Optical amplifier and multicore fiber

1. An optical amplifier, comprising:

a pump light source that outputs pump light; and

a multicore fiber that includes:

a pumping core, the pump light being input to the pumping core by coupler,

a first signal light core doped with an active substance for optical amplification, and

a second signal light core doped with an active substance for optical amplification,

wherein the pump light propagates in the pumping core and thereby excites the active substance in the first signal light core and the active substance in the second signal light core, so as to optically amplify a signal light propagating through the first signal light core or a signal light propagating through the second signal light core.

2. The optical amplifier according to claim 1 , further comprising:

a reflective element,

wherein the reflective element reflects leaked pump light, the leaked pump light being the pump light output from the pumping core, the reflected leaked pump light being input to the pumping core again.

3. The optical amplifier according to claim 1 , wherein

the first signal light core has a first end and a second end,

the second signal light core has a first end and a second end,

a signal light enters the first end of the first signal light core, propagates through the first signal light core to thereby be optically amplified, and thereafter exits the second end of the first signal light core, and

the optical amplifier further comprising:

a reflective element disposed at the second end of the first signal light core so that the signal light exiting the second end of the first signal light core is reflected by the reflective element and thereby input to the second end of the second signal light core to propagate through the second signal light core from the second end of the second signal light core to the first end of the second signal light core, and

an optical filter disposed between the second end of the first signal light core and the reflective element, the optical filter optically filtering the signal light exiting from the second end of the first signal light core.

4. The optical amplifier according to claim 1 , wherein

the first signal light core has a first end and a second end,

the second signal light core has a first end and a second end,

a signal light enters the first end of the first signal light core, propagates through the first signal light core to thereby be optically amplified, and thereafter exits the second end of the first signal light core, and

the optical amplifier further comprising:

a reflective element disposed at the second end of the first signal light core so that the signal light exiting the second end of the first signal light core is reflected by the reflective element and thereby input to the second end of the second signal light core to propagate through the second signal light core from the second end of the second signal light core to the first end of the second signal light core, and

the signal light exiting the second end of the first signal light core and reflected by the reflective element is specific signal light of a specific wavelength band.

5. The optical amplifier according to claim 1 ,

wherein, in the multicore fiber, the pumping core is disposed at a center of the multicore fiber, and

wherein the first and second signal light cores being disposed around the pumping core.

6. The optical amplifier according to claim 1 , wherein

the multicore fiber includes a cladding between the pumping core and the first signal light core and between the pumping core and the second signal light core,

the pumping core has a refractive index at which the pump light radially propagates through the pumping core,

the refractive index of the pumping core being an index lower than a refractive index of the first signal light core and a refractive index of the second signal light core, and higher than a refractive index of the cladding.

7. A multicore fiber, comprising:

a pumping core, pump light being input to the pumping core;

a first signal light core doped with an active substance for optical amplification; and

a second signal light core doped with an active substance for optical amplification,

wherein the pump light radially propagates in the pumping core and thereby excites the active substance in the first signal light core and the active substance in the second signal light core, so as to optically amplify at least one of a signal light propagating through the first signal light core and a signal light propagating through the second signal light core.

8. The multicore fiber according to claim 7 , wherein

the multicore fiber includes a cladding between the pumping core and the first signal light core and between the pumping core and the second signal light core,

the pumping core has a refractive index at which the pump light radially propagates through the pumping core, the refractive index of the pumping core being an index lower than a refractive index of the first signal light core and a refractive index of the second signal light core, and being higher than a refractive index of the cladding.

9. A multicore fiber comprising:

a first pumping core;

a first signal light core doped with an active substance for optical amplification;

a second signal light core doped with an active substance for optical amplification; and

a cladding between the first pumping core and the first signal light core, and between the first pumping core and the second signal light core,

wherein the first pumping core has a refractive index with respect to a refractive index of the first signal light core, a refractive index of the second signal light core, and a refractive index of the cladding, and the first and second signal light cores are disposed with respect to the first pumping core, so that pump light input to the first pumping core radially propagates in the first pumping core and thereby excites the active substance in the first signal light core and the active substance in the second signal light core, to thereby optically amplify at least one of a signal light propagating through the first signal light core and a signal light propagating through the second signal light core.

10. The multicore fiber according to claim 9 , further comprising:

a second pumping core;

a third signal light core doped with an active substance for optical amplification; and

a fourth signal light core doped with an active substance for optical amplification,

wherein

the cladding is between the second pumping core and the third signal light core, and between the second pumping core and the fourth signal light core, and

the second pumping core has a refractive index with respect to a refractive index of the third signal light core, a refractive index of the fourth signal light core, and a refractive index of the cladding, and the third and fourth signal light cores are disposed with respect to the second pumping core, so that pump light input to the second pumping core radially propagates in the second pumping core and thereby excites the active substance in the third signal light core and the active substance in the fourth signal light core, to thereby optically amplify at least one of a signal light propagating through the third signal light core and a signal light propagating through the fourth signal light core.

11. An optical amplifier comprising the multicore fiber of claim 9 .

12. An optical amplifier comprising the multicore fiber of claim 10 .