Abstract: It is disclosed a optical transmitter for an optical network unit of a multi-wavelength passive optical network comprising an optical line termination and a number of further optical network units for transmitting upstream signals to said optical line termination on multiple upstream channels. The optical transmitter is configured to generate and transmit an optical activation signal carrying activation information to be transmitted to said optical line termination on an upstream channel, the activation signal having an optical power lower than the optical power of each one of said upstream signals. The optical transmitter comprises an optical source, a first electric source configured to modulate the optical source with a first electric signal carrying the activation information; and a second electric source configured to directly modulate the optical source with a second electric signal so as to produce a frequency chirp on the optical activation signal.

Abstract: A method for activating an ONU in a multi-wavelength PON. Other ONUs may be already active and transmit upstream signals to the OLT on various upstream channels. The new ONU transmits an activation signal superimposed to such upstream signals. Since the ONU may include an uncalibrated tunable transmitter, initially the activation signal wavelength might be different from that upon which the ONU shall be activated. The activation signal optical power is lower than the other upstream signals, so as not to impair their reception at the OLT. The OLT operates the ONUs already active on the upstream channel on which the new ONU shall be activated to suspend transmission for one or more time gaps, during which the OLT detects the activation signal. This improves activation signal detection conditions, thereby allowing to increase its bitrate. An acceptable duration of the activation procedure can then be achieved.

Abstract: It is disclosed a optical transmitter for an optical network unit of a multi-wavelength passive optical network comprising an optical line termination and a number of further optical network units for transmitting upstream signals to said optical line termination on multiple upstream channels. The optical transmitter is configured to generate and transmit an optical activation signal carrying activation information to be transmitted to said optical line termination on an upstream channel, the activation signal having an optical power lower than the optical power of each one of said upstream signals. The optical transmitter comprises an optical source, a first electric source configured to modulate the optical source with a first electric signal carrying the activation information; and a second electric source configured to directly modulate the optical source with a second electric signal so as to produce a frequency chirp on the optical activation signal.

Abstract: A method for activating an ONU in a multi-wavelength PON. Other ONUs may be already active and transmit upstream signals to the OLT on various upstream channels. The new ONU transmits an activation signal superimposed to such upstream signals. Since the ONU may include an uncalibrated tunable transmitter, initially the activation signal wavelength might be different from that upon which the ONU shall be activated. The activation signal optical power is lower than the other upstream signals, so as not to impair their reception at the OLT. The OLT operates the ONUs already active on the upstream channel on which the new ONU shall be activated to suspend transmission for one or more time gaps, during which the OLT detects the activation signal. This improves activation signal detection conditions, thereby allowing to increase its bitrate. An acceptable duration of the activation procedure can then be achieved.

Abstract: An electrically controlled optical oscillator for a single subcarrier optical phase-locked loop, which includes: an electrically controlled electrical oscillator having an input, which receives an electrical driving input signal, and an output, which supplies an electrical driving output signal that has a frequency that is a function of the electrical driving input signal; a continuous-wave laser source, which supplies an optical carrier; and an optical modulator, which has an optical input connected to the laser source and receives the optical carrier, an electrical input, which is connected to the output of the electrically controlled electrical oscillator and receives the electrical driving output signal, and an optical output that modulates the optical carrier with the electrical driving output signal and generates an optical modulated signal. The optical modulator generates an optical modulated signal with single optical subcarrier.

Abstract: An electrically controlled optical oscillator for a single subcarrier optical phase-locked loop, which includes: an electrically controlled electrical oscillator having an input, which receives an electrical driving input signal, and an output, which supplies an electrical driving output signal that has a frequency that is a function of the electrical driving input signal; a continuous-wave laser source, which supplies an optical carrier; and an optical modulator, which has an optical input connected to the laser source and receives the optical carrier, an electrical input, which is connected to the output of the electrically controlled electrical oscillator and receives the electrical driving output signal, and an optical output that modulates the optical carrier with the electrical driving output signal and generates an optical modulated signal. The optical modulator generates an optical modulated signal with single optical subcarrier.

Abstract: An optical phase locked loop (1), comprising an optical phase detector (2) receiving as inputs an optical signal to be locked (symbol I) and a locked optical signal (symbol II) and providing as its output an electrical error signal (VPD) indicating the phase shift existing between the optical signal to be locked (symbol I) and the locked optical signal (symbol II); an electrical loop filter (3) receiving the electrical error signal (VPD) and outputting a filtered electrical error signal (VPDF), and an optical voltage controlled oscillator (4) receiving as an input the filtered electrical error signal (VPDF) and outputting the locked optical signal (symbol II).