Optical repeater, optical transmission system, and connection method of optical repeater

1 . An optical repeater comprising:

a first fan-in/fan-out (FIFO) including a first multi-core fiber (MCF) connectable to a first MCF transmission path and a first SCF (single-core fiber) group including a plurality of SCFs relevantly connected to each core of the first MCF; and

a monitoring light circuit that outputs, based on a fixed loss, monitoring light being input to a first core included in the first MCF, from light being output from a first SCF being an SCF included in the first SCF group and being an SCF relevant to the first core.

2 . The optical repeater according to claim 1 , wherein the monitoring light circuit includes a loop back circuit that loops back, from the first SCF, the monitoring light to a second SCF different from the first SCF of the first SCF group.

3 . The optical repeater according to claim 1 , further comprising:

a second FIFO including a second MCF connectable to a second MCF transmission path including a multi-core fiber and a second SCF group relevantly connected to each core of the second MCF;

an optical processing circuit that is disposed between the first SCF group and the second SCF group and executes predetermined processing on light propagating through each of a pair of SCFs different in transmission direction from each other; and

a loop back circuit that loops back, in a direction of the optical processing circuit toward input of the first FIFO, light being input from the first FIFO to the optical processing circuit and output from the optical processing circuit to the second FIFO.

4 . The optical repeater according to claim 2 , wherein the loop back circuit loops back only light having a wavelength of the monitoring light.

5 . The optical repeater according to claim 1 , wherein the monitoring light circuit includes an optical coupler that splits, from the first SCF, the monitoring light propagating through the first SCF and outputs the split monitoring light to outside of the optical repeater.

6 . The optical repeater according to claim 5 , wherein

the optical coupler includes an optical filter that outputs only light having a wavelength of the monitoring light to outside of the optical repeater, and

the monitoring light circuit includes

an optical interface for connecting the split monitoring light to an optical power meter and

a termination unit that reduces, when the optical power meter is not connected to the optical interface, a reflection attenuation amount of the optical interface.

7 . The optical repeater according to claim 1 , further comprising:

a second FIFO including a second MCF connectable to a second MCF transmission path including a multi-core fiber and a second SCF group relevantly connected to each core of the second MCF; and

an optical processing circuit that is disposed between a third SCF being one SCF of the second SCF group and the first SCF and executes predetermined processing on input light, wherein

the monitoring light circuit is connectable, based on a fixed loss, between the first SCF and the third SCF by using a bypass circuit bypassing the optical processing circuit.

8 . The optical repeater according to claim 7 , wherein the monitoring light circuit configures, between the first SCF and the third SCF, the bypass circuit bypassing the optical processing circuit, by using at least one of an optical switch and an optical coupler.

9 . An optical transmission system comprising:

an optical repeater including

a first fan-in/fan-out (FIFO) including a first multi-core fiber (MCF) connectable to a first MCF transmission path and a first SCF (single-core fiber) group including a plurality of SCFs relevantly connected to each core of the first MCF and

a monitoring light circuit that outputs, based on a fixed loss, monitoring light being input to a first core included in the first MCF, from light being output from a first SCF being an SCF included in the first SCF group and being an SCF relevant to the first core;

a light source device including a light source that inputs, via the first MCF transmission path, the monitoring light to the first FIFO, and an optical power meter that measures power of the monitoring light that is looped-back to the first FIFO and propagated through the first MCF transmission path; and

a fusion machine that performs optical axis adjustment and fusion splicing between the first MCF transmission path and the first MCF, by using power of the monitoring light measured by the optical power meter.

10 . A connection method of an optical repeater, comprising:

inputting monitoring light to a first multi-core fiber (MCF) transmission path of an optical repeater including a first fan-in/fan-out (FIFO) including a first MCF connectable to the first MCF transmission path and a first single-core fiber (SCF) group including a plurality of SCFs relevantly connected to each core of the first MCF, and a monitoring light circuit that outputs monitoring light being input to a first core included in the first MCF, from light being output from a first SCF being an SCF included in the first SCF group and being an SCF relevant to the first core;

measuring power of the monitoring light being output from the monitoring light circuit; and

performing, by using the power of the monitoring light, optical axis adjustment to the first MCF transmission path and the first MCF.