An Optical Communication System for Transmitting RF Signals Downstream and Bidirectional Telephony Signals Which Also Include RF Control Signals Upstream
A method of transmitting TV signals and bidirectional telephone communication signals on a single optical fiber, existing telephone twisted pair infrastructure, and existing coaxial cable infrastructure. In addition to allowing the downstream transmission of television channels as well as bidirectional telephone communication, the single optical fibers also provides for the upstream travel of television related signals while requiring minimal changes of the existing infrastructure.
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This application is a continuation application of U.S. application Ser. No. 09/879,395 filed Jun. 12, 2001 and now U.S. Pat. No. 7,058,966 issued Jun. 6, 2006, which is a continuation of U.S. application Ser. No. 09/309,717 filed May 11, 1999 and now U.S. Pat. No. 6,460,182 issued Oct. 1, 2002, each of which is hereby incorporated herein by reference.
TECHNICAL FIELD OF THE INVENTIONThe present invention relates to methods and apparatus for carrying on simultaneous communications over a single optical fiber by using two different operating frequencies, and more specifically to methods and apparatus for use with WDM (wave division multiplexing) at two different wavelengths of light to provide bidirectional telephonic communication using TDM (time division multiplexing) at one wavelength of light and transmitting TV signals down stream only at another wavelength. TV control signals are returned by the telephonic communication path to the TV source by multiplexing the control signals with the telephonic signals.
BACKGROUND OF THE INVENTIONThe communications industry is using more and more optical or light fibers in lieu of copper wire. Optical fibers have an extremely high bandwidth thereby allowing significantly more information than can be carried by a copper wire transmission line such as twisted pairs or coaxial cable.
Of course, modem telephone systems require bidirectional communications where each station or user on a communication channel can both transmit and receive. This is true, of course, whether using electrical wiring or optical fibers as the transmission medium. Early telephone communication systems solved this need by simply providing separate copper wires for carrying the communications in each direction, and this approach is still used in part of the transmission path. It is especially used as the signals get closer to the end users. Although twisted pairs and coaxial cables are used in homes and distribution terminals close to the home end user, some modem telecommunication systems now use micro-wave and optic fibers as transmission mediums. In addition TCM (time compression multiplexing) is often used in optical transmission so that a signal optical fiber can carry communications in both direction.
However, because of extremely high band widths available for use by an optical fiber, a single fiber is quite capable of carrying a great number of communications in both directions. One technique of optical transmission is WDM (wavelength divisional multiplexing) and uses different wavelengths for each direction of travel.
Yet another and simpler technique for using a single optical fiber for telephone systems is TCM (time compression multiplexing) and is sometimes referred to as a “ping-pong” system. The system operates at a single frequency or wavelength of light and uses a single optical fiber and often even a single diode, for both converting electrical signals to optical signals and converting received optical signals to electrical signals. TCM systems have the obvious advantage of requiring fewer components.
However, as mentioned above, optical fibers have extremely high band widths and use of an optical fiber for a single ping-pong telephone channel is a very ineffective use of the fiber and, in fact, the available bandwidth of an optical fiber makes it possible to use a transmission technique such as TCM or ping-pong at one frequency and then by the use of WDM technology to use another technique at a second frequency.
Another area of rapidly growing technology is providing unidirectional TV signals by cable to a multiplicity of subscribers or users. In the past, such signals were and still are typically transmitted by the use of coaxial cables (e.g. cable TV). However, the use of optical fibers for transmission allows broad band transmission to a large numbers of customers and, since substantially all of the transmission of TV signals is one way (i.e. unidirectional), if a single optical fiber were used solely for the TV signals there would be almost no use of the selected wavelength of light for carrying return signal, which are typically control or information signals.
Therefore, a technique for transmitting bidirectional telephonic signals and unidirectional TV signals would make efficient use of an optical fiber.
It would also be advantageous to provide return control signals to the TV signal source or station with respect to each customer or subscriber without having to dedicate a frequency or wavelength of light full time to said seldom used or RF Return transmitted signals.
SUMMARY OF THE INVENTIONThe above objects and advantages are achieved in the present invention by methods and apparatus which comprise transmitting light at a first wavelength to carry telephonic signals between a first telephone-related device and a second telephone-related device, or location and also transmitting light at a second wavelength to carry TV signals from a TV signal source to an end user(s). The wavelengths or light are carried through a single optical fiber from a first-end to a second-end. The first and second wavelengths of light are received at the second-end of the optical fiber, and the signals on the first wavelength of light are detected and converted to first electrical signals at a first frequency band suitable for carrying telephonic signals such as voice telephone and computer modem signal, at a frequency band of about 64 KHz. The received second wavelength of light is also detected, and the detected light is converted to electrical signals, within a second frequency band, typically between 5 and 800 MHZ and are representative of TV channel signals. The telephonic electrical signals are transmitted to a receiving telephone or other telephone-related device and the electrical signals representative of TV signals are transmitted to a TV signal receiving device. The return electrical telephonic signals are then generated at the receiving telephone-related device at the same frequency band the original telephonic signal were transmitted and are representative of return telephone information which could be modem information or voice information. TV related electrical signals such as control signals, information signals or TV show ordering signals are also generated at a third frequency band. The return electrical telephonic signal at the first frequency band of about 64 HKz and the TV related electrical signal generated at about 5 to 50 MHZ are multiplexed together. The multiplexed electrical signals are converted to light signals at the first wavelength and carry both the return telephonic signal and the TV related signal. The light at the first wavelength is transmitted through the single optical fiber from the second end to the first end where it is received and detected such that electrical signals representative of the return telephonic signals and the electrical signal representative of the TV related information are generated. The return electrical telephonic signals are transmitted to the first telephone-related device and the electrical TV related signals are transmitted to the TV signal source.
BRIEF DESCRIPTION OF THE DRAWINGSA better understanding of the present invention will be realized from the detailed description that follows, taken in conjunction with the accompanying drawings, in which:
Referring now to
Also shown is a typical telephone system or POTS which of course is two-way communication typically carried by means of a twisted pair of wires. In the example shown in
As demands increase for more and more TV channels and better and more efficient transmission techniques without disruption and interference, the long runs of coaxial cable are simply becoming inefficient and inadequate. Thus as is shown in
Referring now to
At distribution terminal 20, and as will be discussed in detail later, the 1550 nanometer downstream traveling signals are then reconverted to electrical TV signals having a band width of between 50 and 80 MHZ. They are then distributed to various locations including home or building 22 as was discussed with respect to
As was discussed with respect to the system of
Although in the embodiment shown in
Thus, there has been discussed to this point generalized concepts for a new and improved telephonic and TV signal distribution systems.
Referring now to
Also as shown, multiplexed telephone service POTS at the DS1 level (i.e. information from up to 24 TV customers) on copper wire 65 is provided to distribution box 52 wherein the electrical telephonic signals typically having a frequency band up to about 60 MHZ are provided to another laser diode 66. These electrical signals are then converted by laser diode 66 to light signals having a wavelength of 1310 nanometers. This light is provided to optical fiber 54 as shown. As was discussed earlier, telephone service is typically TCM (time compression multiplexing) so as to provide for bidirectional communication at a single wavelength of light. Therefore as shown, light traveling upstream and leaving optical fiber 54 is directed toward a photo or a light detection diode 68 which receives the light and converts the 1310 nanometer light to telephonic signals having a frequency of about 60 KHz or less. Thus, the input electrical signal to laser diode 66 from line 65 on the output electrical signal from light detector 68 on line 70B actually represents a typical pair of twisted wires 71 used in normal POTS telephonic service. In the embodiment shown, the output telephonic signals on line 70A is first provided to a diplex circuitry 72 where the TV related control signals from the customer are split out on line 74 and the regular telephonic communications such as voice and computer modem server continues on output line 70B. The 5-50 MHZ on line 74, is then provided to a band pass filter circuit 70 which will only pass the 5-50 MHz, and which has an output 78 provided to a combining circuitry 80 which receives other similar signals from other TV customers up to a total of at least 16 (8+8) customers. The output of combining circuitry 80 is then provided to an 8 bit 90 MSPS (megsamples per second) analog-to-digital converter 81. The digital signals from A/D converter 81 are then provided to a 90 MHZ 8 bit to 12 bit adder 82. Added 82 as shown can receive the output from 8 A/D converters such as A/D converter 82. Thus, it will be appreciated that the output from adder 82 going to the parallel to serial converter 84 will be carrying information related to at least 128 TV customers (16×8). The output of the P/S converter 84 may then provided to another E/O (electrical-to-optical) device 86 operating at 1 Gbps (giga bit per second). This output may then be transmitted by optical fiber 87 to CMTS (cable modem transmission source) at location 88 where the TV signal source 10 is also located. The light traveling through optical fiber 87 is then received by O/E (optical-to-electrical) converter 89 and the resulting electrical signals are provided to SIP (serial-to-parallel) converter 90. This parallel digital information is then provided to D/A converter 92, which in turn provides an analog signal to the TV signal source 10. This analog signal may of course be a control signal or other information related to a specific TV customer or subscriber.
Referring now to
Now referring again to the input cable 42A which, in addition to carrying light having a wavelength of 1550 nanometers as was previously discussed, is also carrying light at 1310 nanometers for the bidirectional telephone communication using TCM (time compression multiplexing). Thus, the light having a wavelength of 1310 nanometer is split and provided to a photo detector 108 which converts the 1310 nanometer light traveling downstream to telephonic electrical signals which travel on wires 109. These telephonic electrically signals will typically be POTS signals at the DS1 (up to 24 customers) or DS2 (up to 96 customers) level and are provided to the multiplexer 110 and eventually by means of wires 32B to the telephone circuitry in house or building 22. It should be appreciated that the wire 32B connecting home 22 to the distribution panel 20 is a normal twisted pair of telephone wires. The upstream traveling POTS service travels on wire 111 to multiplex circuit 106 where it is combined with the 5 to 50 MHZ signals and provided on output line 112 to a laser diode 114. Laser diode 114 then converts the electrical signals carrying the 5 to 50 MHZ television related signals as well as the telephonic signals to light having a wavelength of 1310 nanometers which light is then coupled again to fiber optic 42A. Thus, as was discussed earlier, the fiber optic 42A carries the upstream traveling 1310 nanometer light to distribution panel 18 where it is split out for both telephonic service and television related signal service.
Thus, there has been discussed to this point a new and novel communication transmission system using a single optical fiber as part of the communication path along with parts of an existing telephone communication system and parts of an existing cable TV distribution system.
The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed.
Other changes, substitutions and alterations are also possible without departing from the spirit and scope of the present invention, as defined by the following claims.
Claims
1. An optical distribution terminal, comprising:
- a laser diode operable to receive an electrical signal, the electrical signal corresponding to a video source signal, the laser diode operable to generate a video optical signal at a first wavelength in response to the electrical signal;
- a multiplexer operable to receive the video optical signal at the first wavelength, the multiplexer operable to receive a telephony optical signal at a second wavelength over a first optical fiber, the multiplexer operable to transmit the video and telephony optical signals in their respective first and second wavelengths over a second optical fiber, the multiplexer operable to receive a return video optical signal and a return telephony optical signal at the second wavelength over the second optical fiber, the multiplexer operable to transmit the return video and telephony optical signals at the second wavelength over the first optical fiber.
- distribution circuitry for transmitting the received video and telephony signals to a plurality of subscribers and for receiving the telephony return signals and the video return signals from the plurality of subscribers; and
- a multiplexer for combining the telephony return signals and the video return signals to generate the multiplexed return signals.
2. The optical distribution terminal of claim 1, wherein the first wavelength is 1550 nm.
3. The optical distribution terminal of claim 1, wherein the second wavelength is 1310 nm.
4. The optical distribution terminal of claim 1, wherein the electrical signal has a bandwidth between about 50 and 800 MHz.
5. The optical distribution terminal of claim 1, further comprising:
- an amplifier operable to receive the video optical signal from the laser diode, the amplifier operable to amplify the video optical signal for presentation to the multiplexer.
6. The optical distribution terminal of claim 1, further comprising:
- a photodiode operable to convert the return video and telephony optical signals into an electrical signal format.
7. The optical distribution terminal of claim 6, further comprising:
- a diplexer operable to split the electrical signal format into a return telephony electrical signal and a return video electrical signal.
8. The optical distribution terminal of claim 7, wherein the return video electrical signal has a bandwidth between about 5 and 50 MHz.
9. The optical distribution terminal of claim 7, wherein the return telephony electrical signal includes plain old telephone service signals.
10. The optical distribution terminal of claim 1, further comprising:
- a light splitting circuit operable to receive the video optical signal, the light splitting circuit operable to provide the video optical signal to multiple destinations.
11. A method for transmitting optical signals, comprising:
- receiving a video electrical signal;
- converting the video electrical signal to a video optical signal having a first wavelength;
- receiving a telephony optical signal having a second wavelength;
- multiplexing the video optical signal with the telephony optical signal;
- transmitting the video optical signal at the first wavelength and the telephony optical signal at the second wavelength over an optical fiber;
- receiving return video and telephony optical signals at the second wavelength over the optical fiber.
12. The method of claim 11, wherein the first wavelength is 1550 nm and the second wavelength is 1310 nm.
13. The method of claim 11, wherein the video electrical video signal has a bandwidth of about 50 to 800 MHz.
14. The method of claim 11, further comprising:
- extracting video electrical signals and telephony electrical signals from the return video and telephony optical signals.
15. The method of claim 11, further comprising:
- amplifying the video optical signal prior to multiplexing with the telephony optical signal.
16. A system for transmitting optical signals, comprising:
- means for receiving a video electrical signal;
- means for converting the video electrical signal to a video optical signal having a first wavelength;
- means for receiving a telephony optical signal having a second wavelength;
- means for multiplexing the video optical signal with the telephony optical signal;
- means for transmitting the video optical signal at the first wavelength and the telephony optical signal at the second wavelength over an optical fiber;
- means for receiving return video and telephony optical signals at the second wavelength over the optical fiber.
17. The system of claim 16, wherein the first wavelength is 1550 nm and the second wavelength is 1310 nm.
18. The system of claim 11, wherein the video electrical video signal has a bandwidth of about 50 to 800 MHz.
19. The system of claim 11, further comprising:
- means for extracting video electrical signals and telephony electrical signals from the return video and telephony optical signals.
20. The system of claim 11, further comprising:
- means for amplifying the video optical signal prior to multiplexing with the telephony optical signal.
Type: Application
Filed: Jun 5, 2006
Publication Date: Oct 26, 2006
Applicant: Tellabs Bedford, Inc. (Bedford, TX)
Inventor: George BuAbbud (Southlake, TX)
Application Number: 11/422,172
International Classification: H04N 7/173 (20060101);