PASSIVE OPTICAL NETWORK SYSTEM AND WAVELENGTH ASSIGNMENT METHOD

• US 20110091213A1
• Filed: 12/20/2010
• Published: 04/21/2011
• Est. Priority Date: 01/09/2007
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: KAWAZA, Tohru, Nishino, Ryosuke, Sakamoto, Kenichi
• Granted Patent: US 8,260,135 B2
• Time in Patent Office: Days
• US Class Current: 398/68
• CPC Class Codes: H04J 14/0226 Fixed carrier allocation, e.g. according to service
• CPC Class Codes: H04J 14/0246 using one wavelength per ONU
• CPC Class Codes: H04J 14/025 using one wavelength per ONU, e.g. for transmissions from-ONU-to-OLT or from-ONU-to-ONU
• CPC Class Codes: H04J 14/0282 WDM tree architectures

Abstract

In a PON system with WDM, at the time of initial setting, each ONU negotiates with an OLT, and automatically acquires a wavelength which can be used by the ONU. One wavelength for negotiation of assigned wavelength is fixed as a default, and a newly connected ONU first uses the wavelength. The OLT 200 includes a plurality of light sources for downstream communication. The ONU 300 includes a wavelength variable filter selectively receiving one of wavelengths of downstream communication, and a wavelength variable light source selectively emitting light of one of plural wavelengths for upstream communication. The ONU 300 uses a transmission wavelength (for example, λu32) for negotiation and transmits a wavelength assignment request 1000 to the OLT 200. The OLT 200 selects a wavelength λu1 to be assigned from unused wavelengths, and transmits wavelength information to the ONU 300. The OLT 200 and the ONU 300 communicates using the notified wavelengths.

Claims

1-8. -8. (canceled)

9. 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.

10. The passive optical network system according to claim 9,

wherein the optical line termination

refers to the wavelength management table when the control message is received, and assigns the second downstream wavelength and the second upstream wavelength, which are not used for the communications with other optical network units, to the communication with the optical network unit, and

transmits, by using the first downstream wavelength, a second control message to notify information of assigned second downstream wavelength and information of assigned second upstream wavelength to the optical network unit, and

wherein

the optical network unit receives the second control message by the second receiver set to the first downstream wavelength, sets the transmission wavelength of the second transmitter to the second upstream wavelength, and sets the reception wavelength of the second receiver to the second downstream wavelength by the wavelength control unit based on the second downstream wavelength, and

the optical network unit and the optical line termination communicate with each other with the second downstream wavelength and the second upstream wavelength.

11. The passive optical network system according to claim 9, wherein

the optical line termination

detects that connection with the optical network unit is disconnected when the first or the second upstream wavelength assigned to the optical network unit is not received by the first receiver for a specified time, and

disables the first transmitter of the first or the second downstream wavelength paired with the first or the second upstream wavelength by the transmission enabling control unit.

12. (canceled)

13. 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.