Multiple star wavelength division multiplexing passive optical networks using a wavelength assignment method

1. A multiple star wavelength division multiplexing passive optical network system using a wavelength assignment method, the system comprising:

an optical line termination (OLT) comprised of a first wavelength division multiplexer/de-multiplexer (WDM) and a plurality of first optical transceivers being connected to the first WDM;

a first remote node (RN) comprising a band splitting wavelength division multiplexer/de-multiplexer (BSWDM) being connected to the OLT by an optical fiber, wherein the BSWDM splits a wavelength band for certain down-stream signals into a plurality of first wavelength sub-bands and combines a plurality of second wavelength sub-bands, into which a wavelength band for certain up-stream signals is split, with the wavelength band for the certain up-stream signals;

a plurality of second RNs being connected to the first RN by a plurality of optical fibers, wherein each of the second RNs is comprised of a second WDM; and

a plurality of optical network terminations (ONTs) being connected to the plurality of the second RNs by a plurality of separate optical fibers, wherein each of the plurality of ONTs comprises a second optical transceiver,

wherein a guard band (λ gb ) positioned between an up-stream basic band being used for the wavelength band for the certain up-stream signals and a down-stream basic band being used for the wavelength band for the certain down-stream signals is given by a formula of λ gb =λ gi +m[λ gi +(n−1)×λ c ],

wherein n indicates a number of channels which exist within either the first wavelength sub-bands or the second wavelength sub-bands;

wherein λ gi indicates a guard band positioned either between the first wavelength sub-bands split from the down-stream basic band or between the second wavelength sub-bands split from the up-stream basic band;

wherein λ c indicates a wavelength interval between the channels;

wherein m is a natural number including number 0;

wherein the BSWDM at the first RN comprises an arrayed wavelength grating (AWG) having a periodic transmission wavelength characteristic, and each WDM at the second RNs comprises an arrayed wavelength grating (AWG) having a periodic transmission wavelength characteristic;

a free spectrum range (FSR) of the AWG at the second RNs is given by a formula of FSR=λ gi +(n−1)λ c and is the same as a wavelength range of the wavelength sub-bands which are split by the BSWDM, and each of the plurality of AWGs at the second RNs have the same FSR characteristic as one another;

the second optical transceiver positioned at each ONT is the same type of an optical transceiver which splits only either the wavelength band for the certain up-stream signals or the wavelength band for the certain down-stream signals; and

the ONTs employ only a filter for splitting D-band in the wavelength band for the certain down-stream signals as the down-stream basic band and U-band in the wavelength band for the certain up-stream signals as the up-stream basic band, each of which is a basic band, independently of the split sub-bands.

2. The multiple star wavelength division multiplexing passive optical network system of claim 1 , wherein a distributed-feedback laser diode (DFB LD) is used as a light source for the certain up-stream signals and a light source for the certain down-stream signals.

3. The multiple star wavelength division multiplexing passive optical network system of claim 1 , wherein a wavelength-locked Fabry-Perot laser diode (F-P LD) by an incoherent light source injected from outside is used as a light source for the certain up-stream signals and a light source for the certain down-stream signals.

4. The multiple star wavelength division multiplexing passive optical network system of claim 1 , wherein a spectrum-sliced light emission diode (LED) is used as a light source for the certain up-stream signals and a light source for the certain down-stream signals.

5. The multiple star wavelength division multiplexing passive optical network system of claim 1 , wherein a semiconductor optical amplifier into which an incoherent light source is injected from outside is used as a light source for the certain up-stream signals and a light source for the certain down-stream signals.

6. The multiple star wavelength division multiplexing passive optical network system of claim 1 , wherein one or more band different from the wavelength band for the certain up-stream signals and the wavelength band for the certain down-stream signals is used as either one or both of the wavelength band for the certain up-stream signals and the wavelength band for the certain down-stream signals.

7. The multiple star wavelength division multiplexing passive optical network system of claim 1 , wherein one or more band different from the wavelength band for the certain up-stream signals and the wavelength band for the certain down-stream signals is used as a band for monitoring the multiple star wavelength division multiplexing passive optical network system.

8. A multiple star wavelength division multiplexing passive optical network system using a wavelength assignment method, the system comprising:

an optical line termination (OLT) comprised of a first wavelength division multiplexer/de-multiplexer (WDM) and a plurality of first optical transceivers being connected to the first WDM;

a first remote node (RN) comprising a wavelength division multiplexer/de-multiplexer (WDM) being connected to the OLT by an optical fiber, wherein the WDM splits a wavelength band for certain down-stream signals into a plurality of wavelength sub-bands and combines a plurality of wavelength sub-bands, into which a wavelength band for certain up-stream signals is split, with the wavelength band for the certain up-stream signals;

a plurality of second RNs being connected to the first RN by a plurality of optical fibers, wherein each of the second RNs is comprised of a BSWDM; and

a plurality of optical network terminations (ONTs) being connected to the plurality of the second RNs by a plurality of separate optical fibers, wherein each of the plurality of ONTs comprises a second optical transceiver,

wherein a guard band (λ gb ) positioned between an up-stream basic band being used for the wavelength band for the certain up-stream signals and a down-stream basic band being used for the wavelength band for the certain down-stream signals is given by a formula of λ gb =λ gi +m[λ gi +(n−1)×λ c ],

wherein n indicates a number of channels which exist within either the first wavelength sub-bands or the second wavelength sub-bands;

wherein λ gi indicates a guard band positioned either between the first wavelength sub-bands split from the down-stream basic band or between the second wavelength sub-bands split from the up-stream basic band;

wherein λ c indicates a wavelength interval between the channels; and

wherein m is a natural number including number 0;

wherein the WDM at the first RN comprises an arrayed wavelength grating (AWG) having a periodic transmission wavelength characteristic, and each BDWDM at the second RNs comprises an arrayed wavelength grating (AWG) having a periodic transmission wavelength characteristic;

a free spectrum range (FSR) of the AWG at the second RNs is given by a formula of FSR=λ gi +(n−1)λ c and is the same as a wavelength range of the wavelength sub-bands which are split by the BSWDM, wherein each of the plurality of AWGs at the second RNs have the same FSR characteristic as one another;

the second optical transceiver positioned at each ONT is the same type of an optical transceiver which splits only either the wavelength band for the certain up-stream signals or the wavelength band for the certain down-stream signals; and

the ONTs employ only a filter for splitting D-band in the wavelength band for the certain down-stream signals as the down-stream basic band and U-band in the wavelength band for the certain up-stream signals as the up-stream basic band, each of which is a basic band, independently of the split sub-bands.