An extended branching device , comprising: first branching means comprising a first port coupled to a first terminal station and adapted to receive a wavelength division multiplex, WDM, signal transmitted by the first terminal station , a second port coupled to a second terminal station , a third port , a fourth port , and a switch to couple the first port with one of the second port and the third port and couple the second port with the fourth port ; second branching means comprising a fifth port coupled to the third port and adapted to receive the WDM signal transmitted by the first terminal station , a sixth port coupled to the fourth port , a seventh port coupled to a third branching means , and a first separating means for outputting, to the sixth port , a light signal of a first wavelength among the wavelengths inputted from the fifth port and outputting, to the seventh port , the other wavelengths inputted from the fifth port ; wherein the second branching means is configured to be separable from the first branching means and; the third branching means , disposed between the second branching means and the third terminal station , comprising a ninth port coupled to the seventh port , a tenth port coupled to an eighth port of the second branching means , an eleventh port coupled to the third terminal station , and a second separating means for outputting to the tenth port a light signal of a second wavelength among the wavelengths inputted from the ninth port and outputting to the eleventh port a light signal of a third wavelength among the wavelengths inputted from the ninth port , wherein the third branching means is configured to be separable from the first branching means and the second branching means . first branching means comprising a first port coupled to a first terminal station and adapted to receive a wavelength division multiplex, WDM, signal transmitted by the first terminal station , a second port coupled to a second terminal station , a third port , a fourth port , and a switch to couple the first port with one of the second port and the third port and couple the second port with the fourth port ; second branching means comprising a fifth port coupled to the third port and adapted to receive the WDM signal transmitted by the first terminal station , a sixth port coupled to the fourth port , a seventh port coupled to a third branching means , and a first separating means for outputting, to the sixth port , a light signal of a first wavelength among the wavelengths inputted from the fifth port and outputting, to the seventh port , the other wavelengths inputted from the fifth port ; wherein the second branching means is configured to be separable from the first branching means and; the third branching means , disposed between the second branching means and the third terminal station , comprising a ninth port coupled to the seventh port , a tenth port coupled to an eighth port of the second branching means , an eleventh port coupled to the third terminal station , and a second separating means for outputting to the tenth port a light signal of a second wavelength among the wavelengths inputted from the ninth port and outputting to the eleventh port a light signal of a third wavelength among the wavelengths inputted from the ninth port , wherein the third branching means is configured to be separable from the first branching means and the second branching means . <EOS>