receivers
  • the high frequency electrical output from each of HPOR's 150, 151 and 152 is conducted to respective preliminary amplifiers 153, 154 and 155.
  • a circuit of high frequency signal splitters such as 160 and switches such as 161, directs the signals to apparatus for any respective coaxial cable output.
  • the signals provided to HPOR 151 is preferably the main broadcast signal with programs modulated at 70 to 560 MHz.
  • the splitter switching circuit directs a copy of this signal to every coaxial cable output.
  • the signals provided to HPORs 150 and 152 are Preferably, narrow cast signals with programs modulated at frequencies, for example, between 550 and 750 MHz.
  • the switches such as 161 allow switching both narrow cast signals off for a particular coaxial cable output, or switching the signals from either HPOR 150 or 152 but not both, to be received at each particular coaxial cable output.
  • the output apparatus includes a post amplifier 161, 162, 163 and 164 for each respective coaxial cable output. Also, a diplexer 170, 172, 173 and 174 for each respective coaxial output 175, 176, 177 and 178 separates return signals provided by the customer from the signals provided by the cable system.
  • the return signals from the customers are typically modulated at 50 to 70 MHz.
  • the return signals are routed to combiner 180 which combines the customer signals.
  • the combiner remodulates the customer signals to various frequencies and multiplexes the signals so that a large volumn of return signals from the customers can be transmitted. In such a scheme each distribution node in the system has its own return path so that there may be a large number of return paths back to the head end.
  • Transmitter 181 converts the electrical signal received from combiner 180 into an optical signal and outputs the optical signal through optical cable 126.
  • HPOR 183 converts the optical signal from cable 126 into electrical signals transmitted onto output 184.
  • receiver 183 is an HPOR of the invention as described above in relation to figure 1 , and its use improves the performance of the return path.
  • Other distribution nodes in the network have their own return path such as optical cable 190 back to their own HPOR such as HPOR 186 at the head-end, and their own output cable such as cable 187.
  • Figure 3 illustrates a digital computer network in which, optical fiber cables 201 and 202 interconnect nodes 203 and 204 of the network. Only two cables and two nodes are shown but typically such systems have hundreds or thousands of distribution nodes and large numbers of optical cables interconnecting the nodes. The layout of the cables depends on the type of communication network. Such a network could be an Eithernet, token ring network, ARCnet, Internet, telephone network, or digital television cable network. Since the nodes are illustrated as approximate mirror images, only node 204 will be discussed herein. Node 204 receives optical signals from optical cable 201 into receiver 205 which is a HPOR of the invention described above with relation to figure 1.
  • the use of such HPOR allows the digital network to provide higher throughput and faster reaction times and/or to provide greater distances between nodes for a given bit rate or to provide a higher bitrate for a given distance, and may eliminate the requirement for digital repeaters in the network thus conserving energy and other resources.
  • the node also includes a microcomputer or microcontroller (CPU) 210 communicating with a memory 211 containing buffers 212 and 213 to store data received into or to be transmitted from the computer, and programs 214 and 215 which control the operation of the CPU and the input circuit 216, output circuit 217 and input and/or output circuits 218- 220 of the node.
  • Program 214 controls CPU 210 and IC 216 to copy data from HPOR 205 into input buffer 212.
  • Program 215 controls the CPU and OC 217 to copy data from output buffer 213 to output circuit 217 from which it is output by transmitter 221 onto optic cable 202.
  • Transmitter 221 converts the electrical signals provided by output circuit 221 into optical signals transmitted through optic fiber cable 202 to node 203.

Landscapes

  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Signal Processing (AREA)
  • Optical Communication System (AREA)

Abstract

Ce récepteur optique, destiné à convertir un signal optique dans un câble à fibres optiques en signal électrique haute fréquence, comporte un répartiteur optique fournissant une partie de signal dans chaque photodiode faisant partie d'un ensemble comportant au moins deux photodiodes, lesquelles photodiodes convertissent le signal optique en une pluralité de signaux électriques séparés. On ajuste la phase des signaux électriques ou l'on sélectionne la longueur des conducteurs relatifs au signal séparé de sorte que, lorsque les signaux séparés sont combinés, ils sont en phase et le rapport signal/bruit du signal combiné est supérieur à celui des signaux séparés, la distorsion du signal combiné n'ayant, toutefois, pas augmenté sensiblement par rapport à celle des signaux séparés.
EP98955866A 1997-12-31 1998-12-07 Recepteur optique grande puissance Withdrawn EP0965228A2 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US210497A 1997-12-31 1997-12-31
US2104 1997-12-31
PCT/IB1998/001974 WO1999035767A2 (fr) 1997-12-31 1998-12-07 Recepteur optique grande puissance

Publications (1)

Publication Number Publication Date
EP0965228A2 true EP0965228A2 (fr) 1999-12-22

Family

ID=21699265

Family Applications (1)

Application Number Title Priority Date Filing Date
EP98955866A Withdrawn EP0965228A2 (fr) 1997-12-31 1998-12-07 Recepteur optique grande puissance

Country Status (3)

Country Link
EP (1) EP0965228A2 (fr)
JP (1) JP2001515683A (fr)
WO (1) WO1999035767A2 (fr)

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4926477A (en) * 1988-06-14 1990-05-15 General Instrument Corporation Cable television descrambler
US5627879A (en) * 1992-09-17 1997-05-06 Adc Telecommunications, Inc. Cellular communications system with centralized base stations and distributed antenna units
EP0800315B1 (fr) * 1996-04-05 2002-11-06 Nippon Telegraph And Telephone Corporation Convertisseur AM/FM et système de transmission de signaux optiques

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO9935767A3 *

Also Published As

Publication number Publication date
WO1999035767A3 (fr) 1999-09-16
JP2001515683A (ja) 2001-09-18
WO1999035767A2 (fr) 1999-07-15

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