RF return optical transmission

• US 7,103,907 B1
• Filed: 08/07/2000
• Issued: 09/05/2006
• Est. Priority Date: 05/11/1999
• Status: Expired due to Term

• Current Assignee: Tellabs Bedford, Inc. (Infinera Corp.)
• Original Assignee: Tellabs Bedford, Inc. (Infinera Corp.)
• Inventors: Buabbud, George H.
• Primary Examiner(s): Srivastava, Vivek
• Application Number:
  US09/633,320
• Time in Patent Office: 2,220 Days
• Field of Search: 725/105, 725/106, 725/118, 725/119, 725/121, 725/122, 725/126, 725/127, 725/129
• US Class Current: 725/129
• CPC Class Codes: H04J 14/0226 Fixed carrier allocation, e.g. according to service
• CPC Class Codes: H04J 14/0232 for downstream transmission
• CPC Class Codes: H04J 14/0247 Sharing one wavelength for at least a group of ONUs
• CPC Class Codes: H04J 14/0252 Sharing one wavelength for at least a group of ONUs, e.g. for transmissions from-ONU-to-OLT or from-ONU-to-ONU
• CPC Class Codes: H04J 14/0282 WDM tree architectures
• CPC Class Codes: H04J 14/0298 with sub-carrier multiplexing [SCM]
• CPC Class Codes: H04N 7/10 Adaptations for transmission by electrical cable H04N7/12 takes precedence
• CPC Class Codes: H04N 7/17309 Transmission or handling of upstream communications
• CPC Class Codes: H04N 7/22 Adaptations for optical transmission

Abstract

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.

Claims

1. A method of providing first RF signals within a first frequency band from a first location to a multiplicity of second locations, providing bidirectional telephony signals between said first location and at least two of said multiplicity of said second locations, and providing second RF signals within a second frequency band from said at least two second locations to said first location on at least two separate optical paths and comprising:

transmitting light at a first wavelength modulated by said first RF signals from said first location to at least two intermediate locations via said at least two separate optical paths and from each of said at least two intermediate locations to said multiplicity of second locations on a multiplicity of first paths, each having at least two electrical conductors;

bidirectionally transmitting light at a second wavelength for carrying telephony signals both upstream and downstream on said at least two optical paths between said first location and said at least two intermediate locations and from said at least two intermediate locations to said second locations on a multiplicity of second paths having at least two electrical conductors;

transmitting first and second RF signals at selected frequencies within a second frequency band from at least two of said multiplicity of second locations one each to said at least two intermediate locations on at least two of said multiplicity of first paths;

further modulating said transmitted light having said second wavelength traveling from said at least two intermediate locations to said first location on said at least two optical paths with said first and second RF signals from said at least two second locations; and

receiving said first and second RF signals within said second frequency band at said first location;

receiving said light having said second wavelength at said first location traveling from a first one of said at least two intermediate locations on a first one of said at least two optical paths;

receiving said light having said second wavelength at said first location traveling from a second one of said at least two intermediate locations on a second one of said at least two optical paths;

recovering and attenuating first telephony signals received from light carried by said first one of said at least two optical paths by a first amount such that said first telephony signals are substantially at a preset value;

recovering and attenuating second telephony signals received from light carried by said second one of said at least two optical paths by a second amount such that said second telephony signals are also substantially at said preset value; and

recovering and attenuating said second RF signals traveling to said first location on said first one and said second one of said at least two optical paths by said first and second amounts respectively such that each of said attenuated second RF signals have substantially the same signal strength.

2. The method of claim 1 and further comprising:

comparing the strength of recovered second RF signals within said second RF frequency band to a preset threshold; and

inhibiting further transmission of said RF signals within said second RF frequency band if said compared signals are not equal to or greater than said preset threshold.

3. The method of claim 2 wherein recovering said second RF signals from said light waves comprises:

receiving light traveling upstream and having said second wavelengths from said at least two optical paths by a photo diode having an anode and a cathode;

recovering said second RF signals at one of said anode and cathode of said photo diode; and

recovering telephony signals at the other one of said anode and cathode of said photo diode.

4. Communication apparatus comprising:

a source for generating first RF signals at a first frequency band and adapted for distribution to a multiplicity of users;

at least two transmission paths between a first location having said source and a least two of said multiplicity of users at least two second locations, at least a portion of each at least two transmission paths being optical;

a first light generator for generating light at a first wavelength of light, said light being modulated to carry said first RF signals within said first frequency and on said optical portions of said transmission path;

at least two pairs of second light generators one each of each pair located at an end of said optical portions of said at least two transmission paths and each second light generators for generating light at a second wavelength modulated to carry bidirectional telephony signals traveling between said first and said at least two second locations on said optical portions of said at least two transmission paths;

second and third RF signals within a second frequency band generated at the two second locations and carried to said source one each on said at least two transmission paths by modulating said light having said second wavelength;

an attenuator for attenuating first telephony signals recovered from the optical portion of a first one of said at least two transmission paths by a first amount such that said first telephony signals are at a preset value;

an attenuator for attenuating second telephony signals recovered from the optical portion of a second one of said at least two transmission paths by a second amount such that said second telephony signals are at said preset value; and

attenuators for attenuating said second and third RF signals recovered from the optical portions of said first and second transmission paths respectively such that each of said attenuated second and third RF signals have substantially the same signal strength.

5. The communication apparatus of claim 4 wherein at least one of said photo detectors is a photo diode having a cathode and an anode, and wherein said second RF signals are recovered at one of said anode and a cathode and said telephony signals are recovered at the other one of said anode and cathode.

6. The communication apparatus of claim 4 wherein said RF signals within said first frequency band have a frequency of between about 50 and 870 MHz.

7. The communication apparatus of claim 6 wherein said second and third RF signals within said second frequency band have a frequency of between about 5 and 50 MHz.

8. A method of providing first RF signals within a first frequency band from a first location to a multiplicity of second locations, providing bidirectional telephony signals between said first location and at least two of said multiplicity of said second locations, and providing second RF signals within a second frequency band from said at least two second locations to said first location on at least two separate optical paths and comprising:

transmitting light at a first wavelength modulated by said first RF signals from said first location to at least two intermediate locations via said at least two separate optical paths and from each of said at least two intermediate locations to said multiplicity of second locations on a multiplicity of first paths, each having at least two electrical conductors;

bidirectionally transmitting light at a second wavelength for carrying telephony signals both upstream and downstream on said at least two optical paths between said first location and said at least two intermediate locations and from said at least two intermediate locations to said second locations on a multiplicity of second paths having at least two electrical conductors;

transmitting first and second RF signals at selected frequencies within a second frequency band from at least two of said multiplicity of second locations one each to said at least two intermediate locations on at least two of said multiplicity of first paths;

further modulating said transmitted light having said second wavelength traveling from said at least two intermediate locations to said first location on said at least two optical paths with said first and second RF signals from said at least two second locations; and

receiving said first and second RF signals within said second frequency band at said first location;

amplifying at least one of said first and second RF signals within said second frequency band;

amplifying the telephony signals traveling upstream, and amplification of said RF signals and said telephony signals occurring prior to said signals modulating said second wavelength of light;

monitoring the signal strength of said amplified upstream telephony signals as a proportion of the modulated light having said second wavelength and generating a control signal therefrom; and

adjusting the amplitude level of said RF signals and said upstream telephony signals in response to said generated signal.

9. Communication apparatus comprising:

a source for generating first RF signals at a first frequency band and adapted for distribution to a multiplicity of users;

at least two transmission paths between a first location having said source and at least two of said multiplicity of users at least two second locations, at least a portion of each of said at least two transmission paths being optical;

a first light generator for generating light at a first wavelength of light, said light being modulated to carry said first RF signals within said first frequency and on said optical portions of said transmission path;

at least two pairs of second light generators one each of each pair located at an end of said optical portions of said at least two transmission paths and each second light generators for generating light at a second wavelength modulated to carry bidirectional telephony signals traveling between said first and said at least two second locations on said optical portions of said at least two transmission paths;

second and third RF signals within a second frequency band generated at the two second locations and carried to said source one each on said at least two transmission paths by modulating said light having said second wavelength;

a first amplifier to amplify the upstream telephony signals and a second amplifier to amplify the RF return signals, said first and second amplifier providing electrical signals to modulate light at said second wavelength traveling upstream;

a photo diode located at said at least one of said at least two second locations for monitoring the corresponding one of said pair of second light generators;

circuitry connected to said photo diode to provide a control signal representative of the upstream telephony signal strength as a proportion of the output power of said one of said pair of second light generators; and

said control signal connected to said first and second amplifiers for controlling the output signal strength of said first and second amplifier as a selected proportion of said light output at said second wavelength.