Method and arrangement for signal transmission and compensation of back reflections in optical acces pon systems

Abstract

In a network terminal (ONU) of an optical network near end crosstalk (NEC) is compensated by a digital generated cancellation signal. To establish a connection with another terminal (OLT) signals avoiding NEC are transmitted and the compensation is performed while the power of the transmitted signal is increased in steps.

1 . A method for data processing of an optical network unit, comprising:
 receiving configuration information at the optical network unit;   adjusting a light signal to a wavelength or wavelength range indicated by the configuration information;   demodulating an incoming optical signal by means of the light signal;   mixing the demodulated incoming optical signal with a signal generated by an oscillator; and   generating a modulated optical upstream signal modulating the light signal by means of a software radio, so that the resulting optical upstream frequency is shifted with respect to the frequency of the local oscillator by a programmable amount.   
     
     
         2 . The method according to  claim 1 , wherein the light signal is provided by a laser. 
     
     
         3 . The method according to  claim 1 , wherein generating the modulated optical upstream signal includes multiplying the light signal by the factor of e −2πiΔ71  . 
     
     
         4 . The method according to  claim 1 ,
 wherein the signal generated by the oscillator is set to a predefined or arbitrary frequency;   wherein the light signal is adjusted to improve reception of the incoming optical signal and to receive the configuration information.   
     
     
         5 . The method according to  claim 1 , wherein bandwidth of the modulated optical upstream signal is lower than bandwidth of the incoming optical signal. 
     
     
         6 . The method according to  claim 1 , wherein the configuration information is provided by an optical line termination. 
     
     
         7 . The method according to  claim 1 , wherein the light signal used for upstream modulation is adjusted to a wavelength or wavelength range indicated by the configuration information by reducing a signal-to-noise ratio. 
     
     
         8 . The method according to  claim 1 , wherein the optical network unit is a subscriber unit of a passive optical network. 
     
     
         9 . A device, comprising:
 a light source providing a light signal;   a receiver to which the light signal is fed, wherein the receiver provides an electrical output signal;   wherein the light source is adjustable to a wavelength or wavelength range provided by received configuration information received;   an oscillator and a mixer, wherein a signal of the oscillator and the electrical output signal from the receiver are conveyed to the mixer and wherein the signal of the oscillator is tunable to improve a reception of the incoming signal at the device; and   a modulator to which the light signal of the light source is fed to provide a modulated optical upstream signal.   
     
     
         10 . The device according to  claim 9 , wherein said device is an optical network unit. 
     
     
         11 . the device according to  claim 9 , wherein said device includes a Digital Signal Processor. 
     
     
         12 . The device according to any of  claim 9 , wherein the signal of the oscillator is tunable to improve a signal-to-noise ratio of an output signal of the mixer. 
     
     
         13 . A communication system comprising at least one device according to  claim 9 .