Passive optical network system and wavelength assignment method

A passive optical network system which comprises an optical line termination, an optical splitter, an optical fiber, and a plurality of optical network units connected to the optical line termination through the optical splitter and in which the optical line termination communicates with the optical network units in wavelength division multiplexing,

• wherein the optical line termination includes:
• a plurality of first transmitters having light source respectively which wavelengths are different from each other;
• a plurality of first receivers to receive signals of a plurality of wavelengths;
• a wavelength management table to manage information of a wavelength assigned for communication with each of the optical network units for each of identifiers of the optical network units;
• a first control unit to receive a control message to assign a wavelength from the optical network unit and to assign the wavelength for the communication between the optical line termination itself and the optical network unit;
• and
• a transmission enabling control unit to cause only a wavelength under communication with the optical network unit to be outputted by enabling or disabling each of the plurality of first transmitters,
• wherein each of the optical network units includes:
• a second receiver to receive a signal of a set wavelength;
• a second transmitter to transmit a signal of a set wavelength;
• a reception power detection unit to detect reception power in the second receiver;
• a second control unit to transmit the control message to assign the wavelength through the second transmitter;
• and
• a wavelength control unit to variably control a transmission wavelength of the second transmitter and a reception wavelength of the second receiver,
• wherein the second control unit of the optical network unit
• sequentially changes the reception wavelength of the second receiver by the wavelength control unit to each of transmission wavelengths of the plurality of first transmitters of the optical line termination,
• detects reception power of a downstream signal from the optical line termination to the optical network unit by the reception power detection unit for each wavelength, obtains a first downstream wavelength not used for other communications based on the reception power,
• sets the reception wavelength of the second receiver to the first downstream wavelength by the wavelength control unit, and sets the transmission wavelength of the second transmitter to a first upstream wavelength paired with the first downstream wavelength, and
• transmits, by using the first upstream wavelength, a control message to request assignment of a wavelength to be used for communication with the optical line termination to the optical line termination,
• wherein the optical line termination
• according to receiving the control message, assigns the first downstream wavelength and the first upstream wavelength to communication with the optical network unit, or refers to the wavelength management table to assign a second downstream wavelength and a second upstream wavelength, which are not used for other communications, to communication with the optical network unit, and
• enables the first transmitter corresponding to the first downstream wavelength or the second downstream wavelength by the transmission enabling control unit, and
• wherein the optical network unit and the optical line termination communicate with each other with the first downstream wavelength and the first upstream wavelength, or the second downstream wavelength and the second upstream wavelength.

A wavelength assignment method in a passive optical network system which includes an optical line termination, an optical splitter, an optical fiber, and a plurality of optical network units connected to the optical line termination through the optical splitter and in which the optical line termination communicates with the optical network units in wavelength division multiplexing, wherein

• the system includes a plurality of wavelengths for communication between the optical line termination and the optical network units, a first wavelength among the plurality of wavelengths is previously determined as a wavelength for transmission and reception of a control message, and the wavelength assignment method is for assigning a second wavelength for communication with each of the optical network units among the plurality of wavelengths including the first wavelength, and wherein
• the optical network unit transmits a first control message to request assignment of the second wavelength to be used for communication between the optical line termination and the optical network unit itself to the optical line termination by a transmitter previously set to the first wavelength,
• when the optical line termination receives the first control message from the optical network unit, the optical line termination refers to a wavelength management table for managing information of the second wavelength assigned for communication with each of the optical network units, assigns the second wavelength, which is not assigned to other communications, to communication with
• the optical network unit, and transmits, by using the first wavelength, a second control message to notify the information assigned second wavelength to the optical network unit, the optical network unit receives the second control message by a receiver previously set to the first wavelength, and sets a transmission wavelength of a transmitter and a reception wavelength of the receiver to the assigned second wavelength based on the second control message, and
• the optical network unit and the optical line termination communicate with each other with the second wavelength.

A wavelength assignment method in a passive optical network system which includes an optical line termination, an optical splitter, an optical fiber, and a plurality of optical network units connected to the optical line termination through the optical splitter and in which the optical line termination communicates with the optical network units in wavelength division multiplexing,

• wherein the optical network unit
• sequentially changes a reception wavelength of a receiver of the optical network unit to each of transmission wavelengths of a plurality of transmitters of the optical line termination, detects reception power of a downstream signal from the optical line termination to the optical network unit for each wavelength,
• obtains a first downstream wavelength not used for other communications based on the reception power,
• sets the reception wavelength of the receiver of the optical network unit to the obtained first downstream wavelength, and sets the transmission wavelength of the transmitter of the optical network unit to a first upstream wavelength paired with the first downstream wavelength, and
• transmits, by using the first upstream wavelength, a control message to request assignment of a wavelength to be used for communication with the optical line termination to the optical line termination,
• wherein the optical line termination
• according to receiving the control message, assigns the first downstream wavelength and the first upstream wavelength to communication with the optical network unit, or refers to a wavelength management table for managing wavelength information assigned for communication with each of the optical network units for each of identifiers of the optical network units, assigns a second downstream wavelength and a second upstream wavelength, which are not used for other communications, to communication with the optical network unit, and
• enables the transmitter of the optical line termination corresponding to the first downstream wavelength or the second downstream wavelength, and
• wherein the optical network unit and the optical line termination communicate with each other with the first downstream wavelength and the first upstream wavelength, or the second downstream wavelength and the second upstream wavelength.