Bidirectional Router and a Method of Bidirectional Amplification

Abstract

The invention relates to a router which may be used for amplification of a bidirectional optical signal using a single optical amplifier. An advantageous embodiment of the invention comprises two 3 dB couplers which are serially connected via a delay element. According to the embodiment, the delay element comprises a difference in distance L between the two optical branches which connect the two 3 dB couplers.

1 . A method for amplifying optical signals, comprising: 
 transmitting a first optical signal on a first optical path from a first bidirectional port to a first unidirectional port;    inducing a phase shift in the first optical signal on the first optical path, the phase shift being induced independently of a length of the first optical path.    
   
   
       2 . The method of  claim 1 , further comprising: 
 changing a refractive index of the first optical path in order to induce the phase shift in the first optical signal.    
   
   
       3 . The method of  claim 2 , further comprising: 
 applying an electrical field to the first optical path in order to change the refractive index.    
   
   
       4 . The method of  claim 3 , further comprising: 
 providing a pair of electrodes on the first optical path to apply the electrical field in order to change the refractive index and induce the phase shift.    
   
   
       5 . The method of  claim 1 , further comprising: 
 transmitting the first optical signal from the first unidirectional port through an amplifier to a second unidirectional port; and    transmitting the first optical signal from the second unidirectional port to a second bidirectional port on a second optical path.    
   
   
       6 . The system of  claim 5 , further comprising; 
 transmitting a second optical signal on a second optical path from a second bidirectional port to the first unidirectional port;    transmitting the second optical signal from the first unidirectional port through the amplifier to the second unidirectional port; and    transmitting the second optical signal from the second unidirectional port to the first bidirectional port.    
   
   
       7 . The method of  claim 6 , further comprising: 
 providing the first and second optical signals to the first bidirectional port and the second bidirectional port respectively, and from there to the first unidirectional port and further through an optical amplifier connected to the first and second unidirectional ports, and from there through the second unidirectional port and to the second bidirectional port and the first bidirectional port respectively.    
   
   
       8 . An optical router, comprising: 
 a first coupler having first and second input/output ports and first and second bidirectional ports, the first coupler operable to receive a first optical signal at the first input/output port and provide the first optical signal to the first bidirectional port;    a second coupler having a first and second input unidirectional ports and first and second output unidirectional ports;    a delay element coupled to the first bidirectional port and the first input unidirectional port on a first optical path, the delay element operable to induce a phase shift in the first optical signal on the first optical path, the phase shift being induced independently of a length of the first optical path.    
   
   
       9 . The optical router of  claim 8 , wherein the delay element is operable to change a refractive index of the first optical path in order to induce the phase shift in the first optical signal.  
   
   
       10 . The optical router of  claim 9 , wherein the delay element is operable to apply an electrical field to the first optical path in order to change the refractive index.  
   
   
       11 . The optical router of  claim 10 , wherein the delay element includes a pair of electrodes on the first optical path to apply the electrical field in order to change the refractive index and induce the phase shift.  
   
   
       12 . The optical router of  claim 8 , further comprising: 
 an amplifier coupled to the first output unidirectional port and the second input unidirectional port, the amplifier operable to transmit the first optical signal from the first output unidirectional port to the second input unidirectional port.    
   
   
       13 . The optical router of  claim 12 , wherein the second coupler is operable to transmit the first optical signal from the second output unidirectional port to the second bidirectional port on a second optical path.  
   
   
       14 . The optical router of  claim 13 , wherein the first coupler is operable to provide a second optical signal received at the second input/output port to the first input unidirectional port on the first optical path, the second coupler operable to provide the second optical signal received at the first input unidirectional port to the second input unidirectional port through the first output unidirectional port and the amplifier.  
   
   
       15 . The optical router of  claim 14 , wherein the second coupler is operable to provide the second optical signal from the second input unidirectional port to the first bidirectional port of the first coupler.  
   
   
       16 . A system for amplifying optical signals, comprising: 
 means for transmitting a first optical signal from a first bidirectional port of a first coupler to a first unidirectional port of a second coupler connected to the first coupler by a delay element, the delay element including a pair of electrodes arranged along a first optical path between the first and second couplers to induce a phase shift in the first optical signal.    
   
   
       17 . The system of  claim 16 , further comprising: 
 means for transmitting the first optical signal from the first unidirectional port of the second coupler through an amplifier to a second unidirectional port of the second coupler; and    means for transmitting the first optical signal from the second unidirectional port of the second coupler to a second bidirectional port of the first coupler.    
   
   
       18 . The system of  claim 17 , further comprising; 
 means for transmitting a second optical signal on a second optical path from a second bidirectional port of the first coupler to the first unidirectional port of the second coupler;    means for transmitting the second optical signal from the first unidirectional port of the second coupler through the amplifier to the second unidirectional port of the second coupler; and    transmitting the second optical signal from the second unidirectional port of the second coupler to the first bidirectional port of the first coupler.    
   
   
       19 . The system of  claim 16 , wherein the first optical signal is at a first wavelength.  
   
   
       20 . The system of  claim 18 , wherein the second optical signal is at a second wavelength.