Transponder for a radio-over-fiber optical fiber cable

Abstract

The invention is a transponder for a radio-over-fiber (RoF) optical fiber cable. The transponder includes a converter unit made up of an electrical-to-optical (E/O) converter and an optical-to-electrical (O/E) converter. The optical fiber cable optically couples the converter unit to a head-end unit that sends and receives optical RF signals. A dipole antenna system is operably coupled to the converter unit and is arranged so as to create elongate picocell in a direction perpendicular to the optical fiber cable when the transponder is in communication with the head-end unit. The asymmetric picocell shape allows for creating a picocellular coverage area using fewer optical fiber cables than is possible with prior art transponders.

1 . A transponder for a radio-over-fiber (RoF) optical fiber cable, comprising:
 an electrical-to-optical (E/O) converter;   an optical-to-electrical (O/E) converter; and   a dipole antenna system operably coupled to the E/O converter and the O/E converter and arranged relative to the optical fiber cable so as to create an elongate picocell in a direction locally perpendicular to the optical fiber cable when the transponder is addressed.   
   
   
       2 . The transponder of  claim 1 , wherein the dipole antenna includes a transmitting antenna formed from a first wire electrically coupled to the O/E converter, and a receiving antenna formed from a second wire electrically coupled to the E/O converter, wherein the first and second wires are arranged locally parallel to the optical fiber cable. 
   
   
       3 . The transponder of  claim 1 , wherein the optical fiber cable has an outer coating, and wherein at least a portion of the transponder resides outside of the outer coating. 
   
   
       4 . The transponder of  claim 1 , wherein the dipole antenna system has includes one or more power dividers and corresponding one or more antenna elements electrically coupled to respective power dividers. 
   
   
       5 . The transponder of  claim 1 , wherein the E/O converter and the O/E converter constitute a converter unit, and wherein the dipole antenna system includes one or more wires electrically coupled to the converter unit via respective one or more radio-frequency (RF) cable sections. 
   
   
       6 . A radio-over-fiber (RoF) picocellular wireless system, comprising:
 a head-end unit adapted to send and receive optical RF signals;   one or more transponders according to  claim 1 ; and   one or more optical fiber cables that include the one or more transponders and that optically couple the head-end unit to each transponder.   
   
   
       7 . The system of  claim 6 , wherein each optical fiber cable includes, for each transponder:
 a downlink optical fiber optically coupled to the head-end unit and to the transponder O/E converter; and   an uplink optical fiber optically coupled to the head-end unit and to the transponder E/O converter.   
   
   
       8 . The system of  claim 7 , wherein each optical fiber cable includes an electrical power line adapted to provide electrical power to each transponder in the corresponding optical fiber cable. 
   
   
       9 . A transponder for forming a picocell as part of a radio-over-fiber (RoF) system having an optical fiber cable optically connected to a head-end unit, comprising:
 a converter unit adapted to convert electrical signals to optical signals and vice versa; and   a dipole antenna system arranged relative to the optical fiber cable so as to create a picocell formed by creating a dipole radiation field directed perpendicular to the optical fiber cable at the dipole antenna system location.   
   
   
       10 . The transponder of  claim 9 , wherein the dipole antenna system includes one or more antenna elements each electrically coupled to the converter unit via corresponding one or more radio-frequency (RF) cable sections. 
   
   
       11 . The transponder of  claim 9 , wherein the optical fiber cable includes an outer coating, and wherein at least a portion of the transponder resides outside of the outer coating. 
   
   
       12 . The transponder of  claim 11 , wherein some or all of the dipole antenna system resides outside of the outer coating. 
   
   
       13 . A radio-over-fiber (RoF) picocellular wireless system, comprising:
 one or more transponders according to  claim 9 ;   a head-end unit adapted to send and receive optical RF signals;   one or more optical fiber cables each having at least one transponder and corresponding one or more optical fiber RF communication links that optically couple the one or more transponders to the head-end unit; and   wherein the one or more transponders form a picocellular coverage area made up of elongate picocells formed by each transponder.   
   
   
       14 . The system of  claim 13 , wherein the head-end unit is adapted to send and transmit optical RF signals having different frequencies, and the dipole antenna system is adapted to transmit and receive electromagnetic signals having the different frequencies. 
   
   
       15 . The system of  claim 13 , further including:
 a power supply operably connected to the head-end unit via an electrical power line that runs through the one or more optical fiber cables so as to provide electrical power to each transponder.   
   
   
       16 . The system of  claim 13 , wherein each optical fiber cable has an outer coating, and at least a portion of some or all of the one or more transponders reside outside of the outer coating. 
   
   
       17 . A method of forming an elongate picocell for a radio-over fiber (RoF) system that includes an optical fiber cable, comprising:
 transmitting optical RF signals to a transponder via an optical fiber RF communication link in the optical fiber cable;   converting the optical signals to electrical RF signals at the transponder;   converting the electrical signals to electromagnetic RF signals at the transponder using a dipole antenna system that creates the elongate picocell in a direction locally perpendicular to the optical fiber cable.   
   
   
       18 . The method of  claim 17 , wherein the optical fiber cable has an outer coating and including providing at least a portion of the dipole antenna system outside of the outer coating. 
   
   
       19 . The method of  claim 17 , including performing the acts therein for multiple transponders so as to form a picocellular coverage area made up of multiple elongate picocells. 
   
   
       20 . The method of  claim 17 , including orienting the picocell by orienting the optical fiber cable.