Telecommunications system

Abstract

An optical communications network includes a terminal which can simultaneously receive and modulate an optical signal. The terminal includes an optical modulator which is controlled by varying the bias voltage applied to it.

1 . A method of communicating between a first node and one or more further nodes in an optical communications system, the method comprising: 
 i) receiving at the first node, an optical signal transmitted from a first further node over an optical fibre link;    ii) detecting, at the first node, the optical signal using an electro-absorption modulator and producing thereby an electrical signal representing information carried by the optical signal; and    iii) imposing, using said electro-absorption modulator, an information-carrying modulation onto the received optical signal and feeding the thus modulated optical signal into an optical fibre link to transmit it to a second further node; wherein step ii and step iii are carried out with the electro-absorption modulator subject to the same DC operating conditions.    
     
     
         2 . A method as claimed in  claim 1 , wherein step ii and step iii are carried out simultaneously.  
     
     
         3 . A method as in  claim 1 , wherein said first further node and said second further node are a single node.  
     
     
         4 . A method as claimed in  claim 1 , wherein said electrical signal is an RF or microwave signal.  
     
     
         5 . A method as claimed in  claim 4 , wherein the electrical signal is applied to an antenna.  
     
     
         6 . A method as claimed in  claim 1 , wherein in step iii said information-carrying modulation is an RF or microwave signal.  
     
     
         7 . A method as claimed in  claim 6 , wherein said information-carrying signal is an RF or microwave signal provided from an antenna.  
     
     
         8 . A method as claimed in  claim 7  wherein the electrical signal is applied to an antenna, the antenna to which the electrical signal is applied and the antenna which provides said information carrying signal are constituted by a single antenna.  
     
     
         9 . A method as claimed in  claim 7 , wherein the electrical signal is applied to a single antenna.  
     
     
         10 . A method as claimed in  claim 9 , wherein the base station, in use, supports the GSM and DECT systems.  
     
     
         11 . An optical communications network includes a remote terminal characterised in that said terminal comprises an electro-absorption modulator that 
 i) detects an incoming optical signal from a first portion of the optical communications network whilst simultaneously    ii) modulating said incoming optical signal, said optical signal being transmitted to a further portion of the optical communications network.    
     
     
         12 . An optical communications network according to  claim 11 , wherein the optical communications network uses a frequency division multiplexing system.  
     
     
         13 . A bi-directional optical-electrical signal transducer comprising: 
 an electro-absorption modulator having optical signal input and output ports and an electrical signal input/output port, whereby:    first information-bearing optical signals presented to said optical signal input port produce corresponding first information-bearing electrical signals at said electrical signal input/output port, and    second information-bearing electrical signals presented to said electrical signal input/output port produce corresponding second information bearing optical signals modulated onto an optical signal at said optical signal output port.    
     
     
         14 . A bi-directional optical-electrical signal transducer as in  claim 13  wherein said electro-absorption modulator functions simultaneously and at the same DC operating bias conditions to produce said output optical and electrical signals.  
     
     
         15 . A bi-directional optical-electrical signal transducer as in  claim 13  further comprising at least one RF antenna electrically connected to said electrical signal input/output port.