Trans-impedance amplifier arrangement and control module

Abstract

A trans-impedance amplifier arrangement has an input configured to receive an output from a photo-detector, a current monitoring circuit configured in use to provide a current monitor signal dependent on a current through the photo-detector, and an output configured to output said current monitor signal to a control module, said output further configured to receive control information from said control module. A control module is configured to receive the current monitor signal and to provide the control information.

What is claimed is: 
     
         1 . A trans-impedance amplifier arrangement comprising:
 an input configured to receive an output from a photo-detector;   a current monitoring circuit configured in use to provide a current monitor signal dependent on a current through said photo-detector; and   an output configured to output said current monitor signal to a control module, said output further configured to receive control information from said control module to adjust the performance of said trans-impedance amplifier arrangement during the normal function of said arrangement for reception of optical signals carrying information.   
     
     
         2 . The trans-impedance amplifier arrangement of  claim 1  wherein said output is further configured to provide said received control information to a control circuit. 
     
     
         3 . The trans-impedance amplifier arrangement of  claim 2 , wherein said control circuit is configured to compare at least part of said received control information with a predetermined code. 
     
     
         4 . The trans-impedance amplifier arrangement of  claim 3 , wherein said control circuit is configured to provide configuration information to one or more configurable modules of said trans-impedance amplifier arrangement in dependence on said the result of said comparing. 
     
     
         5 . The trans-impedance amplifier arrangement of  claim 2 , wherein said control circuit comprises a shift register for receiving said control information. 
     
     
         6 . The trans-impedance amplifier arrangement of  claim 1 , wherein said output is further configured to transmit information relating to at least one of configuration and internal circuit operating conditions of said trans-impedance amplifier arrangement to said control module, wherein said trans-impedance amplifier information is transmitted by said current monitor signal during the normal function of said trans-impedance amplifier arrangement for reception of optical signals carrying information. 
     
     
         7 . The trans-impedance amplifier arrangement of  claim 6 , comprising a selector configured to modulate said current monitor signal to transmit said trans-impedance amplifier operational information. 
     
     
         8 . The trans-impedance amplifier arrangement of  claim 6 , wherein one or more discrete current values are added at different times so as not to alter an average current value of said current monitor signal and to provide said trans-impedance amplifier operational information. 
     
     
         9 . The trans-impedance amplifier arrangement of  claim 6  comprising:
 a first current source; 
 a second current source; and 
 a selector configured to connect the output to said first and second current sources dependent on said trans-impedance amplifier operational information. 
 
     
     
         10 . A control module comprising:
 an input configured, in use, to receive data from a trans-impedance amplifier arrangement; and   a control circuit configured, in use, to provide control information to said trans-impedance amplifier arrangement via an output, said control data configured to adjust the performance of said trans-impedance amplifier arrangement during the normal function of said trans-impedance amplifier arrangement for reception of optical signals carrying information.   
     
     
         11 . The control module of  claim 10 , wherein said control information comprises a control header. 
     
     
         12 . The control module of  claim 11  wherein said control information comprises configuration information for one or more configurable modules of said trans-impedance amplifier arrangement to adjust the performance of said trans-impedance amplifier arrangement during the normal function of said arrangement for reception of optical signals carrying information. 
     
     
         13 . The control module of  claim 10  wherein said control circuit is configured to transmit said control information with a modulated signal. 
     
     
         14 . The control module of  claim 13 , wherein one of a voltage and a current is modulated to provide said control information. 
     
     
         15 . The control module of  claim 10 , wherein said received current monitor signal comprises an average current signal and one or more discrete current values corresponding to trans-impedance amplifier information. 
     
     
         16 . The control module of  claim 10 , wherein said control module comprises a voltage selector configured to modulate a voltage of said output by modulating a reference voltage. 
     
     
         17 . The control module of  claim 16 , comprising an operational amplifier and wherein in use:
 an inverting input of said operational amplifier arrangement is provided to said output; and   an non-inverting input of said operational amplifier arrangement is modulated in dependence on said control information.   
     
     
         18 . The control module of  claim 17 , wherein a compensation current is provided to said inverting input of said operational amplifier so as to substantially cancel out voltage changes at said output of said operational amplifier arrangement caused by modulating said non-inverting input. 
     
     
         19 . The control module of  claim 16 , comprising:
 a transistor configured to one of draw current from or supply current to said inverting input of said operational amplifier arrangement, said transistor being controlled by an output of said operational amplifier arrangement; and   a load resistor configured to convert said current drawn or supplied by said transistor to a voltage.   
     
     
         20 . The control module of  claim 15  comprising at least one of:
 a filter configured to extract said current monitor signal; and 
 a filter configured to extract a signal corresponding to trans-impedance amplifier arrangement information.