System for long reach xDSL over fiber

System for connecting a plurality of digital subscribers to a data network offering xDSL service, where digital subscribers send analogue upstream signals to the data network and the data network sends digital downstream signals to the digital subscribers, comprising a local part, located at a central office, connected by an optical fiber link to a remote part, located at an intermediate place between the central office and the digital subscribers, and said local part further comprising a plurality of digital subscriber line access multiplexer line cards with xDSL over fiber transceiver (2b), each digital subscriber line access multiplexer line cards with xDSL over fiber transceiver comprising:

• a plurality of xDSL lines comprising:
• in downstream direction:
• an analog front end which comprises an digital-analogue converter (58) to transform a transmitted digital downstream signal into an analogue downstream signal at a original frequency and at least one amplifier;
• an oscillator (80) which fixes an oscillation frequency for the xDSL line;
• a mixer (71), directly connected to the output of the at least one amplifier to convert the analog downstream signal into the oscillation frequency;
• a band pass filter (91a) centred at the oscillation frequency which filters the converted analog downstream signal;
• in upstream direction:
• a band pass filter (91b) centred at the oscillation frequency which filters an analogue upstream signal;
• an oscillator (81) which fixes an oscillation frequency for the xDSL line;
• a mixer (71), directly connected to the output of the band pass filter to convert the analogue donwnstream signal into the original frequency;
• a low pass filter (60) to avoid aliasing;
• an analogue front end which comprises an analogue-digital converter (59) to transform the converted analogue upstream signal into a digital upstream signal, and at least one amplifier;
• an adder circuit (300) to combine the analogue downstream signals received from each xDSL line;
• an optical upconverter (320) centred at a downstream wavelength, receiving upstream signals from the remote part through the wavelength division multiplexer;
• an optical downconverter (330) centred at an upstream wavelength, directly connected to a wavelength division multiplexer;
• a wavelength division multiplexer (6) which is connected through a point to point single model fiber (7) to the remote part.