Methods and Devices for Wavelength Alignment in WDM-PON

A passive optical network system comprising at least one optical network unit (30-1) and an optical line terminal (10), the system configured to:

• initiate an upstream wavelength (wUS) for an upstream signal (US) from the optical network unit (30-1) to the optical line terminal (10),
• iteratively, until an iteration criterion is met,
• i) transmit the upstream signal (US) from the optical network unit (30-1) to the optical line terminal (10),
• ii) measure, at the optical line terminal (10), a power level of the received the upstream signal (US),
• iii) transmit from the optical line terminal (10) to the optical network unit (30-1) power level data (p) indicative of the measured power level, and
• iv) set, at the optical network unit (30-1), the upstream wavelength (wUS) for the upstream signal (US) to a new wavelength-value, and
• adjust, at the optical network unit (30-1), the upstream wavelength to a wavelength-value previously set for the upstream signal (US) and associated with power level data corresponding to a certain power level.

A method in an optical network unit (30-1) for a passive optical network (5), the method comprising:

• initiating (205) an upstream wavelength (wUS) for an upstream signal (US) from the optical network unit (30-1) to an optical line terminal (10),
• iteratively, until an iteration criterion is met,
• i) transmitting (206) the upstream signal (US) to the optical line terminal (10),
• ii) receiving (208′) from the optical line terminal (10) power level data (p) for the upstream signal (US) as measured by the optical line terminal (10), and
• iii) setting (209) the upstream wavelength (wUS) to a new wavelength-value, and
• adjusting (211) the upstream wavelength (wUS) to a wavelength-value previously set for the upstream signal (US) and associated with power level data corresponding to a certain power level.

A method in an optical line terminal for a passive optical network (5), the method comprising receiving from an optical network unit (30-1) an upstream signal (US) having an upstream wavelength (wUS), the method further comprising:

• continuously
• i) receiving (206″) the upstream signal (US) from the optical network unit (30-1),
• ii) measuring (207) a power level of the received the upstream signal (US), and
• iii) transmitting (208) to the optical network unit (30-1) power level data (p) indicative of the measured power level.

A method in a passive optical network system comprising at least one optical network unit (30-1) and an optical line terminal (10), the method comprising:

• initiating (205) an upstream wavelength (wUS) for an upstream signal (US) from the optical network unit (30-1) to the optical line terminal (10),
• iteratively, until an iteration criterion is met,
• i) transmitting (206) the upstream signal (US) from the optical network unit (30-1) to the optical line terminal (10),
• ii) measuring (207), at the optical line terminal (10), a power level of the received the upstream signal (US),
• iii) transmitting (208) from the optical line terminal (10) to the optical network unit (30-1) power level data (p) indicative of the measured power level, and
• iv) setting (209), at the optical network unit (30-1), the upstream wavelength (wUS) for the upstream signal (US) to a new wavelength-value, and
• adjusting (211), at the optical network unit (30-1), the upstream wavelength to a wavelength-value previously set for the upstream signal (US) and associated with power level data corresponding to a certain power level.